which relay is better , instantaneous or IDMT relay .
Answers were Sorted based on User's Feedback
Answer / karthik
for metering, protection all will be taken in one CT --only core will be varied in that CT
for measurement -1s1,1s2
for protection - 2s1,2s2
only one CT is used
Is This Answer Correct ? | 0 Yes | 0 No |
Answer / biswaindu parida
In a substaion we use different ratio of CTs for different purposes. Such as 200/1 for metering 400/1 for another back up, 800/1 for protection like wise. So suppose if a fault comes say around of 1200A then the secoundary level current for different Cts will not be same.
Lets analyse them indivisually.
1) The 800/1 Ct will read it as 1.5A. For that we can simply use Over current relay and trip the breaker.
2) The 400/1 Ct will read it as 3A . here we can use IDMT relay.
As per its function it will sends trip command to the breaker as soon as possible...because here the time of trip is inversely proportional to the amount of fault current
3) But however in case of 200/1 CT, it will read it as 6A. If it is a metering CT then it should be protected 1st. because it has less saturation point as compared to protection or back up CT. So here we will use instantaneous relay so that it will trip suddenly when the fault current goes above some pre defined value.
Is This Answer Correct ? | 0 Yes | 3 No |
what are the advantages of having high voltage in transmission lines?
what is meant by transformer differential protection ?
what is the use of 6.6kV/6.6kV Transformer???
give types of Air conditioners commonly used &its use?
why should series motor be started with load and shunt motor should be started without load??????
what do you understand by dressing a HT/LT pole
1 Answers Federal Polytechnic Nekede,
what kind of motor is used for lifting applications
In LT Line What is the minimum clearance required between phase to phase busbar & between Phase to body of the panel? Also between Neutral &phase, & Neutral & body of panel. as per standards.
Why synchronous motor runs at a fixed speed? what is the name of that fixed speed?
why we did not get shock by touching +ve OR -ve busbar (Which are going to supply cell voltage) of Rectifier- Tranformer in electrolysis plant?
There is two transformers of 2MVA & 3MVA, which transformer is located at the sending end & which is at receiving end. why?
Totally how much power will be consumed in 1 hour cotinuous running of electric train engine?