GP 16-12-01 - Switchgear, Control Centers, And Bus Duct (Version 3.0.0, JAN 2006, Except DIOL 3.0.0...

GP 16-12-01 Switchgear, Control Centers, and Bus Duct January 2006

Switchgear, Control Centers, and Bus Duct

GP 16-12-01

Scope1) [I] This Global Practice (GP) covers low and medium voltage switchgear, control centers, and bus

duct, including relaying for motor branch circuits. 2) [I] An asterisk (*) indicates that a decision by Purchaser is required or that additional information is

furnished by Purchaser.3) * [I] The following are not established in this Practice and must always be specified separately:

a) Type of switching device for medium voltage control center.b) Type of circuit breaker for medium voltage switchgear.c) Relaying for other than motor branch circuits.

RFCH For ExxonMobil Use Only Version 3.0.0

of 35 ExxonMobil Development Company


Table of Contents

1. Required References1.1. Global Practices–ExxonMobil Engineering Practices1.2. ExxonMobil Data Sheets1.3. IEC–International Electrotechnical Commission1.4. IEEE–Institute of Electrical and Electronics Engineers1.5. NEMA–National Electrical Manufacturers Association1.6. UL–Underwriters Laboratories, Inc.

2. Definitions3. Documentation4. Switchgear and Control Center Construction Practices5. Switchgear

5.1. Low-Voltage Switchgear5.2. Medium-Voltage Switchgear5.3. Switchgear Control Power (LV and MV)

6. Control Centers6.1. Low-Voltage Control Centers6.2. Medium-Voltage Control Centers

7. Control and Protective Relaying of Motor Circuits7.1. Control Switches for Motor Controllers7.2. Reacceleration Control7.3. Protective Relaying7.4. Protective Relaying for MV Motors7.5. Protective Relaying for LV Breaker-Controlled Motors7.6. Remote Metering7.7. Motor Space Heater Control7.8. Motor Off Alarms

8. Space Heaters9. Bus Duct10. Inspection and Testing




10.1. Inspection10.2. Testing

Record of ChangeAttachment: Purpose Codes Definitions




1. Required ReferencesThis Section lists Specifications and Standards that are generically referenced and assumed to be a part of this document. Unless otherwise specified herein, use the latest edition.[I] Purchase and use of equipment covered by this Practice shall conform to nationally recognized codes and standards which are approved by Owner's Engineer and which are acceptable within the country where the equipment will be used. Sections 1.4 through 1.6 list specifications and standards which shall be applied for equipment purchased to U.S. standards. Section 1.3 lists specifications and standards for IEC purchased equipment.

1.1. Global Practices–ExxonMobil Engineering Practices

GP 16-01-03 Protection of Electrical Equipment in Contaminated Environments

GP 16-04-01 Grounding and Overvoltage Protection

1.2. ExxonMobil Data Sheets

ExxonMobil Data Sheets

Data Sheet Home Page

D161201C01 Documentation Requirements Sheet - Switchgear, Control Centers, and Bus Duct

I161201C01 Inspection and Testing Requirements - Switchgear, Control Centers, and Bus Duct

T161201C01 Technical Data Sheet - Low Voltage Switchgear - Customary Units

T161201C02 Technical Data Sheet - Metal Enclosed Bus - Customary Units

T161201C03 Technical Data Sheet - Medium Voltage Switchgear - Customary Units

T161201C04 Technical Data Sheet - Low Voltage Motor Control Centers - Customary Units

T161201C05 Technical Data Sheet - Medium Voltage Motor Control Centers - Customary Units

T161201M01 Technical Data Sheet - Low Voltage Switchgear - Metric Units

T161201M02 Technical Data Sheet - Metal Enclosed Bus - Metric Units

T161201M03 Technical Data Sheet - Medium Voltage Switchgear - Metric Units




T161201M04 Technical Data Sheet - Low Voltage Motor Control Centers - Metric Units

T161201M05 Technical Data Sheet - Medium Voltage Motor Control Centers - Metric Units

1.3. IEC–International Electrotechnical Commission

IEC 60439-1 Low-Voltage Switchgear and Controlgear Assemblies - Part 1: Type-Tested and Partially Type-Tested Assemblies

IEC 62271-200 High-voltage switchgear and controlgear - Part 200: AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV

IEC TR 61641 Enclosed Low Voltage Switchgear and Controlgear Assemblies - Guide for Testing under Conditions of Arcing Due to Internal Fault

1.4. IEEE–Institute of Electrical and Electronics Engineers

IEEE C37.13 Standard for Low-Voltage AC Power Circuit Breakers Used in Enclosures

IEEE C37.20.1 Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear

IEEE C37.20.2 Standard for Metal-Clad Switchgear

IEEE C37.20.7 Guide for Testing Medium-Voltage Metal-Enclosed Switchgear for Internal Arcing Faults

IEEE C37.23 Guide for Metal-Enclosed Bus and Calculating Losses in Isolated-Phase Bus

IEEE C57.13 Standard Requirements for Instrument Transformers

1.5. NEMA–National Electrical Manufacturers Association

NEMA ICS 1 Industrial Control and Systems General Requirements

NEMA ICS 2 Starters, Contactors & Overload Relays, Rated Not More Than 2000 Volts AC or 750 Volts DC




NEMA ICS 3 Industrial Control and Systems: Medium Voltage Controllers Rated 2001 to 7200 Volts AC

NEMA ICS 4 Terminal Blocks

NEMA ICS 6 Industrial Control and Systems Enclosures

NEMA SG 4 Alternating-Current High-Voltage Circuit Breakers

1.6. UL–Underwriters Laboratories, Inc.

UL 347 UL Standard for Safety High Voltage Industrial Control Equipment

UL 489 UL Standard for Safety Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures

UL 1558 UL Standard for Safety Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear

2. Definitions

Term [I] Description

Arc-resistant switchgear

Equipment designed to withstand the effects of an internal arcing fault as indicated by successfully meeting the test requirements of the IEEE C37.20.7.

Drawout To be removable and arranged with a mechanism for moving the switching and interrupting device physically between connected and disconnected positions and equipped with self-aligning and self-coupling power and control disconnecting devices. Removal of the device may be accomplished without the necessity of unbolting connections or mounting supports.




Fully insulated bus bars

Bars fully coated or covered with solid insulating material, or individual bars fully surrounded by solid insulating material, so as to safely isolate personnel from live bars, and to prevent the propagation of arcs between phases or between phase and ground. The use of solid insulation coatings, coverings, or barriers shall not result in reducing the air-insulation clearances between the bars, or between the bars and ground.

"Healthy trip" pilot light

A pilot light that supervises the condition of a circuit, which trips a circuit breaker or other switching device either directly or through an auxiliary relay. When energized, the light shows that the circuit, including series connected trip coils of the switching device or auxiliary relay, is continuous and ready to function if its associated protective device operates.

Low voltage (LV) switchgear or control center

0 to 1000 volts

Medium voltage (MV) switchgear:

1001 to 34500 volts

Metal-clad switchgear

a) The main switching and interrupting device is of the removable (drawout) type arranged with a mechanism for moving it physically between connected and disconnected positions and equipped with self-aligning and self-coupling primary disconnecting devices and disconnectable control wiring connections.

b) Major parts of the primary circuit, that is, the circuit switching or interrupting devices, buses, voltage transformers, and control power transformers, are completely enclosed by grounded metal barriers that have no intentional openings between compartments. Specifically included is a metal barrier in front of, or a part of, the circuit interrupting device to ensure that, when in the connected position, no primary circuit components are exposed by the opening of a door.




c) All live parts are enclosed within grounded metal compartments.

d) Automatic shutters cover primary circuit elements when the removable element is in the disconnected, test, or removed position.

e) Primary bus conductors and connections are covered with insulating material throughout.

f) Mechanical interlocks are provided for proper operating sequence under normal operating conditions.

g) Instruments, meters, relays, secondary control devices, and their wiring are isolated by grounded metal barriers from all primary circuit elements with the exception of short lengths of wire such as those at instrument transformer terminals.

Metal-enclosed switchgear

Switchgear surrounded by a metal case or housing, usually grounded.

MV control center:

1001 to 7200 volts

Plug-in To be arranged for moving the switching and interrupting device physically between connected and disconnected positions and equipped with self-aligning and self-coupling power supply side disconnecting devices. Removal of the device may be accomplished without the necessity of unbolting power supply connections or mounting supports.

Switchgear A general term covering switching and interrupting devices and their combination with associated control, metering, protective, and regulating devices, and with assemblies of these devices with associated interconnections, accessories, enclosures, and supporting structures used primarily in connection with the generation, transmission, distribution, and conversion of electric power.

Switching device The device in a motor controller (or starter) that makes and breaks motor current such as a




magnetic contactor or vacuum switch. Such device may also break fault current when so rated and applied for this purpose.

Undervoltage protection

As applied to motor control, causes the motor controller to trip either instantaneously or after a predetermined time interval upon a dip or loss of motor supply voltage. Upon restoration of normal supply voltage, the controller does not reclose or only recloses if supply voltage is restored within a predetermined time interval.

3. Documentation1) [M] The following documentation shall be provided by the Manufacturer:

a) Plan and section drawings.b) Front and rear elevation drawings.c) Device internals and switch development drawings.d) Wiring diagrams, showing physical location of all equipment, terminal blocks in cubicles, and all

remote wiring.e) Schematic diagrams (covering both a-c and d-c control and metering circuits) showing individual

wire numbers, terminal blocks and all device terminal numbers.f) Three-line diagrams, showing all current transformers, potential transformers, metering and

protective relaying connections, main bus and breaker configurations.g) Instruction books, including assembly instruction and details, parts lists, and all individual

components.h) [M] Typical engineering schematics and wiring diagrams, which shall not be used without

approval. Connection diagrams shall show wiring within each piece of equipment and are not a substitute for interconnection diagrams. Interconnection/point-to-point diagrams shall show the same terminal numbers and device and conductor designations that appear on the connection diagrams. They shall also indicate locations of terminals if the equipment has terminals in more than one location. Supplier shall supply sample interconnection wiring drawings with the quotation for the buyer's review and approval.

i) [M] Schematic/elementary logic diagrams. These shall be furnished for control circuits of motors and other equipment. They shall be shown on a single drawing and shall include all equipment and devices associated with the circuit that are in the Supplier's scope of work. Logic diagrams showing only functions used shall be provided for each numerical type relay used. The diagram shall show all inputs, their interaction in the logic and all resulting outputs of the relay. The logic diagram shall be shown on one drawing, not multiple sheets.

4) [M] Vendor shall provide documentation showing that equipment meets the approval requirements of the local authority. Approval requirements may include labeling, listing, or other certification by a




nationally recognized testing organization acceptable to the local authority.

4. Switchgear and Control Center Construction Practices1) [O], [R] Switchgear construction shall be used for LV drawout air circuit breakers and for MV

drawout circuit breakers (all types). Units of the same size and ratings shall be field interchangeable. The scope of supply shall include all the necessary special tools to facilitate equipment maintenance and operation.Cautionary Note: LV circuit breakers may come with protective relays fitted on the circuit breaker. LV circuit breakers shall be checked for protective devices before they are interchanged.

5) [O], [R] LV control center construction shall be used for the following plug-in equipment:a) Fused contactorsb) Fused switchesc) Fused switch combination startersd) Molded case breakerse) Molded case breaker combination starters

6) [O], [R] MV control center construction shall be used for drawout controllers consisting of latched or magnetically held switching devices with or without fuses or fused isolating switches.

7) [R] Aluminum shall not be used for current carrying parts of switchgear and control centers without the specific approval of Owner's Engineer.

8) [O], [M] A wiring identification system shall be provided for all secondary circuits to facilitate trouble-shooting and maintenance. System may consist of color coding, printed identification on the wires, securely mounted wire markers at each end of a circuit wire, or a combination of these methods. All wires shall be tagged at both ends per the destination method. If the Manufacturer's standard method is individual wire name, then he shall add destination in parenthesis after wire name at both ends. All wire tags shall be clearly readable after installation.

9) [M] A minimum of 20 percent spare terminals shall be provided in each unit.

[S] CT circuits shall be terminated using ring lugs to prevent accidental removal and exposure to high voltage. DC and PT circuit connections shall be made using spade lugs where practical. RATIONALE: [S] Secondary side of a current transformer must always be short-circuited. Opening secondary terminal on an energized CT causes a very high voltage on the secondary terminals and represents a dangerous situation. Use of ring lugs on CT circuits reduces the probability of accidentally opening the secondary loop.

10) [M], [R] Name tag lettering shall be at least ¼ in. if located at eye level (~ 4-6 ft). If name tags are below or above this level, the lettering size shall be increased to be clearly visible without stooping or using a ladder.

11) [S] Starters, breakers and PT drawers shall be equipped with a mechanical interlock which prevents drawing the device out in a single motion to prevent dropping the device on the worker.

RATIONALE: [S] MCC draw out equipment, like starters and breakers, represent a potential hazard to operator if the equipment accidentally is drawn too far out because there is nothing to stop it from sliding out. This applies especially on heavy starters. Mechanical interlock helps to




prevent such hazards.

5. Switchgear1) * [S] Low-voltage switchgear shall be metal-enclosed low-voltage power circuit-breaker switchgear

type as defined in IEEE C37.20.1 or "Form 4" per IEC 60439-1. All medium-voltage switchgear shall be metal-clad switchgear type as defined in IEEE C37.20.2 or "LSC2B" per IEC 62271-200.

2) * [S] Medium-voltage switchgear shall be arc-resistant as per IEEE C37.20.7 or IEC 62271-200. If specified, use of nonarc-resistant switchgear shall be submitted for approval by Owner's Engineer.

RATIONALE: [S] An internal arcing fault causes a rapid rise in the temperature of the surrounding air and rapid rise in pressure inside the enclosure. Conventional switchgear is not designed to withstand such a high pressure which could pose a potential arc-flash hazard to people in the vicinity of the switchgear. Arc-resistant switchgear is designed and tested to provide high degree of protection to persons against such hazards. Use of nonarc-resistant switchgear should be avoided or its use limited to cases where people are not likely to be present. For example, locations with remote breaker open/close operation and remote breaker rack in/out systems are locations where conventional (nonarc-resistant) metal-clad switchgear may be used.

12) [S] All switchgear shall have drawout power circuit breakers contained in individual grounded metal compartments. Mechanical interlocks shall be provided on all switchgear to prevent connecting the circuit breaker while closed, and to prevent the closing of the circuit breaker unless the power drawout disconnecting devices are fully coupled (connected) or separated by a safe distance.

RATIONALE: [S] The mechanical interlocks are designed to prevent dangerous conditions due to improper operations or operator error.

13) * [C] If specified, use of fixed pattern medium-voltage switchgear (nonwithdrawable circuit breakers) shall be submitted for approval by Owner's Engineer.

14) * [O] A closed door racking system is preferred for all switchgear. When specified closed door racking shall allow the racking into and out of the cubicle with the door closed.

15) * [S] All switchgear shall have a ground bus, which shall extend throughout the length of the switchgear assembly. Bus shall be capable of carrying the maximum ground fault current without damage (to the bus or its supports) for the time allowed by the slowest responsive relay. Purchaser shall specify available current and relay time.

RATIONALE: [S] The switchgear can fail and burn with a resultant loss of power if the ground bus is not rated to carry the expected maximum ground fault current. Guidance on the ground bus-rating basis is provided to avoid such a failure.

16) [S] All switchgear shall have fully insulated main and vertical bus bars and bus connections. Boot insulation at bus joints and bolted connections are preferred. Taped insulation shall be used only with Owner's approval. If taping is required, kits shall be provided to enable taping in field to permit checking bolt torque. Other bus insulation, isolation, or segregation methods may be proposed for approval by Owner's Engineer.




RATIONALE: [S] A switchgear bus fault can result in severe equipment damage and injury to personnel. Insulated bus bars reduce the probability of a bus fault. Arc propagation barriers limit the extent of damage in the event of an internal switchgear fault.

17) Arc propagation barriers shall be provided to prevent the following:a) Arcs occurring in incoming bus duct from flashing through or around the main incoming breaker

to the main bus or bus taps off the main bus.b) Arcs occurring on the load side of feeder breakers from flashing through or around the feeder

breaker to the main bus or bus taps off the main bus.c) Arcs occurring in one main bus from flashing through or around the bus tie to the other main bus

in secondary-selective and spot networks.d) Arcs occurring in one vertical section from flashing into adjacent vertical sections.

18) [O], [M] Each protective device shall have provisions for testing and calibrating the device using an external power supply without disconnecting the permanent wiring. Each protective device shall also have provisions for test tripping its associated circuit breaker(s) by applying a test current or voltage, manually operating a test trip button or by manually operating the device.

19) [O], [M] The protective-device test provision shall consist of built-in test plugs or switches, or separately mounted test terminal blocks. The test provisions shall permit the shorting of any current transformer circuit and for the selective disconnection of the protective device from current transformers, potential transformers, auxiliary power, and circuits controlled by the device.

20) [O], [M] All protective devices and devices initiating reacceleration, load shedding and transfer schemes, such as overcurrent, undervoltage, underfrequency, and thermal overload relays, shall have targets or other devices to indicate when relay operates regardless of relay's mounting location. Targets or indicating devices shall be visible from the front of lineup without the need to open relay covers or compartment doors.

21) [R], [S] Current transformers shall be mounted in the switchgear stationary part, not on the circuit breakers, and shall be located such that:a) Their current ratio and polarity markings can be readily identified after their primary connections

have been made.b) For transformers having secondary terminals, the terminals and shorting bars (if any) are

accessible and the shorting bar position is visible after the primary connections have been made.

RATIONALE: [R], [S] Current transformers shall not be operated with the secondary circuit open because hazardous crest voltages may result. By making sure the shorting bar position is visible, it is possible to verify that the current transformer secondary circuit is not open.

d) The current transformers can be isolated and removed safely while the main bus is energized.22) [O], [M] Engraved nameplates shall be provided per the following:

a) * On the front and rear of the enclosure of each circuit breaker, identifying its service by name or equipment number.

b) On the outside of drawers or doors of drawout potential transformers supplying motor undervoltage relays. Nameplates shall be engraved white on red background and shall read:

WARNING




OPENING DRAWER (OR DOOR) TRIPS MOTOR

e) On the front of panels, identifying each relay, showing the device function number such as 51-1, 27M-2, 86T.

f) On the front of panels, giving reset instruction for transformer protection lockout relays, 86T (when provided).

g) On the front of panel, identifying remote trip pushbutton for source breaker (when provided).h) Adjacent to each protective and auxiliary relay which trips more than one circuit breaker.

Nameplates shall be provided for both front-panel mounted relays and relays that are mounted inside compartments. Nameplates shall be engraved white on red background and shall read:

WARNING

OPERATION OF THIS RELAY TRIPS MORE THAN ONE CIRCUITBREAKER AS LISTED: BREAKER ____________ BREAKER ____________

i) On the front of the enclosure of each circuit breaker located in the same vertical section as the bus tie breaker. Nameplate shall identify which bus the circuit breaker is connected to.

j) Identification nameplates shall be mounted above all control switches and below all meters. Metering should be mounted immediately above or adjacent to any control switches which affect the reading on the meter or provide guidance for use of the control switch. Metering should be mounted near eye level for ease of use.

23) [S] Battery ventilation. Provisions shall be made to prevent accumulation of an explosive mixture inside outdoor switchgear of standard or protected aisle construction, when batteries are housed within the switchgear. Provisions shall be:a) For standard outdoor construction, ventilating louvers shall be provided in the battery enclosures.b) For protected aisle outdoor construction, an adequate rate of air changes shall be provided for the

protected aisle enclosure, and battery enclosures, if used, shall have ventilating louvers.Note: Determination of air changes required shall be based on the charge method and battery Vendor estimate of H2 evolved. Credit may be taken for air changes resulting from enclosure leakage.

RATIONALE: [S] During charging, batteries produce hydrogen. In order to prevent the accumulation of an explosive mixture, ventilation to keep the hydrogen level below 2 percent by volume shall be provided.

24) [O] All circuit breaker trip coils and all lockout relay coils shall be supervised by normally energized "healthy trip" pilot lights, using long-life lamps. It is preferred that the breaker trip coil light be the red "breaker closed" pilot light.

25) [O], [M] Breaker and starter operating handles shall be easily accessible while standing on the floor.26) [O], [M] Breakers, starters, auxiliary units, etc. which require both front and rear access shall have

identical unique front and rear identification labels in ½ in. minimum lettering.27) [M] Stick-on type control wire tie down devices shall not be used. Wire tie down devices shall be

screwed into the cabinet or otherwise affixed using metal retainers. Glued-on devices to hold wire in place shall not be used.




5.1. Low-Voltage Switchgear1) [R] Electrically operated breakers shall be used for transformer secondary and bus tie breakers in

secondary selective and spot network systems. All other breakers shall be manually operated except where electrical operation is required to:a) Permit remote operation such as for motor control.b) Meet applicable codes, standards, or the breaker Manufacturer's requirements for safe operation

without instantaneous protective trip devices.c) Conform to Manufacturer's standard design.

28) [R] Relays are preferred as the protective devices for incoming circuit breakers in spot network substations. Relays plus circuit breakers with direct acting trip devices (with shunt trip capability) may be used with the approval of Owner's Engineer.

29) * [R] If main bus neutral is specified without specifying its current rating, the rating shall be 50 percent of the phase bus current rating.

30) [R] Motor starter temperature rise shall be maintained within its design limits. To avoid excessive heating due to internal losses and heat contribution from adjacent motor starters, a diversity factor based on the maximum design operating load of all equipped and possible future motor starters shall be applied.

31) * [R] Main bus neutrals, when specified, shall extend the length of the switchgear, and shall be insulated from ground.

32) [R] A means for isolating neutral busses from the supply system source neutral, such as a bolted link, shall be provided.

33) [S] Potential transformer fuses, control fuses, and control power switches shall be accessible for replacement or operation. These devices shall be isolated from or located a safe distance away from uninsulated normally energized parts of the switchgear. Potential transformer fuses and the connection circuit between these fuses and the main bus shall be located and physically protected in such a way as to prevent accidental contact with energized parts during routine maintenance and inspection.

RATIONALE: [S] Contact with exposed live parts operating at 50 volts or more can result in severe injury or death. By designing the mounting of these devices to allow access and by providing proper guarding, accidental contact with energized parts can be avoided.

5.2. Medium-Voltage Switchgear1) [R] All breakers shall be electrically controlled, with either a stored energy (preferred) or a solenoid

operating mechanism.34) [S] Potential transformers and their fuses shall be mounted in a separate compartment of drawout

construction or equivalent. The primary connection shall be disconnected before the transformer or its primary fuses become accessible. A similar arrangement shall be provided for the primary fuses of control power transformers.

RATIONALE: [S] Contact with exposed live parts operating at 50 volts or more can result in severe injury or death. By designing the mounting of these devices to allow access and by providing proper guarding, accidental contact with energized parts can be avoided.

35) [O] Ammeters are required in outgoing circuits as follows:




a) In one phase for motor controllers.b) In other circuits either a triplex meter or single meter and selector switch for three (3) phases.

36) [M] Indoor switchgear installations and protected aisle outdoor switchgear shall be provided with a test cabinet for the breakers. This will permit the operation and inspection of the removable breaker elements outside the switchgear structure. For bulk oil breakers, an untanking and inspection rack shall be provided.

37) [M] Outdoor switchgear installations that are not of the protected aisle type shall be provided with test jumpers to permit operation of the removable breaker elements outside the switchgear structure.

38) [M]* When specified, relays shall have dedicated test sockets with corresponding test leads/plugs provided or have draw out construction for testing.

5.3. Switchgear Control Power (LV and MV)1) * [R] Switchgear control power voltages shall be specified. Switchgear control power busses shall be

arranged so that a separate switchgear is provided for each of the following:a) Each power bus or power bus section for all its outgoing circuit breakers.b) The incoming line circuit breaker in radial and primary selective substations.c) The incoming line circuit breakers and bus tie circuit breaker in secondary selective substations.d) In spot network substations, each breaker (bus-tie and incoming breakers) shall have separate

control power supplies. The cable runways must be independent of each other and should be run outside the switchgear to the extent possible.

e) The reacceleration scheme for latched motor controllers.39) [R] A disconnect switch common to both the close and trip circuits shall be provided in each control

circuit branch, and shall be readily accessible in the front compartment of the switchgear cubicle.40) [R] Overcurrent protection shall be provided in the closing circuit of each breaker with solenoid

closing or electrically charged stored energy closing. Protection of tripping circuits may be omitted or combined according to Manufacturer's preferred practice from the configurations below in Figure 1. A close coil or close motor may have a separate fuse.

Figure 1: Circuit Configurations




41) * [R] Voltage for control power busses shall be supervised by normally energized auxiliary relays located inside the switchgear assembly. Relays shall be suitable for continuous operation at control power bus voltage without tendency to stick in the energized position and shall be time delay on drop-out. Time delay shall be long enough to prevent operation on transient voltage dips. One relay shall be provided for each control power bus, and its coil shall be connected to the bus at the furthest point from the supply connection to the bus. A normally open contact from each relay shall be wired in series and used to actuate a "Loss of Control Power" alarm in the substation alarm panel. When specified, a separate relay shall be provided for each cell in the switchgear lineup to monitor separately the trip and close control-power circuits and to initiate a single control-power loss alarm. The relays shall be installed on the secondary side of the control-power fuse(s).

6. Control Centers1) * [R] Control centers shall be free-standing metal-enclosed structures. Structures shall consist of

vertical sections. These sections may be assembled into a group that has a common power bus and forms an enclosure to which additional sections may readily be added. Each vertical section shall be subdivided into compartments containing the various control and protective devices. Each compartment shall have a nameplate identifying its service by name or equipment number, as specified. All components of control centers shall be completely accessible from the front of the control center, unless rear access is approved by Owner's Engineer.

2) [S], [R] Mechanical screens or barriers shall be provided to prevent tools/metal objects from dropping from upper units into energized portions of lower units.

RATIONALE: [S] During maintenance on disconnected parts of a switchgear, the use of metallic tools may represent a potential hazard. Tools can accidentally fall down onto other live parts inside the switchgear and cause a short circuit representing a hazard situation for the workers.




Barriers or screens between sections will help prevent such incidents.

42) [R] Isolation between device, bus, and cable spaces shall provide the following:a) [S] Permit cables to be pulled safely into the center, and extended to device compartments, with

the center energized. It is preferred that no uninsulated energized parts be located in the cable pulling spaces. It is acceptable if guarded cable terminals are located there, providing temporary insulation can be installed in one piece during cable pulling.

RATIONALE: [S] A switchgear bus fault can result in severe equipment damage and injury to personnel. Insulated bus bars reduce the probability of a bus fault. Arc propagation barriers limit the extent of damage in the event of an internal switchgear fault.

Contact with exposed live parts operating at 50 volts or more can result in severe injury or death. By designing the mounting of these devices to allow access and by providing proper guarding, accidental contact with energized parts can be avoided.

k) Prevent arcs and retard arc products originating in device compartments from entering bus spaces.

l) Prevent transmission of arcs, and retard migration of arc products, between device compartments even when an intervening device assembly has been removed.

m) Permit personnel to work safely within an empty device compartment, or one from which the control device assembly has been removed, with the bus energized.

n) * Unless otherwise specified, fully insulated main and vertical bus bars and bus connections shall be provided. Other bus insulation, isolation, or segregation methods may be proposed for approval by Owner's Engineer.

6.1. Low-Voltage Control Centers1) * [R] Main bus neutrals, when specified, shall extend the length of the control center, and shall be

insulated from ground. If main bus neutral is specified without specifying its current rating, the rating shall be 50 percent of the phase bus rating.

2) * [R] Control device assemblies shall have plug-in line connections or otherwise be arranged so the assembly can be removed without de-energizing the center. The plug-in unit shall engage the vertical ground bus of the control center section at least 1/8 in. (3.2 mm) before the power stabs are energized, and shall disengage from the ground bus at least 1/8 in. (3.2 mm) after the power stabs are disconnected upon removal of the plug-in unit. If size or weight of the assembly makes its removal as a unit impractical, assemblies having fixed connections may be proposed for approval by Owner's Engineer.

3) [I] Molded case breakers used in combination motor starters shall have an interrupting rating at least equal to the short circuit rating of the motor control unit; i.e., breakers with reduced short circuit rating (based on testing the breaker in combination with starter) shall not be used.

4) [S] Fused switches shall have been demonstrated, in combination with the largest fuses to be used, to be capable of making onto any value of fault current up to the available current.

RATIONALE: [S] By ensuring safe operation with the largest fuse, avoids the possibility of an incident if the operator replaces the specified fuse with a larger fuse.




43) [R] A control switch shall be provided on the outside of the access door of each starter-fuse combination not having a disconnect switch. The control switch shall have two maintained positions; one marked "trip," and the other marked "remote." Turning the switch to "trip" shall deenergize the starter coil and disconnect control power to all remote control stations. Turning the switch to "remote" shall connect control power so that the starter may be operated from the remote control stations.

44) [S], [M] Access doors shall be interlocked so that the door cannot be opened when switch or breaker is closed. A door interlock bypass shall be provided to permit maintenance personnel to open the door with the switch or breaker closed. The access-door-shall be interlocked as follows:a) With circuit breaker, for breaker type feeder or for combination starter with breaker.b) With disconnect switch, for fused switch type feeder or for combination starter with disconnect.c) With control switch, for starter-fuse combination without disconnect switch.

RATIONALE: [S], [M] The mechanical interlocks are designed to prevent dangerous conditions due to improper operations or operator error.

45) [S] For starter-fuse combinations without disconnect switch, a mechanical interlock is preferred so that they cannot be withdrawn to disconnect their plug-in contacts when the starter magnet structure is closed. Alternatively, a neon or similar long-life pilot light, energized from the load side of the starter to warn if starter remains closed after its coil has been deenergized, is acceptable. It is preferred that pilot light be mounted on the (starter) assembly and be visible through an opening in the access door rather than be mounted on the door.


46) [M] Each motor control center plug-in unit shall be limited to one starter, or one circuit breaker. Dual (molded case) feeder breakers mounted in a single plug-in unit compartment is not allowed.

47) [M] Power and control fuses shall be accessible for replacement without need to remove any components from the control device assembly or to disconnect any of the assembly wiring.

48) * [S] Control power transformers, if required, shall be provided separately in each starter. Secondary side of control power transformers shall be grounded. Grounding of one side is preferred.

RATIONALE: [S] A control power transformer reduces the high voltage in the power circuit to a safer level for use in the control circuit. A separate control power transformer in each starter avoids the possibility of cross energization.

49) [R] Starter coils supplied at system voltage and protected by control circuit fuses shall preferably be supplied line-to-ground. Coils supplied at system line-to-line voltage and protected by control circuit fuses shall have operating characteristics or their control circuits arranged to ensure they drop-out should one control circuit fuse operate and leave the coil energized at system line-to-ground voltage.

50) [R] Control circuit conductors shall be protected against overcurrent. When a control power transformer is provided, fuses shall be provided in the ungrounded conductors of the secondary circuit. For control circuits not supplied from a control power transformer, fuses shall be provided in the circuit.

51) [M] Terminal blocks shall be provided for connection of external wiring and shall be conveniently located, clearly numbered, and identified. Terminal blocks for power wiring terminations shall be




designed to accommodate compression-type wire lugs. Control wire terminal blocks shall be of the screw type designed to accommodate pre-insulated crimp-type wire lugs, and shall accept a minimum of two 12 AWG (4 mm²) wires. A minimum of 10% spare control terminal points shall be provided. All terminal blocks for current transformers must be of the shorting-terminal type.

52) [M] All wiring shall be marked on each end with permanently embossed wire markers of the heat-shrinkable or slip-on type. Wrap-around, adhesive, and rigid snap-on markers are NOT acceptable. Wire markers reflecting phase identification shall be provided at the ends of all phase conductors. Wire numbers shall match the Supplier's drawings.

53) [M], [R] If the LV MCC serves loads more than 400 ft. from the MCC, the MCC shall have oversized wire-ways and oversized cable lugs and terminations to accommodate the oversized power conductors.

54) [M] IEC-design LV starters shall have a means to connect to the starter controls with the starter disconnected from the bus without having to completely withdraw the starter from the MCC. Design shall permit external connection of power to controls and connection to control interface wiring.

6.2. Medium-Voltage Control Centers1) [O], [M] Control center construction shall be as follows:

a) Controller switching device and preferably the whole controller shall be of drawout or plug-in construction.

b) Vendor proposals for more than 2 controllers per vertical section shall be submitted to Purchaser for approval by Owner's Engineer.

55) [S] Mechanical interlocks shall be provided to:a) Prevent access to medium-voltage compartments until all parts are deenergized and isolated from

the bus.b) Prevent operating the isolating device or withdrawing or inserting the controller, with the

switching device closed.c) Prevent closing the switching device unless the isolating device is fully closed or open, and

unless the controller is fully inserted or safely drawn out.d) Prevent energizing a deenergized main bus when testing a switching device with auxiliary low

voltage.


56) [O] Ammeters are required as follows:a) Motor controllers shall be equipped with a single phase indicating ammeter.b) Other controllers shall be equipped with either a triplex ammeter or a single ammeter and selector

switch for 3 phases.57) [R] Magnetically held switching devices should obtain control power from an individual control

power transformer for each branch circuit.58) * [R] Latched switching devices shall derive their control power from individual control power

transformers or from a battery-based d-c control power system, as specified.59) [R] Primary side protection of the control power transformer shall be provided by current limiting

fuses connected downstream of the main circuit fuses.60) [R] Secondary side of control power transformer shall be grounded; however, this ground connection




shall be located, or automatically switched, to eliminate the risk of a ground fault when testing the control circuit with an auxiliary source of power whose grounded conductor is not identified. Grounding of one side is preferred. Mid-point grounding is acceptable only if necessary for proper equipment operation.

61) [R] Contactors and relays shall be able to ride through voltage dips to 75% of nominal voltage for a duration of 5 seconds, such as those experienced during the starting of motors.

62) [M] Terminal blocks shall be provided for connection of external wiring and shall be conveniently located, clearly numbered, and identified. Terminal blocks for power wiring terminations shall be designed to accommodate compression-type wire lugs. Control wire terminal blocks shall be of the screw type designed to accommodate pre-insulated crimp-type tongue wire lugs, and shall accept a minimum of two 12 AWG (4 mm²) wires. A minimum of 10% space control terminal points shall be provided. All terminal blocks for current transformers must be of the shorting-terminal type.

63) [M] All wiring shall be marked on each end with permanently embossed wire markers of the heat-shrinkable or slip-on types. Wrap-around, adhesive, and rigid snap-on markers are not acceptable. Wire markers reflecting phase identification shall be provided at the ends of all phase conductors. Wire numbers shall match the Supplier's drawings.

64) [S] Two high MCC units shall have a full screen barrier between the top and bottom units so that any items accidentally dropped when working in the upper unit will not fall and enter into the unit below.

RATIONALE: [S] During maintenance on the upper part, metallic tools or parts may fall down an cause a short circuit representing a hazard situation for the worker. A barrier (metal plate) between the MCC units will prevent such incidents.

7. Control and Protective Relaying of Motor Circuits7.1. Control Switches for Motor Controllers1) [S] Breakers used as controllers shall be provided with an externally operable control switch. The

switch shall have 3 positions marked remote-trip-off (trip in center position) and shall be non-spring return with contacts arranged to perform the following:a) The remote position shall give control of the circuit breaker to the control station at the motor.b) The trip position shall open the circuit breaker and lock out control of the breaker from the

control station at the motor.c) The off position shall isolate the control station at the motor from all control and alarm circuit

voltage.

RATIONALE: [S] In the trip and off positions, the control switch isolates the control station. This ensures that the field wiring is deenergized.

65) [M] For breakers without maintenance closing button on the removable element, the externally operable control switch shall have four positions with labels as follows: "REMOTE," "TRIP," "OFF," and "MAINT. CLOSE."The maintenance close button and the control switch (when in "MAINT. CLOSE" position) shall close the breaker only when the breaker is in test position.




66) [S] For controllers other than circuit breakers, means shall be provided on the face of the enclosure (without opening doors or drawers) to:a) Deenergize the motorb) Isolate the control station from the control circuit voltage.c) Isolate the control station from the alarm circuit voltage.Note: This may be accomplished by separate devices if they are labeled with their intended function.

RATIONALE: [S] In the trip and off positions, the control switch isolates the control station. This ensures that the field wiring is deenergized.

7.2. Reacceleration Control1) * [R] If reacceleration is specified for a motor, the motor shall reaccelerate automatically only if it

was running prior to a supply voltage dip or loss, and only if supply voltage returns within a specified time. Control of stepped reacceleration shall be via fixed-time steps or voltage-controlled steps per specification, or as approved by Owner's Engineer. The detailed design of reacceleration control systems shall be approved by Owner's Engineer. The following guidelines shall apply:a) Reclosure of motor controllers that open prior to reacceleration shall be sufficiently delayed to

avoid damage to the motor and the drive train due to out-of-phase reclosure. Delay is not necessary when a motor and drive train are designed to withstand 100 percent out-of-phase reclosure. The delay requirement can be waived with the approval of Owner's Engineer.

b) Fixed-time steps may be controlled via relays or "smart" motor controllers. When reacceleration relays are used in low-voltage control centers, they shall be incorporated into the plug-in removable part of the each motor controller, requiring no interconnecting wiring between compartments or special field wiring. This requirement may be waived with the approval of Owner's Engineer.

c) Voltage-controlled steps may be controlled via a separate relay-logic or via a separate programmable logic controller (PLC). Owner's Engineer shall provide a functional specification when a separate PLC control system is specified or approved.

d) Medium-voltage motor stepped-reacceleration shall be implemented via voltage-controlled steps or fixed-time steps, as specified, or as approved by Owner's Engineer.

e) Low-voltage motor stepped-reacceleration shall be implemented via PLC voltage-controlled steps or via fixed-time steps, as specified, or as approved by Owner's Engineer.

f) Step-delay timers and voltage-controlled stepping logic shall be fully reset if the voltage drops during reacceleration to a value low enough to drop out contactors, or if the voltage drops low enough and long enough to require tripping of controllers that do not drop out.

67) [R] For motors reaccelerated via voltage-controlled steps, the reacceleration scheme shall provide for the following:a) Means shall be provided for each motor to permit changing the selection of whether the motor

reaccelerates or not and, if so, in which step if more than one step is needed. Such change shall be effected solely by a simple selection process that does not require changes in wiring between cubicles.

b) For motors with controllers that are mechanically latched, held in by batteries, or have rectifier-supplied DC operating coils, tripping on undervoltage shall be initiated by two relays on separate phases for each bus. These relays shall be set to drop out instantaneously at approximately 70%




bus volts. Both relays must sense undervoltage to result in tripping. Tripping delay shall be provided as follows:i) * Motors in the initial or only step, with controllers that are mechanically latched or held in

by batteries, shall only be tripped if the supply voltage does not return within the specified time set on the memory timer. Memory timers shall have an adjustable delay up to 10 seconds unless otherwise specified.

ii) All other motors shall be tripped after a time delay adjustable up to one second, with the delay set at 0.3 seconds unless another delay is approved by Owner's Engineer. This delay is to allow the motors to ride over short dips in the supply voltage.

o) Step reacceleration shall be controlled by a voltage relay for each bus, initiating sequential steps when sufficient voltage is available, subject to any delay required to avoid damage due to out of phase reclosure per Item 1a above. This relay shall have a dropout/pickup ratio of at least 0.95. A recognition delay between steps is needed to allow time for motor controllers to close and for the resulting load increase to be sensed by the step control voltage relay.

p) At secondary selective substations, the step control of the two busses shall be paralleled if the bus tie is closed.

q) In case of another voltage dip or of an automatic transfer occurring during a step reacceleration, step control shall reset to step zero to give priority to the proper motors.

r) In case of failure of one or more controllers to close in their proper sequence, the steps shall be repeated.

s) For all motors arranged to reaccelerate, test provisions shall be incorporated which shall allow tripping and automatic reclosing of one or more selected motors when their controllers are in the test position. Provisions shall permit such tests with the plant running and without tripping running motors. The interconnection between bus control schemes shall be checked by the test.

7.3. Protective Relaying1) [R] All motors shall have undervoltage protection without lockout. Low-voltage motors on

magnetically held contactors with AC holding coils are normally protected from undervoltage by overload devices for voltages above contactor drop-out. Motors with controllers that are mechanically latched, held in by batteries, or have rectifier-supplied DC operating coils shall be protected from undervoltage by two independent bus-undervoltage relays connected between separate phases of the same bus. Both relays must sense the undervoltage to result in tripping. These relays may be part of a stepped-reacceleration control scheme. Potential transformers that feed these relays must be fused in both primary leads if only two transformers are used. The use of a single undervoltage relay in each motor-control unit requires the approval of Owner's Engineer.

68) [R] Motor protection shall include the following:a) Control equipment shall have protection devices that protect the motor against overload, locked

rotor, and phase and ground fault conditions. Devices shall have time current characteristics, which permit the motor to accelerate the driven equipment to full load speed under all normal operating conditions, including reacceleration at reduced voltage with protective devices warm. Devices shall provide a minimum of four (4) seconds delay at locked rotor current for warm starts of motors driving loads of normal inertia, such as pumps.

b) * Overcurrent protection devices shall provide a minimum of four (4) seconds delay at locked rotor current for warm starts of motors driving loads of normal inertia (such as pumps), unless




otherwise approved by Owner's Engineer.c) * Ground fault relays shall be provided for LV motors on low-resistance or solidly grounded

systems when the motor's phase-fault protection does not operate within 2 seconds for a line-to-ground arcing fault at the end of the feeder. An arc voltage drop of 40 volts shall be assumed to be in phase with the line-to-neutral source voltage. Refer to the section entitled "Ground Returns" in GP 16-04-01 for ground return practices.

d) * When ground fault relays for motor protection are specified, the relays shall be supplied from zero-sequence window-type current transformers. The relay and current transformer shall be purchased as a unit specifically designed for motor protection. The relay shall be the instantaneous type. If the combination starter cannot safely interrupt the full range of available ground-fault current in response to an instantaneous trip signal, Contractor shall submit alternative proposals to Owner's Engineer for approval.

69) [O], [M] Overload relays shall be of the thermal type for both breaker and contactor controllers and shall preferably be field adjustable for hand or automatic reset. If adjustable relays cannot be supplied, hand reset types shall be used. Manual reset device shall be operable from the front of the controller enclosure without opening doors or drawers.Overload relays shall not operate a lockout relay that is also used for fault protection relays.* When specified, relays shall be of the ambient compensated type.

70) * [S] When specified, a single thermal overload alarm relay shall be provided in the motor controller to actuate a winding high temperature alarm. The alarm relay shall be in addition to the thermal relays used for tripping and shall be capable of being set to operate at a lower value of current than the tripping relays. Provisions shall be made to extend the alarm relay contacts to the alarm location.A nameplate shall be mounted on the outside of the controller front panel. The nameplate shall be engraved white letters on red background and shall read:

WARNING

ALARM THERMAL RELAY CONTACTSMAY BE ENERGIZED FROM EXTERNAL SOURCE

RATIONALE: [S] The warning sign alerts the operator to the presence of an alternate power source that could energize the relay contacts even though the controller is isolated.

7.4. Protective Relaying for MV Motors1) [R] Ground fault relaying shall be provided on low-resistance or solidly-grounded systems. Relays

shall be the instantaneous type, supplied from zero-sequence window type current transformers. Contactors of magnetic starters, either on their own or in conjunction with their current-limiting fuses, shall be fully protected against trying to interrupt a current that exceeds contactor interrupting capacity.

71) [R] Hand-reset lockout shall be provided with all relays used for fault protection. This may be accomplished mechanically within the relay, provided that controller reclosing is blocked and not simply that retripping is provided. Alternatively an auxiliary lockout relay may be used. Series-type auxiliary lockout relays are preferred for latched controllers, with the lockout relay coil in series with




the trip coil of the motor controller. When a shunt-type lockout relay is used, its coil shall be supervised by a "healthy trip" pilot light.

72) [R] Breaker red pilot lights (closed) shall preferably supervise both series lockout relay coils and breaker trip coils.

73) [O], [M] For all types of lockouts, the reset shall be accessible on the front panel exterior.74) * [R] Motors 2501 hp (1801 kW) and larger shall have differential relay protection, with the relays

mounted in the switchgear or control center. Type of relaying (self-balancing or conventional) and responsibility for supply of motor side current transformers and the relays shall be specified.

75) * [R] Locked rotor protection shall be provided either by a separate relay or by a multi-purpose motor protection relay having a specific locked rotor protective function. Relay shall be adjustable and capable of being set to operate at or below the locked rotor damage time specified by Purchaser. Unless otherwise specified, relay shall be hand reset either directly or by use of an auxiliary relay.

7.5. Protective Relaying for LV Breaker-Controlled Motors1) [R] Low-voltage (switchgear) circuit breakers used as motor switching devices shall have direct

acting overcurrent trip devices. Operation of the overcurrent device shall lock out the closing of the circuit breakers, and the lockout device shall be reset by hand. Undervoltage protection shall be provided and operation of the undervoltage protection shall not lock out the closing of the circuit breaker.Time-delay and instantaneous overcurrent direct acting trip elements shall be separately adjustable. Time-delay element range shall have a nominal pickup setting minimum range of 100–150 percent of motor full load current. Instantaneous element range shall have a nominal pickup setting minimum range of 133–200 percent of motor locked rotor current.

76) * [R] Breaker direct acting overcurrent devices shall be backed up by a thermal relay in one phase, for motor overload and locked rotor protection. However, this may be omitted if the motor is provided with winding temperature detectors arranged to trip.

77) [R] Ground fault relaying shall be provided on low resistance or solidly grounded systems. Relays shall be the instantaneous type, supplied from zero-sequence current transformers.

7.6. Remote Metering1) * [R] If remote meters are specified, they shall not be supplied from current transformers connected

to protective relaying. Meters outside of a switchgear or control-gear lineup shall be supplied via transducers. "Remote" meters within a given lineup shall be supplied by transducers, or by separate current transformers with open circuit protection.

2) [R] Potential transformers secondary leads supplying remote meters shall be individually fused at the potential transformer.

7.7. Motor Space Heater Control1) * [S] Controllers for motors equipped with space heaters shall be provided with an auxiliary contact

that can be connected in the space heater circuit to deenergize the space heater when the motor is running and to energize the space heater when the motor is not running. The contact shall remain closed or be automatically bypassed when the controller is in the test or withdrawn position. Controllers requiring this contact and the space heater voltage and watt rating shall be specified.




A nameplate shall be mounted on the front panel of each controller supplying a motor having space heaters. The nameplate shall be engraved white letters on red background and shall read:

WARNING

AUXILIARY CONTACT CONTROLLING MOTOR SPACE HEATERMAY BE ENERGIZED FROM EXTERNAL SOURCE


7.8. Motor Off Alarms1) * [S] Controllers for motors having a "motor off" alarm shall have a normally open auxiliary contact

for connection to the alarm circuit to operate the alarm. The contact shall remain closed or be automatically bypassed when the controller is in the withdrawn or test position. Controllers requiring this contact and the alarm voltage shall be specified.* A nameplate shall be mounted on the front panel of each controller supplying a motor having a "motor off" alarm. The nameplate shall be engraved white letters on red background and shall read:

WARNING

AUXILIARY CONTACT CONTROLLING MOTOR OFF ALARMMAY BE ENERGIZED FROM EXTERNAL SOURCE


8. Space Heaters1) [R] Space heaters shall be provided to eliminate condensation within the unit. Each space heater

circuit shall be provided with a manually-controlled cut off switch mounted at the control center. A circuit breaker switch shall be provided for overload protection. An ammeter shall be provided on the enclosure door to indicate that the space heater is working. The full load amps shall be marked on the ammeter. Space heaters shall be provided with safety screen covers.

2) * [R] All indoor and outdoor switchgear and control centers shall be provided with space heaters located in all compartments, including the cable compartments, and bus duct. Voltage and source of power shall be specified separately.

78) [R] A space heater control shall be furnished for each equipment, consisting of the following:a) A differential thermostat shall be used to control the heater so that the equipment interior

temperature is maintained at 7–10F (4–5.5C) above the air temperature.b) The differential thermostat shall be cut off by one or more automatic devices set for a maximum

equipment interior temperature of 95F (35C). The devices shall reset at 90F (32C). Devices




shall be located in enough typically loaded sections to prevent overheating.79) [R] For outdoor equipment, the space heater system shall be completely wired and shall include a

manual disconnect.80) * [R] When specified, space heaters shall be provided in bus ducts. For buses which pass from

outside to inside buildings, a heater element shall be located immediately inside and immediately outside the building wall to limit condensation on the insulation barrier. Voltage, source of power, and method of control for the heaters shall be specified.

9. Bus Duct1) [R] All bus duct shall be metal-enclosed per IEEE C37.23. Aluminum shall not be used for current

carrying parts of bus duct without the specific approval of Owner's Engineer. All bus bars shall be fully insulated with air separation between the buses and between the buses and the enclosure. Alternative isolation or segregation designs require approval by Owner's Engineer. Bus duct construction (such as sandwich design) with only solid insulation between buses, or between buses and the enclosure, are not acceptable. Non-ventilated enclosures are preferred. If ventilated enclosures are used, they shall meet the following requirements:a) Ventilating openings shall be of a size or guarded to prevent the entrance of a 1/4 in. (6 mm)

diameter probe.b) Ventilating openings shall not be located in the topside of the enclosure.

81) [R] Outdoor portions of metal enclosed bus duct or metal enclosed cable-bus duct shall be weatherproof. A tight fitting barrier made of a flame resistant, non-conducting material shall be located at the building or enclosure wall in duct connecting outdoor transformers with indoor switchgear or with protected aisle outdoor switchgear.

82) * [R] If neutral bus is specified without specifying its current rating, the rating shall be 50 percent of the phase bus current rating.

83) [S] Drain openings shall be provided to remove condensed moisture from low points of outdoor bus runs. Openings shall be of a size or guarded to prevent the entrance of a 1/4 in. (6 mm) diameter probe.

RATIONALE: [S] Contact with exposed live parts operating at 50 volts or more can result in severe injury or death. By properly sizing the openings or guarding, accidental contact with energized parts can be prevented.

84) * [R] The enclosure of the bus duct assembly shall provide an electrically continuous path from supply to load end. The assembled enclosure shall be capable of safely conducting the maximum phase-to-ground fault current available for a period of two seconds. All enclosure joints shall be designed to form a low resistance electrical bond between duct sections and at terminations. Any non-conductive coatings, such as paint, shall be removed or penetrated to ensure a good electrical contact. Fault current magnitude shall be specified.

85) [R] Bus ducts shall have gasketed removable covers where required for assembly and inspection purposes. Gasketing material shall be neoprene or equivalent. Stick-on foam type gasketing material shall not be accepted. Outdoor sections of bus ducts shall have covers that prevent accumulation of




rainwater.

10. Inspection and Testing10.1. Inspection1) [I] The term Inspector as used in this Practice refers to Owner's Representative.2) * [I] Inspection shall include a visual examination of all assembled equipment components, and

witnessing of tests, as specified by the Inspector.

10.2. Testing1) [R] All switchgear, control centers, and bus ducts shall be tested in the Manufacturer's plant. The

tests shall consist of Manufacturer's standard factory tests.Testing of switchgear and control centers shall also include the following: a) High potential tests on main busses, control power busses, and control wiring.b) Operational tests on at least one of each type of selected circuit breakers, starters, and contactors.

Control wiring shall be energized and electrically operated devices shall be electrically operated in both normal and test positions. Circuit breakers shall also be manually operated. Each circuit breaker involved in an automatic transfer system shall be tested.

c) All automatic transfer systems shall be tested to demonstrate proper operation under simulated normal and abnormal conditions. The test shall be performed with control wiring energized. A switched variable voltage supply shall be used to simulate undervoltages on the supply and bus to confirm correct 27, 27R, 27I, and 27M operation during the testing. The procedure used shall be equivalent to the one included in EM Electrical Equipment Acceptance Manual Standard TMEE 064

d) Operation of all meters shall be tested with the meters energized.e) Operation of all protective relays shall be tested by manually operating the relay with its control

circuit energized to demonstrate that the relay will trip its associated circuit breaker(s) or other control device(s).

f) Remote control systems shall be tested to demonstrate proper operation under simulated conditions.

g) Operation of key and electrical interlock systems shall be tested.h) Operation of space heaters shall be tested with the heaters energized.i) Operation of all ground detecting systems shall be tested with the systems energized and by

simulating faults on each line.t) Current shall be injected on the bus using a high current ductor to prove all relaying circuits and

confirm function of ground relaying. Numerical relays shall be adequately programmed to read currents.

86) [R] Operational tests shall be conducted per the following:a) Tests shall be made with circuit breakers and starters being supplied on the order. Testing with

shop "dummy" type equipment is not acceptable.b) It is not necessary that all breakers or starters be used for testing, but at least one of each type




shall be available to demonstrate operability.c) On automatic transfer systems, all breakers involved in the transfer scheme shall be available.




Record of Change

Version 1.0.0

Date: 03/02

Location Action Description

Initial Publish.

Version 1.0.0

Date: 07/03

Global Practice version number and format updated to comply with new process; however, original publish date remains, and no content was modified.

Version 2.0.0

Date: 04/05

General Addition Added some references within the text.

Section 1.2 Addition Added data sheets.

Section 1.5 Deletion Removed withdrawn standards.

Section 1.6 Addition Added reference to UL 1558.

Section 5.2 New New heading for Medium Voltage Switchgear. Former Section 5.2 became 5.3.

Section 7.3, Item (1)

Additions Added "Potential transformers that feed these relays must be fused in both primary leads if only two transformers are used."

Version 3.0.0

Date: 01/06

Section 1.1 Addition Added reference to GP 16-01-03.

Datasheets Addition Added line 125 in T161201C05 & M05 about "relay test sockets."

Section 1.4 Addition Added reference to IEEE C37.20.7.

Section 2 Additions Added definition of the terms "Switchgear," "Metal-enclosed switchgear," "Metal clad switchgear," and "Arc-resistant switchgear."

Section 3 Additions Added new Items (1h) and (1i) both about requirements for documentation.

Section 4 Additions Added new Items (7, 8 and 9) about requirements for CT circuits,




labeling and motor starter interlocks.

Section 5, Item (1)

Modification Item rewritten. Issue about arc-resistant switchgear deleted and moved to separate section. Numbering of the other items was changed.

Section 5, Item (2)

Addition Added a separate Item (2) for arc-resistant switchgear.

Section 5, Item (4)

Addition Added new Item (4) ("fixed pattern switchgear").

Section 5, Item (7)

Addition Added more text in Item (7) (former Item (4)): "Boot insulation at bus joints and bolted connections are preferred. Taped insulation shall be only used with Owner's approval. If taping is required, kits shall be provided to enable taping in field to permit checking bolt torque."

Section 5, Item (13h)

Addition Added new Item (former section 5.9) about location of nameplates and metering.

Section 5, Items (16, 17, 18)

Additions Added Items (16, 17 and 18) about breaker and starter operating handles, labeling, and control wiring.


Addition Added new Item (4) (issue about motor starter temperature).

Section 5.1 Modifications Former Items (4, 5, and 6) are now numbered 5, 6, and 7.


Addition Added new Item 6 about test sockets for relays.

Section 5.3, Item (1d)

Addition Replaced Item (1d) with more detailed requirements for control power voltages in spot networks.

Section 6 Addition Former Item (2) is now Item (3). Added new Item (2) about mechanical screens/barriers in control centers.

Section 6.1 Modifications Former Items (8, 9, 10, and 11) are now numbered 9, 10, 11, and 12.


Addition Added new Item (8) about motor control center plug-in units.

Section 6.1 Additions Added new Items (13, 14, 15, and 16) about terminal blocks and wiring, wire marking, sizing and motor starter test-position.

Section 6.2 Additions Added new Items (8, 9, 10, and 11) about voltage dips, terminal blocks, and wire marking.

Section 8 Modifications Former Items (1, 2, 3, and 5) are now numbered 2, 3, 4, and 5.

Section 8, Item (1)

Addition New Item (1) about space heater requirements.

Section 8, Item (2)

Addition Added to Item (2) (former Item 1): "…located in all compartments including the cable compartments and bus duct."




Section 8, Item (5)

Addition Added to Item (5) (former Item (4)):"… For buses which pass from outside to inside buildings, a heater element shall be located immediately inside and immediately outside the building wall to limit condensation on the insulation barrier."

Section 9, Item (6)

Addition Added new Item (6) about bus duct gaskets.

Section 10.2, Item (1c)

Addition Added to Item (1c): "A switched variable voltage supply shall be used to simulate undervoltages on the supply and bus to confirm correct 27, 27R, 27I, and 27M operation during the testing. The procedure used shall be equivalent to the one included in EM Electrical Equipment Acceptance Manual Standard TMEE 064."

Section 10.2, Item (1j)

Addition Added new Item (1j) about high current injection test.

Version 3.0.0

Date: 01/10


Correction "A minimum of 10% space..." was changed to "A minimum of 10% spare..."




Attachment: Purpose Codes Definitions

Code Description

C Assigned to paragraphs containing specifications whose primary purpose is reduced costs. Reduced cost in this context refers to initial investment cost and does not include Life-Cycle cost considerations. Life-Cycle cost considerations are captured under reliability, maintainability, or operability purpose codes.

E Assigned to paragraphs containing specifications whose primary purpose is driven by environmental considerations. Environmental considerations typically include specifications intended to protect against emissions/leakage




to the air, water, and/or soil. Deviations from the specifications contained in such paragraphs require formal review and approval according to local environmental policy.

I Assigned to paragraphs that provide only clarifying information such as Scope statements, definitions of terms, etc.

M Assigned to paragraphs containing specifications whose primary purpose is to provide for maintainability of equipment or systems. Maintainability provisions are those that facilitate the performance of maintenance on equipment/systems either during downtimes or during on-stream operations.




O Assigned to paragraphs containing specifications whose primary purpose is to assure operability of equipment or systems. Operability is the ability of the equipment/system to perform satisfactorily even though conditions are off-design, such as during start-ups, process swings, subcomponent malfunction, etc.

R Assigned to paragraphs containing specifications whose primary purpose is to improve or assure the reliability of equipment or systems. Reliability is a measure of the ability of equipment/systems to operate without malfunction or failure between planned maintenance interventions.




S Assigned to paragraphs containing specifications whose primary purpose is avoidance of personnel or operational safety incidents. Any deviation from the specifications contained in such designated paragraphs requires formal review and approval according to local safety policy.

Personnel Safety: Refers to the avoidance of recordable personnel injuries—e.g., burns, cuts, abrasions, inhalation, or exposure to dangerous substances, etc., that could result in medical treatment, restricted work, lost-time incidents, or fatalities.

Operational Safety:

Refers to the prevention and control of process releases, fires, explosions, etc.



GP 16-12-01 - Switchgear, Control Centers, And Bus Duct (Version 3.0.0, JAN 2006, Except DIOL 3.0.0...

Documents

Transcript of GP 16-12-01 - Switchgear, Control Centers, And Bus Duct (Version 3.0.0, JAN 2006, Except DIOL 3.0.0...