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TR41.7-09-08-005-2564-AppGuidev5.0
PN-3-0340-RV4 to be published as TIA/TSB187
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Document Cover Sheet
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Project Number
Document Title
PN-3-0340-RV4 to be published as TIA/TSB187
UL Subject 2564 Outline of Investigation for Low-Voltage Surge
Withstand
Telecommunications Overcurrent Protector Components
Application Guide
Draft 5.0 (2009-05-06)
Source
TR41.7.5
Contact
TR41.7 Chairman – Randy Ivans
1285 Walt Whitman Rd.
Melville, NY 11747
Distribution
TR41.7 / TR-41.7.1 / TR41.7.5
Intended Purpose
of Document
(Select one)
X
Phone: 631-546-2269
Fax:
Email: Randolph.j.ivans@us.ul.com
For Incorporation Into TIA Publication
For Information
Other (describe) -
The document to which this cover statement is attached is submitted to a Formulating Group or
sub-element thereof of the Telecommunications Industry Association (TIA) in accordance with the
provisions of Sections 6.4.1–6.4.6 inclusive of the TIA Engineering Manual dated March 2005, all of
which provisions are hereby incorporated by reference.
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Abstract
This draft of the application guide for UL Subject 2564 was completed by the TR41.7.5
WG at the May Indianapolis meeting. It is for review and comment with final review
expected at the November 2009 TR41.7 meeting.
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Working Cover Page
UL Subject 2564 Outline of Investigation for
Low-Voltage Surge Withstand
Telecommunications Overcurrent Protector Components
Application Guide
Draft 5.0
(2009-05-06)
Warning: This Document is a “work in progress” by TIA TR41.7.5 and as such it’s
contents may change.
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FOREWORD
This Document is a TIA Telecommunications Systems Bulletin (TSB), produced by
Working Group TR-41.7.5 under subcommittee TR-41.7 of Engineering Committee TR41, User Premises Telecommunications Requirements, under the sponsorship of the
Telecommunications Industry Association [TIA]. Telecommunications Systems Bulletins
are not standards and are distinguished from TIA Standards in that TSBs contain a
compilation of engineering data or information useful to the technical community and
represent approaches to good engineering practices suggested by formulating group
TR-41.7.
This Bulletin is not intended to preclude or discourage other approaches which similarly
represent good engineering practice, or which may be acceptable to, or have been
accepted by, appropriate bodies such as the Federal Communications Commission
[FCC]. Parties who wish other approaches to be considered for inclusion in future
revisions of this Bulletin are encouraged to bring them to the attention of the formulating
group TR41.7. It is the intention of this formulating group to revise and update this TSB
from time to time as may be occasioned by changes in technology, industry practice,
government regulations, technical criteria, or other appropriate reasons.
This Document offers enhancements and clarifications for the technical criteria
contained in the following documents:
UL SUBJECT 2564 - OUTLINE OF INVESTIGATION FOR LOW-VOLTAGE SURGE WITHSTAND
TELECOMMUNICATIONS OVERCURRENT PROTECTOR COMPONENTS
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TR-41.7 MEMBERS AND TSB-187 CONTRIBUTORS
People on this list either where a voting member of TR41.7 at the time this document
was voted to publication or made contributions to the development of this document.
SEE TIA OPERATIONAL GUIDELINES Version 1.4
Organization Represented
ADTRAN, Inc
Bourns Ltd.
Cisco Systems
Cooper Bussmann Inc.
Embarq
Bournes Ltd.
Hewlett-Packard
Littelfuse Inc.
Mobile Engineering
Sanmina - SCI
SOC America Inc.
Telcordia Technologies
Thomson Inc.
Tyco Electronics
Underwriters Labs
Underwriters Labs
Verizon
Vtech Engineering
Name of Representative
Bell, Larry
Maytum, Michael
Lawler, Tim
Giblin, Dan
Ray, Amar
Wiener, Paul
Roleson, Scott
Havens, Phillip
Bipes, John
Tarver, Peter L.
Lindquist, Carl
McCarver, Randall
Hunt, Roger
Martin,Al
Ivans, Randy
Ladonne, Frank
Bishop, Trone
Whitesell, Steve
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CONTENTS
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FOREWORD ......................................................................................................................................................... I
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TR-41.7 MEMBERS AND TSB-187 CONTRIBUTORS ...................................................................................... II
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CONTENTS ....................................................................................................................................................... III
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LIST OF FIGURES ..............................................................................................................................................IV
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1
INTRODUCTION ........................................................................................................................... 5
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SCOPE........................................................................................................................................... 6
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REFERENCES .............................................................................................................................. 7
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DEFINITIONS, ACRONYMS AND ABBREVIATIONS ................................................................. 7
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SERVICE ENVIRONMENT CONDITIONS ................................................................................. 10
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MARKING .................................................................................................................................... 19
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TEMPLATES................................................................................................................................ 20
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EXAMPLE: SUBJECT 2564, FIGURE A1 – TEMPLATE A .............................................................................. 21
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TEST SEQUENCE FLOW CHART ............................................................................................. 22
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EQUIPMENT STANDARDS........................................................................................................ 22
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PARTS ......................................................................................................................................... 22
5.1
Temperature ...............................................................................................................11
5.2
Surge Current .............................................................................................................11
CLASSIFICATIONS..................................................................................................................... 15
6.2
Voltage Groups ...........................................................................................................15
KEY PARAMETERS.................................................................................................................... 16
7.3
Maximum limited duration voltage rating .....................................................................17
9.1
Template rationale ......................................................................................................20
9.2
Template application...................................................................................................20
9.3
Template temperature correction ................................................................................21
12.1 Part 1 is the main portion of Subject 2564. It provides all the testing procedures and
requirements for meeting this standard..................................................................................22
12.2
Parts 2 through 5 ........................................................................................................22
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LIST OF FIGURES
No table of figures entries found.
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INTRODUCTION
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UL Subject 2564 provides safety requirements for several different technologies that
can be employed to protect against excessive current. Each protector technology has
unique current protection characteristics. Subject 2564 Templates reflect the timecurrent characteristics of overcurrent protectors for specific telecommunication
standards. Characteristics of each type protector are provided using “Current-Time
Templates”, “Voltage Groups”, “Categories” and Environmental “Classes” in order to
characterize different technologies that may be employed for meeting these
requirements. Physical size and shape have not been standardized or established in
this document.
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Overcurrent protectors covered in this Application Guide are intended for wire line
paired cable telecommunications ports, including Ethernet. Some, such as fuses and
Line Feed Resistors (LFR) are non-resettable, while others, such as Polymer or
Ceramic Positive Temperature Coefficient (PTC) Protectors and Electronic Current
Limiters (ECL’s) are resettable. Since each technology has its own strengths and
weaknesses, they must be evaluated carefully for each application.
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Protector current ratings have been eliminated in favor of current-time templates
showing ACCEPTABLE and UNACCEPTABLE Regions. Voltage ratings are replaced
with Voltage Groups (VG). Specific environmental conditions are captured in
Environmental Classes. For a given application, a Template, Voltage Group,
Environmental Class and Category should be determined.
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SCOPE
This guide has been prepared to aid in the use and understanding of UL Subject 2564
“Outline of Investigation Low-Voltage Surge Withstand Telecommunications
Overcurrent Protector Components”. This includes associated Parts covering specific
overcurrent technologies. The overcurrent protectors withstandlightning surges, yet will
safely interrupt or reduce overload current when it exceeds current levels deemed safe
for equipment and wire. This guide only covers protectors intended for applications
described in UL Subject 2564.
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REFERENCES
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2. ANSI/TIA-968-A-1 (2003), Telecommunications – Telephone Terminal Equipment Technical Requirements for Connection of Terminal Equipment to the Telephone
Network
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3. ANSI/TIA-968-A-2 (2004), Telecommunications – Telephone Terminal Equipment Technical Requirements for Connection of Terminal Equipment to the Telephone
Network
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4. ANSI/TIA-968-A-3 (2005), Telecommunications – Telephone Terminal Equipment Technical Requirements for Connection of Terminal Equipment to the Telephone
Network
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5. ANSI/TIA-968-A-4 (2006), Telecommunications – Telephone Terminal Equipment Technical Requirements for Connection of Terminal Equipment to the Telephone
Network
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6. Telcordia GR 1089, Issue 4, Electromagnetic Compatibility and Electrical Safety –
Generic Criteria for Network Telecommunications Equipment.
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7. UL 497A, Secondary Protectors For Communication Circuits
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8. UL 1459, Third Edition, Telephone Equipment
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9. UL 60950-1 Second Edition, Safety of Information Technology Equipment
The following documents contain provisions that may be useful in applying these
guidelines and carrying out the recommended test procedures for determining
compliance with UL 2564. At the time of publication, the editions indicated were valid.
All documents are subject to revision, and parties to agreements based on this
document are encouraged to investigate the possibilities of applying the most recent
published edition of the documents.
1. ANSI/TIA-968-A (2002), Telecommunications – Telephone Terminal Equipment Technical Requirements for Connection of Terminal Equipment to the Telephone
Network
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DEFINITIONS, ACRONYMS AND ABBREVIATIONS
Refer to UL Subject 2564 for definitions of terms used in that document. For the
purposes of this document, the following definitions apply:
Ceramic Positive Temperature Coefficient (CPTC) Thermistor
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A thermistor constructed of ceramic semiconductor material, which exhibits a step-like
increase of a factor of 100 or more in resistance with increasing temperature.
Note: CPTC thermistors covered by this document are intended for use as current limiting protection
elements.
Current Interruption
The act of reducing current to a predetermined level, or zero, to protect a circuit and its
components.
Current Limiter
Non-linear device that automatically restricts the value of current when the current
attempts to exceed a given value for a sufficient time
DUT
Abbreviation - Device Under Test
Electronic Current Limiter (ECL)
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Protection device which electronically limits currents above a specific threshold current.
Fuse
A protective device which opens a circuit during specified overcurrent conditions by
means of a current responsive element.
Fusing Resistor
A resistor intended to interrupt a current flow at a predetermined time when the current
passing through it exceeds a predetermined value.
Note: A Fusing Resistor is intended to be replaced following operation.
Hold current (Ih)
See Maximum continuous current.
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Line Feed Resistor (LFR)
A fusing resistor used for AC overcurrent protection of telecommunications circuits.
NOTE: An LFR may incorporate multiple resistive elements, thermal links, which melt and limit the
maximum long-term temperature rise, and PTC thermistor elements to give a self-restoring function at low
levels of AC. After fusing, the LFR has a permanent increase of resistance value exceeding 100 times the
original resistance.
Maximum continuous current (Imco) [Sometimes referred to as Hold current (Ih)]
Highest current that may be conducted by the protector without operation or permanent
degradation at specified ambient temperature.
Maximum continuous operating voltage (Vmco)
Maximum continuous DC source voltage of the circuit in which the protector will be
installed.
Note: This term ignores telecommunications alerting signals.
Maximum limited duration fault current (Ildf)
The highest prospective rms symmetrical alternating current that a protector will safely
interrupt under specified conditions and for the defined duration at the maximum limitedduration voltage (Vmld) and is the highest value shown in the appropriate current-time
template.
Maximum limited duration voltage (Vmld)
Maximum rms symmetrical alternating voltage to which the protector will be subjected
during fault conditions for a specified minimum time duration.
NOTE 1: Maximum limited duration voltage (Vmld) is typically greater than Maximum continuous operating
voltage (Vmco).
NOTE 2: Typically, the minimum specified fault duration is either 1.5 or 5 seconds.
NOTE 3: Maximum limited duration voltage (Vmld) is selected from the Voltage Group associated with a
given Template.
Microclimate
Immediate environment of the device.
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Polymer Positive Temperature Coefficient (PPTC) Thermistor
A thermistor constructed of polymeric composite material, which exhibits a step-like
increase of a factor of 100 or more in resistance with increasing temperature.
Note: PPTC thermistors covered by this document are intended for use as current limiting protection
elements
Prospective current
Current that would flow at a given location in a circuit if it were short-circuited at that
location by a link of negligible impedance.
Surge Current
A transient current that rises rapidly to a peak value and then falls more slowly to zero.
Surge Current (Impulse) Withstand Rating
Maximum current surge waveform the DUT will safely withstand without loss of function
after repeated predefined current surge impulses.
Surge Voltage
A transient voltage that rises rapidly to a peak value and then falls more slowly to zero.
Trip Current (It)
Lowest current that will cause the thermistor to trip to a high resistance condition at a
specified temperature (preferably 23°C) and within a time to be specified.
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Service Environment Conditions
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The electrical assessment normally concentrates on surge testing, as it is the highest
electromagnetic environment stress.
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The common ambient environmental parameters are temperature, humidity and air
The service environment is a combination of the electromagnetic environment and the
ambient environment local to the component (microclimate). Depending on the
component sensitivity, it is assessed either at an environmental parameter extreme or
the parameter extremes, possibly with additional testing being done at a reference
value.
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pressure. For these components, temperature is considered the main ambient
environmental sensitivity. In special cases, other ambient environmental parameters
such as vibration, mechanical shock, contaminants and condensation may need to be
considered.
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Temperature
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These components will normally be mounted inside an equipment enclosure. Being
inside the equipment enclosure means that the component local ambient temperature
may not be the same as the local ambient temperature surrounding the equipment. The
equipment design may set the internal temperature (microclimate) by using natural
cooling, forced air-cooling or some form of local temperature control. The most severe
ambient temperature condition is normally for natural cooling.
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For natural cooling the lowest microclimate temperature will be the same as the lowest
ambient temperature surrounding the equipment. The highest microclimate temperature
will be the highest ambient temperature surrounding the equipment plus the internal
temperature rise inside the equipment enclosure. The component temperature range
must be based on these parameters.
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Equipment locations using temperature control have a typical ambient range of 5 °C to
40 °C. The corresponding controlled microclimate temperature range is 5 °C to 70 °C.
Equipment locations with uncontrolled temperature have a typical ambient range of 40 °C to 70 °C. The corresponding uncontrolled microclimate temperature range is 40 °C to 85 °C. Manufacturers may define special microclimates with different maximum
and minimum temperature values to cover non-standard microclimates.
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Surges result from AC supply power faults and nearby lightning strikes. The local
surge environment is the result of many factors including the equipment location
and installation conditions.
Surge Current
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5.3
AC Power Fault Surges
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AC power fault testing is conducted with voltages to simulate contact to a mains supply
operating at 120/240 V, 120/208 V 3 phase-Y or 277/480 V 3 phase-Y. Testing is also
conducted at levels up to 600 V AC for contact or induction faults from higher voltage
AC lines, limited by a primary protector. Testing is done at various short-circuit current
magnitudes and durations.
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Table 1 below lists the various generator capabilities used for AC power fault testing.
The table rows are arrangedby open-circuit voltage, short-circuit current and reference
document.
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Even though Table 1 has multiple generator test capabilities identifiedseparate AC
generators are not necessarily required. A single generator can be designed to provide
the required capability for multiple rows. For example, a generator with a variable
voltage up to 600 V ACand a current capability of 60 A AC per line for the test time
specified will meet all the power fault test requirements with suitable series power
resistors.
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The starting phase angle of the applied voltage for the 600 V AC, 60 A and 40 A tests
and the 120 V AC tests needs to be controlled to values of 5°, 45°, 90°and 135° with a
tolerance of +/- 1 degree.
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Table 1: AC power fault tests and their related equipment standards
Generator
AC open-circuit
voltage
(rms)
600 V
Generator
AC short-circuit current
(rms),
maximum test time
60 A, 5 s
Note 3
600 V
(Default-voltage
limiting
primary)
425 V
(Medium-voltage
limiting
primary) Note 1
283 V
(Low-voltage limiting
primary) Note 1
30 A, 25 A, 20 A, 12.5 A
10 A, 7 A, 5 A, 3.75 A, 3 A,
,
2.6 A and 2.2 A, 900 s
30 A, 25 A, 20 A, 12.5 A
10 A, 7 A, 5 A, 3.75 A, 3 A,
,
2.6 A and 2.2 A, 900 s
30 A, 25 A, 20 A, 12.5 A
10 A, 7 A, 5 A, 3.75 A, 3 A,
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2.6 A and 2.2 A, 900 s
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Equipment Standard
Reference
GR-1089-CORE, Issue 4, clause
4.6.12
clause 4.6.15, Table 4-13, test
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Table 4-15, test 10
GR-1089-CORE, Issue 4, clause
4.6.11,
clause 4.6.14
GR-1089-CORE, Issue 4,
Table 4-13, test 9, test 14
Table 4-15, test 13
GR-1089-CORE, Issue 4,
Table 4-13, test 9, test 14
Table 4-15, test 13
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special value
(Specific-voltage
limiting
primary) Note 1 and
Note 2
600 V AC
30 A, 25 A, 20 A, 12.5 A
10 A, 7 A, 5 A, 3.75 A, 3 A,
,
2.6 A and 2.2 A, 900 s
GR-1089-CORE, Issue 4, clause
4.6.14,
Table 4-13, test 9, test 14
Table 4-15, test 13
40 A, 1.5 s
Note 3
UL 60950-1, clause 6.4, clause
NAC.3.3
UL 1459, Issue 3, clause 59.18
7 A, 5 s
UL 60950-1, clause 6.4, clause
NAC.3.3
UL 1459, Issue 3, clause 59.18
2.2 A, 1800 s
UL 60950-1, clause 6.4, clause
NAC.3.3
UL 1459, Issue 3, clause 59.18
120 V AC
25 A, 900 s
GR-1089-CORE, Issue 4, clause
Note 3
4.6.17,
Table 4-8, test 1a
25 A, 1800 s
UL 60950-1, clause 6.4, clause
Note 3
NAC.3.3
UL 1459, Issue 3, clause 59.18
Note 1. Used when there is an agreed or integrated primary protector.
Note 2. Manufacturer defined primary protector, not covered by the medium- or lowvoltage limiting
categories. The open-circuit voltage is equal to the highest AC voltage that will not
operate the specific
agreed or integrated primary protector. Limiting voltage should not be lower than 120 V
ms to avoid
operation during 120 V AC tests
Note 3: Applied voltage starting phase angle controlled to 5°, 45°, 90°and 135° with a
tolerance of ±1°.
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Lightning Impulse Surges
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Table 2 lists the various generator capabilities used for lightning surge impulse testing.
These surges simulate the variety of surge conditions possible in the environment The
table rows are by test type, generator capability and equipment standard reference.
The test type column has two row blocks. One is for impulse and the other is for
coordination.
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The coordination row tests for interaction between a primary protector and a secondary
protector. The impulse row does not.
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Table 2 has multiple generator test capability rows. This doesn’t mean that separate
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impulse generators are required for each row since a single generator may provide the
required capability for multiple rows. For example a 2 kV, 200 A, 10/1000 generator can
be used for the 1 kV, 100 A, 10/1000 testing. The commercial impulse generators used
for the ACTA-adopted ANSI/TIA-968-A (formerly FCC Part 68) typically provide test
capabilities for 1.5 kV, 10/700 impulses, 800 V, 100 A, 10/560 impulses and 1.5 kV, 200
A, 10/160 impulses.
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Table 2: Lightning impulse tests and their related equipment standards
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Test Type
Impulse
Generator Capability
1 kV, 100 A, 10/1000 s
Equipment Standard Reference
GR-1089-CORE, Issue 4, clause 4.6.6, Table
4-2, Test 3
GR-1089-CORE, Issue 4, clause 4.6.8, Table
5 kV, 500 A, 2/10 s
4-4
1.5 kV, 100 A, 2/10 sor GR-1089-CORE, Issue 4, clause 4.6.9, Table
4-5, Test 2,
1.5 kV, 100A, 1.2/50Table 4-6
8/20 s
UL 60950-1, clause 6.2.2.1 and ANSI/TIA
1.5 kV, 10/700 s
968-, clause 4.2.2.1
800 V, 100 A, 10/560 s ANSI/TIA 968-, clause 4.2.2.1
1.5 kV, 200 A, 10/160 s ANSI/TIA 968-, clause 4.2.2.2
Coordination 2 kV, 200 A, 10/1000 s GR-1089-CORE, Issue 4, clause 4.6.7, Table
4-3
GR-1089-CORE, Issue 4, clause 4.7, Table 44 kV, 500 A, 10/250 s
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Classifications
6.1
Microclimate Environments
As discussed in clause 4.1.1 of UL Subject 2564, equipment controlled, and
uncontrolled ambient temperature ranges set the component controlled and
uncontrolled microclimate assessment temperature ranges. Manufactures define the
special microclimate assessment temperature ranges. The three microclimates
specified in UL Subject 2564 are:
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


6.2
controlled microclimate: 5°C to 70°C for Class I environment components
uncontrolled microclimate: -40°C to 85°C for Class II environment
components
special microclimates: minimum and maximum temperatures are defined
by the manufacturer for Class III environment components
Voltage Groups
Four Voltage Groups (VG) are defined in 4.1.2 of UL Subject 2564:
Group I - 600 Vrms
Group II - 425 Vrms
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Group III - 283 Vrms
Group IV - 120 Vrms
Voltage Groups I, IIand III correspond to Categories defined in GR-1089-CORE as
“High-Voltage Limiting Category”, “Medium-Voltage Limiting Category” and “LowVoltage Limiting Category”, respectively. These categories are used for equipment that
is designated to be tested as either “Agreed Primary Protectors” or “Equipment with
Integrated Primary Protectors.” Group I is also the default voltage used for Power Fault
testing. Group IV corresponds to the GR-1089-CORE Intrabuilding Power Fault test
level. Note: The Group IV test level is also used for the L5 tests of UL60950-1 and
UL1459 However, this alone is not sufficient to qualify a device for use in UL60950-1 or
UL1459 since other test voltage levels are specified.
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Another option to these four Voltage Groups is a “specific voltage limiting category” as
defined in Table 6.
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Key Parameters
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7.1
DC resistance range
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This parameter is intended to provide basic information regarding 1) consistency
of components from lot-to-lot and part-to-part and 2) the potential affect of the
protector on circuit operation due to voltage drop across the component. The
resistance measurement is made using a low level current to limit heating of the
device. We often refer to this as “cold resistance”. Non-resettable protectors,
such as a fuse, are often measured to determine if the DC Resistance is
relatively consistent. This parameter can vary a considerable amount from
device to device without significantly affecting the component function or
precision. In most cases, the second issue is far more important. Both
resettable and non-resettable protectors will have some cold resistance, but they
may have an even higher resistance at the typical circuit operating current.
7.2
Maximum continuous operating voltage rating
Protectors covered in UL Subject 2564 are employed in telecommunications
circuits where the DC voltage and current levels are relatively low. Therefore, a
DC voltage rating for these devices is not required. The main purpose for these
protectors is to insure isolation of the communications circuit from a
communication line that has been accidentally placed in contact with an AC
power line.
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7.3
Maximum limited duration voltage rating
3
4
5
6
7
8
9
10
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12
This rating is based on the AC voltage with the highest fault current thatcan be
impressed on the communications line during accidental line cross for a limited
time. The upper limits for this voltage are related to the overvoltage protector
type that is shunting the surge current to the ground. These voltage protectors
can be carbon blocks, gas tubes or solid state devices. It is accepted
throughout the telecommunications industry that the worst case voltage will be
600 Vac based on legacy installations using carbon blocks. It has been
determined that the maximum duration of this overvoltage will not exceed 5
seconds, or 1.5 seconds, depending on the equipment standard being
employed.
13
14
15
Overvoltage limits are provided for each Annex A template description, based on
the related equipment standard. These range from 120 V ac to 600 Vac, as noted
in the Voltage Groups (VG) in section 4 of UL Subject 2564.
16
7.4
Maximum continuous current
17
18
19
The Annex A templates of UL Subject 2564 provide for ACCEPTABLE and
UNACCEPTABLE regions for device operation, but do not identify how much
current a specific device can carry over extended periods of time.
20
21
22
23
Maximum continuous current or “hold current” is the lowest current point on the
device I-t curve. Protectors are expected to continuously carry this current for
900 seconds, minimum. This device I-t curve must comply with the appropriate
template in Annex A, whose selection is dependent on the application.
24
25
26
Continuous current for extended time periods in non-resettable protectors at the
maximum continuous current level can result in significant temperature rises for
small devices and may require special design considerations.
27
28
29
Though rare, encountering maximum continuous current levels is possible. This
hold current (maximum continuous current) value is intended to provide
guidance to help prevent nuisance tripping in applications.
30
31
32
33
34
35
7.5
Maximum limited duration fault current carrying rating
Different equipment standards require the protectors covered in UL Subject
2564 to safely interrupt a maximum fault current at the rated maximum limited
duration open circuit voltage. Examples include the ability to safely open a
circuit with a full fault at 60A, 600 Vac, 40A, 600 Vac or 25A, 120 Vac. The
levels are defined for applications described in Annex A templates.
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2
3
4
As noted in the explanation of maximum limited duration voltage rating, above,
these tests will be applied for a time duration not exceeding 5 seconds or 1.5
seconds, depending on the equipment standard.
7.6
Surge current impulse withstand rating
5
6
7
8
9
10
Equipment in the field may be exposed to lightning surges. Protectors covered
by UL Subject 2564 will be able to safely withstand these lightning induced
surge currents. Non-resettable, resettable and ECL protectors must also be
able to withstand multiple lightning surges defined in UL Subject 2564 while
continuing to meet the appropriate normative Annex A template requirements. .
They must remain operational after withstanding such multiple hits.
11
12
13
14
The surge current impulse withstand rating is a measure of the device’s ability to
withstand a variety of surges defined for the appropriate template as found in
Table 5 of UL Subject 2564.
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8
Marking
2
3
4
The information marked on all protectors covered by this outline shall be legible,
permanent and include the following information with the corresponding unit of
measurement:
5
a)
The manufacturer’s name, trademark, or both
6
b)
Unique identifier (part number, Type, etc);
7
c)
Maximum limited duration voltage rating;
8
d)
Factory ID Code (if manufactured in multiple locations).
9
e)
Templates met
10
11
12
Note: Minimum marking on the component shall include (a) and (b). Minimum marking
on the smallest package label shall include all parameters of those listed.
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9.1
Templates
Template rationale
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5
6
7
8
9
10
11
12
Defining protection of wire in a communications system has been accomplished in the
past by employing “wire simulators”. The logic was that if the “wire simulator” (typically
a specific type and current rated commercially available fuse) was not opened, a given
type and size wire employed in the field would not be damaged due to current overload
or significant lightning surge currents. The use of these “wire simulators” was cost
effective and easy to implement. The problems associated with use of these
“simulators” were that they were not consistent in constant current carrying or surge
withstand capability from device to device or from lot to lot. Some “wire simulators” of a
given construction were discontinued by the manufacturer and replacement devices
were not exactly the same.
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14
15
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17
In an effort to better standardize these devices, it was decided to use the I-t curves for
the given “simulators” rather than use the simulators themselves. The resulting set of
curves is now referred to as “Templates” in Annex A. It should be noted that the limits
established by the templates have sufficient derating from currents that could cause
cable wire damage or overheating.
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19
20
Each protector test, including voltage, current and time parameters are associated with
a specific test number, Groups, Templates and relevant Equipment Standards in Table
3 of Subject 2564.
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22
9.2
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29
30
31
32
33
Template application
Measurements of steady state current for durations and current limits defined by the
templates will provide a test mechanism for protection of the associated circuit wire at
23 °C. Those protectors limiting current for a maximum time, as defined by the
template ACCEPTABLE region, are acceptable for use with the associated type of
application for a given template. If the protector under test permits the current to
exceed the maximum limit and time for a given template, this will be considered
UNACCEPTABLE. This fixed line will set ACCEPTABLE/UNACCEPTABLE limits for
any type of non-resettable or resettable protector that is intended for use with the
specified equipment standards.
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100
Current (A rms)
Unacceptable Region
10
1
Acceptable Region
0.1
0.01
10
100
1000
Figure 1 (Example: Subject 2564, Figure A1 – Template A)
3
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1
Duration (Seconds)
1
2
4
5
6
7
8
9
10
11
0.1
Care has been taken to set these templates at levels that will assure protection of a
transmission wire regardless of the associated load impedance. In many instances,
circuit related impedance and line impedance will limit the current that passes through
the protector. Since protector manufacturers do not know where a given protector will
be installed, it was decided to set the curves for the worse case scenario.
9.3
Template temperature correction
All current protectors covered in UL 2564 will be affected by ambient temperature
changes. Each type of protector has its own sensitivity to temperature. Some are linear
and some are non-linear. Most have positive temperature coefficients. Subject 2564,
Table 2 and Informative Annex D, have been included to provide guidance for Template
curve adjustments for each type of protector technology. Most protectors will be
employed in temperature controlled facilities. However, temperatures in a given cabinet
or on a specific board may differ considerably. Ambient temperature variations can also
be extreme.
21
22
See Service Environment Conditions in 1.2, above, as well as Section 3 and
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Environmental Classifications in Section 4 of Subject 2564 for further information.
2
10
3
4
Test Sequence Flow Chart
10.1 See attached chart
11
Equipment Standards
5
Telcordia GR 1089, Issue 4 (Central Office Equipment)
6
UL 60950-1, Second Edition (Customer Premises Equipment)
7
8
UL 497A, Third Edition (Secondary Protectors for Communications
Circuits)
9
TIA 968--5
10
UL 1459, Third Edition
11
12
13
14
15
16
17
12
Parts
12.1 Part 1 of UL Subject 2564 contains the general requirements for low-Voltage
Surge Withstand Telecommunications Overcurrent Protector Components, . It provides
all the testing procedures and requirements for meeting this standard.
18
19
20
21
22
23
24
25
26
Parts 2 through 5 are each directly related to Part 1, and contain modifications
associated with each technology covered. These Parts are assigned to the following
technologies:
27
28
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30
31
32
33
34
35
12.2.1 Fuses are tested to Parts 1 and 2. These fuses will have been tested to all of the
requirements of Part 1, as amended or expanded by Part 2. The only additions
in Part 2 include recommended standardized test boards for surface mount and
through-hole fuses.
12.2
Parts 2 through 5
Part 2 – Fuses
Part 3 – Polymeric PTC Thermistors
Part 4 – Line Feed Resistors (LFR)
Part 5 – Electronic Current Limiters (ECL)
12.2.2 Polymeric PTC Thermistors are tested to Parts 1 and 3.
A polymeric PTC is made by mixing carbon black into a suitable polymer, typically
polyethylene. This mixture is extruded into a thin sheet, upon which foil electrodes are
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pressed. The resulting material is divided into chips, which are then packaged to form
the finished device.
The amount of carbon black in the polymer is adjusted so that under normal operation
the carbon black is relatively densely packed. In this state many conductive paths are
formed between the two electrodes, and the resistance of the device is low [see Figure
1]. This state is maintained at low currents.
heats up
cools down
Figure 2. Morphology of a polymeric PTC device as it heats up and cools down.
As the current through the device increases, it heats up. Heating causes the device to
expand, breaking many of the conducting chains [again see figure 1].
As heating continues, the device reaches a temperature at which the device resistance
increases rapidly with further increase in temperature [see Figure 2]. The current at
which this rapid increase in resistance occurs is called the tripping current. For currents
equal to or greater than the trip current, the device is said to be tripped. In the tripped
state the device has a high resistance, which is maintained by a small current. When
this current is removed, the device cools down and reverts to its original low-resistance
state. The overall process is illustrated in Figure 1.
Currents lower than the trip current are called hold currents. For a given device, the
maximum hold current and the minimum trip current are the same. For a group of
devices the hold (trip) current will vary over a range, due to production spreads. So a
data sheet will typically specify the bottom of this range as the hold current, and the top
of the range as the trip current.
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Switched
Resistance
1
2
3
4
5
6
7
8
9
10
11
12
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14
15
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17
18
19
20
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Normal
Temperature
Figure 3. A typical RT curve for a Polymeric PTC device
Heat energy may be supplied to the device in two forms: the thermal environment, and
I2R heating due to current flowing through the device. As the heat from the environment
increases due to increased temperature, the amount of I2R heating the device can
accommodate without tripping decreases. So the hold and trip currents for a device are
temperature dependent. This temperature dependence leads to a thermal derating for
the device. The thermal derating is captured in clause 3.1.2, Table 2 of Subject 2564.
Surge tests such as the one described in clause 7.5 of Subject 2564 may have enough
energy to trip a polymeric PTC device. If that happens the voltage of the surge is often
high enough to cause the device to flash over, which can affect the ability of the device
to perform its intended function. In this case the device selected may require additional
series resistance in order to pass the surge current test of clause 7.5. The device
manufacturer should be consulted for applications that fall into this category.
In running the test in clause 7.6 of Subject 2564, it may matter which type of
overvoltage protection is used in the test. A GDT (Gas Discharge Tube) with a limiting
voltage specified at 1000 V/μsec has a lower limiting voltage on a 10/1000 surge than a
thyristor with a limiting voltage specified at 1000 V/μsec; leading to the possibility of
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passing the test with a GDT, but failing the test with a thyristor. For this reason the type
of overvoltage protector used needs to be specified.
12.2.3 Line Feed Resistors (LFR) are tested to Parts 1 and 4
The basic Line Feed Resistor (LFR) consists of thick-film resistors screen-printed onto a
ceramic substrate. Attached “Tulip” clip headed leads provide through hole for surface
mounting of the component. The thick-film resistor can be laser trimmed for accurate (1
%) matching of dual resistor LFRs. Thick-film resistors have the ability to withstand high
voltage impulses without flashover making the LFR an excellent primary-secondary
protection coordination element. The range of resistance values is typically from a few
ohms to several hundred ohms.
13
14
15
16
17
LFRs can be made into complex hybrids by integrating on the substrate additional
resistors, multiple devices, surface mount fuses, or even a different protection
technology. Adding such things as overvoltage protectors gives coordinated subsystems.
18
19
Operation
20
21
22
23
24
25
26
27
AC current interruption occurs when the high temperature developed by the resistor(s)
causes mechanical expansion stresses that result in the ceramic breaking open. Low
current power induction may not break the LFR open, creating long-term surface
temperatures of more than 300 °C. To avoid heat damage to the PCB and adjacent
components, maximum surface temperature can be limited to about 250 °C by
incorporating a series thermal fuse (solder) link on the LFR. The link consists of a solder
alloy that melts when high temperatures occur for periods of 10 seconds or more.
28
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30
Figure 4 shows the two current interruption mechanisms; fuse link operation and
ceramic fracture.
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Figure 4.Current interruption by fuse link operation and by ceramic fracture
3
4
5
6
7
Figure 5 shows an LFR current interruption characteristic. Up to about ten
seconds there is little difference if fuse links are fitted or not. Over ten seconds,
the fuse links cause the LFR to interrupt at lower currents. Overall there is little
difference if one or two resistors are powered.
8
Dual Resistor LFR — Current vs Operate Time
Ceramic Only (co), Fuse link version (f)
LFR in Single Resistor (s) and Dual Resistor (d) Modes
20
cos_current
cod_current
fs_current
fd_current
RMS Current per Resistor Element – A
10
5
3
2
1
0.5
0.3
0.01 0.02
9
10
0.05
0.1
0.2
0.5
1
2
5
10
20
50
100
Operate Time – s
Figure 5. LFR current interrupt times
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3
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5
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An LFR can be made to operate at lower currents (and temperatures) by integrating a
series connected PTC thermistor. Although PTC thermistors may be used alone, series
connection with an LFR reduces peak currents and thereby allows smaller cross-section
PTC thermistors to be used. The thermal coupling of an integrated module also ensures
that the LFR heating further increases the rate of PTC thermistor temperature rise
during AC faults causing faster low current tripping. The series LFR resistance will
reduce the impulse current increase of ceramic thermistors and reduce the relative
effect of the polymer thermistor trip resistance change.
10
11
Testing considerations
12
13
14
15
16
The LFR weight and high operating temperature could result in desoldering and
movement, causing displacement on the PCB or ultimately falling off. Both these
conditions can be tested for by the use of a test PCB at specific orientations as
shown in Figures 5-2 and 5-3 of Subject 2569.
17
18
19
20
21
Under high current conditions the LFR will fragment and under low-current
conditions the LFR will run at high temperatures. Two avoid an unrealistic test
evaluation, the cheesecloth hazard indicator must be spaced off from the LFR as
described in Subject 2569.
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25
12.2.5 Electronic Current Limiters are tested to Parts 1 and 5.
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Start
Verify Supplier
Datasheet
(5.1)
Review Applicable
Device Section
(Parts 2-6)
Record
Environment Class
(4.0)
Record Voltage
Group
(4.1.2)
Identify Template
(Table 1)
Verify Part Marking
(6.0)
Test
(7.0)
A
1
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A
Maximum
Continuous
Current
(3.4.2)
Resistance
(3.4.3)
Limited
Duration
Current
(3.4.5)
Max.
Limited
Duration
Current
(3.4.4)
Surge
Current
(3.4.1)
Surge
Current
(3.4.1)
Surge
Current
(3.5.1)
Limited
duration
carrying
current
(3.5.2)
Temp.
Cycle
(3.4.2)
Resistance
(3.4.3)
Temp.
Cycle
(3.4.5)
Temp.
Cycle
(3.4.4)
Temp.
Cycle
(3.4.1.1)
Temp.
Cycle
(3.4.1.2)
Temp.
Cond.
(3.2a or
3.3a)
Temp.
Cond.
(3.2a or
3.3a)
Test
(7.3)
Test
(7.4)
Test
(7.5)
Test
(7.6)
Test
(7.5 and
7.6)
Test
(7.3)
Criteria
(7.1.6)
Criteria
(7.1.6)
Criteria
(7.1.6)
Criteria
(7.1.6)
Criteria
(7.1.6)
Criteria
(7.3.4)
Test
(7.2)
Criteria
(7.1.6)
Criteria
(3.4.3.3)
Finish
1
29