why neutral of 6.6 kv star connected sq. cage induction
motor does not get earthed, though for earth fault
protection it is must.
Answer Posted / engr. l. o. osuji
Hi Pratikjain,
The answer in #4 is partly correct. Your question is on the
motor and not on the feeder. Provide appropriate cts and
wire correctly using an over-current earth fault relay.
Note, this relay has three operating elements known as red,
yellow and blue-phase elements. The yellow-phase element is
for earth fault. This relay works on the principle that Ir
+ Iy + Ib = 0 for a balanced load. This summation is
algebraic. In times of an earth fault the above equation is
no longer equal to zero hence the residual current flows
through the yellow-phase element as an earth fault provided
your cts and relay are properly connected. In this way the
cb for the motor is tripped by the yellow-phase element as
an earth fault if the relay is properly set.
Is This Answer Correct ? | 2 Yes | 4 No |
Post New Answer View All Answers
How to calulate Locked rotor amper(LRA) for compressor type motors?
In a 3 phase 4-wire system. For a 3.5 core cable if all loads are single phase and balanced, what will be neutral current? will it be sum of all phase currents? Or it will be zero? And if loads are unbalanced what will be neutral current?
do we use links in a dc circuit?if so what s its use in it?
what are the things that can cause a three phase motor to crawl?
is it possible to say motor horsepower number without seeing name plate(when name plate damaged)
electrical ques
Briefing the effects of ASR and ACR of a double closed-loop speed regulating system.
Why is back emf used for a DC motor? Highlight its significance.
What is a difference between indoor transformer and outdoor transformer of same rating
Please tell me in DETAIL about the following 3 types of fuses or recommend me a good power system protection book or a website link ? 1.Dropout Fuse 2.Striker Fuse 3.Empulsive fuse (not sure if its impulsive or explosion fuse , sorry)
What the formula for calculating no.of earthings & size of earth strip for 100mX90m shop.
If oil and air can withstand a high MeV when used as an insulator in a transformer, what are the values of how high for each material?
What is the basic of DTH.
what is the difference between unarmoured & Flexible cable? How to identified?
How to know of any cable size if there are not written on cabl?