What is the basic difference between 90% stator earth fault
and 100% stator earth fault, and its phenmenona?

Answer Posted / a.p.nanjappa

This is an application with power plant genrator protection.
In early 1950-75,only 90% stator earth fault protection
used for Generator Stator winding.
GE,westinghouse,hitahachi,GEC,BBC,KWU.ON 1975 ONWARDS,
THEN 100% STATOR EARTH FAULT DEVELOPED USING OPEN DELTA
VOLTAGE OFGENERATOR AND USING FIRST AND THIRD HARMONIC
BRIDGE.
WEST AND EUROPE,INDIA USED GENERATOR NETRAL GROUNDING
TRANSFORMER AND ON SECONDARY OF THIS TRANSFORMER90%STATOR
EARTH FAULT PROTECTION IS USED.
FOR 100% STATOR EARTF FAULT USE OPEN DELTA VOLTAGE.
Russian practice is use voltage transformer for generator
neutral gounding.
when I was DISCUSSING this with european manufacturer, they
want to delete 100% protection.In a generator it is meaning
less.fault is fault.It is time consuming for repair.
As a new challenge-generator manufacture claim 100%
availabilty of Generator with VIP.
/MICADOUR ELASTIC INSULATION. In gas turbine a single
generator rating is selected for single shaft gas turbine
and steam turbine. upto 275MW. AND 400MW

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