P3T32 Utilize for Cable Differential

[Vasutha]

Hi Team, we have got the challenge from Customer to utilize P3T32 - 87T for cable differential protection for bus-tie feeder.

I understand that, in the principle of differential protection, it's able to apply but I'm not sure about protection relay setting and parameter configuration concerned.

Could you please advise whether it is possible to apply P3T32?

[Rudolf_Simon · Accepted solution]

Hello Vasutha,

you're correct, differential protection in principle can be applied, also a "transformer differntial" like P3T32, if the distance between IED and CTs at cable ends can be managed by CT sizing (mainly by cross section of wires).
In such application (like in generator protection) no transformer specific settings apply:

• Set vector group = Yy0
• No zero-sequence current elimination
• Same nominal voltage on both sides
• Nominal power should reflect rated (or maximum) load current of the protected cable (e.g. for max. load current = 100 A and nominal voltage 10 kV, I would set nominal power = (100 A * 10 kV * sqrt(3) = 1 732 kVA) => 2000 kVA

These P3T32 settings are in GENERAL/Scaling: 

regards

Rudolf

[Vasutha]

Hello Rudolf,

Thank you for your reply and advice. I would like to ask for detail setting about "power direction (outgoing or incoming)" in Easergy Pro.

Because, actually, the power will be both direction which is depended on Incoming A or B and bus-tie closing. 

[Rudolf_Simon]

Hello Vasutha,
this 'power direction' setting defines, in which direction measured power is with positive sign.
So, 'outgoing' means power flowing from the bus to the feeder is with positive sign, power flowing from the feeder to the bus with negative sign. That's all.
It does not affect protection functions. 

regards

Rudolf