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IEEE P2406/D02, January 2014
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IEEE P2406™/D02
Draft Standard for Design and
Construction of Non-Load Break
Disconnect Switches for Direct
Current Applications on Transit
Systems
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Sponsor
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Rail Vehicle Transit Interface Standards Committee
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Approved <XX MONTH 20XX>
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IEEE-SA Standards Board
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Copyright © 2010 by the Institute of Electrical and Electronics Engineers, Inc.
Three Park Avenue
New York, New York 10016-5997, USA
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This document is an unapproved draft of a proposed IEEE Standard. As such, this document is subject to
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IEEE P2406/D02, January 2014
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Abstract: This Standard is a basis for the design, application, and usage of direct current nonload (no-load) break disconnect switches for the purpose of isolating direct current power
distribution circuits for transit applications.
Keywords: non-load break disconnect switches, bolted pressure switches, knife switches,
grounding switches, silver insert switches, high voltage direct current disconnect switches
Copyright © 2010 IEEE. All rights reserved.
This is an unapproved IEEE Standards Draft, subject to change.
IEEE P2406/D02, January 2014
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IEEE P2406/D02, January 2014
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Introduction
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This introduction is not part of IEEE P2406/D02, Draft Standard for Design and Construction of Non-Load Break
Disconnect Switches for Direct Current Applications on Transit Systems.
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This document is a collaboration of manufacturers, design engineers, installing contractors, and transit
authorities to provide a means to standardize the design and production of Non-Load Break Disconnect
Switches for Direct Current Applications on Transit Systems. The basis of knowledge used to author this
Standard is drawn from decades of practical experience as well as other similar Standards such as DC knife
switch Standards, European Standards, IEC Standards, and other DC switchgear Standards. This document
is intended to aid in the specification, design, and manufacturing process for Non-Load Break Disconnect
Switches for Direct Current Applications on Transit Systems. This is not a governing document which
specifies which switches should be used and when they should be used. This is only a Standard which is a
means to consistency throughout the industry for switch design and production. The end user is always
responsible for specifying ratings, switch type, operator type, and any other details specific to their design
criteria. This Standard can then be applied to the specification, manufacturing, testing, and commissioning
of Non-Load Break Disconnect Switches for Direct Current Applications on Transit Systems.
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Notice to users
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Laws and regulations
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IEEE P2406/D02, January 2014
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IEEE P2406/D02, January 2014
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Participants
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At the time this draft standard was submitted to the IEEE-SA Standards Board for approval, the Overhead
Contact Systems Working Group had the following membership:
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Jerry Woodruff, Co-Chair
Daren Szekely, Co-Chair
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Christopher B. Tyrrell
Fred Greenberg
Calvin Shankster
Pranaya Shrestha
Kelvin Zan
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Marv Miletsky
Suresh Shrimavle
Ron Clark
The following members of the <individual/entity> balloting committee voted on this standard. Balloters
may have voted for approval, disapproval, or abstention.
(to be supplied by IEEE)
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Balloter1
Balloter2
Balloter3
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Balloter4
Balloter5
Balloter6
Balloter7
Balloter8
Balloter9
When the IEEE-SA Standards Board approved this standard on <XX MONTH 20XX>, it had the following
membership:
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(to be supplied by IEEE)
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Michael Kelner
Eric Wan
Scott Baumli
Dick Angert
Paul F. White
<Name>, Chair
<Name>, Vice Chair
<Name>, Past President
<Name>, Secretary
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SBMember4
SBMember5
SBMember6
SBMember7
SBMember8
SBMember9
*Member Emeritus
Also included are the following nonvoting IEEE-SA Standards Board liaisons:
<Name>, NRC Representative
<Name>, DOE Representative
<Name>, NIST Representative
<Name>
IEEE Standards Program Manager, Document Development
<Name>
IEEE Standards Program Manager, Technical Program Development
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Copyright © 2010 IEEE. All rights reserved.
This is an unapproved IEEE Standards Draft, subject to change.
IEEE P2406/D02, January 2014
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Contents
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1. Overview .................................................................................................................................................... 1
1.1 Scope ................................................................................................................................................... 1
1.2 Purpose ................................................................................................................................................ 1
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2. Normative references .................................................................................................................................. 2
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3. Definitions, Abbreviations, and Acronyms ................................................................................................ 2
3.1 Definitions ........................................................................................................................................... 2
3.2 Abbreviations and Acronyms .............................................................................................................. 3
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4. Application Considerations ........................................................................................................................ 5
4.1 Scope of Applications .......................................................................................................................... 5
4.2 General ................................................................................................................................................ 5
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5. Types of DC Disconnect Switches ............................................................................................................. 5
5.1 Switch Configurations ......................................................................................................................... 5
5.2 Switch Styles ....................................................................................................................................... 6
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6. Interlock Considerations ............................................................................................................................. 9
6.1 Mechanical Interlocks .......................................................................................................................... 9
6.2 Electrical Interlocks ............................................................................................................................10
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7. Switch Operation Types ............................................................................................................................10
7.1 Manually Operated .............................................................................................................................10
7.2 Motor Operated...................................................................................................................................10
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8. Mounting and Enclosure Types .................................................................................................................11
8.1 Open Style ..........................................................................................................................................11
8.2 Enclosed Style ....................................................................................................................................11
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9. Disconnect Switch Ratings ........................................................................................................................11
9.1 Insulating Rating.................................................................................................................................11
9.2 Current Rating ....................................................................................................................................12
9.3 Short Circuit Rating ............................................................................................................................12
9.4 Heat Rise Limitations for Traction Power Switches ...........................................................................12
9.5 Aux Contact Ratings ...........................................................................................................................13
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10. Cable Termination Considerations ..........................................................................................................13
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11. Fuse Considerations.................................................................................................................................13
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12. Testing Considerations ............................................................................................................................13
12.1 Specifications and Applicable Standards ..........................................................................................13
12.2 Design Tests .....................................................................................................................................14
12.3 Factory Acceptance Testing..............................................................................................................15
12.4 Witness Testing ................................................................................................................................17
12.5 Documentation and Submittals .........................................................................................................17
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13. Grounding Considerations .......................................................................................................................18
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IEEE P2406/D02, January 2014
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14. SCADA Interface Considerations............................................................................................................19
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15. Signage and Labeling ..............................................................................................................................19
15.1 General Warning Signs .....................................................................................................................20
15.2 High Voltage Signs ...........................................................................................................................20
15.3 Arc Flash Signs .................................................................................................................................20
15.4 Non-Load Break Signs .....................................................................................................................20
15.5 General Sign Information .................................................................................................................21
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16. Arc Flash Considerations.........................................................................................................................21
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17. Installation Considerations ......................................................................................................................22
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18. Maintenance Considerations ....................................................................................................................22
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Copyright © 2010 IEEE. All rights reserved.
This is an unapproved IEEE Standards Draft, subject to change.
IEEE P2406/D02, January 2014
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Draft Standard for Design and
Construction of Non-Load Break
Disconnect Switches for Direct
Current Applications on Transit
Systems
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IMPORTANT NOTICE: This standard is not intended to ensure safety, security, health, or
environmental protection. Implementers of the standard are responsible for determining appropriate
safety, security, environmental, and health practices or regulatory requirements.
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This IEEE document is made available for use subject to important notices and legal disclaimers.
These notices and disclaimers appear in all publications containing this document and may
be found under the heading “Important Notice” or “Important Notices and Disclaimers
Concerning IEEE Documents.” They can also be obtained on request from IEEE or viewed at
http://standards.ieee.org/IPR/disclaimers.html.
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1. Overview
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1.1 Scope
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This Standard covers basic design parameters and features for Direct Current Disconnect switches used on
Transit Systems for Non-Load Break applications
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1.2 Purpose
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This Standard covers design criteria of direct current disconnect switches pertaining to current and voltage
ratings, physical clearance spacing for gap and creep, and auxiliary control equipment.
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Special considerations not addressed in this Standard or beyond the scope of this Standard shall be
considered by specific owners on a case by case basis. The intent of this Standard cannot cover these
instances.
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Copyright © 2010 IEEE. All rights reserved.
This is an unapproved IEEE Standards Draft, subject to change.
IEEE P2406/D02, January 2014
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2. Normative references
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The following referenced documents are indispensable for the application of this document (i.e., they must
be understood and used, so each referenced document is cited in text and its relationship to this document is
explained). For dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments or corrigenda) applies.
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British Standard BSN EN 50124-1:2001 Railway Applications – Insulation coordination
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IEC International Standard 61992 Railway Applications – Fixed Installations – DC Switchgear
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Canadian Electrical Code (CEC)
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Canadian Standard Association (CSA)
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IEEE Standard Dictionary of Electrical and Electronics Terms, IEEE Std 100
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IEEE Draft Standard P1791 OCS Terminology
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IEEE Draft Standard P1833, Guide for Design of Direct Current Overhead Contact Systems for Transit
Systems Section 5.9.4.1.4
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National Electrical Code (NEC)
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National Electrical Manufacturers Association (NEMA)
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National Electrical Safety Code (NESC)
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IEEE P1901-2010 - PLC Standard
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IEEE PC37.1/D1.9 Draft Standard for SCADA and Automation Systems
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National Communications System Technical Information Bulletin 04-1, October 2004: SCADA Systems
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IEEE Std C37, 14-1999, STANDARDS FOR LOW-VOLTAGE DC POWER, Section 6.1
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UL 363 DC Knife Switch Standards
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3. Definitions, Abbreviations, and Acronyms
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3.1 Definitions
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For the purposes of this document, the following terms and definitions apply. The IEEE Standards
Dictionary: Glossary of Terms & Definitions should be consulted for terms not defined in this clause.1
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Arcing Distance: The largest distance of dry air through which a current path will make to ground
dependent on the voltage.
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Clearance: Shortest distance in air between two conductive materials.
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The IEEE Standards Dictionary: Glossary of Terms & Definitions is available at http://shop.ieee.org/.
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Copyright © 2010 IEEE. All rights reserved.
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IEEE P2406/D02, January 2014
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Creep Distance: Shortest distance along the surface of the insulating material between two conductive
materials.
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Electrical Section: Part of an electrical circuit having its own voltage rating for insulation coordination.
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Electrification System: All parts of the OCS as well as any supplementary conductors, components,
supports and wayside equipment which make up a fully operational electrified transit system.
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Grounded: Electrical section intentionally connected to earth that is not interrupted.
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Insulated: All components isolated from the energized parts by at least one level of insulation.
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Nominal Voltage: Value assigned to a circuit or system approximately equivalent to the working voltage
for designating the voltage class.
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Over Voltage: Voltage having a peak value exceeding the maximum steady state voltage at normal
operating conditions.
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Rated Voltage: Value of voltage assigned to a component, device or piece of equipment.
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Rated Impulse Voltage: Value of voltage assigned to the equipment referring to the specified withstand
capability of the insulation against transient over voltages.
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Rated Insulation Voltage: RMS withstand voltage assigned to the equipment referring to the specified
permanent (over five minutes) withstand capability of the insulation between energized components and
earth.
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Overhead Contact System (OCS): Contact wire or wires and any supporting messenger wire electrically
in parallel and their supporting components.{check dictionary}
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Supplementary Cable: Cable connected in parallel with OCS is called positive supplementary cable.
Cable connected in parallel with running rail is called negative supplementary cable.
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Grounding Switch: An electrical switch typically between an OCS conductor and a ground rod, to enable
the conductor to be grounded for safety when de-energized.
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3.2 Abbreviations and Acronyms
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AC
Alternating Current
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ANSI
American National Standards Institute
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AREMA
American Railway Engineering and Maintenance of way Association
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ASTM
American Society for Testing and Materials
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AWG
American Wire Gauge
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DC
Direct Current
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ETB
Electrified Trolley Bus
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FRA
Federal Railroad Administration
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IEEE P2406/D02, January 2014
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FAT
Factory Acceptance Testing
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ICLP
International Conference on Lightning Protection
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IEC
International Electrotechincal Commission
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IEEE
Institute of Electrical and Electronics Engineers
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ISO
International Organization for Standards
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Hi-Pot
High Potential
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LRV
Light Rail Vehicle
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NEC
National Electrical Code (NFPA-70)
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NEMA
National Electrical Manufacturers Association
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NESC
National Electrical Safety Code
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NETA
National Electrical Testing Association
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NFPA
National Fire Protection Association
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OCS
Overhead Contact System
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OEM
Original Equipment Manufacturer
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OSHA
Occupational Safety and Health Administration
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PLC
Programmable Logic Controller
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RMS
Root Mean Square
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ROW
Right-of-way
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SCADA
Supervisory Control and Data Acquisition
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TES
Traction Electrification System
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UBC
Uniform Building Code
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UL
Underwriters Laboratories
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USASI
United States of America Standards Institute
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Copyright © 2010 IEEE. All rights reserved.
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IEEE P2406/D02, January 2014
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4. Application Considerations
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4.1 Scope of Applications
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This section provides an overview of DC non-load break disconnect switches as they pertain to traction
power systems including third rail and overhead contact systems. This Standard covers typical switch
ratings, configurations, driving mechanisms, and enclosure requirements
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4.2 General
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This Standard covers non-load break switches.
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Disconnect switches shall be applied within their assigned maximum voltage rating, continuous current
rating, and any other applicable rating as required in a given system. Disconnect switches can provide
circuit isolation between a power source and a load. Disconnect switches can also provide circuit
sectionalizing as a tie switch. Disconnect switches can also provide a means to bypass circuits. Interlocks
and safety precautions shall be implemented to never open a disconnect switch under load.
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When closed, disconnect switches shall provide a very low resistance path across their contacts. When
fully open, the disconnect switch shall break the circuit without the potential for arcing across the open
contacts or blades.
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Where possible, the load side of the switch shall be connected to the opening blades or contacts of the
disconnect switch, or hinge side of the switch. The bus or line side of the switch shall be connected to the
jaw side of the switch. This will keep the bulk of the disconnect switch de-energized when open, and all
dangerous potentials will only be present on the jaw terminal.
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Interlocks and safety precautions shall be implemented to prevent personnel exposure to voltage potentials.
Signage and warning labels shall be clearly visible to the public and always followed or obeyed by any
operators or maintenance personnel.
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5. Types of DC Disconnect Switches
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5.1 Switch Configurations
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Switch configurations are defined by the number of poles and number of throws.
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Each pole is capable of connecting and disconnecting a single circuit. Multiple poles can be ganged to
connect or disconnect multiple circuits with a single operating mechanism.
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The number of throws is the amount of positions a switch can have. Typically a disconnect switch used for
circuit isolation has only one throw, thus is called a Single Throw Switch. A switch that can switch from
two positions would be designated a Double Throw Switch. In addition a transfer switch is considered a
double throw because it connects a load to two sources, but it shall have a center “off” or “isolation”
position. That position is not considered a throw. Figures 1 and 2 show several switch configurations for
reference. Figure 1 shows Single Pole Double Throw and Figure 2 shows Single Pole Single Throw.
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IEEE P2406/D02, January 2014
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5.2 Switch Styles
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Two main switch styles exist: the Knife Type and Bolted Pressure Type.
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5.2.1 Knife Switch
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There are two types of knife switch considered in this standard: the basic knife switch, and the silver insert
switch.
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5.2.1.1 Basic Knife Switch
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The switch consists of two parallel contact jaws with a moving connection blade or “Knife” to complete the
circuit. Knife switches can be designed per the end user’s needs to include multiple throws or poles.
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Contact pressure is applied through spring force of the contact jaws and connection blade. Figure 1 shows
a basic single pole, double throw knife switch.
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Figure 1 — Single Pole, Double Throw Knife Switch
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5.2.1.2 Silver Insert Switch
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This switch type has similar construction to the basic knife type switch with the addition of silver inserts or
buttons. These silver surfaces allows for a higher current carrying capacity. Enough silver contact surfaces
shall be provided to pass micro ohms and heat rise tests per section 12. Pressure shall be provided by
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spring washers on either side of the blades on both Jaw and Hinge sides of switch. See figure 2 for basic
components of a single pole single throw silver tip insert switch.
Figure 2 — Single Pole, Single Throw Silver Insert Switch
5
5.2.2 Bolted Pressure Switch
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This switch consists of two parallel movable blades with stationary contacts at each end. The blades rotate
about a fixed hinge terminal and close into a jaw terminal. The jaw side and the hinge side of the switch
have a bolt assembly which threads into a fixed nut assembly. See Figure 3.
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Figure 3 — Bolted Pressure Switch Construction
The assembly has a double acting feature. When the switch closes, a lock strap assembly forces the nut to
tighten into the bolt which provides the contact pressure. The hinge side bolt assembly and jaw side bolt
assembly tighten as the switch closes. Conversely, as the switch opens, the first action is the jaw and hinge
side bolts rotating to loosen the blades, and then the second action is the switch opening. See Figures 4 and
5 for double action details.
Figure 4 — Bolted Pressure Switch Opening, Action 1
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The result is a connection with current carrying capacity similar to bolted bus bar. All contact surfaces
must be silver plated.
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6. Interlock Considerations
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The interlocking of the switch is done to prevent inadvertent or unsafe operation. The two main types of
interlocks are mechanical and electrical.
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6.1 Mechanical Interlocks
Figure 5 — Bolted Pressure Switch Opening, Action 2
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10
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The simplest form of mechanical interlock is the padlock. Provisions must be supplied on the switch
assembly to apply a padlock to either lock the switch open or closed. This requirement supports local
authority lockout/tag out procedures.
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The next type of mechanical interlock is the Key Interlock. Special types of key interlocks are installed on
the switch assembly. Locking mechanisms present on multiple switches require a single key for operation.
This prevents simultaneous operation of both switches. The nature of the key interlock is to ensure a
specific sequence of events takes place when opening or closing the switch assembly. Again provisions
must be supplied to either lock the switch closed or open depending upon the sequence of events desired.
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Another type of mechanical interlock restricts access to the switch in an enclosed switch assembly with the
disconnect closed. A mechanical block rotates with the disconnect handle. When the switch is fully
closed, this block prevents the opening of the enclosure door to restrict personnel access with the switch
closed and therefore the majority of the internal bus and switch components energized.
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Mechanical interlocks outside the scope of the switch are not specifically covered in this Standard.
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6.2 Electrical Interlocks
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Electrical interlocks are typically solenoid driven mechanical locking mechanisms. The solenoid receives a
signal from an external source to either energize or de-energize. The switch can be toggled to the opposite
state upon the solenoid action depending on the design of the interlock.
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The switch position can drive auxiliary contacts which can be interlocked with other electrical systems. The
auxiliary contact can also be used for SCADA inputs for indication and control. In motor operated
disconnects, an electrical interlock can be as simple as a normally open contact from a relay or limit switch
controlled by another device which must be satisfied to operate the switch.
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Electrical interlocks outside the scope of the switch are not specifically covered in this Standard.
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7. Switch Operation Types
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7.1 Manually Operated
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A manually operated switch is actuated by manual interaction by an operator. These switches include hook
stick, side mounted handle, front mounted handle, or pole mounted handles. Standard convention is when
the handle is raised, the switch is closed. When the handle is lowered, the switch is open. Handle must be
fully insulated from energized bus conductors and meet dielectric withstand requirements of section 12.
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Switches may be operated by handle directly mounted to blades of switch. Handle must be sufficiently
insulated from energized parts of switch to meet dielectric withstand requirements of section 12.
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Switches may be operated by hookstick with an eyehook fixed directly to switch actuator. The operating
bar or stick from handle to hook must be insulated and meet dielectric withstand requirements of section
12.
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Switches may be operated through pole or rod driven linkages. The final linkage must be non conductive
material insulated from the operating handle to the energized parts of the switch. This must meet dielectric
withstand requirements of section 12.
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Enclosed switches may be operated by linked handles mounted to exterior of enclosure. This handle can be
mounted to the front or side of switch assembly enclosure. The handle must be sufficiently insulated from
all energized parts of the switch as to meet dielectric withstand requirements of section 12.
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7.2 Motor Operated
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A motor operated switch is actuated by a motor or drive mechanism linked with the switch operator. The
motors are typically fractional horsepower in rating. Motor operating voltages are typically 120VAC-Single
Phase-50/60Hz or 125VDC. Available control power configurations may depend on the needs of the
system owner. These switches shall be manufactured with mechanical operator handles such that they can
be cycled with no control power. When mechanically operated, the motor operated switch shall be either
de-coupled from the motor, or control power shall be secured. This is due to manual cycling causing the
rotor of the motor to spin causing a generated voltage. Essentially, this reverse powers the motor as a small
generator. This can cause damage to the circuit.
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Limit switches shall be used to turn off the motor when fully cycled to desired position. Control power
circuit shall be fused or protected by thermal cutout in case of limit switch or other failure thus preventing
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an uncontrolled continuous operation of the motor. If the motor tends to over travel, dynamic braking
circuits shall be used to ensure disconnect stays in intended position when limit switch cuts power to motor.
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Motor Operated switches may sometimes have load breaking abilities. Load break disconnect switches are
not covered by this standard.
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8. Mounting and Enclosure Types
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Open style switch units can be supplied for either indoor or outdoor application. The specific requirement is
decided upon by the system owner. Indoor switch operations are typically installed in larger enclosures
with additional equipment. Outdoor switch considerations include the climate, environment, installation
location, and type of operation. NOTE— Motor operated switch units are usually supplied with enclosures
for outdoor mounting.
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8.1 Open Style
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Open style switches can be pole mounted or wall mounted. The operation is either from a hook stick or
ground level linkage. Outdoor linkages are usually made from steel and are galvanized for corrosion
protection. The ground level linkage must be insulated from the switch. The operating handle, linkages,
and switch assembly shall be adequately designed for site location.
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8.2 Enclosed Style
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Enclosed style switches can be pole mounted, pad mounted, or wall mounted. Disconnect switches are
enclosed to protect the switch assembly from the elements and to protect personnel from exposure to the
energized circuit components.
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The enclosed switch units can be mounted indoors or outdoors. The enclosure rating guidelines shall follow
NEMA (NEMA 250, Enclosure Types) or IEC (IEC Publication 60529 - Classification of Degrees of
Protection Provided by Enclosures) ratings.
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The enclosure material is an additional consideration. Enclosures can be supplied in Steel, Stainless Steel,
Aluminum, or Fiberglass. Each style of enclosure must be reviewed for the specific location and grounding
considerations.
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The size of the disconnect enclosure shall take into consideration termination access, direction, and type of
conductors entering the enclosure. It shall also allow the switch to meet heat rise considerations per section
9.4 and heat rise testing requirements of section 12. Auxiliary equipment shall also be considered for
enclosure sizing. Cable bending space can be determined by NEC (NEC Article 320.24) practices and
guidelines.
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9. Disconnect Switch Ratings
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9.1 Insulating Rating
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DC disconnect switches shall be sufficiently insulated from bus potential to other potentials, dead metal,
grounds, and negative returns. The rating is determined by end user specifications and is met by the
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manufacturer per testing section 12. Creepage distance, air gap distance, and other design criteria
associated with insulation requirements are not specifically detailed in this Standard. Rather, they shall be
designed by switch manufacturers to meet or exceed high potential testing per testing section 12.
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All metal extending outside of enclosure or exposed on open type disconnects shall be insulated from
energized bus based on rated voltage of the switch. Energized bus shall also be sufficiently insulated from
other bus potentials, control power potentials, grounded metal or bus, negative returns, or opposite pole of
switch in fully open position. Based on rated voltage of switch, dielectric withstand testing from bus to
these other potentials shall be completed in accordance with testing section 12.
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9.2 Current Rating
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The current rating of DC disconnect switches must be rated to sufficiently supply the load without
exceeding heat rise limitations per section 9.4. End user specifications determine the minimum current
requirement of the disconnect switch. Current density of copper must be considered in the design of the
switch. Number of poles, size of copper poles, size of pads for lugs or bus bar shall be sufficiently sized to
meet or exceed end user specified current rating. Micro-ohms testing in accordance with section 12 shall
be used as an indication of closed switch pressure. Manufacturers shall construct disconnects such that
they carry rated current in fully closed position indefinitely without generating excess heat, or causing
surface defects such as spot welding, galling, or pitting. Switches can also be subject to over current testing
as outlined in section 12.
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9.3 Short Circuit Rating
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Disconnect switches shall be manufactured to withstand short circuit conditions without opening.
Recommended typical fault current values shall not be less than 100 kA asymmetrical and typical fault
current duration is 15ms.
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9.4 Heat Rise Limitations for Traction Power Switches
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Disconnects shall be manufactured to meet heat rise limitations of testing in section 12. When closed, there
will be a resistance developed across the contact surfaces from hinge to blades and from the blades to the
jaw. Heat will develop across the contact resistances proportional to the resistance and to the current
squared. Heat rise limitations set parameters for how much heat shall be generated by steady state rated
current across a switch in a controlled environment.
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Heat Rise Limitation considerations:
30
See testing requirements for heat rise limitation testing in section 12.
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For bolted pressure switches:
32
Temperature Rise shall not exceed 50°C rise over a maximum ambient temperature of 40°C.
33
For silver insert switches:
34
Temperature Rise shall not exceed 50°C rise over a maximum ambient temperature of 40°C.
35
For basic clip type knife switches:
12
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The use of these switches in systems rated 600A and higher is not recommended due to low contact
pressure. Heat Rise limitations for these disconnects shall meet the Standards of ANSI/UL363.
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9.5 Aux Contact Ratings
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Auxiliary contacts are mainly defined by the number of contacts provided, their current and voltage rating,
and by their characteristics, (i.e.: N.O., N.C., or SPDT). The ratings must meet the minimum requirements
of the circuit in which they are installed. Interposing relays shall be used when auxiliary load currents are
higher than the auxiliary contact rating.
8
The end user shall specify the minimum number of auxiliary contacts required.
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Auxiliary contacts and the circuits which they are installed must be sufficiently insulated from high voltage
potentials present within the switch assembly.
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10. Cable Termination Considerations
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DC Disconnect switches shall be designed to accept cable terminations. Sufficient surface area shall be
supplied to meet the minimum current rating of the switch. The mounting pad must be silver plated. The
mounting pad must be located such that it does not impede the operation of the switch. All potentials which
connect to this pad shall meet insulation ratings per section 9.1, and testing considerations in section 12.
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11. Fuse Considerations
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When specified, DC disconnects shall be designed to accept fuses. Fuse blocks must be provided to accept
specified fuses based on end user requirements. Fuse blocks must meet current and voltage ratings of the
switch. The location of the fuse block and fuse must not interfere with operation of the switch. Any
exposed high voltage potentials must meet insulation ratings per section 9.1, and testing considerations in
section 12.
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Fuse ratings are beyond the scope of this Standard. For specific fuse specifications, refer to the following:
23
IEEE Std C37.40-2003: Service Conditions and Definitions for High Voltage Fuses
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IEEE Std C37.41-2008: Design Tests for High Voltage (>1000v) Fuses
25
12. Testing Considerations
26
12.1 Specifications and Applicable Standards
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The equipment shall be product design tested by an accredited third party testing laboratory to qualify it as
conforming to the Job Contract Specifications.
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In addition to the contract specifications issued, testing shall be in accordance with the applicable sections
of the latest edition of this standard.
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Where a conflict arises between the references and the customer issued specifications, the differences shall
be brought to the attention of the customer and mutually agreed upon with the O.E.M. The following
standards are the basis for this section:
a)
IEC 61992-1 Railway Applications - Fixed Installations - DC Switchgear General
b)
IEC 61992-3 Railway Applications - Fixed Installations - DC Switchgear - Indoor DC
Disconnectors, Switch - Disconnectors, and Earthing Switches.
c)
IEC 61992-4 Railway Applications - Fixed Installations - DC Switchgear - Outdoor DC
Disconnectors, Switch - Disconnectors, and Earthing Switches.
12.2 Design Tests
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Design testing is required to ensure that the equipment will perform in a satisfactory manner based on the
loading criteria specified for both voltage and current.
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It must demonstrate that the assembly is free from design defects and is adequate for its intended
application. It must also demonstrate that it meets the expected “life cycle” - both for “total” number of
open / close cycles. Switch shall be cycled a minimum of 200 times for lifetime test. The tested switch
shall meet the requirements of factory acceptance testing in section 12.3 after endurance test is completed.
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NOTE— This is NOT intended to mean that a “test-to-failure” test is required.
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Section 12.3 covers factory acceptance testing.
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A complete set of Design Tests will be required on one (1) switch of the exact type. The results of design
tests shall be kept on file and be available upon request by end user.
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The customer may reserve the option to waive the requirement of DESIGN TESTING if one of the
following applies: (i) a certified test report for a switch substantially of the same design and rating or (ii)
end user has equipment of identical or near identical type and rating.
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The following are the recommended minimum tests needed in addition to lifetime test:
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a)
temperature rise
b)
short circuit/short time withstand
c)
dielectric withstand
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All shall be determined in accordance with the latest applicable sections of IEC standards as referenced in
section 12.1. Temperature Rise shall meet the ratings section of Section 9.4 of this Standard as well as the
considerations of section 12.2.1.
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12.2.1 Heat Rise Test Considerations
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Ambient temperature – the ambient temperature is considered a baseline temperature from which the heat
rise of the current carrying switch is compared. This shall be maintained during any heat rise test as a
control. Ambient temperature will affect the overall temperature of the switch, so it must be as constant as
possible to remove it as a variable. The ambient temperature is defined as the average temperature of the
cooling air adjacent to the switch parts. When the switch is inside an enclosure, ambient shall be measured
outside the enclosure approximately 305 mm (12 inches) away from external surface of enclosure.
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Switch Type – Silver insert, conventional knife switch, and bolted pressure switches all have different
contact surfaces and pressures and will generate a different heat rise due to this fact.
3
Current Applied – Current applied shall be nominal expected current level for the system.
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Length of test – The length of the test does not have to be quantified in terms of time. When temperatures
have stabilized for four consecutive tests of a sample size no less than 15 minutes (1 hour total), the intent
of the test is met. Stabilization shall be considered consecutive temperatures with no change greater than
1°C. Duration of the test shall be defined as reaching this steady state condition and not a set time.
8
Limits – Heat rise limits are defined in Heat Rise Limitation Ratings Section 9.4.
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Refer to IEEE Std. C37.34-1994, Sections 6.4 through 6.6 for temperature taking methodology.
10
12.2.2 Design Test Witnessing and Final Inspection
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All laboratory DESIGN tests shall be witnessed by both O.E.M and the End User (or their authorized
representative) if not completed by an accredited independent testing laboratory. Additional parties may
also be invited such as Consulting Engineer or Accreditation association representative. Witness testing
may be waived in part or its entirety by either of the primary affected parties.
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Final Inspection: This section describes the actions to be taken by lab technician and/or witness personnel
to ensure that the equipment was tested per the outlined requirements:
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After testing is complete, operate switch to “open” and “closed” positions.
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Compare and note in report any difference/degradation in the ‘before’ and ‘after’ conditions.
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Physically examine all visible parts to check for damage. This applies to the switch and the
enclosure plus accessories provided.
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Verify that all required tests have been performed.
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Complete certified or witnessed test report for manufacturer’s records
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12.3 Factory Acceptance Testing
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12.3.1 Contract Specifications and Standards
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The equipment shall be manufactured in accordance with the issued Job Contract Specifications and any
Contract Drawings issued to be used by the O.E.M vendor.
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In addition to the contract specifications issued, equipment shall be manufactured in accordance with
guidelines of this Standard. Proposed testing is based on the following Standards:
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a)
IEC 61992-1 Railway Applications - Fixed Installations - DC Switchgear General
b)
IEC 61992-3 Railway Applications - Fixed Installations - DC Switchgear - Indoor DC
Disconnectors, Switch - Disconnectors, and Earthing Switches.
c)
IEC 61992-4 Railway Applications - Fixed Installations - DC Switchgear - Outdoor DC
Disconnectors, Switch - Disconnectors, and Earthing Switches.
15
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12.3.2 Typical Factory Tests
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12.3.2.1 Mechanical Operation
3
A mechanical operation test shall consist of the following:
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
Fully Open disconnect.
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Fully Close disconnect
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Verify there are no signs of binding, galling, uneven wear or other physical tolerance issues.
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Verify blade alignment evenly makes on either side of jaw terminal.
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All mechanical linkages for manual operating handle assemblies shall move freely and not hinder
operation of disconnect.
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This test is required to ensure that the assembled switch does not have any production defect or major
misalignment. Disconnect shall be cycled no less than 10 times. This test shall be completed at room
temperature (10°C to 32.2°C or 50°F to 90°F).
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For those units that are electrically operated, they must also be operated manually during factory testing to
ensure it is possible to change switch position when control power is lost.
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12.3.2.2 Dielectric Withstand Test
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This test is sometimes referred to as “high potential” test. Apply the stated voltage per the contract
specification for a period of one (1) minute. Refer to the applicable sections of IEC 61992-3 and 61992-4.
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Voltage level of high potential or dielectric withstand test shall depend on rated voltage of the switch.
Rated voltage is specified by end user. Test shall consist of applying high potential to test points listed
below for a duration no less than 1 minute. Voltage level shall be no less than twice rated voltage plus
1000V. Voltage must be DC. Satisfactory testing will indicate no breakdown current for the duration of
the test.
23
At a minimum, each switch is subject to testing as follows:
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With switch “closed”, across switch and operator shaft.
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
With switch “closed”, across switch and base mounting bolts or other metal exposed to exterior of
enclosure.
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
With switch “open”, across ‘jaw’ and ‘hinge’ sides. If multiple switch modules operate as a single
device (example: two pole), test each module separately.
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CAUTION
Voltage presence detection circuits shall be disconnected from circuit before high potential testing to avoid
false leakage indication or damage to these circuits.
NOTE— Power Frequency tests are not applicable to high voltage DC switches. These tests are designed to
stress insulation under AC conditions at or near rated frequency. The proper test for insulation withstand in
DC Switches is covered under the previous section, Dielectric Withstand Test.
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12.3.2.3 Electric Resistance of Current Path
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The function of this test is to demonstrate that there is a minimum resistance to current flow across the
conducting parts of the disconnect switch.
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Since current path resistance is a function of several factors such as number of “clamped” joints, cross
sectional area, material quality, etc, the expected value shall be stated by the O.E.M. With the switch
“closed”, apply test probes to the ends of ‘jaw’ and ‘hinge” contacts. Take a reading of resistance on the
order of uOhms. This reading shall meet or exceed design test reading for the same or similar type of
switch.
9
12.3.2.4 Motorized (Electric) Switch Operation
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There are several types of drive mechanisms that are used to operate disconnect switches. These include
units operated by (a) geared electric motor, (b) electric motor driven linear actuator, (c) chain drive electric
motor, and (d) other type. Operating voltages are specified by end user.
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Fully cycle switch electrically no less than 5 times. Use pushbuttons if provided locally. Switch shall be
set up to simulate remote operation if applicable. Electrical interlocks, and other circuit features specific to
each switch design shall also be tested to operate satisfactorily.
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12.3.2.5 Final Inspection
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This section describes the actions to be taken by QC inspector to ensure that the equipment conforms to the
order requirements. In addition to the previous Factory Acceptance Tests, check the following:
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
Cosmetic flaws – both internal and external
20

All bolting is torqued to proper values
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
Nameplate data meets requirements of section XX
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
Apply all QC tags for customer information
23
12.4 Witness Testing
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Manufacturer shall notify Customer Representative at a minimum of two (2) weeks in advance for witness
testing. Witness testing shall consist of factory acceptance testing as outlined in section 12.3 with customer
representatives or approved third party present. Witness testing can be waived in part or whole by end
user.
28
12.5 Documentation and Submittals
29
12.5.1 Design Test Documentation and Submittals
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Manufacturer shall produce a document that outlines all the testing that shall be performed at the third party
laboratory to satisfy the DESIGN TEST requirements of the customer / end user specifications. Changes
and revisions are permitted at any time so long as agreement has been reached prior to actual testing.
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The document shall cover all testing as specified in section 12.1. The test report shall include scope of
testing, a set of completed data sheets, description and calibration records of test equipment, and
photographs of the test set-up. It shall also include the date each test was performed.
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6
The contract specification and or purchase order may specify that the Design Testing document must be
submitted for customer approval prior to the start of the test. In such cases, the document shall be submitted
no less than twenty (20) working days prior to the anticipated test start date.
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Laboratory shall issue one (1) paper copy and one (1) electronic copy of the complete and final Test
Report. This shall happen no less than two weeks after completion of all testing. Time schedule may be
modified as mutually agreed upon. All test reports shall be signed by qualified test engineer and any
witnesses present.
11
12.5.2 Factory Acceptance Testing Documentation and Submittals
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14
Manufacturer shall produce a document that outlines all the testing that shall be done to meet contract
specifications for disconnect switches. The document shall include testing procedures as outlined in section
12.3.
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In addition to the test reports, manufacturer shall maintain a completed set of documentation to ensure the
proper testing of disconnect switches has been met. Switches shall be serialized with a unique number
which can be referenced in this QC archive.
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The contract specification and or purchase order may specify that the FAT document must be submitted for
customer approval prior to the start of the test. Upon completion of testing, contract specification and or
purchase order may specify time table for submitting completed FAT reports.
21
12.5.3 Certificate of Compliance Testing Documentation and Submittals
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24
Certificate of Compliance shall be a document signed by the Manufacturer certifying that products comply
with the outlined equipment requirements and performance. When required, this shall serve as a “blanket”
document and cover all quantities produced of this exact type.
25
13. Grounding Considerations
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Disconnects may be grounded in the fully open position to shunt the load side circuit to ground. This
dissipates stray currents and any capacitive or induced potential on the load side of the circuit to ground.
This is typically used as a safety measure to protect personnel from exposure to such dangerous potentials.
Any exposed Earth ground terminals or bus must meet the dielectric withstand test requirements of section
12.
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35
The presence of grounds or negative returns within switch enclosures increases the risk of flash over from
high voltage to these dangerous return paths under extreme fault conditions. However, it is acceptable to
have ground and negative return potentials in switch enclosures when properly insulated. It is up to the
discretion of the end user to determine if grounds or negative returns are allowed in the switch enclosure.
Negative Return potentials must meet the dielectric withstand test requirements of section 12.
36
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Metal enclosures, metal conduit, and un-insulated switch handles on nonmetallic enclosures may be earth
grounded. Earth grounding shall be left up to the discretion of the end user. Any exposed Earth ground
terminals or bus must meet the dielectric withstand test requirements of section 12.
18
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14. SCADA Interface Considerations
2
For SCADA system design, construction, and field implementation, refer to the followings standards:
3

IEEE P1901-2010 - PLC Standard
4

IEEE PC37.1/D1.9 Draft Standard for SCADA and Automation Systems
5
6

National Communications System Technical Information Bulletin 04-1, October 2004: SCADA
Systems
7
8
Supervisory Control and Data Acquisition (SCADA) systems are used for remote monitoring and control of
traction power and OCS systems, including non-load break direct current disconnect switches.
9
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11
For DC disconnect switches, SCADA accommodations include terminal boards or connections to I/O
devices or remote terminal units (RTU). When specified by end user, the following connection points to
SCADA shall be provided by OEM:
12

Switch position: OPEN or CLOSED
13

Voltage or current sensing relays: OPEN or CLOSED
14
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
Voltage, Current, Power Metering: Analog signal representative of sensed value. Specified by end
user as 4-20mA or 0-5VDC.
16

Emergency Trip System, Interlock, or alarming conditions as specified by end user.
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
For active inputs to SCADA I/O drops, voltage and current ratings must be specified by the end
user for integration between the SCADA system and disconnect switch monitoring or indicating
devices.
SCADA is also used to control operation of switches and relays remotely. These connection points shall
align power to motor coils, relay coils, or whatever load that SCADA is to control. Typical configuration is
a normally open contact controlled by SCADA’s remote terminal unit which is opened or closed remotely.
The following can be controlled by SCADA:
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
Indicating lights, beacons, or horns.
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
Emergency trip signals.
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
Close or open signals on motor operated switches
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
Any other application that can be energized through a dry contact as specified by end user.
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15. Signage and Labeling
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Signs must be used to identify electrical shock hazards to both equipment and personnel. The following is
considered the minimum requirement for enclosures that encase DC voltages:
Voltages:
<30VDC
30VDC-1000VDC
>1000VDC
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High Voltage signs
N/A
2
2
Arc Flash Signs*
N/A
2
2 and 3**
General Warning Signs:
1
1
1
Table 1 —Voltage Designation and Sign Requirements
* - Arc flash signs are only required when requested specifically by end user.
19
Copyright © 2010 IEEE. All rights reserved.
This is an unapproved IEEE Standards Draft, subject to change.
IEEE P2406/D02, January 2014
1
2
** - Required to include Arc Flash survey statistics in accordance with Section 16; Arc Flash
Considerations
3
15.1 General Warning Signs
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5
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In systems where voltage is <30V, it is recommended that any access cover or door to enclosure or
boundary that includes voltage potentials have an “ELECTRICAL SHOCK HAZARD” warning sign.
“WARNING”, “CAUTION”, or “DANGER” shall be included with lettering or background in RED,
ORANGE, or YELLOW coloring. In systems where voltage is ≥30VDC, the intent of General Warning
Signs is met by the required High Voltage Signs.
9
15.2 High Voltage Signs
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15
At a minimum, a warning sign must be on any access cover or door to any enclosure or boundary in which
high voltage dc is contained. The background or lettering must be red, orange, or yellow in color. The
following text must be included:
a)
"HIGH VOLTAGE" OR "####V", where #### is the actual voltage present
b)
"DANGER" or "WARNING" in red, orange, or yellow letters or background.
c)
For example, see figure 6:
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Figure 6 — Danger High Voltage Sign
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15.3 Arc Flash Signs
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When required by end user, within an enclosure or near exposed DC voltage potentials, an ARC FLASH
sing shall be provided. All arc flash considerations for DC traction power switchgear and OCS components
are restricted to the guidelines of IEEE 1584 and NFPA 70E-2012.
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15.4 Non-Load Break Signs
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A sign shall be provided on the enclosure either centered on access panel/door, near operating controls or
lever, or at eye level which clearly states EITHER of the following:
20
Copyright © 2010 IEEE. All rights reserved.
This is an unapproved IEEE Standards Draft, subject to change.
IEEE P2406/D02, January 2014
1
2

“DO NOT OPERATE UNDER LOAD” If it is a non-load break switch that is rated to open or
close while the bus is energized, but not break any load current
3
4

“DO NOT OPERATE WHILE ENERGIZED” If it is a non-load break and is not rated to open or
close with rated voltage applied, with or without load current.
5
15.5 General Sign Information
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In DC systems, circuit isolating components such as circuit breakers, disconnect switches, and/or fuses
shall be labeled with unique identifying designations. These designations shall meet the following
requirements:
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14
15
16
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a)
They shall be clearly marked, where label is visible after installation
b)
They shall be unique, and not repeat with any other designation within the same electrical system.
c)
They shall correspond to system one line electrical schematics.
Manufacturer information shall be included on all Disconnect switch assemblies or enclosures. The
following information shall be included: (See figure 1 for example)
a)
Manufacturer’s name.
b)
Manufacturer’s address to include city and state at a minimum.
c)
Component or component’s catalog designation or equivalent part number or assembly number
d)
Electrical Ratings to include the following at a minimum:
e)
1)
Rated Voltage
2)
Rated Current
3)
Alternating or Direct Current
Date of manufacturer
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If multiple components are enclosed, include all ratings if they differ from listed ratings on manufacturer’s
label. For fuses, include number of fuses, type of fuse, fuse ratings, and any applicable information for fuse
replacement. Fuse information may be located on the inside of the enclosure near the fuse itself, but at a
minimum must be located in O&M manual and in the one line diagram drawings.
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16. Arc Flash Considerations
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Manufacturers must provide Arc Flash signage and labeling in accordance with Section 15 when it is
required by the customer. If specific DC arc flash requirements have not been approved in IEEE 1584 or
NFPA 70E-2012, then the guidelines for AC arc flash labels and maintenance procedures must be followed
in accordance with IEEE 1584, with the exceptions noted in the following document:
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33
34

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 5, SEP./OCT. 2010:
DC-Arc Models and Incident-Energy Calculations
OEM is not responsible for Arc Flash studies, or content of Arc Flash signs. These must be provided by
end user.
21
Copyright © 2010 IEEE. All rights reserved.
This is an unapproved IEEE Standards Draft, subject to change.
IEEE P2406/D02, January 2014
1
17. Installation Considerations
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3
4
Guidance shall be provided by manufacturers to contracting entities on installation process. The
installation instructions shall consider setting up the disconnect switches for long operational lifetime, ease
of operation, and the safety of those installing the switch.
5
Installation instructions shall be provided to prevent:
6

Improper setup
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
Binding or excessively tight operation
8

Irregular operation of the switch
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
Any considerations which would cause damage to switch, or shorten operational lifetime of switch
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14
Provisions shall be provided to transport, move, and install enclosures or switches.
CAUTION
Under no circumstance shall the switch itself or any part of the switch’s energized parts to be used as an
anchoring point for other installation considerations such as pulling cable, aligning other switches, or
moving the switch. The base, support structure, or enclosure may be used if approved by manufacturer.
15
18. Maintenance Considerations
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DC switching component manufacturers and OCS traction power component manufacturers shall generate
maintenance manuals or packages which will include at a minimum:
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
Maintenance Precautions specific to component
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
Recommended Maintenance Procedures
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
Recommended Maintenance Schedule
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
All applicable drawings, instructions, and procedures to complete maintenance
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Maintenance proposals shall be made to allow for safe operation of DC traction power and OCS
components. They shall extend the life of any component such that it won’t degrade and cause material
failure, electrical fires, damage to equipment, or injury to personnel. Actual component lifetime is subject
to the specific component and is not governed by this document.
22
Copyright © 2010 IEEE. All rights reserved.
This is an unapproved IEEE Standards Draft, subject to change.