SOME circuit breakers are ‘fixed pattern' and some are ‘withdrawable'. The fixed pattern circuit breakers are fixed in position and can't be isolated from the busbars or the cable that feeds them. Withdrawable circuit breakers can be withdrawn from the service position into an isolated position and locked into that position.
A circuit breaker that has this facility is used as a safety measure. If, for example, a motor has to be worked on, or a pump driven by a motor has to be worked on, then you want to be very sure that the motor will not be energised without warning.
One can hang any number of signs on a circuit breaker saying ‘Don't Switch On' or ‘Do not Operate' but fundamentally, if a circuit breaker is disconnected by withdrawing it from contact with the busbars and the associated feeder cables... then you are safe and so is everybody else.

The process of withdrawing a circuit breaker from contact with the busbars and the cable is called ‘racking out' and the process of putting it back into service is called ‘racking in'.
Just about all medium voltage circuit breakers are withdrawable. Very often they have connection spouts that are racked in via ports, which are covered with shutters that open and close automatically (open to rack in, close to rack out).
The shutters prevent anybody reaching through the circuit breaker ports and touching the cable or the busbars. Frequently, the shutters can be locked closed, which will prevent the circuit breaker being racked in, unless the padlock is removed.

There are some rules about this whole process that you should take note of. When you are racking a circuit breaker in or out then you are causing it to make contact with live busbars. If the circuit breaker is faulty, then this is when it will blow up or flashover.
So, if you do this operation in a short sleeved shirt with your eyes unprotected then you can potentially end up burned all over, with damaged eyesight.
So wear long sleeves and safety glasses. If you don't have the glasses, close your eyes and look away. Sound silly? Wait until you're lead around by the arm because you did something stupid and brave. Others I know just look away.
Have you ever seen a 35 000 amp flashover? (This is quite possible with the switchgear of today.)
Well, very few have lived to describe what they saw.

With older medium voltage switchgear there will always be a ‘hissss' as the circuit breaker spouts come close to contact with the live busbars. This is due to the circuit breaker charging up. Don't, for heaven's sake, stop cranking the racking handle. Hear the hiss and crank on until the circuit breaker is in the service position. The same applies when racking out. Don't stop when you hear the hiss. If you do stop that's when it will become dangerous.
It is always a good idea to take the locks off the shutters before you rack a circuit breaker in. If you don't, you end up trying to force the circuit breaker spouts or contacts through the shutters. The shutters are made of steel so you will not succeed. All that will happen is that you will damage the circuit breaker.

Racking handles: I think the SA Navy Dockyard has the finest collection of racking handles in South Africa, if not the world. They have English Electric gear, Reyrolle LMT, BBC, ABB and Siemens.
This is the result of the Department of Public Works giving contracts to the lowest tenderer whose offer meets the specification. The problem with all of this is that the artisans who work on this equipment will have to become experts on which racking handle belongs to what equipment - which is really nothing they should have to worry about. Stick to one type of circuit breaker.

Finally, electrically driven racking equipment - where circuit breakers are racked in and out using a small motor, remotely controlled. In my opinion, this is rubbish. Don't even go there. The operator should be able to feel what is happening - manually. You really can't do that remotely...
Email: machoy@iafrica.com