when the cable of a motor shorted then differetial relay act
differential protection relay
They're completely different, used for different applications (usually). A distance relay uses both current and voltage. A differential relay uses only current. A differential relay usually has harmonic restraint capability, while distance relays ideally track system frequency. Differential relays require fast operation, while distance relays may not be required to operate as quickly. Distance relays have more issues with operating for out of zone problems than differential relays. There are many more, but this gives an idea.
I am going to assume that you are asking about a differential relay. It is basically just that- it compare two different sources and will trip at a set value value of the difference. These can be directional as well. A couple of examples are transformer protective relays and bus differential. A transformer relay will measure the amount of current coming into the transformer and the amount of current going out. If there is a disparity due to an internal fault the relay will trip the supply source and deenergize the transformer. Same for the Bus differential.
This is basically a differential relay that contains an additional restraining coil with the operating coil connected at its midpoint used to prevent the unnecessary pick up of the relay.
It depends what you mean by an '11-kV transformer'; do you mean a primary transformer (33/11-kV transformer) or a distribution transformer (11-kV/400-230-V transformer). Differential protection IS offered on primary transformers.
differential protection relay
In power transformer, a differential relay is a relay that verifies the balance of current between the primary and the secondary face of a transformer. It is also employed in other components of the power system like in protecting cables. Differential relay is also called a unit protection.
when the cable of a motor shorted then differetial relay act
CT's are used as inputs to the differential. If the CT is bad, or it is not wired to the differential correctly, it will cause differential current to be seen by the relay, resulting in a trip.
Power Transformer
They're completely different, used for different applications (usually). A distance relay uses both current and voltage. A differential relay uses only current. A differential relay usually has harmonic restraint capability, while distance relays ideally track system frequency. Differential relays require fast operation, while distance relays may not be required to operate as quickly. Distance relays have more issues with operating for out of zone problems than differential relays. There are many more, but this gives an idea.
I am going to assume that you are asking about a differential relay. It is basically just that- it compare two different sources and will trip at a set value value of the difference. These can be directional as well. A couple of examples are transformer protective relays and bus differential. A transformer relay will measure the amount of current coming into the transformer and the amount of current going out. If there is a disparity due to an internal fault the relay will trip the supply source and deenergize the transformer. Same for the Bus differential.
This is basically a differential relay that contains an additional restraining coil with the operating coil connected at its midpoint used to prevent the unnecessary pick up of the relay.
Differential relays should only operate for faults within the zone of protection, so there is no coordination issue. The reason to coordinate relays is for backup protection (a relay at a remote substation sees faults that should be cleared by another relay, for example). A differential will not see this fault, since it is external to it's zone of protection.
, The zone of protection for 2 , 3 or multi windings transformers differntial relay is decided by the location of CT.s at the respective sides i.e. HV. IV OR LV SIDES . Ideally on any fault within zones of these C.T.s the differential relay should act. However sometimes inadequecy of C.T. s ratings like low burden rating, less knee point voltage or improper biased settings may cause the differential relay to operate even on line faults. Regards, J.M.SHAH
Metrosil is a non linear resistor and used with high impedance differential protection.During an internal fault ,the voltage developed across the relay can be very high and the metrosil limits the voltage across the relay ,thus protecting the relay and the wiring from any damage
It depends what you mean by an '11-kV transformer'; do you mean a primary transformer (33/11-kV transformer) or a distribution transformer (11-kV/400-230-V transformer). Differential protection IS offered on primary transformers.