Generator 100% Earth Fault Protection
Generator 100% Earth Fault Protection
(OP)
Dear Folks,
With reference to the attached protection schematic diagram of 153.5MVA@0.8 lag Generator, 100% E/F protection was not considered. With my experience, such higher rating machines require 100% E/F protection. If someone knows, please discuss general / standard criteria of installing 100% E/F protection for such higher rated machines.
Advanced Thanks for your participation...
With reference to the attached protection schematic diagram of 153.5MVA@0.8 lag Generator, 100% E/F protection was not considered. With my experience, such higher rating machines require 100% E/F protection. If someone knows, please discuss general / standard criteria of installing 100% E/F protection for such higher rated machines.
Advanced Thanks for your participation...






RE: Generator 100% Earth Fault Protection
RE: Generator 100% Earth Fault Protection
Quote
An undetected fault near the neutral end of the generator will bypass the grounding transformer and the ground-fault relaying. If a second ground occurs in the same phase near the generator terminal it will be undetectable and unrestricted by the grounding impedance. The generator differential relay would not operate for this fault, because current at each end of the winding would be the same. This extremely high magnitude fault would persist until it evolved into a phase-to-phase fault that is detectable by the differential relay.
Unquote
With refer to above discussion, seems 100% E/F protection is required for higher rated machines.
RE: Generator 100% Earth Fault Protection
RE: Generator 100% Earth Fault Protection
A better use 100%-yes, requerements-no, maybe some local code, but not some standard.
We have a lot of applications with 95% protections on the 200+ MVA, but..on the 64S voltages principle, not current.
Im also don't see 78-pole slip, are also better, but not requrements . Same for dead-mash protection.
BTW, 24-overflux function is connected to VT on the high side of trafo, is also not so good, preferd on the generator voltages.
Best Regards.
Slava
RE: Generator 100% Earth Fault Protection
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If we learn from our mistakes I'm getting a great education!
RE: Generator 100% Earth Fault Protection
RE: Generator 100% Earth Fault Protection
Aren't protection requirements and not some standard or code.
But, Im not agree with such application.
Supplier used redandancy on the terminal base, but connect all protection ( generator and transfromer) in series to same CT's, isn't good style of design.
And for the stub used only one CT before GCB, imho, you need additional CT after GCB for include GCB and naybe VT's in zone of generator 87G ( only one of relays).
Isn't redandancy for my pinion.
Best Regards.
Slava
RE: Generator 100% Earth Fault Protection
RE: Generator 100% Earth Fault Protection
G60 have this functionality, why not use it. Why connect only current from neutral point of generator.
For additional, possible use also 64REF functionality.
Best Regards.
Slava