Biased Differantial Protection
- Thread starter electrics
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bias here is physical or an action??
http://leconsystem.com/Articles/Differential_Protection(NinadDeo).pdf
Also Google Biased Differantial Protection
Also Google Biased Differantial Protection
rcwilson
Senior Member
- Location
- Redmond, WA
Imagine a differential protection scheme across a transformer. CT's onthe HV side measure curent going in and CT's on the LV side measure current coming out. If IN = OUT teh trasnformer is OK, if they are not the same, there is a fault inthe zone and the relay trips.
The CT's feed the current signals to the differential relay. The relay compares the currents in and currents out after accounting for different voltages and phase shifts either through CT ratios and CT connections or through digital calculations.
What if there is a fault in the load supplied by the transformer? A large current flows in and out. The transformer is OK, so the transformer relay should not trip. That is a through fault.
Fault current is flowing through the differential protection zone to a fault outside the zone. The system has to be designed to not trip for these heavy through faults, even though the high fault currents may saturate the CT's and the relay gets distorted current signals.
The proteciton engineer specifies the CT's and the settings so the relay does not false trip on through faults.
The CT's feed the current signals to the differential relay. The relay compares the currents in and currents out after accounting for different voltages and phase shifts either through CT ratios and CT connections or through digital calculations.
What if there is a fault in the load supplied by the transformer? A large current flows in and out. The transformer is OK, so the transformer relay should not trip. That is a through fault.
Fault current is flowing through the differential protection zone to a fault outside the zone. The system has to be designed to not trip for these heavy through faults, even though the high fault currents may saturate the CT's and the relay gets distorted current signals.
The proteciton engineer specifies the CT's and the settings so the relay does not false trip on through faults.
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