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Question
What is 100% 
protection of 
generator? Why 
95% protection 
is used not 100%?
 Question Submitted By :: Sonu2008
I also faced this Question!!     Rank Answer Posted By  
 
  Re: What is 100% protection of generator? Why 95% protection is used not 100%?
Answer
# 1
Generator having lot of protections rotar-stator wdg. earth
fault,over voltage,over current etc.
For that each relay having setting from 0-100 per. with
time period in seconds
According to type of fault we have to set the setting

example :- for earth fault protection we have set upto 50-
70per. because if we set to 100% every and each small
leakage relay trip

so my thinking is only that the setting of each protection
is depend up application of DG only on what load
 
Is This Answer Correct ?    14 Yes 16 No
Sandip Upare
 
  Re: What is 100% protection of generator? Why 95% protection is used not 100%?
Answer
# 2
BECAUSE IF WE USE 100% PROTECTION FOR THE GENERATORS THEN
IT CAN'T BE WORK PROPERLY. IF ANYONE HAVE ANY DOUBTS THEN
CALL ME...... 09729722179
 
Is This Answer Correct ?    2 Yes 53 No
Dalveer
 
 
 
  Re: What is 100% protection of generator? Why 95% protection is used not 100%?
Answer
# 3
to provide the 100% protection for alternator ,it interrupts
the operation of generation even low level faults, so we can
provide protection for alternator 95% instead of 100%
 
Is This Answer Correct ?    4 Yes 9 No
Vijaybharadwaj202
 
  Re: What is 100% protection of generator? Why 95% protection is used not 100%?
Answer
# 4
generators are basically synchronizing machine if a fault
occurs, they fall out of synchronization. but if the fault
is temporary or for a very small duration micro seconds or
seconds then the alternator/ generator may again achieve
synchronization without permanent interruption of supply.
this is the reason why the 95% protection is provided
instead of 100% protection.

otherwise for even for the small fault we would experience a
cut off eg: a small fault like contact of two phase
conductors due to sudden wind. which is a temporary fault.
 
Is This Answer Correct ?    37 Yes 11 No
Shailesh Tankni
 
  Re: What is 100% protection of generator? Why 95% protection is used not 100%?
Answer
# 5
since few turns of wdg have very small voltage therefore
fault current flowing through secondary of CT is less than
preset value for relay operation.Hence relay will not
operate for that much portion of winding.
 
Is This Answer Correct ?    7 Yes 3 No
Dayanidhikinkar
 
  Re: What is 100% protection of generator? Why 95% protection is used not 100%?
Answer
# 6
If a fault occurs at say 98%th portion of generator phase
winding reconed from the phase terminal, the voltage
induced in that balance 2% winding is not sufficient to
drinve a fault current through the differential relay.
Hence intentionally 100% protection relay is not used.
 
Is This Answer Correct ?    1 Yes 3 No
Dr. S.r.krishnamurthy
 
  Re: What is 100% protection of generator? Why 95% protection is used not 100%?
Answer
# 7
Because in the case of Generator if we choose the 100%
protection then the protection system cost more than the
generator cost. thats why we will choose 95% of protection.

In India generally 92-93% protection is used whereas inother
country it is 95-96%.
 
Is This Answer Correct ?    2 Yes 0 No
Rohit Singh
 

 
 
 
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