Answer / nitin lothe

Its the protection scheme used for Power Transformers to
detect internal faults n also termed as Differential
Protection. If there is difference in currents on HV and
corresponding LV side of transformer of the same phase,
protection will operate.

Answer / shyam kishor

Merz-Price protection is the method used for protection of alternators. it is a most common system used for the protection of stator winding faults employs circulating current principle. in this scheme of protection,current at the two ends of the protected section are compared. under normal operating conditions,these currents are equal but may become unequal on the occurrence of a fault in the protection section. the difference of the currents under fault condition is arranged to pass through the operating coil of the relay. the relay then closes its contacts to isolate protected section from the system.(Ref. book on power system v.k mehta and rohit mehta)

Answer / sudipt jena

Merz Price is also called Differential protection. And is used to protect alternator and also transmission line.For this we have two engage CT's at both the ends of the portion/equipment to be protected. In this method breaker trips, if fault occurs within both the CT's only, and not for outer zone.

Answer / satish

This type of protection provides a continuous check on faults within the points, where the C.T.s are used as in shown in fig 2. There are two sets of C.T.s; each set is mounted on either end of the stator phase. The secondaries of these current transformer sets are connected in star and their ends are connected together through pilot wires. The over current inverse time relay is connected across the equipotential points in the pilot wires, which will naturally be in center of these wires as shown in fig 2. But it’s convenient to locate these relays adjacent to the main circuit breaker; this can be achieved by inserting balancing resistance in series with the pilot wires to achieve equipotential point near the main circuit breaker as shown in fig 3. If there is no fault in the generator, same current will pass through the C.T.s at both the ends and there will be no current spilling into the relay.



Now if earth fault occurs as shown in fig 2, there will be an increase in current through set C.T.1 as compared to current through C.T.2. Thus there is no current balance any more resulting into spilling of current through the relay R hence tripping the circuit. If there is short circuit between the two phases as in fig3 it will also cause operation of relay R and tripping of the circuit breaker. This scheme does not provide protection for the turns of same phase

Answer / vinay

merz pricr protection mean voltage will be balanced under
no fult condition if fult occur it will unbalanced

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