March 22nd, 2009
You are currently browsing the articles from circuitmaniac.com written on March 22nd, 2009.
In this type of protection, transmission lines are used to carry protective currents at carrier frequency (30 to 200 kc/s) or at an ultra high frequency (above 900 mega cycles). When the transmission lines carry protective currents at carrier frequency it is called carrier current-pilot protection and when it carries protective current at ultra high [...]
Written by John on March 22nd, 2009 with 2 comments.
Read more articles on Feeder protection and Power System and Switchgear&Protection.
The distance impedance relays are normally used for phase- to-phase faults as for such faults the loop impedance between the phase is obtained which remains constant, but in case of earth fault the loop impedance consists of impedance of one line and the impedance of the earth fault which is a variable factor. Practically it [...]
Written by John on March 22nd, 2009 with 2 comments.
Read more articles on Feeder protection and Power System and Switchgear&Protection.
When a generating station supplies to three sub-stations radially, it is desired to isolate all those sub-stations beyond the fault point. This can be achieved by the use of time delayed over current relay but the main disadvantage is that if the fault is near the power station it will take much longer time to [...]
Written by John on March 22nd, 2009 with no comments.
Read more articles on Feeder protection and Power System and Switchgear&Protection.
This relay operates at a constant time for all faults independent of the distance of occurrence of fault. For its application consider Fig 10 which represents a power station feeding transforming sub-station. The power transformer is protected independently by inverse-time over current relay. Let, it be required to provide a relay at the input side [...]
Written by John on March 22nd, 2009 with 2 comments.
Read more articles on Feeder protection and Power System and Switchgear&Protection.
Although the protection for cable feeders (only non-pilot wire type) can be used for transmission lines also, but generally such protections for transmission lines are not used as the transmission lines are longer and work at much higher voltage and there are frequent faults. For protection of transmission lines usually distance protections are used, the [...]
Written by John on March 22nd, 2009 with 1 comment.
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The probability of faults occurring on the lines is much more due to their greater length and exposure to atmospheric conditions. This has called for many protective schemes which have no application to the comparatively simple cases of alternators and transformers. The requirements of line protection are: (i) In the event of a short circuit [...]
Written by John on March 22nd, 2009 with no comments.
Read more articles on Feeder protection and Power System and Switchgear&Protection.
