Recent content by khadisa

Actually with Zone 1 setting of 70KM it will show zone 1 trip at a location of 220KM and sometimes the fault location will be much more than the length of the entire line.

Hi We have a Distance Relay From ALSTOM, Type LFZP111. The Line is 132KV and about 300KM Long. There are transformers at various point along the line. We set 80% (70KM) of the first segment as Zone 1 and the entire length of the line as Zone 2. What distance do We set as the length of the line...

Regarding the NCT, it was on the neutral bushing but changed by mounting an external one when this problem started. This problem normally comes when there is a through fault or a fault on one of the 330KV lines emanating from the same swithchyard.

We have a 90MVA, 330/132KV, Y/Y transformer that is tripping on REF on the secondary and bucholtz but when re-energised it remain in service. We carried out magnitization, ratio, short circuit and insulation resistance tests which show the transformer to be healthy. What other tests can we...

On the relay I have been seeing, they have a hi set different from instateneous and it can be timed. What we normally do is to provide the IDMT with a higher time than the hi set and a lower current setting. As such the time of relay operation will be graded according to the level of the fault.

I am sorry for the omission. The MBCH12 relay come in single phase units. So, the terminals 27 of the three relays are linked and nothing is connected to them.

Hello, We have an old CT that is of British Standard, of class 0 & T10 on one core and the other core T10. I want to know the equivalent class in IEC standard. Also another CT is rated 2 x 4/1200, Siemens type of BS standard. What does this signify?

Thanks to everybody, I have got a drawing on how to connect the relay from the manufacturers (AREVA).

Your understanding is wrong a430. The main CTs on primary and secondary are wired in star. So without the ICTs I have something to connect to terminal 27.

I have an REF relay in the primary circuit and a floating delta on both primary and secondary ICTs is used for zero sequence filtering.

Please, I want to wire an MBCH12 (ALSTOM) differential relay to protect a 132/11KV, 15MVA, Yy0 transformer. It is to replace an old relay. In the present scheme the primary and secondary CTs are wired in star while interposing CTs on both primary and secondary are wired in star/delta. The...

amps21 We have a bucholz relay but there was no bucholz alarm nor trip.

Sometimes it is operated 4 to 5 times in a day due to fault or load shedding.

Whether step up or step down, a transformer is just a medium for power transfer at a desired voltage level. The input power does not matter but you should not overload the transformer. When you use a transformer of high rating to supply a small load you will have no problem but that of under...

RalphCristie have mentioned most of the differences, but in my place, where the breakers are operated quite often, we find the Sf6 breakers more suitable. We always have a gas density monitor and alarm. It can easily be refilled.