A generator is provided with restricted earth-fault protection. The ratings are 11 kV, 5000 kVA. The percentage of winding protected against phase to ground fault is 80%. The relay setting such that it trips for 25% out of balance. Calculate the resistance to be added. in neutral to ground connection.

A generator is provided with restricted earth-fault protection. The ratings are 11 kV, 5000 kVA. The percentage of winding protected against phase to ground fault is 80%. The relay setting such that it trips for 25% out of balance. Calculate the resistance to be added. in neutral to ground connection.

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter10: System Protection

Section: Chapter Questions

Problem 10.26P

See similar textbooks

Similar questions

Consider a single line to ground fault at the neutral end of a Y-connected stator winding of a generator. Now, propose a primary protection scheme for the fault along with appropriate diagram. Also, justify the level of protection of your proposed scheme.
Draw the fault current direction both in Current transformer and operating relay coils for internal and external double line to line and double line to ground faults in the Modified Differential Protection System and Restricted Earth Fault Protection system for Alternator Stator Winding. Its a topic of Switchgear protection in power system
Figure 2 shows the circuit of a simple power system. The ratings of the generators, transformers and the motors are as shown in the figure. The reactance of lines 1 and 2 are 40 ohms and 50 ohms respectively. Assume that system is unloaded, and the generators are generating their rated voltage. Select the generator G₁ ratings as base values. Choose the fault location in bus 3. And give the bellow answer For a symmetrical three phase fault on the bus 3 1.Draw the reactance diagram for the fault with all the reactances marked in per unit. 2.Determine the Thevenin's equivalent circuit which can be used to calculate the fault current. (3) Calculate the fault current in ampere and fault power in MVA and the fault current contribution from the generator connected to the bus 3.
A star-connected, 3-phase, 10 MVA, 6.6 kV alternator is protected by differential current protection scheme using 1000/5 amperes current transformers. The star point of the alternator is earthed through a resistance of 7.5 ohm. If the minimum operating current for the relay is 0.5 A, calculate the following parameters such that the each phase of the stator winding which is unprotected against earth-fault when machine is operating at normal voltage. (i) Per phase voltage (in Volts) (ii) Minimum fault current (in Amp) to operate the relay (iii) Unprotected part of alternator winding (in percent) (iv)The emf induced in the unprotected part of the alternator winding
I. Further simplify this diagram to a Thevenin model with (Vf) as the generator. 2. Determine the per unit current flowing and the actual current that flows through the fault switch when closed (assume Ibase is 251 A). 3. Describe the operational features of power relay and circuit breaker designed to protect a radial power feeder, include in your description forms of protection provided by the relay and methods of obtaining line data
A resistance of 8 Ohms is used to ground a 30-MVA, 11 kV alternator. Its relay is set to operate when a 2.2 A out of balance current occurs. The CTs have a ratio of 1000/6. If we consider the reactance of the alternator to be negligible, how much percentage of the stator winding is protected against earth faults? To make this 95%, what is the minimum value of earthing resistance to be used?
Give the names of shaft misalignments occuring in power transmission systems, draw the sketches for each of them and explain their features. For each kind of misalignment propose at least one type of appropriate coupling, which can assure the proper way of operation.give solution as soon as possible.
Draw the fault current direction both in Current transformer and operating relay coils for internal and external double line to line and double line to ground faults in the Merz Price Differential Protection System, Modified Differential Protection System and Restricted Earth Fault Protection system for Alternator Stator Winding. Its a topic of Switchgear protection in power system
Figure 2 shows the circuit of a simple power system. The ratings of the generators, transformers and the motors are as shown in the figure. The reactance of lines 1 and 2 are 40 ohms and 50 ohms respectively. Assume that system is unloaded, and the generators are generating their rated voltage. Select the generator G₁ ratings as base values. Choose the fault location in bus 3. And give the bellow answer For a symmetrical three phase fault on the bus 3 1. Calculate the fault current in ampere and fault power in MVA and the fault current contribution from the generator connected to the bus 3.
The load current in a system is 100 A. The short-circuit current for the smallestfault is 1000 A. An over-current relay capable of carrying a current of 5 Acontinuously is to be used.(a) Suggest a suitable CT ratio.(b) What will be the relay current for the smallest fault?(c) Will the protective CT be able to faithfully reproduce the fault current?
Describe the key principles behind power system protection schemes and their importance in preventing faults and failures.
Explain fault ride through for wind farms