VT/PT Secondary as point of isolation

[dfdt]

Most of us know that during planned outage of primary plant/equipment its customary to isolate all possible points/sources of energisation and secondary of voltage transformer being one of them. Our issue is that we also check for the status of PT/VT mcb as one of the condition required to close Earth switch (presence of under/no voltage provided mcb is closed. Hence we are in quandary i.e. continue with out practice of opening & tagging the mcb or let it remain closed so the earth switch interlock is reliable.
Any comments or suggestions?

 

[waross]

Check your primary voltage with a Modiewark.

Link

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Ohm's law
Not just a good idea;
It's the LAW!

 

[davidbeach]

Just check on the VT side of the MCB. Opened or closed ceases to matter.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[dfdt]

Voltage tester/sensors may be alright for medium voltages but can these be used for voltages 220kV and above?

 

[davidbeach]

That one says up to 750kV.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[waross]

$299 doesn't seem like a lot of money to spend for safety.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[RRaghunath]

Is it necessary to isolate VT secondary side when primary side is already isolated and locked??
I haven't come across such practice.

 

[dfdt]

Raghu - In our case Primary side is not isolated as its hard on connection to Air Insulated Busbar (outdoor switchyard)

 

[beyond86]

bholas, but you should have earth switch to grounding equipment.

 

[stevenal]

Isolate test and ground in that order. If the system is not set up so that can be done, it is time to make changes so it can be.