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NEPTUNE
Oceanworks Junction Box Operations Manual
Contents
1.
General Instructions ............................................................................................................................... 2
1.1.
Safety Warnings ............................................................................................................................ 2
1.1.1.
General .................................................................................................................................. 2
1.1.2.
Electrical ................................................................................................................................ 3
1.1.3.
Optical ................................................................................................................................... 3
1.2.
Handling Precautions .................................................................................................................... 3
2. Scope ..................................................................................................................................................... 4
3. Reference Documents ........................................................................................................................... 4
4. Junction Box Overview .......................................................................................................................... 4
5. Specification Details............................................................................................................................... 7
5.1.
Uplink Interfaces ........................................................................................................................... 7
5.2.
Distribution Architecture ................................................................................................................ 7
5.3.
Communications Architecture ....................................................................................................... 8
5.4.
Downlink Interfaces ....................................................................................................................... 8
5.4.1.
Design Philosophy................................................................................................................. 8
5.4.2.
Low Voltage Interfaces .......................................................................................................... 9
5.4.3.
High Voltage Interfaces ......................................................................................................... 9
6. Engineering Details .............................................................................................................................. 10
6.1.
Physical Characteristics .............................................................................................................. 10
6.2.
Transportation and Incoming Inspections ................................................................................... 10
6.3.
Galvanic Isolation ........................................................................................................................ 10
6.3.1.
Power Lines ......................................................................................................................... 10
6.3.2.
Serial Communications ....................................................................................................... 11
6.4.
Over-voltage Protection .............................................................................................................. 11
6.5.
Grounding and Ground Fault Detection ...................................................................................... 12
6.6.
Low Voltage Interfaces ................................................................................................................ 13
6.7.
High Voltage Interfaces ............................................................................................................... 14
6.7.1.
Soft-Start ............................................................................................................................. 14
6.8.
Communications ......................................................................................................................... 16
6.8.1.
Serial Communications ....................................................................................................... 16
6.9.
Telemetry .................................................................................................................................... 16
6.10. Subsea Controller ....................................................................................................................... 16
6.10.1.
Controller Overview ............................................................................................................. 16
6.10.2.
Power ON/OFF and Initiation of Software ........................................................................... 17
6.11. Start-up Sequence of Events ...................................................................................................... 17
6.11.1.
Subsea Controller Software ................................................................................................ 17
6.11.2.
Downlink Interfaces ............................................................................................................. 17
7. System Integration Guidelines ............................................................................................................. 18
7.1.
Extension Cables ........................................................................................................................ 18
7.2.
Selection of Connectors .............................................................................................................. 18
7.3.
Downlink Interface Voltage and Power Selection ....................................................................... 18
7.4.
Electrical Noise............................................................................................................................ 19
7.5.
Transient Surge Protection ......................................................................................................... 20
8. Operational Guidelines ........................................................................................................................ 20
8.1.
General ........................................................................................................................................ 20
8.2.
Subsea Controller Software ........................................................................................................ 21
8.2.1.
FET Timing .......................................................................................................................... 21
8.3.
Setting Alarm Thresholds ............................................................................................................ 22
8.3.1.
Over-Current Alarm ............................................................................................................. 22
8.3.2.
Over-voltage Alarm ............................................................................................................. 23
8.3.3.
Under-voltage Alarm ........................................................................................................... 23
8.3.4.
Isolation Resistance (Ground Fault).................................................................................... 23
8.4.
Telemetry Data Monitoring and Analysis .................................................................................... 25
9. Periodic Maintenance .......................................................................................................................... 25
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9.1.
General Recommendations ........................................................................................................ 25
9.2.
Return Procedure ........................................................................................................................ 26
10.
Junction Box Test PRocedures ....................................................................................................... 26
10.1. Testing by Oceanworks ............................................................................................................... 26
10.1.1.
Qualification......................................................................................................................... 26
10.1.2.
Factory Acceptance ............................................................................................................ 27
10.2. NEPTUNE Canada Tests ............................................................................................................ 27
10.2.1.
Receiving ............................................................................................................................. 27
10.2.2.
Deployment and Start-up .................................................................................................... 27
10.2.3.
Qualification......................................................................................................................... 27
10.3. Node-JB Integration Testing ....................................................................................................... 27
10.3.1.
Integration Test Results Sheets – Phase 1 ......................................................................... 27
10.3.2.
Integration Test Results Sheets – Phase 2 ......................................................................... 28
1.
GENERAL INSTRUCTIONS
The instructions below apply to both the junction box and the electrical and optical equipment that may be
connected to it (either via uplink or downlink interfaces).
It is recommended that the junction boxes not be opened or serviced other than by qualified personnel in
a suitably equipped workshop. However, in the event that the devices are serviced, the precautions below
shall be observed.
1.1.
1.1.1.
Safety Warnings
General
DO NOT SERVICE OR ADJUST EQUIPMENT WHEN ALONE. No person should work on any part of
the equipment without a second person (assistant) being available in case of need.
The total equipment weight exceeds 200kg. Use material–handling equipment to lift equipment. Safety
boots must be worn when handling the JB.
When placing the JB, ensure that it is has sturdy support and is securely braced to prevent it from rolling.
Ensure that there is adequate clearance around the unit to move around unimpeded.
Only open the JB in clean, dry, ventilated, and temperature-controlled rooms.
Testing and operating must be performed in a clearly designated testing area. Access to the testing area
shall be limited. Unauthorized persons and persons unfamiliar with the testing must not enter the testing
area.
Persons operating the equipment must do so with extreme caution using appropriate tools and equipment
and adhering closely to the written operating procedures.
During transportation and installation, the NEPTUNE Lifting Frame Assembly should be used to move the
JB whenever possible. All lifting devices, slings, support fixtures, cradles and other equipment used to
move or secure the JB must be rated for safe working loads that exceed that of the JB (crated and uncrated).
The JB must not be powered during marine installation or recovery activities.
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1.1.2.
Electrical
Both lethal and dangerous voltages are present within the equipment. Do not wear conductive jewellery
while working on the equipment. Always observe all safety precautions.
When operating the JB on land, it must be solidly grounded by means of a connection to the protection
ground terminal of the site electrical plant, before any other electrical connections are made. This ensures
that there is no potential between the JB chassis and earth ground. This bonding protects personnel who
are either floating with respect to earth or bonded to earth via ESD measures. This bonding can be
achieved by connecting the JB to earth ground with a #6 AWG or larger wire. The holes in the pressure
vessel heads used to fasten the can head mounting jig are an ideal bonding point for the JB. Earth leads
must be tested before energizing equipment.
Personnel must be protected from live equipment by appropriate housings or suitable barriers.
Equipment must be safely de-energized before opening housings or removing barriers.
Never attempt to connect or disconnect connectors from the JB when the JB is energised.
When powering the JB on land, all of the energised parts of the system shall be cordoned off and
signposted with high voltage danger warning signs.
1.1.3.
Optical
Under normal operating conditions, the optical fibre equipment forms part of a closed system, i.e. the
invisible radiation produced is contained within closed paths. However, when the path is broken, (e.g.
during testing) exposure to the radiation is possible. The focusing ability of the eye makes it susceptible to
damage and safe-working practices must be adopted to minimise the risk to exposure.
This optical uplink switch in the JB produces invisible class 3B laser radiation, which could be hazardous
under fault conditions. Do not stare into the fibre ends and do not use optical aids to look at fibres that
may be lit.
Practices
1. Ensure good housekeeping, maintaining cleanliness of fibres and handle with care.
2. Never view an un-terminated optical fibre or connector unless the optical source has been turned
off.
3. Never view a broken fibre unless the optical source has been turned off.
4. Never use a magnifying glass as an aid to viewing any part of a fibre or connector.
5. Only use approved methods and materials for cleaning optical fibres.
1.2.
Handling Precautions
The electrical circuit boards within the JB are electrostatic sensitive. Observe correct anti-static handling
precautions (i.e. wear a fully working ESP wristband attached to an earth bonding point (e.g. an ESP stud
on an earthed rack or workbench) at all times when circuit boards are being handled).
Fibres need to be cleaned and checked before any connections are made.
Ensure that optical connector dust caps are in place whenever the equipment is powered or connectors
are not plugged in to a closed system.
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Ensure that dust caps are placed over all exposed connector ends when servicing the unit or
attaching/detaching instrument whips.
If operating the JB out of seawater, care should be taken to ensure that the internal operating
temperature of the device remains within design limits (i.e. below 35°C). Although the unit will continue to
operate at higher temperatures, the life expectancy of the electronics will be dramatically reduced with
increasing temperature. This has to be monitored using the JB telemetry – the temperature on the surface
of the housing is not representative of the ambient temperature within it.
2.
SCOPE
This document is to be used by operators of the NEPTUNE Canada ocean observatory, with regards to
configuring, operating and monitoring of junction boxes deployed on the submarine network. During predeployment trials, the junction boxes may be operated on shore, and the constraints with regard to
operating the devices in this environment will be addressed.
This document consolidates much of the information that is available in numerous formal documents
issued by Oceanworks, engineering drawings, design notes and correspondence. The goal is to provide
the operators of the JB all of the information they need in a concise format in one place. However, this
document is not intended to replace the detailed engineering and reference documentation that has been
provided by Oceanworks.
The theory of operation of the junction box will be described, as an understanding of the design
philosophy and operation of its subsystems is important when trouble-shooting or setting configuration
parameters, as well as verifying the suitability of instruments to be connected. Limitations of the JB will be
explained, as well as the associated implications for characteristics that must be met for any instruments
that are connected to the JB.
This document is not intended as a reference for doing any work on the JB housing, opening the JB or
altering the internal wiring or circuitry.
3.
REFERENCE DOCUMENTS
Document Number
0848-RPT001
0848-RPT002
848-250 series
drawings
0820-100SWA10520
Description
NEPTUNE Junction Box Housing System Design Document
0848-RPT002 Subsea System User Manual
Oceanworks - NEPTUNE Canada - Subsea Junction Boxes
Contract
Exhibit A - Performance Requirements
Oceanworks as-built chassis, schematic, detail and tooling
drawings
Junction Box Telnet Command Manual
The NEPTUNE Ground Fault Sensor Model
NEPTUNE UDP Data Structure
4.
Revision
3.0
1.1
Issue 7.3
Various
1.4
0.1
JUNCTION BOX OVERVIEW
For full details of the contractual requirements for the JB, refer to Exhibit A (CV-4) of the Oceanworks JB
contract. The salient specifications of the junction box, as may be applicable to the operator, are as
follows:
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1. Support for up to ten downlink interfaces plus one uplink interface.
2. The uplink interface receives power at 300-400VDC at up to 22.5A and may comprise one of the
following communications links:
a. 100Base-T Ethernet
b. 1000Base-LX Ethernet on two single mode fibres.
c. Dual 1000Base-LX Ethernet links using four single mode fibres
3. The power supply for each downlink interface can be selected from the following at the time of
ordering the JB from Oceanworks, for a maximum of ten downlink interfaces in total:
a. Up to three high-voltage (300-400V) DC ports at 15 amps per downlink interface.
Hereafter these ports will be referred to high voltage (HV) ports
b. One port of up to 600 watts at 48V.
c. Up to 10 power supplies of 75 watts at 12V, 15V, 24V, or 48V.
d. Up to 3 power supplies of 150 watts at 15V, 24V or 48V.
4. Each JB shall accommodate up to ten 10/100Base-T downlink interfaces and up to four isolated
serial data links (EIA-232, EIA-422, or EIA-485 serial data at up to 115.2 Kb/s). As an option, the
JB may support up to eight isolated serial data links by eliminating two of the 300-400V DC
downlink circuits.
5. Each downlink port can be configured with any available power and data interface at the time of
ordering. Once the JB has been assembled, the power and data interfaces cannot be changed,
except that the serial communications protocol may be changed via software.
6. Provision has been made for optical downlink interfaces, but these are not available in the
present generation.
7. The JB incorporates a surge arrestor on the 400V input to the hotel load and low voltage
interfaces, to protect against transient over-voltages that may occur due to switching of loads.
The 400V interfaces are not protected by the surge arrestor and any instrument connected to a
400V port should have its own surge protection.
8. The JB measures and reports voltages and currents on all downlink interfaces. Isolation
resistance (ground fault) is measured on all low voltage interfaces but not on the 400V ports.
Vicor DC-DC converters are used to step the 400V input voltage down to the voltage required to operate
the JB control circuitry (i.e. the “hotel” load) at 24V, as well as each of the low-voltage supplies for the
downlink interfaces.
A high-level schematic view of the JB configuration is provided in Figure 1.
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Oceanworks Junction Box Operations Manual
Figure 1 – Junction Box Schematic Diagram
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5.
SPECIFICATION DETAILS
The specification details outline the high-level design requirements to which the JB was built. For full
details, refer to Exhibit A - Performance Requirements of the contract between UVic and Oceanworks for
the design and manufacture of the junction boxes. The salient specifications as they relate to operations
are highlighted below.
5.1.
Uplink Interfaces
The JB receives 300-400V DC at up to 22.5 amps on the uplink interface from which all internal and
external loads are powered. The 400V power bus is referenced to seawater ground at the node such that
the two power leads are nominally +200V and -200V with respect to seawater ground. The JB is
designed to continue to operate with a seawater ground fault on either the +200V or -200V line.
The communications interface for the uplink interface may be one of the following:
1. 100Base-T Ethernet
2. 1000Base-LX Ethernet on two single mode fibres.
3. Dual 1000Base-LX Ethernet links using four single mode fibres.
In the existing configuration, optical dual 1000Base-LX Ethernet communications using four fibres are
used on junction boxes that connect directly to nodes. These have ODI hybrid optical/electrical wet-mate
connectors on the uplink interface. Electrical 100Base-T Ethernet interfaces are used on junction boxes
that are downstream of other junction boxes.
During testing, the JB has been shown to operate with input voltages as low as 250V. However, for
purposes of designing the extension cables, the minimum input voltage used was 300V. Since switching
on of large loads could potentially cause transient voltage dips, it is recommended that the 300V
minimum be observed for future planning and design purposes, to provide a margin of safety.
5.2.
Distribution Architecture
Unconditioned power received from the uplink interface is distributed within the JB to the populated High
Voltage Breakers and an Over Voltage Protection unit (OVP). The OVP supplies power to the Low
Voltage Power Supplies and the Hotel Power Supply (Hotel).
The JB is provided with a cross-connect power termination block at the connector end of the housing,
which has 11 ports (1 input and 10 outputs). This allows any chassis position to be connected to any port
on the JB head. Molex Mini-Fit Sr. connectors are used on the bulkhead due to their isolation
performance, current carrying capacity and connection robustness. All of the power connections into and
out of the JB pass through the cross-connect block.
The power distribution is designed such that a failure in one subsystem does not affect the other
subsystems. Each low-voltage power supply is isolated by means of the Vicor DC-DC converters.
A single Vicor DC-DC power supply provides 150W at 24VDC to the JB’s hotel loads and is critical to the
operation of the JB. The hotel loads are separated into primary and secondary categories. The output
from the hotel power supply is split into a fused bus and an un-fused bus. The primary loads are powered
directly from the un-fused bus and the secondary loads are powered by the fused rail. The reasoning
behind the separation of the devices is that the loss of a single primary load would represent a total loss
of the JB, while the loss of secondary loads would result in limited functionality of the JB. All subsystems
that are powered by the hotel power supply are individually fused.
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Refer to the Neptune Chassis Assembly Schematic (0848-100-S10000) for more details.
5.3.
Communications Architecture
JB data communications are handled by three devices, a MOXA EDS-510A Managed Ethernet Switch, a
MOXA EDS-508A Managed Ethernet Switch and a MOXA NPort 5450I Ethernet Serial Server (a nonstandard configuration containing a second NPort serial server is available). The EDS-510A provides
seven 100BaseT Ethernet ports and three 1000BaseSFP small form-factor pluggable transceiver (SFP)
slots. Two MOXA 1000BaseLX 1310nm SFP modules, one each for the primary and secondary JB uplink,
are installed in the SFP slots for JBs with fibre optic uplinks. The EDS-508A provides eight 100BaseT
Ethernet ports and handles the majority of the instrument Ethernet links and secondary equipment links.
The NPort 5450I converts 4 serial data signals originating at the instruments to Ethernet and can be
software-configured to handle EIA232, EIA422 or EIA485 (2-wire or 4-wire).
Fully managed Ethernet switches were used to provide the user with full network management of the JB.
The capabilities of the selected switches include the following:







Software configurable
Remotely controlled via telnet and http
Remotely upgradable software
Restore default settings
Active troubleshooting of the communications status from DMAS
Set up Virtual Local Area Networks (VLANs)
Support Internet Protocol (IP) multicast
All communication lines pass through the Communications Bulkhead, which allows a copper link to be
attached to any port on the JB head. Fibre optic links enter the JB via the ODI penetrators (ports J11, J12
and J13) and are terminated on the Fibre Optic Bulkhead located on the JB housing head.
Refer to the Neptune Chassis Assembly Schematic (0848-100-S10000) for more details.
5.4.
5.4.1.
Downlink Interfaces
Design Philosophy
The downlink interfaces can be arranged in a variety of configurations, mixing and matching the voltage
and communications protocol to suit most conceivable instrument requirements. The voltage is
determined during assembly of the JB, because each power circuit board is built with voltage-specific
components. Each low-voltage downlink interface comprises a discrete circuit board containing a Vicor
DC-DC converter, whose ratings determine the output power and voltage specification for the port. The
design of the circuit boards themselves has been standardised as follows:




400V (HV)
Low voltage 600W (48V output only)
Low voltage 150W (15, 24 or 48V output)
Low voltage 75W (12, 15, 24 or 48V output)
There is no particular standard configuration for the port voltages on the JB low-voltage interfaces. The
HV ports have all been provided on ports 8, 9 and 10. There is no physical constraint dictating this
arrangement, but in the interests of consistency and safety the high voltage port assignments have been
kept the same throughout.
The downlink interfaces are all provided with galvanic isolation, to ensure that there is no path for stray
currents to flow when a port is de-energised. This is to safeguard against galvanic corrosion.
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5.4.2.
Low Voltage Interfaces
The design of the 75 and 150W circuit boards (low-power supplies, or LPS) is such that the voltage can
be changed simply by changing the Vicor power supply module as required. The 600W output voltage is
limited to 48V, because lower voltages would result in currents that exceeded the current-carrying
capacity of the existing wiring harnesses, circuit boards etc. The 600W (high-power supply) circuit board
is specific to this power interface.
All Vicor DC-DC converters used within the JB are military grade, and have undergone a 24 hour, 58
power cycle burn in during Vicor’s production process.
The total low voltage port configuration is limited by heat dissipation considerations, as well as the power
rating of the OVP. The JB has been qualified for a maximum low-voltage load of up to:



1 x 600W plus
3 x 150W plus
6 x 75W
In determining the maximum load on the OVP, the JB hotel load needs to be considered as well.
Experience to date indicates that the JB presents an electrical load of around 120W.
Refer to drawing number 0848-250-A11200 for details of the LPS. The LPS has numerous layers of
protection and isolation from the 400VDC system supply. A Negative Thermal Constant thermistor (NTC)
limits the inrush current seen at the high side input HV relay, ensuring that the relay’s rated current is not
exceeded during turn on. The NTC has high resistance at ambient temperature and self heats when
passing current. This self heating causes the resistance to drop and the NTC acts as a constant power
device dissipating power in the range of 1 – 2W. It takes approximately 60 seconds for the resistance of
the NTC to return to its ambient temperature from the time that current stops flowing through it. Therefore,
a 60 second lockout is imposed on a port by the control computer when it is de-energized to ensure that
the thermistor can limit the inrush current for every turn on event.
The positive polarity input of the LPS has galvanic isolation from the 400VDC supply via a high voltage
(HV) relay. This ensures that the input of the Vicor is not energized when the LPS is in a disabled state.
The negative polarity is fused so that current can be broken in the event of a Vicor input short and the
contacts of the HV relay fail to open. The positive polarity HV relay, along with negative polarity rail
fusing, ensures that a fault on the input to the LPS will not propagate to the upstream system.
Refer to section 6.3.1 for details of the galvanic isolation provided on the low voltage interface boards.
5.4.3.
High Voltage Interfaces
The HV downlink interfaces are rated for a maximum current of 15A.
The HV downlink interfaces do not perform any power conditioning on the incoming 300-400V power. The
port switches the incoming 400V using FETs and measures the output voltage and current. The
measurements are compared to current and voltage alarm threshold values and the port shut down if the
thresholds are exceeded. The HV ports are provided with an isolation relay on the positive input power
line and relays on both the positive and negative lines on the output. These breakers are open when the
JB is first energised and close only when their respective HV port is switched on.
There is no monitoring of isolation resistance (i.e. ground fault detection) on the 400V ports. The system
design philosophy is that isolation resistance measurement on the 400V system will be performed by the
node.
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The relay on the input side input of the 400V breaker operates in parallel with a Negative Time Constant
Thermistor (NTC). The NTC resolves power supply and load grounding issues that only occur during dry
land testing.
6.
ENGINEERING DETAILS
6.1.
Physical Characteristics
The NEPTUNE JB is cylindrical, 13.2” (33.5 cm) in diameter by 40” (101.6 cm) in length. It should be
noted that this length does not include the SeaCon connectors which extend approximately 1” (2.5 cm)
beyond the end plate of the JB, or in the case of optical uplink interfaces, the length of the ODI assembly.
The JB weighs approximately 400 lbs (181kg) in air and approximately 202 lbs (91.5kg) in fresh water.
The JB housing is made of titanium and is rated for an operational depth of up to 3000m.
6.2.
Transportation and Incoming Inspections
During transportation the JB must be kept within the temperature range of -20°C to +70°C. The JB should
be transported in crates that provide sufficient protection to the JB and, if fitted, the extruding ODI
penetrator. O-rings for the JB face SeaCon connectors should not be fitted but rather bagged, tagged and
attached to the ODI penetrator. The SeaCon connectors and ODI Remotely Operated Underwater
Vehicle (ROV) connector should have dust caps installed to prevent contaminants from entering them.
Incoming inspection, unpacking and testing should be done in accordance with the applicable procedures
outlined in the Incoming Test Procedures document.
6.3.
6.3.1.
Galvanic Isolation
Power Lines
All of the downlink power interfaces offer full galvanic isolation on their outputs by means of normallyopen double-pole single-throw mechanical relays on the output power lines. This provides the following
benefits:



Ensure that voltage will not appear unexpectedly on an output port of the JB.
Ensures that while the JB is in the start-up state and subject to input voltage transients, the JB
outputs are always known to be turned off.
Prevent current from circulating from a load or any other current path (e.g. fault) through the JB
port. If allowed to persist, such current would likely cause rapid corrosion at the interface between
the fault and sea water.
The relays are rated to break full load current, but in practice the number of times that they can perform
this task before welding closed is limited. Thus the system is designed such that the relays should never
make or break load currents. Switching of the ports is done by the Vicors in the case of the low-voltage
interfaces or FETs for the high voltage ports.
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6.3.2.
Serial Communications
For details of the JB Serial Isolation Card Assembly (SIC), refer to drawing 0848-250-A11500. The SIC
provides galvanic isolation via signal relays for serial links between instruments and the JB.
Each port on the SIC is controlled independently by the associated downlink power interface. The control
signal for the serial port is the same as the relay control signal on the power interface, thus full galvanic
port isolation is controlled by a single logical command.
6.4.
Over-voltage Protection
The JB has been qualified to operate with a steady-state input voltage in the range of 300 to 400V.
Analysis and testing have shown that when electrical loads are switched off at the end of long extension
cables, transient over-voltages as high as 800V, 15ms duration may be generated (the magnitude of the
over-voltage is proportional to the length of the cable and the magnitude of current that was interrupted).
The Vicor DC-DC converters that step the 400V DC down to the required low voltage are susceptible to
damage from transient over-voltages, so the JB is provided with a dedicated Over-voltage Protection
(OVP) device on the input to the JB hotel load and low-voltage power supply boards. The operation of the
OVP is similar to that of a voltage regulator. This is a third-party custom-designed device manufactured
by Schaefer in Germany. Since the design is proprietary, detailed design information on this device is not
available. However, it has been qualified to meet the design requirements.
The OVP is rated to handle up to 6A of input current (~2kW, depending on voltage) of power
continuously. This is the sum of power available to run the hotel load plus all of the downlink low voltage
interfaces. It is also able to withstand transient over-voltages for various durations, as shown in Figure 2.
The bounds of the Safe Operating Area (SOA) curves are dictated by thermal limitations of the
components within the OVP, so repetitive events can be handled provided that sufficient time elapses
between surges to allow the components to cool.
Figure 2 – OVP Safe Operating Area Curves
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6.5.
Grounding and Ground Fault Detection
The JB housing is designed to be fully isolated from both the high voltage supply lines and all of the
downlink power and communications interfaces. The reason for this is to prevent any leakage current
flowing between the housing and seawater that would cause galvanic corrosion at the interface between
the two where the current flow occurred.
A requirement of the JB is to be able to detect the presence of ground faults on the output of each of the
low voltage downlink interfaces. To do this requires that a current return path be provided between the
power conductors of each downlink interface and ground, so that current flow or a change of voltage can
be measured when a current path is created by the presence of a ground fault on the respective downlink
interface. For the JB, a voltage-measurement circuit was chosen because this is far more sensitive than
current-measurement. An overview of the isolation resistance measurement circuit is shown in Figure 3.
Under no-fault conditions, the voltage across the bridge is balanced. If there is a fault between either of
the supply rails and ground, the bridge will no longer be balanced and the measurement circuit will detect
a change in voltage across Rb. If the fault is to the negative rail, the voltage will drop below 2.5V, and if it
is to the positive rail it will increase above 2.5V. Refer to the document “Modeling the Neptune Ground
Fault Sensor v0.1” for details of how the circuit works and the algorithm to determine isolation resistance
from the reported voltage values.
The circuit suffers from a limitation in that if there are faults on both supply rails, the magnitude of fault
apparent from the measurements will be no larger than the difference in resistance between the two
faults. Thus, if the faults have similar resistance values, it is possible that they will not be recognised from
the JB isolation resistance telemetry.
A consequence of the isolation resistance measurement circuit is that when there is a ground fault on a
downlink interface, there is a current-return path back through the resistive bridge. To prevent the return
current flowing through the JB or attached connector housings, an external beryllium copper electrode
has been installed on the JB, to which all of the chassis ground reference points within the JB have been
connected. The JB chassis has been isolated from the housing. Thus, any ground fault return current will
flow through the grounding electrode, avoiding damage to the JB housing.
There is no isolation resistance measurement on the high voltage interfaces. Any ground faults on the
400V system will be detected by the node LVPS.
Note that extension cables with media converters that are installed on high voltage interfaces could have
ground faults that would not be detected. The power supplies for the media converters (and instruments,
where applicable) are isolated, so ground faults downstream from these power supplies would not result
in an upstream current imbalance and there is thus no way to detect such faults. Any instruments that are
installed at the end of media converter extension cables should be provided with wet-mate connectors, so
that if faults develop on the instrument, the instrument can be recovered without having to recover (and
probably damage) the cable.
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Figure 3 – Simplified Representation of the JB Isolation Resistance Measurement Circuit
From Vicor
+ Out
1M
Ω
Ω
1M
Rb
1M
Ω
Ω
1M
From Vicor
Ground Fault
Measure
- Out
6.6.
Low Voltage Interfaces
All of the low voltage interfaces are supplied at 300-400V from the output of the OVP, as shown in Figure
4. The OVP protects the Vicor DC-DC converter from over-voltage transients. Each supply line to and
from the Vicor is capacitively coupled to ground, in accordance with Vicor’s recommendations, to provide
a limited amount of noise filtering.
Figure 4 – Power Block Diagram for Low Voltage Interface
+200V
Overvoltage
Protection
-200V
Control
+200V
+24V
Ethernet
Switch
Serial Server
Low Voltage Power Supply (Typical)
Control
Control
NTC
400-48/24/15/12V
75/150/600W
Vicor
+ Out
Ω
Hall
Effect
Current
Sensor
4.7nF
+48, 24,15 or 12V
1M
10nF
Ω
1M
1M
Ω
400V Surge-Protected Bus
Hotel Power Supply
(Self-starting)
150W
1M
Ω
-200V
0V
Ground Fault
Measure
- Out
Voltage
Measure
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6.7.
6.7.1.
High Voltage Interfaces
Soft-Start
The JB 400V breakers incorporate a soft start turn-on feature, which limits the inrush current that is
supplied to capacitive loads (or short circuits). This capability has been qualified to start loads with
capacitance up to 68μF.
The soft start feature is accomplished by means of a circuit known as a buck converter. The FETs switch
on to allow current to flow into the load through a series inductor. During soft start, if the current to the
load reaches 6A, the FETs switch off and stay off until the current drops to 1A, at which point they turn on
again and the cycle repeats. While the FETs are off, the series inductor continues to provide current to
the load via the fly back diode. For details of the circuit, refer to drawing 0848-250-S11300.
Because the circuit operates on current feedback alone (with limits between 1A and 6A), the switch
frequency and duty cycles are not fixed. They will change based on the characteristics of the cable
feeding the JB, input voltage, load characteristics, etc. (i.e. all of the parameters that affect the rate of
change of current (di/dt) through the circuit). The rate of change of current is also influenced by the
voltage across the load. The switching frequency is defined by the di/dt between the two switch limits of 1
and 6 amps. As an example, with no input cable length, switch rates will be between 10 and 100µs, but
this can change significantly.
The soft start mode is maintained for a set period of time (Ramp Time) after which the FET is turned on;
this period is selectable from 0 to 100ms via software. To stop the FET being tripped by the normal alarm
threshold logic (in particular the hardware-determined under-voltage limit) during the soft start period,
there is a set period during which all trips are inhibited (FET Inhibit Time); this period is selectable from 0
to 100ms. If the load capacitance is not fully charged at the end of the FET Inhibit Time, the voltage
measured across the conductors will be less than the hardware under-voltage alarm value and the FET
will open before the end of the ramp time, protecting the circuitry from a potentially damaging current
surge if the FET were to close at the end of the ramp time and the load capacitance were not fully
charged.
Maximum power transfer to a mixed capacitive/resistive load during ramping is approximately 800W, or
an average 2 amps at a 400VDC JB input voltage. This power is provided for a maximum of 100ms,
settable via the telnet interface command set_fet_timing. If ramp switching is still active at the end of the
ramp interval, the output voltage will not have risen to the level of the input. The resulting imbalance
leads to a current surge as full input voltages are provided to the load without current limiting (At the end
of ramping the FETs turn on full). Should this current surge exceed the hardware current limit (15.5A) of
the HV port, it will trip on over-current (hardware-initiated trip).
Load resistance and capacitance govern if a load is suitable for the JB. At one extreme, a pure resistor,
the JB can turn on into a full 15 amps. While the current is limited during ramp, there is no current
overshoot at the end of the ramp period as there is no capacitance to cause an over-current event. For
this load, the best FET timing is a short interval, to reduce unnecessary switching that may cause line
noise, or confuse the instrument as the voltage swings from near zero to full JB input voltage each time
the FET turns on, due to no capacitance holding up the voltage.
At the other extreme, a pure capacitor, the breaker will ramp and the output volts rise linearly until the
capacitor is charged. The only limit to switching this load is the size of the capacitor, and whether it can
be charged during the ramp interval. For reference, the HV Breaker is qualified to switch on a purely
capacitive load of up to 68µF. The breaker is able to charge this load in 15ms or less.
Mixed capacitive / resistive loads should be tested to ensure compatibility. The issue with mixed loads is
that while the ramp circuit is attempting to charge the load capacitor; the load resistance is discharging it.
Any steady state current draw (via parallel resistance) reduces the power available to charge the load
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capacitance. If the load capacitor or the parallel resistance are too large, then the output voltage will limit
at a level below the full input voltage, leading to an over current trip at the end of the ramping period when
the FETs turn on.
The 400V Breaker has two hardware trips: under-voltage and over-current. The hardware trips are not to
be confused with settable software limits. The hardware trip levels are non-adjustable and only disabled
when the breaker is turning on (trip inhibit in FET timing). Hardware trip settings are 85V ±10V for undervoltage and 15.5A for over-current.
Hardware trips react to events in microseconds; the software trips act on breaker telemetry which is
sampled at about 10 Hz. Therefore software trips will not react in the interval between the end of FET
inhibit time and the end of the ramp time.
When the breaker hardware trips, the software generally reports an under-voltage trip event. The
software is only able to sense telemetry from the breaker; thus if the breaker hardware trips, the telemetry
shows no voltage and no current, which then triggers a low voltage alarm if the software alarm is set to a
value greater then zero volts.
The over-current hardware trip acts as a backup trip to the under-voltage trip condition. The hardware trip
will operate and attempt to shut off the load if the current exceeds 15.5A. (There is a similar software
alarm trip that can be set to any value less than 15.5A).
The FET Inhibit Time must be set to just less than the Ramp Time. If FET Inhibit Time equals or is greater
than Ramp Time then the FET will close at the end of Ramp Time whether or not the load capacitors are
charged; depending on the Ramp Time and capacitance, the subsequent current surge could destroy the
HV port circuit board. The inhibit time cannot be set beyond the ramp time minus 5ms. This is a
constraint that is written in the control software, which prevents FET ramp settings from accidentally being
set to values that could damage the circuitry.
The switching of the HV ports is controlled so as to avoid opening or closing isolation relays when load
current is flowing. Only the FETs in the HV port change state on hardware trip events; the input and
output isolation relays do not open. Upon a trip, the FETs open circuit and the relays remain closed until
commanded to change state. The relays only change state when explicit on/off commands are sent from
the surface, or power is lost in which case they stay open during repower waiting for an on command.
The sequence of events when an HV port is commanded to switch on or off is as follows:
Response to Breaker Close command:
1.
2.
3.
4.
Isolation relays close
After a 1msec delay the Input relay closes
After a 100ms delay the FETs start pulsing current (the “ramp”).
At the end of FET Inhibit Time, if the voltage exceeds Under Voltage Trip Value the ramp
continues; if the voltage is less than the hardware under-voltage trip value the FET trips and
the start-up attempt ends. No breaker operations are possible for 60 seconds due to the hold
off condition.
5. If the ramp completes, at the end of the ramp time, the FETs close and the load is powered.
Response to Breaker Open command:
1.
2.
3.
4.
5.
FETs turn OFF
Delay (order of 100ms)
Input relay opens
Delay (order of 1ms)
Isolation relays open
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6. To improve the relay robustness, they have been sized such that they can make or break
FET design current in the event of a FET failure (i.e. the FETs cannot be shut off) and are
specifically designed for 400V switching. The relays are vacuum sealed.
6.8.
6.8.1.
Communications
Serial Communications
For details of the JB Serial Isolation Card Assembly (SIC), refer to drawing 0848-250-A11500. The SIC
has four DB9 connectors on the serial server side and four RJ45 connectors on the bulkhead side. While
the SIC handles only serial communications, the pin-out of the RJ45 connectors are such that COTS
Ethernet patch cables can be used.
6.9.
Telemetry
The low-voltage interfaces provide telemetry signals in the range of 0 – 5VDC that are optically isolated
from the output. These signals are:




Output voltage (V)
Output current (I)
Line insulation (kΩ)
Port status
The high voltage interfaces provide the same telemetry signals, except for line insulation (because there
is no line insulation monitoring by the JB on the high voltage interfaces).
The 0-5V telemetry signals are each converted to digital by means of 11-bit analogue to digital
converters. This provides digital signals with up to 2048 values for each measurement.
All of the data processing at the sub-sea level is done using the digital values (ticks). The tick values are
reported to the surface via the JB UDP data stream, and software at the surface can convert the digital
tick values to analogue engineering units according to the operator’s preference.
The conversion from tick values to engineering units is done by a linear mapping between the tick values
and engineering units. For the isolation resistance measurement, an additional conversion step is
required to convert from the voltage calculated from the tick value to an estimated isolation resistance
measurement. For details of this algorithm, refer to the Oceanworks document “Modeling the Neptune
Ground Fault Sensor v0.1”.
Due to component tolerances, the slope and intercept of the linear mapping between the A/D tick values
and engineering units needs to be adjusted for each telemetry channel. During the Factory Acceptance
Tests performed by Oceanworks, two measurements are made of the channel’s data using a digital
multimeter while recording the associated tick values. This information is recorded in the calibration data
file for each JB, and should be used when converting between tick values and engineering data for each
JB.
6.10.
Subsea Controller
6.10.1. Controller Overview
The JB control computer is a based on the VENUS SIIM (Scientific Instrument Interface Module), part
number 0820-500-A11520. The core of the design is a BL2600 single board computer from Rabbit
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Semiconductor mounted to an I/O expansion board. The control computer provides multiplexed digital
outputs and analogue inputs. The SIIM interface board can control a maximum of 10 downlink interfaces
and receives all telemetry from them.
A TCP/IP remote programmer for the single board computer is included in each JB. This makes it
possible to flash firmware to the control computer remotely, i.e. subsea.
6.10.2. Power ON/OFF and Initiation of Software
When the JB is powered up, all of the breakers enter a safe state (output disabled) and the control
computer automatically boots the subsea software. A 60 second lockout is imposed on the downlink ports
so that they cannot be switched on before their input Negative Time Constant (NTC) thermistors have
returned to their high impedance value. This protects the ports in the case of a rail crash, e.g. if the JB
loses power from the MVC when its ports are on, the ports cannot be switched back on before it is safe to
do so without causing damage to their circuitry.
Once the subsea software has booted, telemetry data is sent from the JB via the UDP data stream.
6.11.
Start-up Sequence of Events
6.11.1. Subsea Controller Software
The JB control computer starts running the subsea software automatically when the JB is powered up.
Telemetry data is sent to the surface as soon as the subsea software has started.
On start-up, the JB control computer performs the initialization operations as outlined below:
1. The control computer board and Analogue to Digital Converters (ADC) are initialized. This phase
takes approximately 30ms.
2. The Ethernet interface and communications are initialized. This phase takes approximately
3630ms.
3. The Ethernet controller type is determined and appropriate set-up actions are performed based
on the controller type. This phase takes approximately 140ms.
4. Internal data structures for telemetry are set up and the breakers are commanded to enter the
OFF state via software, approximately 3800ms after power on.
5. The JB controller software enters its main loop in which Telnet commands are responded to,
telemetry data is acquired, fault conditions are detected and telemetry is transmitted via UDP.
The main loop is typically started 3900ms after power on.
6.11.2. Downlink Interfaces
When the JB is powered up, all of the downstream ports enter a safe state (output disabled) and the
control computer automatically boots the subsea software. A 60 second lockout is imposed on the
breakers so that they cannot be switched on before their input Negative Time Constant (NTC) thermistors
have returned to their high impedance value. This protects the downlink port power circuitry in the case of
a rail crash, e.g. if the JB loses power from the MVC with its ports on, then the ports cannot be switched
back on before it is safe to do so without causing damage.
After the initial 60 second lockout period has passed, control of the JB breakers via TELNET or surface
control software is possible. While a breaker is in its 60 second lockout condition, bit 9 of its status bytes
will be set to 1 (i.e. decimal 512).
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7.
SYSTEM INTEGRATION GUIDELINES
7.1.
Extension Cables
The design and selection of extension cables, that are used to connect the JB uplink interfaces to nodes
or other junction boxes, or downlink interfaces to instruments, is a multi-disciplinary engineering exercise
that is beyond the scope of this document. However, among the many parameters to be considered, as
related to the JB, is to ensure that the conductor electrical properties are such that the cables can deliver
the maximum foreseeable current to the JB with sufficiently low voltage drop to ensure that the JB
operates within the 300-400V range, and that any instruments on 400V interfaces downstream from the
JB also have sufficient voltage as may be required.
7.2.
Selection of Connectors
Connectors for the downlink interfaces are Seacon MINK-10 (2#14, 8#20)-FCRL-TI. These are dry-mate
connectors, which means that the connections have to be made on the surface. Dry-mate connectors are
significantly cheaper than wet-mate connectors, and typically more reliable.
Where instruments are to be deployed in close proximity to or on the JB frame, the general philosophy
should be to use short whips connected directly to the instruments, so that the use of dry-mate
connectors can be maximised. There may be exceptions to this rule if an instrument has a maintenance
cycle that would require that it be recovered much more frequently than the JB, in which case having a
wet-mate connector would allow the instrument to be unplugged from the JB and brought to the surface
without disturbing the JB and the remaining instruments.
Where wet-mate connections are required (e.g. for long extension cables on the uplink or downlink
interfaces), a short section of pressure-balanced oil-filled (PBOF) hose with a Seacon MINK connector on
the JB end and a wet-mate connector on the other are used. The hose is attached to the JB on the
surface, and then the connection to the cable made by an ROV once the JB has been laid on the sea
floor.
7.3.
Downlink Interface Voltage and Power Selection
In general, the input voltage for scientific instruments to be connected to junction boxes is dictated by the
Vendor, as per their standard product offerings. The JB port downlink voltage should be chosen to match
the instrument specification as closely as possible. For all instruments deployed to date, the voltages
available for the JB downlink interfaces match the input voltage tolerance for the instruments.
If there is an opportunity to choose an input voltage for a particular instrument, it is usually preferable to
choose the highest input voltage that can be supported. This allows smaller conductors to be used
between the JB and instrument, and for the cables to be longer. It also allows for a higher power transfer
capability, which may be beneficial for some instruments.
When determining the power rating of the port, care needs to be taken to size it to meet the peak power
draw of the instrument. Many instruments draw power in short bursts of high current, but with low duty
cycles. Thus, the average power draw may appear low, but the peak current demand could be a lot
higher than the power specifications may suggest. There is very little capacitance on the output of the JB
ports, so the ability to supply excess power to meet transient surges is limited. Thus when selecting the
power rating of a port, it must be chosen to meet the peak current draw and not the average.
It is good practice to choose power supplies with ratings at least 20% higher than the expected instrument
load. This provides a margin of safety, and also ensures that the components in the power supply circuitry
run cooler than their maximum rated values, extending their life significantly.
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7.4.
Electrical Noise
On 400V lines, electrical noise may be present from the node power supplies. This has the characteristics
as shown in Figure 5, which essentially are spikes with peak magnitude of 4V superimposed on + 1.5 V
peak-to-peak waveform at 100 KHz, with no low frequency ripple. The ripple and noise seen at
instruments is expected to be lower than indicated here, due to the filtering effect of the extension cable
impedance.
Figure 5 – MVC Noise and Ripple Characteristics
The noise parameters on the outputs of the low-voltage interfaces are determined by the Vicor DC-DC
converters. The DC-DC converter circuit boards have been designed in accordance with Vicor’s
recommendations. On this basis, the 400V input Vicor noise/ripple output specs are as follows (based on
nominal input and full load, values are maximum peak-to-peak and should be decrease as load
decreases):
12V, 15V: 125mV (1%)
24V, 75W: 150mV (.6%)
24V, 150W: 169mV (.7%)
48V, 75W: 250mV (.5%)
48V, 150W: 113mV (.2%)
48V, 600W: 63mV (.1%)
The frequency of the ripple is a function of the input voltage to the Vicor and the output current (curves for
some Vicor models are available). Simple filter designs could remove ripple for a particular range of
frequencies. To provide perfectly smooth power over the full range of ripple frequencies, then a more
complicated filter circuit would be required. This would add to the cost and size of the junction box and
reduce its reliability and efficiency.
In the absence of particular noise and ripple criteria from any of the instrument vendors, the decision was
taken that no output filtering would be added to the JB. It would make more sense from an economical
and reliability perspective for the overall NEPTUNE system that any instruments that have particular
susceptibility to noise on the input power supply be provided with their own input filtering to address the
problem.
The noise guidelines above should be provided to all instrument vendors at the time of soliciting quotes,
to ensure that any instruments procured are designed to deal with the expected noise levels. In-water
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testing of all instruments, including data quality verification, should be done prior to deployment so that
data integrity is validated.
7.5.
Transient Surge Protection
Power to low voltage (48V and lower) instruments is filtered by the OVP and Vicor power supplies, so
there is little chance of surges being imposed. Therefore, there is no requirement to provide any
additional surge protection on the input to low voltage instruments.
No surge protection is provided for instruments on the HV ports. Thus, any instrument fed from a high
voltage port needs to provided with its own over-voltage protection circuitry on its input.
The magnitude of voltage transients is a function of the extension cable parameters (i.e. length and
resistance/inductance/capacitance per unit length) and the magnitude of load current. The higher the
inductance and the higher the load current, the higher the magnitude of surge voltage will be. Analysis
and simulation of the 10km Barkley Canyon extension cables with load current of about 8A indicated
voltage surges up to 1200V.
When designing over-voltage protection, the instrument in question cannot be treated in isolation.
Switching of other instruments on the 400V system can cause surges on all other devices connected to
the node port in question.
8.
OPERATIONAL GUIDELINES
Refer to the document “Standard Operating Procedures for Neptune Junction Boxes - Pre-Deployment
Shipboard Tests and Post Deployment Actions” for recommended practice for deploying and doing the
initial start-up of the junction boxes. Refer to the “Junction Box Telnet Command” Manual for details of the
commands available for operating and configuring the JB.
8.1.
General
All physical work or operation of junction boxes should be done in strict accordance with written
procedures. In the event that actions need to be performed for which procedures do not exist, then the
operator shall write a detailed step-by-step plan of the proposed work and have it reviewed by another
suitably qualified person prior to executing the work.
Junction boxes should be fully tested prior to deployment. Details of the tests are provided in the test
procedures referenced elsewhere in this document, but to summarise, the pre-deployment activities
should include the following:
1. Incoming inspection of JB and its documentation
2. Verification of each port configuration in relation to the requirements of the instrument to be
connected to it.
3. Connection of all instruments to JB.
4. Powering of JB and configuring all of the software-settable parameters.
5. Salt water tank-testing of JB with all of its associated instruments.
6. Switch on each JB port and operate its instrument, observing the following:
a. Verify communications with the instrument.
b. Check the JB telemetry for abnormal current, voltage or isolation resistance values.
c. Have the instrument data reviewed by a suitably qualified scientist for validity.
d. Based on the JB telemetry for each port, adjust the alarm thresholds as may be required.
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All test results, configuration and baseline data records should be kept and stored in such a way that they
can be readily accessed, so that they can be easily retrieved and compared with data from the devices
post-deployment.
When operating the JB or associated instruments, all commands and configuration settings transmitted
should be recorded. If tools are not available to capture this information automatically, then the operators
must record it manually.
8.2.
Subsea Controller Software
Broadly speaking, the JB commands can be classified as applicable to the overall controller, or applicable
only to a specific breaker.
Refer to the Junction Box Telnet Command Manual r1_4 for details of all of the commands available for
configuring and controlling the JB. The notes that follow are intended to elaborate on some of the
software functionality available in the controller, and are not intended as an exhaustive reference.
The JB controller has a number of settings that require configuring prior to deploying the JB on the
network. Caution should be exercised when making changes to the controller configuration, because
some settings have the potential to damage the JB or lose communications with it. As a safeguard
against setting these parameters accidentally, the controller needs to be placed in maintenance mode
before certain commands can be accepted by the JB.
To enter maintenance mode, use the Telnet command Maintenance (see section 3.15 of the JB Telnet
command manual).
The following operation can only be performed when the JB controller is in maintenance mode:











Set UDP IP Address
Set UDP Port
Auto Calibrate Mode
Blow Fuse
Set FET Timing
Set Hold-off Time
Set IP Address
Set Serial Number
Set TCP Timeout
Watchdog Test
Write IP Address
As a general rule, all configuration and non-routine commands sent to the JB should be written up in a
formal procedure prior to execution. Any deviations from the procedure should be recorded, along with
reasons for the changes.
8.2.1.
FET Timing
Refer to section 6.7.1 for a detailed description of the high-voltage port soft-start feature. The Set FET
Timing command is used to set the ramp and trip inhibit durations for the high voltage ports. The settings
apply to all high voltage ports on the JB.
The default trip inhibit duration is 20 ms and the default ramp time is 30ms. Caution should be used when
changing these values, as extending the ramp time can place stress on the FETs. It may be desirable to
change the defaults when supplying loads with high input capacitance, but this should be done only after
a detailed engineering review that includes consideration of the load characteristics, as well as the
electrical parameters of the cable between the node and JB, and the cable from the JB to the instrument.
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8.3.
Setting Alarm Thresholds
All of the alarm threshold limits that can be adjusted by the operator are software-initiated. In other words,
the JB controller compared each of the values (in ticks) reported by the A/D converters on each telemetry
channel with the alarm threshold, and then instructs the port to switch off if a threshold is crossed. This
process is relatively slow (~100ms). The software-settable alarm thresholds are designed to protect the
infrastructure downstream from the respective JB interface.
The JB ports also have hard-wired alarm thresholds in their circuitry, designed to protect the JB itself from
damage that could be caused by fault conditions. These limits cannot be set with software, and the trips
occur very fast compared to the software trips (i.e. <0.1ms).
The JB subsea controller provides the ability for the operator to set alarm thresholds on the
measurements that are reported via the JB telemetry to the surface. The Telnet commands to set these
limits are described in the Telnet Command Manual.
The subsea software will shut off an interface as soon as the software detects that an alarm threshold is
detected (except for over-current events as described below). The controller samples the port values at
10Hz but only reports data to the surface once per second. Thus, if an alarm threshold is crossed in
between the samples that are transmitted to the surface controller, it will not be apparent to the operator
what the alarm value was that caused the port to trip. However, the port status bit will indicate which
alarms are active, which will indicate what type of fault occurred.
One of the objectives of setting alarm thresholds is to provide an early warning that problems may be
developing on a device. By setting the alarm thresholds close to the normal operating range of an
instrument, any deviations will be quickly notified.
In order to support this functionality, the JB surface control software has the capability to set secondary
alarms, along with hold-off periods for all thresholds. By settings these values in the surface thresholds
just outside the expected operating range of values, any abnormal operating conditions can be identified
and investigated pro-actively. The alarm threshold settings on the sub-sea software should be set at
values that would suggest a significant fault, to protect the instrument. With the exception of over-current,
the subsea software trips the port on any fault within 100ms, which means that any significant noise or
transients can cause nuisance trips if the thresholds are not wide enough.
8.3.1.
Over-Current Alarm
Many instruments are known to draw high transient currents (e.g. devices with capacitance on their input
or motors with high starting currents). It is not desirable to generate alarms for these conditions. To
accommodate these devices, the sub-sea over-current alarm threshold includes a setting for trip inhibit
duration. The port will not trip on a software over-current until the duration of the event exceeds the trip
inhibit duration.
The JB reports instantaneous current (i.e. the current measured at the end of each 1-second
measurement interval) as well as peak current (the maximum reading of the 10 readings taken at 0.1second intervals during the second). The over-current alarm is based on the instantaneous current
readings. This means that if the peak current exceeds the over-current alarm threshold but the
instantaneous current does not, then the port will not trip on over-current.
An initial estimate of the current alarm thresholds can be ascertained by studying the instrument
manufacturers’ literature. The manuals may provide an indication of the peak current or power draw. The
current threshold should be set at 20% higher than this value (or to the maximum current rating of the JB
port, whichever is lower). However, in many cases the instruments do not draw a steady current and the
average current/power specifications provided in the literature may not reflect the peak values that may
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be drawn over short periods. The actual current waveforms should be measured and recorded with an
oscilloscope in the lab for each instrument, configured as it will be when deployed. This will provide an
accurate benchmark against which the current alarm thresholds can be set. In general, setting the tripinhibit timeout period to about 5 seconds will protect against any transient inrush current conditions.
8.3.2.
Over-voltage Alarm
The only time an over-voltage condition could occur on a low-voltage interface is if the Vicor DC-DC
converter malfunctions. To protect against this unlikely scenario, the subsea over-voltage limit should be
set to 10% higher than the port’s nominal voltage.
Transient over-voltage conditions may occur on the high voltage interfaces, typically when switching off
loads on the 400V system at the end of long extension cables. These will be very short duration and the
over-voltage sensing on the JB high voltage ports is unlikely to detect these events. On these ports, an
alarm threshold of 10% above nominal is recommended, to prevent nuisance trips.
Alarm thresholds of 2% above nominal should be set in the surface software, with a hold-off of 5 seconds,
to provide an early warning of any systemic problems.
8.3.3.
Under-voltage Alarm
On the low-voltage interfaces, under-voltage conditions should be very rare. Usually they would be the
result of an over-current condition, and the over-current protection would be expected to shut down the
port if a sustained fault occurred.
Loads with large input capacitors may take a second or two to reach full rated voltage after turn-on. If the
under-voltage alarm threshold is set too low, the port may shut down prematurely. For this reason, it is
recommended that the under-voltage threshold is set to no more than 50% of nominal voltage in the
subsea software. Thresholds of 5-10% below nominal may be set in the surface software, with a 5second hold-off, to provide a warning of any sustained abnormalities.
The voltage on the high-voltage interfaces may drop significantly if the JB is at the end of a long
extension cable and supplies a high current. If the voltage drops sufficiently (below ~250V), the JB
controller will shut down and drop all load. There is little value in having the JB high voltage interfaces
protect against low-voltage conditions, because they will see the essentially the same voltage as that
seen by the JB controller. It is recommended to set the under-voltage threshold to 0 volts on the sub-sea
controller, and about 10V below the lowest expected operational value in the surface software (which will
depend on the cable and load characteristics for each JB).
8.3.4.
Isolation Resistance (Ground Fault)
The no-fault operating range for the ground fault detection is typically between 2.4 to 2.6V. This will vary
from port to port, due to tolerances in the isolation measurement circuit components, and will usually be
somewhat asymmetrical about 2.5V. The relationship between reported voltage and calculated isolation
resistance is highly non-linear, and from the perspective of keeping the management of the alarm
thresholds has simple as possible, it is recommended to just use the voltage values as a reference. The
graph in Figure 6 provides an indication of the relationship between the reported voltage and the actual
isolation resistance measured on the port. A fault value above the ~2.6V threshold indicates that the
positive supply rail is conducting to ground, whereas a value below ~2.4V indicates a fault on the negative
supply rail.
Ground faults generally cause damage to occur on metallic parts of the submerged plant, by impressing a
voltage between the exposed conductor and the current-return path. Galvanic corrosion will occur at the
less noble metal anywhere that the current flows between dissimilar materials. It is practically impossible
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to predict what the current path will be in any given system, so corrosion could occur in places where it
may not be expected if ports with ground faults remain energised for an extended period.
Some instruments have capacitance between either of their supply rails and the seawater ground. When
switched on, there may be a momentary current flow to ground as the capacitors charge up, which the JB
isolation resistance measurement circuit reports as a ground fault. If the ground resistance alarm
thresholds are not wide enough, this can cause the port to shut down as the load is energised. For this
reason, it is recommended that the isolation resistance values not be set in the subsea software (i.e. set
the low resistance threshold to 0V or 0 ticks, and the high value to 5V or 2047 ticks). Set the alarm
threshold values as per the guidelines in Figure 6, with a hold-off of 30 seconds, in the surface software.
Since there is no isolation resistance measurement circuitry in the high voltage interfaces of the JB, the
alarm thresholds on the 400V ports should be set at 0 ticks and 2047 for the low and high values
respectively.
Figure 6 – Ground Fault Voltage-Resistance Characteristics
Note that there have been instances where two instruments have had one of their supply rails bonded
together. This creates the impression of a ground fault on both instruments when both instruments are
energised (with one instrument indicating a fault on the positive rail, and the other an equal magnitude
fault on the negative rail). This arrangement desensitises the ground fault detection circuitry and should
not be deployed.
Note that the JB ground fault detection circuit will not detect a ground fault that is symmetrical between
both supply rails. The circuit works by indentifying a resistance imbalance between the two rails. In the
event that both rails have a similar resistance to ground, the circuit will not report the fault. In practice,
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faults are more likely to develop asymmetrically. Thus it may happen that a ground fault develops on a
port, and then appears to diminish in severity. What is likely happening is that the fault has spread to the
opposite supply rail and is actually worsening, not improving as the readings may suggest.
8.4.
Telemetry Data Monitoring and Analysis
A fundamental requirement for successfully managing the observatory is to continually monitor and
analyse the telemetry data that is reported by all of the infrastructure components of the system.
Where alarm thresholds have been set appropriately, deviations outside of the set thresholds will provide
an immediate warning of problems, and reactionary measures can be taken as required. However,
gradual changes in parameter values will not be reported as alarms until they have crossed the alarm
threshold, at which time severe problems may have developed. By monitoring the telemetry data regularly
using suitable graphing tools, trends can be recognised that could indicate gradual deterioration in an
element, and preventive measures taken where practical.
The most effective way to analyse the telemetry data is to record a representative baseline as early as
possible in the deployment of each device. This would typically be done during pre-deployment tests of
the JB and instruments in a salt-water tank on land. When these measurements are made, the instrument
configuration and applicable calibrations need to be applied and recorded along with the telemetry data,
so that any deviations post-deployment can be seen in context.
Daily monitoring of the telemetry data for each JB interface should include plots of the voltage, current
and isolation resistance versus time. Other JB telemetry (e.g. temperature and pressure) should be
verified as well to check for any changes. The absolute values and waveforms should be compared with
previous values (i.e. previous day, previous week, previous month) at the same time-scales, so that any
changes can be readily identified. With appropriate graphing tools, this exercise would be easy to
perform.
When changes to the characteristic waveforms occur, the root cause should be investigated promptly. In
many cases, waveform changes can be attributable to changes in the instrument mode of operation.
However, inexplicable changes in telemetry should be analysed carefully, as they may be indicative of
faults developing on the system.
9.
PERIODIC MAINTENANCE
9.1.
General Recommendations
For obvious reasons, it is impractical to perform maintenance of the junction boxes when they are on the
sea floor. In general, when JBs are recovered, the reason will likely be either to add, remove or replace
instruments, or because the JB itself has developed a fault and needs repair.
Due to the high cost of ship time, it is recommended that any JB that has been deployed for two years or
longer, that is recovered for any reason, be brought to shore and refurbished prior to being redeployed. In
order to assure ongoing operations at the JB site, a similarly configured JB should be deployed in its
place, changing out instruments onboard the ship (for those with dry-mate connectors) or
unplugging/plugging in the downlink instrument whips or extension cables for wet-mate connections on
the sea-bed. The preferred scenario would be to have spare instruments for each JB and a complement
of spare junction boxes, so that each JB could be tested, along with its instruments, on shore prior to
deployment.
Refurbishment of the JB would involve returning it to Oceanworks, there they would open up the housing
and inspect all of the components for any signs of physical damage. Firmware should be upgraded, any
required configuration changes made and then the device run through a full Factory Acceptance Test
(FAT) before being returned. All of the JB configuration documentation should be updated to reflect the
service and any associated configuration and calibration changes made.
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Although it is not particularly difficult to open or service the JB, it is recommended that this work only be
done by Oceanworks, since they have the full complement of tools, equipment and skills required for this
purpose.
9.2.
Return Procedure
Contractual arrangements regarding the scope, cost and warranty of any service or repair work done by
Oceanworks would need to be arranged prior to shipping any units back to Oceanworks. Since these
matters are largely commercial, they are not covered in this document.
Prior to returning any junction boxes, all downlink instrument whips and extension cables should be
removed. Before disconnecting instrument cables, dry the JB can head so that there is no liquid present
on or around the SeaCon connectors. Compressed air or a heater can be used to make sure that all liquid
is removed.
Exposed SeaCon connectors should be covered with protective caps. An inventory of titanium SeaCon
caps should be made and photographs taken of the JB, to ensure that all of the connector covers are
returned from Oceanworks along with the JB upon completion of the service. It is recommended that the
external ground electrodes be returned to Oceanworks for a detailed inspection, along with the JB.
Assuming that the JB is still operational, the network settings of the controller, serial server(s) and
network switches should be reset to the Oceanworks defaults, as follows:






SIIM Interface Board: 10.70.1.10
Remote Programmer: 10.70.1.11
510A Ethernet Switch: 10.70.1.1
508A Ethernet Switch: 10.70.1.2
Serial Server 1: 10.70.1.3
Serial Server 2 (where fitted): 10.70.1.4
All VLAN tags should be set to 1 and all passwords on the switches removed.
The JB should be packaged in accordance with Section 6.2.
10.
JUNCTION BOX TEST PROCEDURES
The documents below list tests that have been completed to date, and where applicable, test procedures
to be used for ongoing JB work.
10.1.
Testing by Oceanworks
10.1.1. Qualification
Document Number
TR-0848-000-Q10520-00
TR-0848-000-Q11200-00
TR-0848-000-Q11300-00
TR-0848-000-Q11400-00
TR-0848-000-Q11500
TR-0848-000-Q11600
TP-ENGR-82100
Description
Junction Box SIIM Interface Board (JB Controller) Qualification
Junction Box Low Power Supply Qualification Test
Junction Box High Voltage Breaker Qualification Test
Junction Box High Power Supply Qualification Test
Junction Box Serial Isolation Board Qualification Test
Junction Box Hotel Power Supply Qualification Test
Critical Implodable Volume Test Procedure
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10.1.2. Factory Acceptance
Document Number
TP-0848-250-A10000
TP-0848-AST-A10000
TP-0848-FAT-A10000
10.2.
Description
Junction Box Assembly Test Procedure
Junction Box Accelerated Stress Test
Junction Box Factory Acceptance Test Procedure
NEPTUNE Canada Tests
10.2.1. Receiving
Document Number
N/A (Version 1.0, 4th
November 2008)
Description
Test Plan and Procedures for Junction Box Receiving and
Instrument Platform System Integration And Assembly
10.2.2. Deployment and Start-up
Document Number
N/A (Version 1.6, 6th
October 2008)
Description
Standard Operating Procedures for Neptune Junction Boxes PreDeployment Shipboard Tests and Post Deployment Actions
10.2.3. Qualification
Document Number
N/A
Rev A, 7th September 2008
Rev A, 27th October 2008
10.3.
Description
NEPTUNE Junction Box Inrush Test on Saanich Power Supply
(11 September 2008)
NEPTUNE Canada (MTC) Instrument Receiving Procedure
NEPTUNE Canada (MTC) Instrument Functional Test Procedure
Node-JB Integration Testing
Two sets of node-JB integration tests were done at Alcatel’s Greenwich facility. Refer to the
documentation below for details of the procedures and results.
10.3.1. Integration Test Results Sheets – Phase 1
Document Number
N/A, 28th July 2008
N/A, 28th July 2008
N/A, 28th July 2008
N/A, 28th July 2008
N/A, 29th July 2008
N/A, 29th July 2008
N/A, 29th July 2008
N/A, 29th July 2008
N/A, 29th July 2008
N/A, 29th July 2008
N/A, 29th July 2008
N/A, 29th July 2008
N/A, 29th July 2008
Description
Test 1 – Power-on
Test 2a – 26.7Ω Load, 10km Cable
Test 2b – 21.4Ω Load Switching, 10km Cable
Test 2c – 21.4Ω Load Switching, JB Connected Directly to Node
Test 3a – 26.7Ω Load, 7.14km Cable
Test 3b – 21.4Ω Load, 7.14km Cable
Test 3c – 21.4Ω Load, 4.28km Cable
Test 4a – JB Port Switched into Overload
Test 4b – Operational JB Port Overloaded
Test 5 – Node Port Overload
Test 6a – JB 400V Port Resistive Ground Fault
Test 6b – JB 400V Port Short Circuit Ground Fault
Test 6c – JB at Node, 400V Port Short Circuit Ground Fault
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N/A, 29th July 2008
N/A, 30th July 2008
N/A, 30th July 2008
N/A, 30th July 2008
N/A, 30th July 2008
N/A, 30th July 2008
N/A, 30th July 2008
N/A, 30th July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 31st July 2008
N/A, 1st August 2008
N/A, 1st August 2008
N/A, 1st August 2008
N/A, 1st August 2008
N/A, 1st August 2008
N/A, 1st August 2008
N/A, 1st August 2008
Test 6d – JB 400V Port Short Circuit Ground Fault – Bench-top Supply
Test 7a – JB Port Short Circuit, JB at end of 2.86km Cable
Test 7b – JB Port Short Circuit, JB connected Directly to LV-Comms
Port
Test 8a – 26.7Ω, Load, 11µF Capacitance Across end of 10km Cable
Test 8b – 26.7Ω, 11µF Load, 2.86km Cable
Test 9a – 26.7Ω, 11µF Load, 10km Cable
Test 9b – 53.3Ω, 11µF Load, 10km Cable
Test 9c – 106.6Ω, 11µF Load, 10km Cable
Test 10a – JB Test Bench in Series with JB, 10km Cable from Node to
JB
Test 10b – JB Test Bench in Series with JB, 10km Cable from Node,
Capacitive Load
Test 10c – JB Test Bench in Series with JB, 10km Cable from Node,
Overload Test Bench
Test 10d – JB Test Bench in Series with JB, 10km Cable from Node,
S/C Test Bench
Test 10e – JB Test Bench in Series with JB, 10km Cable from Node,
Overload Test Bench
Test 10f – JB Test Bench in Series with JB, 10km Cable from Node,
Capacitive Load
Test 11a – JB Test Bench in Series with JB through 10km Cable,
Resistive Load
Test 11b – JB Test Bench in Series with JB through 10km Cable,
Capacitive Load
Test 11c – JB Test Bench in Series with JB through 10km Cable,
Increasing Load
Test 11d – JB Test Bench in Series with JB through 10km Cable,
Short Circuit
Test 12 – JB Test Bench in Series with JB through 10km Cable,
Ground Fault
Test 13a – JB Test Bench on Node Port 1, Prototype JB on Node Port
6, Overload Port
Test 13b – JB Test Bench on Node Port 1, Prototype JB on Node Port
6, Overload Port
Test 14a – Energizing into Ground Fault on JB Output, JB and Test
Bench at Node
Test 14b – Ground Fault on JB Output, JB Connected Directly to Node
Test 14c – Energizing into Ground Fault on JB Output, JB Connected
Directly to Node
Test 14d – Energizing into Ground Fault on JB Output, JB and Test
Bench at Node
Test 14e – Energizing into Ground Fault on JB Output, JB Connected
Directly to Node
Test 15a – Ground Fault on Node Port 6 Output
Test 15b – Ground Fault on Node Port Output (Previous Node Port
Design)
10.3.2. Integration Test Results Sheets – Phase 2
Document Number
N/A, 15th April 2009
N/A, 15th April 2009
Description
Test 1 – Junction Box Power-on
Test 2 – Junction Box at end of 10km Cable - Power-on
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N/A, 15th April 2009
N/A, 15th April 2009
N/A, 15th April 2009
N/A, 15th April 2009
N/A, 15th April 2009
N/A, 15th April 2009
N/A, 16th April 2009
N/A, 16th April 2009
N/A, 16th April 2009
N/A, 16th April 2009
N/A, 16th April 2009
N/A, 16th April 2009
N/A, 16th April 2009
N/A, 16th April 2009
Test 3 - Junction Box at end of 7.14km Cable - Power-on
Test 4 - Junction Box at end of 7.14km Cable - Power-on to 35.5Ω
Load
Test 5 - Overload 400V Port on Junction Box at end of 2.86km Cable
Test 6 - Verify Surge Suppression Characteristics of Media Converter
Surge Suppression Circuit
Test 7 - Characterise LV Port Output Voltage Ripple on the Junction
Box
Test 8 - Overload Node
Test 9 - Ground Faults on JB 400V Port, JB at end of 5.72km
Extension Cable
Test 10 - Ground Faults on JB 400V Port, JB Connected Directly to
Node
Test 11 - Ground Faults on JB Low Voltage Port, JB Connected
Directly to Node
Test 12 - Short Circuit Fault on JB 400V Port, JB at end of 2.86km
Extension Cable
Test 13 - Short Circuit Fault on JB 48V Port, JB at end of 2.86km
Extension Cable
Test 14a - Node Output Ripple Characterisation, 213.3Ω Load
Test 14b - Node Output Ripple Characterisation – 106.6Ω Load
Test 15 - Junction Box Input Ripple Characterisation for Changes to
Load on a 48V Port
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