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Protection Riddle No.120 - Selective Earth fault protection in multiple generators
Design of protection scheme to detect earth fault and isolate the faulty source in multiple 11kv generators connected to common bus through dedicated breakers.
There are six 11kv generators with star stator windings connected on common bus through dedicated breakers. Proposed scheme of neutral grounding will be one common NGR low resistance and switched neutral through vacuum contactors. What would be the protection scheme so that only the faulty generator will get isolated and the healthy one will remain online.
Only one generator will be grounded and the remaining will be ungrounded. Please specify how the selective relying is achieved if
1- fault occur on Grounded generator
2- fault occur on un grounded generators
Author : Muhammad Waqas - From: Pakistan
 
#1
Thu, July 21st, 2016 - 05:49
This is achive by using directional earthfault relays using the neutral current from the grounding as polarizing or the reference quantity and the using the 3Io from the phases of generator as operate quantity.
 
Author : rian0201 - From: Filipino
 
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