working on CT secondery

[rashy70]

I am using 400/5 A outdoor type current transformer on 33 kV out door switch, I have to modify the wiring in secondary side of the CT which is connected to a relay . One terminal of the primary side of the CT is connected to Live conductor(33kV) , other terminal is connected to load . Since the switch is open there is no current is flowing thru the CT . Please clarify me is there any harm in working on the secondary side of the CT ,since the one of the primary terminal is connected to live conductor (33kV).

 

[waross]

Not a good plan.
Issue #1, capacitive coupling. If the secondary is not grounded, it may charge up as one plate of a capacitor. The capacity is so little that the direct hazard may be slight. The indirect hazard may be more serious. An unexpected electrical shock, however slight may cause involuntary movement and or dropped objects. The movement may cause contact with energized surfaces or it may cause a fall or cut.
Dropped objects may contact energized surfaces and light up an arc or may cause damage or injury to equipment or persons below.
If a CT primary is connected, then the shorting links should always be in place on the secondary before performing any work on the CT secondary wiring.
Safe limits of approach have been established for most jurisdictions in North America. It may be impossible to install the secondary shorting links without infringing on the safe limits of approach for 33kV.
The 33kV should be de-energized and consideration should be given to moving the CT connections to the load side of the 33 kV switch for future work.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[TurbineGen]

Is this an airswitch or a breaker? If it is a breaker, it is usually good practice to not assume the circuit is open when the breaker shows open. You should have a visible disconnect before performing any work. If you are on an air disconnect switch, then it might be permissible to perform work so long as the CT's are shorted.

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If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[rashy70]

It is Air switch, CT is installed ahead of the switch.

 

[scottf]

If you short and ground the secondary terminals of the CT, it is safe to work on the secondary wiring. Of course, if you can get to the CT secondary box, then I would short and ground the secondary terminals and also lift the secondary leads coming in.

Comments above concerning safe limits of approach should also be considered if the line is energized.