BREAKER RACK OUT AND RACK IN Knowledge Requirement 1. Please list down the required PPE for” Rack Out / Rack In “of medium voltage (6.9 KV) KV) breaker.
The required PPE for” Rack Out / Rack In “of medium voltage (6.9 kV) breaker are:
Hard hat (check whether it has any crack cra ck or it is fit for your head)
Safety glass (check it is clear and fit for your eyes) ey es)
Electrically insulated hand gloves (inspect the gloves for proper voltage class, there is is no signs of wear and tear and other damages)
Safety shoes (Should be electrically insulated and should not be wet)
Arc suit (inspect the suit for signs of wear and tear a nd other damages)
Face shield (check it is clear and fit for your face)
Electrically insulated rubber mat. (It should not be torn or wet)
2. Is it safe when you want to Rack Out / Rack in” any any breaker breaker by touching your knee with the floor. If not, what type of precaution you have to take..?
No, it is not safe. We should use insulating Mat under the Knee. 3. What is meant by connection position, test po position, position, isolated position. How you will identify the correct correct position of a breaker..? CONNECTION POSITION:
In this position the main circuit and the control circuit of the breaker is connected to the external circuit for normal service. TEST POSITION:
In this position the main circuit is isolated and the control circuits are connected. This position permits such as breaker close open test, control circuit function test ctc. ISOLATED POSITION:
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In this position the main circuit and control circuits are isolated. In this position the breaker is completely de-energized.
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4. In the plant where we using vacuum circuit breakers, breakers, air circuit breakers and MCCB..? Vacuum circuit breaker /vacuum switch:
In 6.9 kV bus all the load centers/consumers use vacuum circuit breakers. (load centers to 400V bus & 6.9 KV consumers). . Example: GT starting motor breaker Air circuit breaker:
From 400V bus to 400V load centers Air circuit breakers are used. MCCB:
From 400V load centers to 400V consumers MCCBs are used. 5. What basic things you will check before rack out out / Rack Rack In In the breaker..? Breaker rack out time:
Check whether the breaker is “off” by checking the “open” indication on the breaker. (Some breaker Close/open indication is shown by flags. Red flag means breaker is closed and green flag means breaker is open.)
Check to ensure ampere meter is showing zero
Selector switch should be in Local position.
Breaker rack in time:
Check earthing switch is closed or not. There will be an indication on the cubicle for the status of earthing switch. Also the breaker lock key will remain inside the earthing lock keyhole. This key cannot be removed without opening the earthing switch.
Check the Local / Remote switch position (Selector switch should be in Local position.).
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Check the “control power supply plug” position.
Rack in the breaker (as per direction) and check the breaker rack in position.
Check the MCB’s of control supply and heater supply.
6. What things you will will check before closing / opening of earth switch..?
Before closing the earth switch it is essential to check whether the breaker is disconnected or not. The breaker must be isolated.
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7. How you will normalize the breaker for service..?
With Proper PPE the followings are to be followed
Open the earth- switch if applicable.
Rack in the breaker.
Make on the control power (if applicable).
Set the remote/local selector switch to remote.
Reset (push button) the breaker.
8. Is it essential to close earthing switch every time after racking out the breaker..?
Normally there is no need to close the earthing switch every time after racking out the breaker. 9. In what situation earth switch must be closed..?
When there will be any job on motor side( on the O/L of the breaker ) or if there is any probability of getting physical contact with the O/L line of the breaker it is essential to discharge the residual electricity through earthing switch.
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