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Buchholz relay is a gas- actuated relay installed in oil-immersed transformers for protection against all kind of faults. It is used to gives an alarm in case of slow developing faults or incipient faults in the transformer and to disconnect the transformer from the supply in the event of severe internal faults. It is installed [...]
Written by John on March 19th, 2009 with 16 comments.
Read more articles on Power System and Switchgear&Protection and Transformer Protection.
SELF BALANCE SYSTEM The self balance system discussed in the category ‘ protection of generators’ can also be used without any modification for transformers; but the same type of equipments should be used for both primary and secondary windings. OVER CURRENT AND EARTH FAULT PROTECTION The over current protection is needed to protect the transformer [...]
Written by John on March 19th, 2009 with 1 comment.
Read more articles on Power System and Switchgear&Protection and Transformer Protection.
The differential protection used for transformers is based on the principle of current circulation. This type of protection is mostly used for transformers as this responds not only to inter turn fault but also provides protection against phase-to-phase faults. Following are the complicated features in transformers and there remedial measures: 1. In a power transformer, [...]
Written by John on March 19th, 2009 with 6 comments.
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Merz price circulating current system protects against phase-to- ground and phase-to-phase faults. It does not protect against turn-to-turn fault on the same phase winding of the stator. It is because the current that this type of fault produces flows in a local circuit between the turns involved and does not create a difference between the [...]
Written by John on March 19th, 2009 with 3 comments.
Read more articles on Generator protection and Power System and Switchgear&Protection.
The over current and earth fault protection is same as the over current and earth fault protection of transformers which will be discussed later. Fig 6 shows the over current and earth fault protection scheme for generators. Share and Enjoy:
Written by John on March 19th, 2009 with 10 comments.
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This is very sensitive type of earth fault detection scheme, which necessarily consists of two connecting cables connected to the two ends of each phase and the cables are passed through the circular aperture of the ring type C.T as shown in fig 5. Under normal working conditions the current carried by two cables in [...]
Written by John on March 19th, 2009 with no comments.
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The biased circulating relays are useful because they allow non-similarity between two sets of C.T.s. the restraining coil is inserted in series with one of the phases, while the operating coil is connected to the central tapping and the neutral pilot wire as in fig 4. Only one biased relay is shown for simplicity. The [...]
Written by John on March 19th, 2009 with no comments.
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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 [...]
Written by John on March 19th, 2009 with 2 comments.
Read more articles on Generator protection and Power System and Switchgear&Protection.
The major faults in case of generator can be classified as: (a) Failure of prime movers: Whenever there is a fault on prime mover side the conversion of mechanical power to electrical power stops. If this generator works in parallel with other generator sets it will start working as a synchronous motor running at synchronous [...]
Written by John on March 19th, 2009 with no comments.
Read more articles on Generator protection and Power System and Switchgear&Protection.