MV Metal Enclosed Switchgear - MEB TD
Content
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
General Description
B2-1
Description
The assembly, designated MEB (Vacuum Breaker) Switchgear, consists of a switch and vacuum circuit breaker in series. This combination has been designed primarily for unit substation use where low cost protection is desired; and it can eliminate the need for a secondary main circuit breaker on a single ended unit substation. With the vacuum circuit breaker, MEB Switchgear is classified as an overcurrent protective device that provides increased system protection and increased coordination with upstream and downstream devices where these benefits cannot be achieved with a switch and fuse combination. Optionally, the vacuum circuit breaker can also provide precise ground fault protection not achievable with a fuse. MEB provides a minimum footprint utilizing Vacuum Breaker technology. All protective devices and metering are conveniently mounted on the switchgear structure door. VCP-W Vacuum Circuit Breakers have been designed with a patented V-Flex current transfer system that provides a unique non-sliding current transfer arrangement, no maintenance, excellent electrical and thermal transfer, and long vacuum interrupter life. Visible disconnect means is assured by the load break air interrupter switch and viewing window. Both indoor and outdoor non-walk-in enclosures are available. Applications are single units, lineups and transformer primary applications. Configurations with an automatic transfer control system can be accommodated easily. Easily removable vacuum breakers are ideal for high duty cycle as well as applications requiring rapid return to service after a load fault. MEB is the product of choice for ground fault interruption when air interrupters alone would be potentially hazardous if called on to operate above their assigned ratings. Capacitor switching is easily handled by MEB avoiding the restrike hazard presented by air switches. Standardized designs cover most applications while custom designs are also available for unusual requirements. MEB switchgear assemblies are available seismically labeled to meet the seismic zone 4 requirements of either UBC (Uniform Building Code) or California Title 24 or BOCA (Building Officials and Code Administration International, Inc.) up to 15 kV. MEB vacuum switchgear meets or exceeds all applicable NEMA, ANSI, EEMAC, CSA and IEEE standards for metal-enclosed switchgear. MVS switch sections are easily mixed with MEB sections in lineups. No bus transitions are required between them except where bus goes from top to bottom locations.
Table 1: Available Vacuum Breaker Ratings
Rated Maximum Voltage kV Circuit Breaker Type Nominal MVA Rating Interrupting Capacity at Rated Maximum Voltage, kA Sym. rms 29 18 28 25 Rated Continuous Current Amperes rms 1200 1200 1200 1200 Rated Short-Time (3-second) Current kA Sym. rms 36 23 36 25
4.76 15 15 27
50 VCP-W 250 150 VCP-W 500 150 VCP-W 750 270 VCP-W 1250
250 500 750 1250
Construction
Type MEB switchgear uses the same proven enclosure and air switch mechanism as MVS switchgear. It differs in the addition of the easily removable Cutler-Hammer VCP-W vacuum breaker in place of fuses. Current and voltage transformers associated with protection devices such as the Digitrip 3000 electronic overcurrent relay are applied using the same ratings as drawout metalclad switchgear. Devices are mounted on the single front hinged door. The front door may be opened at any time to provide access to low voltage components and the front of the circuit breaker without being exposed to high voltage. The IQ family of electronic meters is normally used when metering functions are required. The circuit breaker is bolted into position but can be unbolted and removed from the enclosure. Routine maintenance can be performed on the circuit breaker mechanism in the enclosure. Standard Breaker and switch insulators are NEMA rated glass polyester. Control power will be required as detailed below. Ac can be supplied integrally if specified. Dc control power, if required, must be furnished by others.
The VCP-W Vacuum Circuit Breaker is easily accessible for routine inspection and maintenance. User friendly, front panel controls and indicators are functionally grouped together for easy operation and include: contact position indicator, closing spring status, close and trip button,operation counter.
If ac control power Digitrip is used, a capacitor trip device is provided. A Digitrip 3000 relay provides fault protection if ac control power is lost eliminating the need for an uninterruptible power source for continuous fault current protection. Once the circuit breaker is closed and the closing spring is recharged the breaker can open, close, and open without spring recharge.
Outdoor Enclosures
Weatherproofing complying with the requirements of NEMA 3R and IEEE standard C37.20.3 is available for MEB switchgear assemblies. The weatherproofing consists of sloped roof panels that are joined together with caps. Doors and rear covers are fully gasketed. Externally accessible louvered filtered covers, top and bottom, front and rear, are provided for ventilation. At least one 250 watt heater is provided in each vertical section. Power for the heaters may be supplied from an external source, or an optional integral control power transformer may be specified to provide power for the heaters. For outdoor walk-in enclosure, please refer to Cutler-Hammer.
MEB with control switches, Digitrip 3000 overcurrent relay and provisions for IQ Analyzer or IQ DP-4000.
B2-2
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Technical Data
Cutler-Hammer
May 2001
Overcurrent Protection
Type MEB breaker can be furnished with Cutler-Hammer type Digitrip 3000 Relay to provide overcurrent and fault protection. Refer to the Cutler-Hammer Power Management Product Guide for more details.
Table 2: Digitrip 3000 Ranges
Phase Overcurrent Pickup Ranges • Long Delay Setting: (0.2 to 2.2) x In (1 to 11) x In, None • Short Delay Setting: • Instantaneous Setting: (1 to 25) x In, None Ground Overcurrent Pickup Ranges • Long Delay Setting: (0.1 to 2.0) x In, None • Short Delay Setting: (0.1 to 11) x In, None • Instantaneous Setting: (0.5 to 11) x In, None
MVS Load Break Switch
Time Delay Settings
3-CTs Digitrip 3000 50/51 50N/51N 52
• Long Delay Time: [@3 x In(Ph)] [@1 x In(Gnd)] • Short Delay Time: • Where In =
Flat Slope: 0.2 to 2 sec. It, I2t, I4t Slope: 0.2 to 40 sec. 0.05 to 1.5 sec. Current Transformer Rated Amperes
VCP-W Vacuum Breaker
➁
1-Zero Sequence CT
Assembly Ratings
Table 3: MEB Switchgear Assembly Main Bus Ratings
Rated Maximum Volts kV 4.76 4.76 4.76 4.76 4.76 4.76 15 15 15 15 15 15 27 27 Rated BIL kV 60 60 60 60 60 60 95 95 95 95 95 95 125 125 Rated Main Bus Current Amperes 600 600 1200 1200 2000 2000 600 600 1200 1200 2000 2000 600 1200 Rated Momentary Current kA rms Asym. 40 61 40 61 40 61 40 61 40 61 40 61 40 40 Rated Short-TIme (2 seconds) Current kA Sym. 25 38 25 38 25 38 25 38 25 38 25 38 25 25
Typical MEB Single Section One Line Diagram
Breaker Control Ratings
Table 4: VCP-W Breaker Stored Energy Mechanism Control Power Requirements
Rated Control Voltage 48 Vdc 125 Vdc 250 Vdc 120 Vac 240 Vac Spring Charge Motor Run Amperes 9.0 4.0 2.0 4.0 2.0 Time Seconds 6 6 6 6 6 Close or Trip Amperes 16 7 4 6 3 Voltage Range Close 38-56 100-140 200-280 104-127 208-254 Trip 28-56 70-140 140-180 104-127 208-254
Surge Arresters
Digitrip 3000
IEEE Standard C62.11 for metal oxide surge arresters lists the maximum rated ambient temperature as 40°C. The ambient temperature inside a MEB switchgear vertical section may exceed this temperature, especially in
outdoor applications where solar radiation may produce a significant contribution to the temperature. Table 5 lists the recommended minimum duty cycle voltage rating for various system grounding methods.
Table 5: Suggested Minimum Ratings (kV) for Metal Oxide Surge Arresters Located in Metal-Enclosed Switchgear➀
System Grounding Nominal System Line-to-Line Voltage (kV) 2.4 Solidly Grounded System Low Resistance Grounded System High Resistance or Ungrounded System 3 3 6 4.16 6 6 6 4.8 6 6 9 7.2 6 6 12 12.0 12 12 18 12.4 7 12 12 18 13.2 12 12 21 13.8 12 12 21 14.4 12 12 24 22.9 21 21 36 24.9 24 24 39 34.5 30 30 54
➀ Surge arrester rating is based upon the ambient air temperature in the switchgear vertical section not exceeding 55°C. ➁ Optional zero sequence 50/51G ground fault protection.
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Technical Data
B2-3
Application Examples
Low Resistance Ground Schemes Medium voltage low resistance ground schemes – these schemes are typically used for medium voltage 5 kV class systems feeding 5 kV class motor loads. The resistor affords both full selectively in tripping on ground faults while limiting ground fault magnitudes to low values (typically 50 to 400 amperes). Reducing the current levels to a faulted motor greatly reduces the damage to the motor and subsequent rewind and repair costs. System tripping during a ground fault on the line side of the secondary main breaker must be cleared by sending a trip signal to the transformer line side protective device. Fusible switches on the line side of the step down transformer (typically rated 15 kV to 5 kV) MAY NOT BE USED FOR THIS PURPOSE. Any ground fault sensed may escalate as the switch is being signalled to trip thereby exceeding its typical 600 ampere maximum current breaking capacity. The MEB breaker, being a fully rated interrupting device, may be tripped regardless of fault level up to its interrupting rating (for example, 500 MVA). Only this type of overcurrent device or a metal clad switchgear drawout breaker may be safely used.
52-1
R 2-51G 52-2 1-51G
Unprotected Zone for Ground Fault Protection 52
R 51G
Complete Secondary Ground Fault Protection Using MEB for Primary Device.
Incomplete Ground Fault Protection Using Fusible Switch Primary Device – NOT RECOMMENDED.
Low Resistance Ground Scheme (Phase protection not shown)
Single Ended Substation Designs In this configuration, the MEB serves as both primary and secondary protection for the transformer. Note the use of 2 sets of current transformers for protecting against secondary ground faults, overloads and short circuits as well as primary winding faults. Savings in both floor space and cost result, due to elimination of the secondary main device. This scheme is only recommended where cost and space prevent the use of secondary main device.
50/51 50N/51N DT3000 52 50/51 50N/51N DT3000
Single Ended Unit Substations
B2-4
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Layout Dimensions
Cutler-Hammer
May 2001
Layout A: MEB Breaker Arrangements, Cable-In and Cable-Out (Single Unit)
Table 6
kV Class Cable In➀ T B T B T B Out➀ T or B T or B T or B T or B T or B T or B Width F➁ 62 62 62 62 78 78 R➁ 42 42 42 42 48 48 Height Indoor F➁
DT
Outdoor R➁ 90.4 90.4 90.4 90.4 110 110 F➁ N/A N/A N/A N/A 117 117 R➁ 98.1 98.1 98.1 98.1 117 117
Depth D ➃ 62 62 70 70 96 96
4.76 15 27
100.4 90.4 100.4 90.4 110 110
52
Figure S3
Layout B: Multiple Vertical Section Arrangements (Lineups)
See MVS switchgear multiple vertical structure arrangements in section B3, Table 2. Table 7
Main Breaker (with Bus Transition) Feeder Section
kV Class 4.76 or 15
DT
Figure
Cable Access F/R➁ R R F F R F R R F F R F
Cable Direction T/B➀ T B T B T or B T or B T B T B T or B T or B
Width
Height➂ Indoor Outdoor 98.1 98.1 N/A N/A 98.1 N/A 117 117 117 117 117 117
Depth D ➃ 70 80 70 70 70 70 96 96 96 96 96 96
➄
L10 L10 L10 L10 L11 L11
42 42 42 62 42 62 48 48 78 78 48 78
90.4 90.4 100.4 90.4 90.4 90.4 110 110 110 110 110 110
DT
52
27
52 (L8)
Figure L10 Figure L11
L10 L10 L10 L10 L11 L11
The arrangements and accompanying tables in this section represent the most common switchgear arrangements. Many other configurations and combinations are available (contact Cutler-Hammer for further information). Dimensions of vertical sections will vary if cabling is different from a maximum of two 500 kcmil, XLP or EPR insulated cables per phase using preformed slip-on cable termination devices, and/or if devices such as surge arresters, instrument transformers, special cable termination devices, etc., are required.
➀ T = Top entry of power cable. B = Bottom entry of power cable. ➁ F = Front only access for installing power cables. R = Rear access for installing power cables. ➂ Height must always match tallest vertical section in complete switchgear assembly. ➃ Depth of any vertical section must always match depth of deepest vertical section. Depths shown are for rear covers. Add 1.2 for optional rear doors. ➄ Transition section width is 15 inches for 4.76 or 15 kV Class and 30 inches for 27 kV Class.
Dimensions in Inches, Not to be used for construction purposes unless approved.
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Layout Dimensions
B2-5
5, 15 kV MEB With Main Bus
Roof for Outdoor Unit
5, 15 kV MEB Without Main Bus
Roof for Outdoor Unit
CTs
CTs
Switch
VT Switch
VT
98.1 Outdoor
98.1 Outdoor
90.4 Indoor Vacuum Breaker
90.4 Indoor Vacuum Breaker
CTs
CTs
Depth Base for Outdoor Unit Base for Outdoor Unit
Depth
27 kV MEB With Main Bus
27 kV MEB Without Main Bus
Roof for Outdoor Unit 117.00
117.00
Roof for Outdoor Unit
110.38
110.38
Product 0 Depth Voltage Amperage MVA
96.25
Product 0 Depth Voltage Amperage MVA
96.25
Dimensions in Inches, Not to be used for construction purposes unless approved.
B2-6
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Layout Dimensions
Cutler-Hammer
May 2001
5 kV and 15 kV Roof Layouts and Floor Layouts
Rear Access Top or Bottom Entry and Exit
13 Optional Rear Door 1.5 8 A&B 16 13 1.2 33 1.5 8 A 16 13 13 16 13
Front Access Bottom Entry, Top Exit
Front Access Top Entry, Bottom Exit
D
D 8 19 B➀
D
42
62 13 1.2
62
Roof Layout
13 Optional Rear Door 5.5 8 A&B 16
Roof Layout
6 8 5.5 8
Roof Layout
33 16 A
D 16 6.3 42 62 B
D
D
62
Floor Layout
Floor Layout Front
Floor Layout
27 kV Roof Layouts and Floor Layouts
REAR ACCESS TOR OR BOTTOM ENTRY AND EXIT
12
3 00
A&B 6 00
36 00
ROOF AND FLOOR LAYOUT
D
48 00
Note: A = Power cable to load, B = Power cable from source. See Tables 6 and 7 as applicable on page B2-4 for dimension D.
➀ Cable location B not available with main bus.
Dimensions in Inches, Not to be used for construction purposes unless approved.
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Layout Dimensions
B2-7
Typical Anchor Plan for Indoor Vertical Sections for 5 & 15 kV
Typical Anchor Plan for Outdoor Vertical Sections for 5 & 15 kV
2.12 (TYP)
30.00 MIN.
ቧ
4.50 (TYP)
ቧ 30.00 MIN.
1.28 (TYP)
5.81 (TYP)
ብ
6.00 MIN. 1.00 MIN.
.53 (TYP) 1.75 (TYP) 6.00 MIN.
ብ
1.00 MIN.
ብ ቢ
ብ ባ
1.75 (TYP) .53 (TYP) 1.28 (TYP)
5.81 (TYP)
1.28 (TYP)
FRONT
FRONT
ቤ
ቦ
MIN.
ቤ
ቦ
MIN.
ቢ ባ
Locations for 0.50 inch anchor bolts. For seismic applications, use SAE grade 5 bolts and torque to 75 foot-pounds. Locations for customer’s tie-down clips. For seismic applications, the tie-down clips must be at least as strong as AISI 1010 steel, be made as shown in the detail view, and overlap the leg of the C-channel by at least 1.00 inches. Use a .50 inch SAE grade 5 bolt torqued to 75 foot-pounds. Door swing equals vertical section width at 90 degrees. Minimum clearance on side. Local jurisdictions may require a larger clearance. Minimum clearance in front is the width of the widest vertical section plus one inch. Local juridictions may require a larger distance. Minimum clearance in rear is 30 inches. If rear doors are supplied, the minimum clearance is the width of the widest vertical section equipped with a rear door plus one inch. Local jurisdictions may require a larger clearance. Finished foundation under the switchgear must be flat, level and in true plane.
Typical Seismic Tie-down Clip for 5 & 15 kV
2.50
ቤ ብ ቦ ቧ
.75 .62 DIA 1.00 2.00
.50
ቨ
B2-8
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Typical Specifications
Cutler-Hammer
May 2001
Ratings Switchgear, Switch and Circuit Breaker A. The 5-kV switchgear assembly ratings shall be as follows: Maximum Design Voltage Basic Impulse Level System Voltage System Grounding 4.76 kV 60 kV ___ kV three-phase [three-] [four-] wire ___ [solid] [low-resistance] [high-resistance] [ungrounded]
Circuit Breaker Closing and Latching Capability (and assembly momentary) ___ kA Symmetrical Circuit Breaker [37][58] Nominal 3-Phase MVA Class ___ kA [500][750] — OR — A. The 27 kV switchgear assembly ratings shall be as follows: Maximum Design Voltage Basic Impulse Level System Voltage System Grounding 27.0 kV 125 kV ___ kV three-phase [three-] [four]wire ___ [solid] [low-resistance] [high-resistance] [ungrounded] kA
2. On vertical sections without a circuit breaker, the door shall be interlocked with the switch so that: a. The switch must be opened before the door can be opened. b. The door must be closed before the switch can be closed. 3. On vertical sections with a circuit breaker, the enclosure door must be capable of being safely opened by barriering off all high-voltage parts with grounded metal, thus providing full access to the front of the circuit breaker control face plate and all lowvoltage control and instrumentation devices. 4. Provision for padlocking the switch in the open or closed position. 5. Permanent OPEN-CLOSED switch position indicators. C. Vertical section construction shall be of the universal frame type using die formed and bolted parts. All enclosing covers and doors shall be fabricated from steel whose thickness shall be equal to or greater than those specified in ANSI/IEEE C37.20.3 and CSA C22.2 No. 31. To facilitate installation and maintenance of cables and bus in each vertical section, a removable top cover and [(a) removable rear cover(s)] [a rear door latched closed by tamper resistant padlockable latches] [bolted rear door] shall be provided. D. Each vertical section containing a switch shall have a single, full length, flanged front door and shall be equipped with two rotary latch type padlockable handles for 5 and 15kV and bolted doors for 27kV. Provision shall be made for operating the switch and storing the removable handle without opening the full length door. A nameplate shall be mounted on the front door of each vertical section. The switch operating handle shall be covered by a hinged door to discourage casual contact by unauthorized personnel. Bus A. All buses shall be [tin-plated aluminum] [tin-plated copper] [silver-plated copper]. B. A neutral bus shall be provided when indicated on the drawings. It shall be insulated for 1000 volts AC to ground. The current rating of the neutral bus shall be 600 amperes.
Short-Time (2-Second) 36 kA Current Main Bus Continuous Current Rating (when main ___ [600][1200][2000] bus is required) Switch Continuous and Load Break ___ [600][1200] Current Rating Circuit Breaker Nominal 3-Phase MVA 250 MVA Class Circuit Breaker Rated Short-Circuit Current at Rated Maximum kV 29 kA Symmetrical Circuit Breaker Closing and Latching Capability (and as58 kA Asymmetrical sembly momentary) — OR — A. The 15-kV switchgear assembly ratings shall be as follows: Maximum Design Voltage Basic Impulse Level System Voltage System Grounding 15.0 kV 95 kV ___ kV three-phase [three-] [four-] wire ––– [solid] [low-resistance] [high-resistance] [ungrounded]
Short-Time (2-Second) 25 Current Main Bus Continuous Current Rating (when main bus is ___ required) Switch Continuous and Load Break 600 Current Rating Circuit Breaker Nominal 3-Phase 1250 MVA Class Circuit Breaker Rated Short-Circuit Current at Rated 25 Maximum kV Circuit Breaker Closing and Latching Capability (and assembly momentary) 40
[600][1200][2000] A MVA
kA Symmetrical
kA Asymmetrical
Main Bus Continuous Current Rating (when main bus is required) Switch Continuous and Load Break Current Rating Circuit Breaker Rated Short-Circuit Current at Rated Maximum kV Short-Time (2-Second) Current
––– [600][1200][2000] ___ [600][1200]
Construction A. The metal-enclosed switchgear assembly shall consist of dead front, completely metal-enclosed vertical sections each containing a non-fused load interrupter switch and a vacuum circuit breaker. Where shown, furnish additional vertical sections containing load interrupter switches and fuses or miscellaneous auxiliary apparatus of the number, rating and type noted on the drawings or specified herein. B. The following features shall be supplied on every vertical section containing a three-pole, two-position open-closed switch and vacuum circuit breaker: 1. A safety glass viewing window that permits full view of the position of all three switch blades through the closed door.
___ kA Asymmetrical [18][28] ___ kA [23][36]
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Typical Specifications
B2-9
Wiring/Terminations A. One terminal pad per phase shall be provided for attaching Contractor supplied cable terminal lugs for a maximum of two conductors per phase of the sizes indicated on the drawings. Sufficient space shall be supplied for Contractor supplied electrical stress relief termination devices. B. Small wiring, fuse blocks and terminal blocks within the vertical section shall be furnished as indicated on the drawings. Each control wire shall be labeled with wire markers. Terminal blocks shall be provided for customer connections to other apparatus. Circuit Breaker A. Each circuit breaker shall be manuallyoperated or operated by a motor-charged spring stored energy mechanism. The spring may be charged manually in an emergency or during maintenance procedures. B. The breakers shall be easily removable. Each breaker shall be mounted on wheels and simply rolls into the MEB structure on steel rails. The breaker fingers shall engage a stab as the breaker is inserted into the structure. The breaker shall be easily removed from the structure by removing bolts in each of the two mounting rails. C. Each circuit breaker shall have three (3) vacuum interrupter assemblies that are separately mounted on glass polyester insulators. Each vacuum interrupter assembly shall have a contact wear indicator which does not require any tools to indicate the contact wear. The current transfer from the vacuum interrupter moving stem to the breaker main conductor shall be a non-sliding design. The breaker front panel shall be removable when the compartment door is open for ease of inspection and maintenance of the mechanism. The circuit breaker shall not require utilization of air or oil dash pots for minimizing vacuum interrupter contact “bounce” upon opening. D. The breakers shall be electrically operated by: [115-] [230-] volt AC CLOSE and AC Capacitor Trip. — OR — [48-] [125-] volt DC CLOSE and Trip. Each breaker shall be complete with control switch and red and green indicating lights to indicate breaker contact position. E. The control voltage shall be [derived from a control power transformer mounted in the switchgear] [as indicated on the drawings].
Trip Units A. The switchgear manufacturer shall furnish and install, in the metal-enclosed switchgear, the quantity, type and rating of protection relays as indicated on the drawings and described hereinafter in this specification. B. Microprocessor Three-Phase Protective Relay 1. Relays for phase time overcurrent, instantaneous overcurrent and ground fault protection, ANSI 50/51, 50/51G, or 50/51N, shall be incorporated into a single device and shall be Cutler-Hammer type Digitrip 3000 or approved equal having all the features and functions herein specified. 2. The relay shall be solid-state microprocessor-based multi-functional type that operates from the 5-ampere secondary output of current transformers. The relay shall provide ANSI 50/ 51N protective functions for each of the three (3) phases, and ANSI 50/51N or 50/51G ground fault protection functions as shown on the plans or as determined by the coordination study. The relay shall be true RMS sensing of each phase and ground. Ground element shall be capable of being utilized in residual, zero sequence, or ground source connection schemes, or deactivated. For a detailed specification on the Digitrip 3000, refer to the Cutler-Hammer Power Management Product Guide. — OR — B. Electromechanical Induction-Disk Type Overcurrent Relay 1. Provide an induction-disk type overcurrent relay mounted in a semi-flush case with drawout provisions. 2. Relay shall have low burden characteristics, high thermal capacity and negligible temperature error. 3. All settings shall be readily visible and accessible from the front of the relay. 4. The Induction-disk shall be designed to compensate for spring wind-up throughout the travel of the moving contact to provide accurate pick-up continuous “between tap” adjustment. 5. Induction-disk relays shall be available with various families of IEEE inverse time current curves including moderately inverse, very inverse and extremely inverse, ANSI Device 51.
6. Where shown on drawings, inductiondisk relays shall be equipped with ANSI Device 50 adjustable pick-up instantaneous coils. 7. Each induction-disk relay shall be furnished with targets to indicate relay operation. Load Interrupter Switches A. Each load interrupter switch shall have a manual over-toggle type mechanism that does not require the use of a chain or a cable for operation, and utilizes a heavyduty coil spring to provide opening and closing action. The speed of opening and closing the switch shall be independent of the operator, and it shall be impossible to tease the switch into any intermediate position. B. The interrupter switch shall have separate main and break contacts to provide maximum endurance for fault close and load interrupting duty. C. The interrupter switch shall have insulating barriers between each phase and between the outer phases and the enclosure. D. A maintenance provision shall be provided for slow closing the switch to check switch-blade engagement and slow opening the switch to check operation of the arc interrupting contacts. Utility Metering A. Where indicated on the drawings, each utility metering vertical section shall contain provisions for current transformers and voltage transformers as required by the utility. The construction shall conform to the utility company‘s metering standards. It shall also conform to the general electrical and construction design of the switchgear specified above. Customer Metering A. Provide customer metering devices where shown on the drawings. Where indicated, provide a separate customer metering compartment with front hinged door. Include associated instrument transformers. B. Provide current transformers for each meter. Current transformers shall be wired to shorting type terminals blocks. C. [Fixed-mounted voltage transformers including primary fuses and secondary devices] [Voltage transformers with a means of disconnecting including primary and secondary fuses] for metering as shown on the drawings.
B2-10
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Typical Specifications
Cutler-Hammer
May 2001
D. Microprocessor-Based Metering System Select devices as required for item. Refer to the Cutler-Hammer Power Management Product Guide for detailed specification for metering. IQ Analyzer IQ DP 4000 IQ Generator IQ 200 Accessories A. Supply key interlocks as shown on the drawings. B. For switchgear, ____ kV [station] [intermediate] [distribution] class surge arresters shall be provided connected at the incoming terminations and securely grounded to the metal structure as shown on the drawings. Outoor Enclosures A. Each outdoor vertical section shall have a weatherproof roof. All external openings shall be screened to prevent the entrance of small animals and barriered to inhibit the entrance of snow, sand, etc. A minimum of one (1) 250-watt, 120-volt space heater shall be provided in each vertical section. Power for the space heater(s) shall be furnished [as indicated on the drawings] [by a control power trans-
former mounted in the switchgear] [by a transformer mounted in the low-voltage switchboard/switchgear]. The design shall be non-walk-in type. All doors and covers to be fully gasketed. Nameplates A. A nameplate shall be mounted on the front door of each switch vertical section in accordance with the drawings. Finish A. Prior to assembly, all enclosing steel shall be thoroughly cleaned and phosphatized. A powder coating shall be applied electrostatically, then fused on by baking in an oven. The coating is to have a thickness of not less than 1.5 mils. The finish shall have the following properties: Impact resistance (ASTM D-2794) Pencil hardness (ASTM D-3363) Flexibility (ASTM D-522) Salt spray (ASTM B117-85 [20]) Color 60 direct/60 indirect H Pass 1/8-inch mandrel 600 hours ANSI 61 gray
Miscellaneous Devices A. Communication equipment where indicated on the drawings, shall have the following features: 1. The communication system shall be Cutler-Hammer type IMPACC/PowerNet. 2. Each vacuum breaker position (open and closed), where shown, shall be communicated via an addressable relay. This relay shall communicate over a local area network consisting of a twisted pair of shielded wires. The relay shall monitor an auxiliary switch contact that monitors the breaker position and shall be rated for the application. Each relay shall have a unique address so that it is possible to “call up” and “read” each breaker’s position from a host computer.
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
General Description
B2-1
Description
The assembly, designated MEB (Vacuum Breaker) Switchgear, consists of a switch and vacuum circuit breaker in series. This combination has been designed primarily for unit substation use where low cost protection is desired; and it can eliminate the need for a secondary main circuit breaker on a single ended unit substation. With the vacuum circuit breaker, MEB Switchgear is classified as an overcurrent protective device that provides increased system protection and increased coordination with upstream and downstream devices where these benefits cannot be achieved with a switch and fuse combination. Optionally, the vacuum circuit breaker can also provide precise ground fault protection not achievable with a fuse. MEB provides a minimum footprint utilizing Vacuum Breaker technology. All protective devices and metering are conveniently mounted on the switchgear structure door. VCP-W Vacuum Circuit Breakers have been designed with a patented V-Flex current transfer system that provides a unique non-sliding current transfer arrangement, no maintenance, excellent electrical and thermal transfer, and long vacuum interrupter life. Visible disconnect means is assured by the load break air interrupter switch and viewing window. Both indoor and outdoor non-walk-in enclosures are available. Applications are single units, lineups and transformer primary applications. Configurations with an automatic transfer control system can be accommodated easily. Easily removable vacuum breakers are ideal for high duty cycle as well as applications requiring rapid return to service after a load fault. MEB is the product of choice for ground fault interruption when air interrupters alone would be potentially hazardous if called on to operate above their assigned ratings. Capacitor switching is easily handled by MEB avoiding the restrike hazard presented by air switches. Standardized designs cover most applications while custom designs are also available for unusual requirements. MEB switchgear assemblies are available seismically labeled to meet the seismic zone 4 requirements of either UBC (Uniform Building Code) or California Title 24 or BOCA (Building Officials and Code Administration International, Inc.) up to 15 kV. MEB vacuum switchgear meets or exceeds all applicable NEMA, ANSI, EEMAC, CSA and IEEE standards for metal-enclosed switchgear. MVS switch sections are easily mixed with MEB sections in lineups. No bus transitions are required between them except where bus goes from top to bottom locations.
Table 1: Available Vacuum Breaker Ratings
Rated Maximum Voltage kV Circuit Breaker Type Nominal MVA Rating Interrupting Capacity at Rated Maximum Voltage, kA Sym. rms 29 18 28 25 Rated Continuous Current Amperes rms 1200 1200 1200 1200 Rated Short-Time (3-second) Current kA Sym. rms 36 23 36 25
4.76 15 15 27
50 VCP-W 250 150 VCP-W 500 150 VCP-W 750 270 VCP-W 1250
250 500 750 1250
Construction
Type MEB switchgear uses the same proven enclosure and air switch mechanism as MVS switchgear. It differs in the addition of the easily removable Cutler-Hammer VCP-W vacuum breaker in place of fuses. Current and voltage transformers associated with protection devices such as the Digitrip 3000 electronic overcurrent relay are applied using the same ratings as drawout metalclad switchgear. Devices are mounted on the single front hinged door. The front door may be opened at any time to provide access to low voltage components and the front of the circuit breaker without being exposed to high voltage. The IQ family of electronic meters is normally used when metering functions are required. The circuit breaker is bolted into position but can be unbolted and removed from the enclosure. Routine maintenance can be performed on the circuit breaker mechanism in the enclosure. Standard Breaker and switch insulators are NEMA rated glass polyester. Control power will be required as detailed below. Ac can be supplied integrally if specified. Dc control power, if required, must be furnished by others.
The VCP-W Vacuum Circuit Breaker is easily accessible for routine inspection and maintenance. User friendly, front panel controls and indicators are functionally grouped together for easy operation and include: contact position indicator, closing spring status, close and trip button,operation counter.
If ac control power Digitrip is used, a capacitor trip device is provided. A Digitrip 3000 relay provides fault protection if ac control power is lost eliminating the need for an uninterruptible power source for continuous fault current protection. Once the circuit breaker is closed and the closing spring is recharged the breaker can open, close, and open without spring recharge.
Outdoor Enclosures
Weatherproofing complying with the requirements of NEMA 3R and IEEE standard C37.20.3 is available for MEB switchgear assemblies. The weatherproofing consists of sloped roof panels that are joined together with caps. Doors and rear covers are fully gasketed. Externally accessible louvered filtered covers, top and bottom, front and rear, are provided for ventilation. At least one 250 watt heater is provided in each vertical section. Power for the heaters may be supplied from an external source, or an optional integral control power transformer may be specified to provide power for the heaters. For outdoor walk-in enclosure, please refer to Cutler-Hammer.
MEB with control switches, Digitrip 3000 overcurrent relay and provisions for IQ Analyzer or IQ DP-4000.
B2-2
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Technical Data
Cutler-Hammer
May 2001
Overcurrent Protection
Type MEB breaker can be furnished with Cutler-Hammer type Digitrip 3000 Relay to provide overcurrent and fault protection. Refer to the Cutler-Hammer Power Management Product Guide for more details.
Table 2: Digitrip 3000 Ranges
Phase Overcurrent Pickup Ranges • Long Delay Setting: (0.2 to 2.2) x In (1 to 11) x In, None • Short Delay Setting: • Instantaneous Setting: (1 to 25) x In, None Ground Overcurrent Pickup Ranges • Long Delay Setting: (0.1 to 2.0) x In, None • Short Delay Setting: (0.1 to 11) x In, None • Instantaneous Setting: (0.5 to 11) x In, None
MVS Load Break Switch
Time Delay Settings
3-CTs Digitrip 3000 50/51 50N/51N 52
• Long Delay Time: [@3 x In(Ph)] [@1 x In(Gnd)] • Short Delay Time: • Where In =
Flat Slope: 0.2 to 2 sec. It, I2t, I4t Slope: 0.2 to 40 sec. 0.05 to 1.5 sec. Current Transformer Rated Amperes
VCP-W Vacuum Breaker
➁
1-Zero Sequence CT
Assembly Ratings
Table 3: MEB Switchgear Assembly Main Bus Ratings
Rated Maximum Volts kV 4.76 4.76 4.76 4.76 4.76 4.76 15 15 15 15 15 15 27 27 Rated BIL kV 60 60 60 60 60 60 95 95 95 95 95 95 125 125 Rated Main Bus Current Amperes 600 600 1200 1200 2000 2000 600 600 1200 1200 2000 2000 600 1200 Rated Momentary Current kA rms Asym. 40 61 40 61 40 61 40 61 40 61 40 61 40 40 Rated Short-TIme (2 seconds) Current kA Sym. 25 38 25 38 25 38 25 38 25 38 25 38 25 25
Typical MEB Single Section One Line Diagram
Breaker Control Ratings
Table 4: VCP-W Breaker Stored Energy Mechanism Control Power Requirements
Rated Control Voltage 48 Vdc 125 Vdc 250 Vdc 120 Vac 240 Vac Spring Charge Motor Run Amperes 9.0 4.0 2.0 4.0 2.0 Time Seconds 6 6 6 6 6 Close or Trip Amperes 16 7 4 6 3 Voltage Range Close 38-56 100-140 200-280 104-127 208-254 Trip 28-56 70-140 140-180 104-127 208-254
Surge Arresters
Digitrip 3000
IEEE Standard C62.11 for metal oxide surge arresters lists the maximum rated ambient temperature as 40°C. The ambient temperature inside a MEB switchgear vertical section may exceed this temperature, especially in
outdoor applications where solar radiation may produce a significant contribution to the temperature. Table 5 lists the recommended minimum duty cycle voltage rating for various system grounding methods.
Table 5: Suggested Minimum Ratings (kV) for Metal Oxide Surge Arresters Located in Metal-Enclosed Switchgear➀
System Grounding Nominal System Line-to-Line Voltage (kV) 2.4 Solidly Grounded System Low Resistance Grounded System High Resistance or Ungrounded System 3 3 6 4.16 6 6 6 4.8 6 6 9 7.2 6 6 12 12.0 12 12 18 12.4 7 12 12 18 13.2 12 12 21 13.8 12 12 21 14.4 12 12 24 22.9 21 21 36 24.9 24 24 39 34.5 30 30 54
➀ Surge arrester rating is based upon the ambient air temperature in the switchgear vertical section not exceeding 55°C. ➁ Optional zero sequence 50/51G ground fault protection.
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Technical Data
B2-3
Application Examples
Low Resistance Ground Schemes Medium voltage low resistance ground schemes – these schemes are typically used for medium voltage 5 kV class systems feeding 5 kV class motor loads. The resistor affords both full selectively in tripping on ground faults while limiting ground fault magnitudes to low values (typically 50 to 400 amperes). Reducing the current levels to a faulted motor greatly reduces the damage to the motor and subsequent rewind and repair costs. System tripping during a ground fault on the line side of the secondary main breaker must be cleared by sending a trip signal to the transformer line side protective device. Fusible switches on the line side of the step down transformer (typically rated 15 kV to 5 kV) MAY NOT BE USED FOR THIS PURPOSE. Any ground fault sensed may escalate as the switch is being signalled to trip thereby exceeding its typical 600 ampere maximum current breaking capacity. The MEB breaker, being a fully rated interrupting device, may be tripped regardless of fault level up to its interrupting rating (for example, 500 MVA). Only this type of overcurrent device or a metal clad switchgear drawout breaker may be safely used.
52-1
R 2-51G 52-2 1-51G
Unprotected Zone for Ground Fault Protection 52
R 51G
Complete Secondary Ground Fault Protection Using MEB for Primary Device.
Incomplete Ground Fault Protection Using Fusible Switch Primary Device – NOT RECOMMENDED.
Low Resistance Ground Scheme (Phase protection not shown)
Single Ended Substation Designs In this configuration, the MEB serves as both primary and secondary protection for the transformer. Note the use of 2 sets of current transformers for protecting against secondary ground faults, overloads and short circuits as well as primary winding faults. Savings in both floor space and cost result, due to elimination of the secondary main device. This scheme is only recommended where cost and space prevent the use of secondary main device.
50/51 50N/51N DT3000 52 50/51 50N/51N DT3000
Single Ended Unit Substations
B2-4
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Layout Dimensions
Cutler-Hammer
May 2001
Layout A: MEB Breaker Arrangements, Cable-In and Cable-Out (Single Unit)
Table 6
kV Class Cable In➀ T B T B T B Out➀ T or B T or B T or B T or B T or B T or B Width F➁ 62 62 62 62 78 78 R➁ 42 42 42 42 48 48 Height Indoor F➁
DT
Outdoor R➁ 90.4 90.4 90.4 90.4 110 110 F➁ N/A N/A N/A N/A 117 117 R➁ 98.1 98.1 98.1 98.1 117 117
Depth D ➃ 62 62 70 70 96 96
4.76 15 27
100.4 90.4 100.4 90.4 110 110
52
Figure S3
Layout B: Multiple Vertical Section Arrangements (Lineups)
See MVS switchgear multiple vertical structure arrangements in section B3, Table 2. Table 7
Main Breaker (with Bus Transition) Feeder Section
kV Class 4.76 or 15
DT
Figure
Cable Access F/R➁ R R F F R F R R F F R F
Cable Direction T/B➀ T B T B T or B T or B T B T B T or B T or B
Width
Height➂ Indoor Outdoor 98.1 98.1 N/A N/A 98.1 N/A 117 117 117 117 117 117
Depth D ➃ 70 80 70 70 70 70 96 96 96 96 96 96
➄
L10 L10 L10 L10 L11 L11
42 42 42 62 42 62 48 48 78 78 48 78
90.4 90.4 100.4 90.4 90.4 90.4 110 110 110 110 110 110
DT
52
27
52 (L8)
Figure L10 Figure L11
L10 L10 L10 L10 L11 L11
The arrangements and accompanying tables in this section represent the most common switchgear arrangements. Many other configurations and combinations are available (contact Cutler-Hammer for further information). Dimensions of vertical sections will vary if cabling is different from a maximum of two 500 kcmil, XLP or EPR insulated cables per phase using preformed slip-on cable termination devices, and/or if devices such as surge arresters, instrument transformers, special cable termination devices, etc., are required.
➀ T = Top entry of power cable. B = Bottom entry of power cable. ➁ F = Front only access for installing power cables. R = Rear access for installing power cables. ➂ Height must always match tallest vertical section in complete switchgear assembly. ➃ Depth of any vertical section must always match depth of deepest vertical section. Depths shown are for rear covers. Add 1.2 for optional rear doors. ➄ Transition section width is 15 inches for 4.76 or 15 kV Class and 30 inches for 27 kV Class.
Dimensions in Inches, Not to be used for construction purposes unless approved.
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Layout Dimensions
B2-5
5, 15 kV MEB With Main Bus
Roof for Outdoor Unit
5, 15 kV MEB Without Main Bus
Roof for Outdoor Unit
CTs
CTs
Switch
VT Switch
VT
98.1 Outdoor
98.1 Outdoor
90.4 Indoor Vacuum Breaker
90.4 Indoor Vacuum Breaker
CTs
CTs
Depth Base for Outdoor Unit Base for Outdoor Unit
Depth
27 kV MEB With Main Bus
27 kV MEB Without Main Bus
Roof for Outdoor Unit 117.00
117.00
Roof for Outdoor Unit
110.38
110.38
Product 0 Depth Voltage Amperage MVA
96.25
Product 0 Depth Voltage Amperage MVA
96.25
Dimensions in Inches, Not to be used for construction purposes unless approved.
B2-6
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Layout Dimensions
Cutler-Hammer
May 2001
5 kV and 15 kV Roof Layouts and Floor Layouts
Rear Access Top or Bottom Entry and Exit
13 Optional Rear Door 1.5 8 A&B 16 13 1.2 33 1.5 8 A 16 13 13 16 13
Front Access Bottom Entry, Top Exit
Front Access Top Entry, Bottom Exit
D
D 8 19 B➀
D
42
62 13 1.2
62
Roof Layout
13 Optional Rear Door 5.5 8 A&B 16
Roof Layout
6 8 5.5 8
Roof Layout
33 16 A
D 16 6.3 42 62 B
D
D
62
Floor Layout
Floor Layout Front
Floor Layout
27 kV Roof Layouts and Floor Layouts
REAR ACCESS TOR OR BOTTOM ENTRY AND EXIT
12
3 00
A&B 6 00
36 00
ROOF AND FLOOR LAYOUT
D
48 00
Note: A = Power cable to load, B = Power cable from source. See Tables 6 and 7 as applicable on page B2-4 for dimension D.
➀ Cable location B not available with main bus.
Dimensions in Inches, Not to be used for construction purposes unless approved.
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Layout Dimensions
B2-7
Typical Anchor Plan for Indoor Vertical Sections for 5 & 15 kV
Typical Anchor Plan for Outdoor Vertical Sections for 5 & 15 kV
2.12 (TYP)
30.00 MIN.
ቧ
4.50 (TYP)
ቧ 30.00 MIN.
1.28 (TYP)
5.81 (TYP)
ብ
6.00 MIN. 1.00 MIN.
.53 (TYP) 1.75 (TYP) 6.00 MIN.
ብ
1.00 MIN.
ብ ቢ
ብ ባ
1.75 (TYP) .53 (TYP) 1.28 (TYP)
5.81 (TYP)
1.28 (TYP)
FRONT
FRONT
ቤ
ቦ
MIN.
ቤ
ቦ
MIN.
ቢ ባ
Locations for 0.50 inch anchor bolts. For seismic applications, use SAE grade 5 bolts and torque to 75 foot-pounds. Locations for customer’s tie-down clips. For seismic applications, the tie-down clips must be at least as strong as AISI 1010 steel, be made as shown in the detail view, and overlap the leg of the C-channel by at least 1.00 inches. Use a .50 inch SAE grade 5 bolt torqued to 75 foot-pounds. Door swing equals vertical section width at 90 degrees. Minimum clearance on side. Local jurisdictions may require a larger clearance. Minimum clearance in front is the width of the widest vertical section plus one inch. Local juridictions may require a larger distance. Minimum clearance in rear is 30 inches. If rear doors are supplied, the minimum clearance is the width of the widest vertical section equipped with a rear door plus one inch. Local jurisdictions may require a larger clearance. Finished foundation under the switchgear must be flat, level and in true plane.
Typical Seismic Tie-down Clip for 5 & 15 kV
2.50
ቤ ብ ቦ ቧ
.75 .62 DIA 1.00 2.00
.50
ቨ
B2-8
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Typical Specifications
Cutler-Hammer
May 2001
Ratings Switchgear, Switch and Circuit Breaker A. The 5-kV switchgear assembly ratings shall be as follows: Maximum Design Voltage Basic Impulse Level System Voltage System Grounding 4.76 kV 60 kV ___ kV three-phase [three-] [four-] wire ___ [solid] [low-resistance] [high-resistance] [ungrounded]
Circuit Breaker Closing and Latching Capability (and assembly momentary) ___ kA Symmetrical Circuit Breaker [37][58] Nominal 3-Phase MVA Class ___ kA [500][750] — OR — A. The 27 kV switchgear assembly ratings shall be as follows: Maximum Design Voltage Basic Impulse Level System Voltage System Grounding 27.0 kV 125 kV ___ kV three-phase [three-] [four]wire ___ [solid] [low-resistance] [high-resistance] [ungrounded] kA
2. On vertical sections without a circuit breaker, the door shall be interlocked with the switch so that: a. The switch must be opened before the door can be opened. b. The door must be closed before the switch can be closed. 3. On vertical sections with a circuit breaker, the enclosure door must be capable of being safely opened by barriering off all high-voltage parts with grounded metal, thus providing full access to the front of the circuit breaker control face plate and all lowvoltage control and instrumentation devices. 4. Provision for padlocking the switch in the open or closed position. 5. Permanent OPEN-CLOSED switch position indicators. C. Vertical section construction shall be of the universal frame type using die formed and bolted parts. All enclosing covers and doors shall be fabricated from steel whose thickness shall be equal to or greater than those specified in ANSI/IEEE C37.20.3 and CSA C22.2 No. 31. To facilitate installation and maintenance of cables and bus in each vertical section, a removable top cover and [(a) removable rear cover(s)] [a rear door latched closed by tamper resistant padlockable latches] [bolted rear door] shall be provided. D. Each vertical section containing a switch shall have a single, full length, flanged front door and shall be equipped with two rotary latch type padlockable handles for 5 and 15kV and bolted doors for 27kV. Provision shall be made for operating the switch and storing the removable handle without opening the full length door. A nameplate shall be mounted on the front door of each vertical section. The switch operating handle shall be covered by a hinged door to discourage casual contact by unauthorized personnel. Bus A. All buses shall be [tin-plated aluminum] [tin-plated copper] [silver-plated copper]. B. A neutral bus shall be provided when indicated on the drawings. It shall be insulated for 1000 volts AC to ground. The current rating of the neutral bus shall be 600 amperes.
Short-Time (2-Second) 36 kA Current Main Bus Continuous Current Rating (when main ___ [600][1200][2000] bus is required) Switch Continuous and Load Break ___ [600][1200] Current Rating Circuit Breaker Nominal 3-Phase MVA 250 MVA Class Circuit Breaker Rated Short-Circuit Current at Rated Maximum kV 29 kA Symmetrical Circuit Breaker Closing and Latching Capability (and as58 kA Asymmetrical sembly momentary) — OR — A. The 15-kV switchgear assembly ratings shall be as follows: Maximum Design Voltage Basic Impulse Level System Voltage System Grounding 15.0 kV 95 kV ___ kV three-phase [three-] [four-] wire ––– [solid] [low-resistance] [high-resistance] [ungrounded]
Short-Time (2-Second) 25 Current Main Bus Continuous Current Rating (when main bus is ___ required) Switch Continuous and Load Break 600 Current Rating Circuit Breaker Nominal 3-Phase 1250 MVA Class Circuit Breaker Rated Short-Circuit Current at Rated 25 Maximum kV Circuit Breaker Closing and Latching Capability (and assembly momentary) 40
[600][1200][2000] A MVA
kA Symmetrical
kA Asymmetrical
Main Bus Continuous Current Rating (when main bus is required) Switch Continuous and Load Break Current Rating Circuit Breaker Rated Short-Circuit Current at Rated Maximum kV Short-Time (2-Second) Current
––– [600][1200][2000] ___ [600][1200]
Construction A. The metal-enclosed switchgear assembly shall consist of dead front, completely metal-enclosed vertical sections each containing a non-fused load interrupter switch and a vacuum circuit breaker. Where shown, furnish additional vertical sections containing load interrupter switches and fuses or miscellaneous auxiliary apparatus of the number, rating and type noted on the drawings or specified herein. B. The following features shall be supplied on every vertical section containing a three-pole, two-position open-closed switch and vacuum circuit breaker: 1. A safety glass viewing window that permits full view of the position of all three switch blades through the closed door.
___ kA Asymmetrical [18][28] ___ kA [23][36]
Cutler-Hammer
May 2001
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Typical Specifications
B2-9
Wiring/Terminations A. One terminal pad per phase shall be provided for attaching Contractor supplied cable terminal lugs for a maximum of two conductors per phase of the sizes indicated on the drawings. Sufficient space shall be supplied for Contractor supplied electrical stress relief termination devices. B. Small wiring, fuse blocks and terminal blocks within the vertical section shall be furnished as indicated on the drawings. Each control wire shall be labeled with wire markers. Terminal blocks shall be provided for customer connections to other apparatus. Circuit Breaker A. Each circuit breaker shall be manuallyoperated or operated by a motor-charged spring stored energy mechanism. The spring may be charged manually in an emergency or during maintenance procedures. B. The breakers shall be easily removable. Each breaker shall be mounted on wheels and simply rolls into the MEB structure on steel rails. The breaker fingers shall engage a stab as the breaker is inserted into the structure. The breaker shall be easily removed from the structure by removing bolts in each of the two mounting rails. C. Each circuit breaker shall have three (3) vacuum interrupter assemblies that are separately mounted on glass polyester insulators. Each vacuum interrupter assembly shall have a contact wear indicator which does not require any tools to indicate the contact wear. The current transfer from the vacuum interrupter moving stem to the breaker main conductor shall be a non-sliding design. The breaker front panel shall be removable when the compartment door is open for ease of inspection and maintenance of the mechanism. The circuit breaker shall not require utilization of air or oil dash pots for minimizing vacuum interrupter contact “bounce” upon opening. D. The breakers shall be electrically operated by: [115-] [230-] volt AC CLOSE and AC Capacitor Trip. — OR — [48-] [125-] volt DC CLOSE and Trip. Each breaker shall be complete with control switch and red and green indicating lights to indicate breaker contact position. E. The control voltage shall be [derived from a control power transformer mounted in the switchgear] [as indicated on the drawings].
Trip Units A. The switchgear manufacturer shall furnish and install, in the metal-enclosed switchgear, the quantity, type and rating of protection relays as indicated on the drawings and described hereinafter in this specification. B. Microprocessor Three-Phase Protective Relay 1. Relays for phase time overcurrent, instantaneous overcurrent and ground fault protection, ANSI 50/51, 50/51G, or 50/51N, shall be incorporated into a single device and shall be Cutler-Hammer type Digitrip 3000 or approved equal having all the features and functions herein specified. 2. The relay shall be solid-state microprocessor-based multi-functional type that operates from the 5-ampere secondary output of current transformers. The relay shall provide ANSI 50/ 51N protective functions for each of the three (3) phases, and ANSI 50/51N or 50/51G ground fault protection functions as shown on the plans or as determined by the coordination study. The relay shall be true RMS sensing of each phase and ground. Ground element shall be capable of being utilized in residual, zero sequence, or ground source connection schemes, or deactivated. For a detailed specification on the Digitrip 3000, refer to the Cutler-Hammer Power Management Product Guide. — OR — B. Electromechanical Induction-Disk Type Overcurrent Relay 1. Provide an induction-disk type overcurrent relay mounted in a semi-flush case with drawout provisions. 2. Relay shall have low burden characteristics, high thermal capacity and negligible temperature error. 3. All settings shall be readily visible and accessible from the front of the relay. 4. The Induction-disk shall be designed to compensate for spring wind-up throughout the travel of the moving contact to provide accurate pick-up continuous “between tap” adjustment. 5. Induction-disk relays shall be available with various families of IEEE inverse time current curves including moderately inverse, very inverse and extremely inverse, ANSI Device 51.
6. Where shown on drawings, inductiondisk relays shall be equipped with ANSI Device 50 adjustable pick-up instantaneous coils. 7. Each induction-disk relay shall be furnished with targets to indicate relay operation. Load Interrupter Switches A. Each load interrupter switch shall have a manual over-toggle type mechanism that does not require the use of a chain or a cable for operation, and utilizes a heavyduty coil spring to provide opening and closing action. The speed of opening and closing the switch shall be independent of the operator, and it shall be impossible to tease the switch into any intermediate position. B. The interrupter switch shall have separate main and break contacts to provide maximum endurance for fault close and load interrupting duty. C. The interrupter switch shall have insulating barriers between each phase and between the outer phases and the enclosure. D. A maintenance provision shall be provided for slow closing the switch to check switch-blade engagement and slow opening the switch to check operation of the arc interrupting contacts. Utility Metering A. Where indicated on the drawings, each utility metering vertical section shall contain provisions for current transformers and voltage transformers as required by the utility. The construction shall conform to the utility company‘s metering standards. It shall also conform to the general electrical and construction design of the switchgear specified above. Customer Metering A. Provide customer metering devices where shown on the drawings. Where indicated, provide a separate customer metering compartment with front hinged door. Include associated instrument transformers. B. Provide current transformers for each meter. Current transformers shall be wired to shorting type terminals blocks. C. [Fixed-mounted voltage transformers including primary fuses and secondary devices] [Voltage transformers with a means of disconnecting including primary and secondary fuses] for metering as shown on the drawings.
B2-10
Medium-Voltage Distribution Equipment
Metal-Enclosed Switchgear – Easily Removable Vacuum Breakers (MEB)
Typical Specifications
Cutler-Hammer
May 2001
D. Microprocessor-Based Metering System Select devices as required for item. Refer to the Cutler-Hammer Power Management Product Guide for detailed specification for metering. IQ Analyzer IQ DP 4000 IQ Generator IQ 200 Accessories A. Supply key interlocks as shown on the drawings. B. For switchgear, ____ kV [station] [intermediate] [distribution] class surge arresters shall be provided connected at the incoming terminations and securely grounded to the metal structure as shown on the drawings. Outoor Enclosures A. Each outdoor vertical section shall have a weatherproof roof. All external openings shall be screened to prevent the entrance of small animals and barriered to inhibit the entrance of snow, sand, etc. A minimum of one (1) 250-watt, 120-volt space heater shall be provided in each vertical section. Power for the space heater(s) shall be furnished [as indicated on the drawings] [by a control power trans-
former mounted in the switchgear] [by a transformer mounted in the low-voltage switchboard/switchgear]. The design shall be non-walk-in type. All doors and covers to be fully gasketed. Nameplates A. A nameplate shall be mounted on the front door of each switch vertical section in accordance with the drawings. Finish A. Prior to assembly, all enclosing steel shall be thoroughly cleaned and phosphatized. A powder coating shall be applied electrostatically, then fused on by baking in an oven. The coating is to have a thickness of not less than 1.5 mils. The finish shall have the following properties: Impact resistance (ASTM D-2794) Pencil hardness (ASTM D-3363) Flexibility (ASTM D-522) Salt spray (ASTM B117-85 [20]) Color 60 direct/60 indirect H Pass 1/8-inch mandrel 600 hours ANSI 61 gray
Miscellaneous Devices A. Communication equipment where indicated on the drawings, shall have the following features: 1. The communication system shall be Cutler-Hammer type IMPACC/PowerNet. 2. Each vacuum breaker position (open and closed), where shown, shall be communicated via an addressable relay. This relay shall communicate over a local area network consisting of a twisted pair of shielded wires. The relay shall monitor an auxiliary switch contact that monitors the breaker position and shall be rated for the application. Each relay shall have a unique address so that it is possible to “call up” and “read” each breaker’s position from a host computer.
