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Dear Friends,

Welcome to our new blog related to sharing of electrical knowledge with all electrical engineers.

If you have to share your knowledge related to electrical engineering then you are most welcome in our new blog & I will post your knowledge with your name.

Share electrical machine, electrical power system, power electronics, basic electrical engineering, electrical circuit & all other electrical subjects knowledge with us.

If you have to post anything please send your knowledge in my mail id...................

patnaik.lakhankumar@gmail.com

Thank You

Lakhan Kumar Patnaik
Electrical Engineer

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One & Half Breaker Arrangement - Substation design (Bus Bar Schemes)

In this scheme, three circuit breakers are used for controlling two circuits which are connected between two bus bars. Normally, both the bus bars are in service. A fault on any one of the bus bars is cleared by opening of the associated circuit breakers connected to the faulty bus bar without affecting continuity of supply. Similarly, any circuit breaker can be taken out for maintenance without causing interruption. Load transfer is achieved through the breakers and, therefore, the operation is simple. However, protective relaying is somewhat more involved as the central (tie) breaker has to be responsive to troubles on either feeder in the correct sequence. Besides, each element of the bay has to be rated for carrying the currents of two feeders to meet the requirement of various switching operations which increases the cost. The breaker and a half scheme is best for those substations which handle large quantities...

Generator Protection - Rotor Earth Fault Protection (64R1/ 64R2)

Rotor Earth Fault Protection (64R1/64R2) The field circuit of generator (i.e. rotor winding) is an isolated D.C. circuit and not earthed anywhere. The field can be exposed to abnormal mechanical or thermal stresses due to vibration, excessive currents or choked cooling medium flow. This may result in a breakdown of the insulation between the field winding and the rotor iron at one point where the stress has been too high. A single earth fault in the field winding or its associated circuits, therefore, gives rise to a negligible fault current and does not represent any immediate danger. If however a second ground fault should occur, heavy fault current and severe mechanical unbalance may quickly arise and lead to serious damage. It is essential therefore that any occurrence of insulation failure is discover and that the machine is taken out of service as soon as possible. Normally the machine is tripped instantly on occurrence of second rotor earth fault. Three method are avai...

Generator Protection - Stator Earth Fault Protection

Stator Earth Fault Protection In most countries, it is a common practice to ground the generator neutral through a Grounding Transformer having a loading resistor across its secondary. This method of earthing is called high impedance earthing where the earth fault current is limited to 5-10 Amps. Tuned reactors which limit the ground fault current to less than 1.0 A are also used. The generator grounding resistor normally limits the neutral voltage transmitted from the high voltage side of the unit transformer in case of a ground fault on the H.V. side to maximum 2-3% of rated generator phase voltage. Short circuits between the stator winding in the slots and the stator core are the most common electrical fault in generators. Interturn faults, which normally are difficult to detect, will quickly develop into a ground fault and will be tripped by the stator ground fault protection. 95% stator ground fault relay for generator For generators with unit tra...

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