Generator Circuit Breaker (Low Voltage)
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| Illustration 1 | g00845373 |
Generator Circuit Breaker (1) Indicator for breaker trip (2) Indicator for accessory (shunt trip) (3) Indicator for accessory (spring release) (4) Indicator for the status of main contacts (5) Indicator for the status of spring charge (6) Push button for closing the breaker (7) Push button for opening the breaker (8) Charging handle for spring charging (9) Instantaneous trip setting (10) Indicator for position of the breaker rack (11) Interlocked lever door | |
Note: There are two possible states for the indicator for status of contacts (4) : "OPEN" and "CLOSED". There are two possible states for the indicator for the status of spring charge (5) : "CHARGED" and "DISCHARGED".
The operator closes the generator circuit breaker in order to energize the connected load and the operator opens the generator circuit breaker in order to de-energize the connected load. During fault conditions or overload conditions, the trip unit automatically opens the generator circuit breaker during fault conditions or overload conditions. All basic operations of the generator circuit breaker can be performed from the front of the generator circuit breaker.
During normal operations, the generator circuit breaker performs the following operations by the use of control power: charging, opening and closing.
Charging the Generator Circuit Breaker
In order to manually charge the generator circuit breaker, pull down on the charging handle for spring charge (8). Pump the handle up and down until the spring is charged. The indicator for the status of spring charge (5) will become yellow. Energy will be stored in the spring. Multiple manual operations of the generator circuit breaker may be performed.
Closing the Generator Circuit Breaker
The generator circuit breaker is normally closed by turning the circuit breaker switch to the CLOSE position.
Push the push button for breaker close (6) in order to close the breaker manually. The generator circuit breaker can only be closed when these conditions exist:
- The generator circuit breaker is open.
- The indicator for the status of spring charge (5) shows that the device is charged.
- The generator circuit breaker has not been tripped by the control.
Opening the Generator Circuit Breaker
Push the push button for opening the breaker (7) in order to manually open the generator circuit breaker.
The generator circuit breaker may be opened remotely through a shunt trip. The shunt trip is operated by any engine fault or optional equipment such as protective relays. Push the indicator for breaker trip (1) in order to reset the generator circuit breaker after a fault for overcurrent.
When the trip is the result of an overcurrent, the fault must be cleared before the generator circuit breaker can be reset.
Accessory Windows for the Generator Circuit Breaker
There are three windows for accessory indication. If an accessory is installed, verification will be made without the necessity of moving the generator circuit breaker out on the rack. One standard accessory is the shunt trip. The shunt trip opens the generator circuit breaker when the shunt trip is energized by the control system.
Spring Release
Another standard accessory is the spring release. The spring release closes the generator circuit breaker when the spring release is energized by the control system.
Instantaneous Setting
The trip unit for the generator circuit breaker is equipped with a setting for instantaneous overcurrent. This setting is set at the factory. This setting may be adjusted in the field.
Levering (Racking) of the Generator Circuit Breaker
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| Illustration 2 | g00845430 |
Moving the generator circuit breaker on the mounting rails is called racking of the generator circuit breaker.
The generator circuit breaker can be racked out of the switchgear for these reasons: inspection, testing, repair and disconnecting the load. The positions are shown in illustration 2. Open the interlocked lever door (11) in order to operate the mechanism. (The generator circuit breaker must be open.) Insert a 0.375 inch drive extension on a ratchet. The entire generator circuit breaker can be racked in and out with the ratchet to the desired position.
See "Air Circuit Breakers Product Guide" for more information. The publication contains further information on the generator circuit breaker: inspection, testing and maintenance.
Generator Circuit Breaker (Medium Voltage)
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| Illustration 3 | g00861409 |
Generator Circuit Breaker (Medium Voltage Switchgear) (12) Potential transformer secondary fuses (generator bus) (13) Thermal overload (motor contactor for the radiator fan) (14) Overload relay OL1 (motor contactor for the radiator fan) (15) Charge or close fuses for the generator circuit breaker (16) Fuses for the trip coil for the generator circuit breaker (17) CT shorting terminal blocks (generator bus current transformers) (18) Generator circuit breaker (19) Manual operating mechanism (20) Package of documentation (21) Local indicator of breaker position (22) Rack mechanism (23) Racking rail insert locations | |
Note: The potential transformer secondary fuses (generator bus) (12) have the following ratings: 120 ACV, 2 Pole and 10 Amperes.
Note: Ensure that the shorting screws are removed from the current transformer shorting terminal blocks (17) before operating the switchgear.
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The secondary wires of the current transformer must be shorted together when they are disconnected from the equipment. Extremely high voltages will be generated at the lead ends if the secondary wires are not shorted together. Bodily contact with high voltage will result in serious injury or death. |
Note: The generator circuit breaker (18) has the following ratings: 5 kV, 250 MVA, 600 A, 3 Pole and drawout.
Note: The racking mechanism (22) is operated with a racking handle that is shipped separately.
Note: Install the rails that are shipped separately into the racking rail insert locations (23) before racking out the generator circuit breaker.
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| Illustration 4 | g00856083 |
Generator Circuit Breaker (24) Socket for manual charge (25) Operations counter (26) Indicator for spring "Charged/Discharged" (27) Indicator for "Open/Closed" (28) Button for manual close (29) Button for manual open | |
Indicator for Spring "Charged/Discharged"
Each generator circuit breaker is equipped with an indicator that shows the state of the spring that provides the stored energy for tripping the generator circuit breaker.
Charging the Generator Circuit Breaker
The generator circuit breaker is charged, opened and closed by the control power circuit during normal operation. Insert the charging handle into the socket for manual charge (24) in order to manually charge the generator circuit breaker. Charge the closing springs with about 38 cycles of the handle. When charging is complete, the closing crank goes over center with an audible click. The indicator for spring "Charged/Discharged" (26) shows the "Charged" indicator. If the springs are charged on a generator circuit breaker that is closed, no click is heard at the end of the charging operation. Discontinue the charging process and remove the charging handle when the "Charged" indicator becomes fully visible. Continued attempts to charge the generator circuit breaker may result in damage to the mechanism. The charging handle should be stored in the power module.
Indicator for "Open/Closed"
The Indicator for "Open/Closed" (27) shows the position of the primary contacts of the generator circuit breaker. This indicator is used as a safety precaution in order to ensure that the power module is disconnected from the load.
Closing the Generator Circuit Breaker
Push the button for manual close (28) in order to close the generator circuit breaker manually. Normally, the generator circuit breaker is closed by turning the circuit breaker switch to the closed position. This is possible only when conditions are correct for closing the generator circuit breaker.
Opening the Generator Circuit Breaker
In order to open the generator circuit breaker manually, push the button for manual open (29). The generator circuit breaker may be opened remotely through the electrical operation of a trip circuit. The trip circuit is operated by any engine fault or other equipment such as a control switch or protective relays. The generator multifunction relay (GMR) must be reset in order to reset the generator circuit breaker after an overcurrent fault has occurred. When the tripping is due to an overcurrent, the fault must be cleared before any attempt at resetting the generator circuit breaker can be made.
Levering (Racking) of the Generator Circuit Breaker
Moving the generator circuit breaker on the mounting rails is called racking of the generator circuit breaker.
The generator circuit breaker can be racked out of the switchgear for the following reasons:
- Inspection
- Testing
- Repair
- Providing an ensured disconnect from the load
The lever is used in order to move the generator circuit breaker between the TEST position and the CONNECTED position. The lever consists of the following items: a drive screw and nut, two side rails and a sliding cage. A red flag indicates that the generator circuit breaker is fully engaged. After tripping the generator circuit breaker, the lever can be engaged and the generator circuit breaker can be withdrawn to the TEST position by turning the lever counterclockwise. This position is indicated by no further motion of the crank. The latch for the generator circuit breaker can be disengaged only by lifting the release for the latch when the generator circuit breaker is in the TEST position. The side rails should be stored in the power module.
Operations Counter
All generator circuit breakers for medium voltage are equipped with an operations counter. When the generator circuit breaker is opened, the linkage that is connected to a pole shaft lever advances the operations counter by one.
Further Information
Further information for the generator circuit breaker is available on the following topics:
- Inspection
- Testing
- Maintenance
See Installation, Operation, and Maintenance Instructions, RENR5895 January 1999, "Cutler-Hammer Instructions for Installation, Operation, and Maintenance of Type VCP-W Vacuum Circuit Breakers I.B. 32-255-1F". This publication is in the package of documentation (20) .