MBCi and unit protection

[rainfire]

Hello,

I have an 11kV substation that utilises Unit and O/C protection and has 6 ring feeders.

The unit protection used a mixture of Tranlsay H and SDP relays.

the relays are being replaced throughout with MBCis. If there is a pilot fault, will the MBCis initiate a trip at both end of the cable?

Thanks guys

 

[rainfire]

The second question is, in order to convert a balanced volatge unit protection scheme to a circulating current scheme, it is just a case of changing the relays and uncrossing the pilots?

 

[DiscoP]

The MBCI circulating current will operate for a open circuit pilot, but not operate for a shorted pilot. It will operate at both ends.

The Translay H Balanced voltage relay will not operate for an open circuit pilot, but should operate for a short circuit pilot.

The pilots are crossed when changing from a Balanced voltage to circulating current.