It is an inverse definite minumum time relay. In IDMT relay
its operating is inversely proportional to fault current
and also a characteristic of minumum time after which this
relay definately operates.
It is inverse in the sense , the tripping time will decrease as the magnitude of fault current increase.
"for a fault current of 25KA-the time delay may be 2s.
& for a fault current of 30KA the tme delay may be 1.5s.thus as the fault current increases the time delay decreases.
is an inverse definite minimum time relay
there are 2 precautions to be considered when using this these precautions are the time setting and the current tap setting
these are to be considered since the relay is dependent on the inverse of time
We have one 500KVA transformer. We have tested REF relay
and commissioned. After one and half year, due to some
ground fault in one of the DB circuit Transformer tripped
by REF relay. What will be cause and remedy. Please advise?
When in a large power system if the demand of power is
larger than the generated power the frequency of the power
system drops.(assume the rated frequency is 50Hz and now it
So does this mean the demand is totally supplied with a
lower value of generated power in a lower frequency?