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Anonymous Poster

HT Motor Tripping

01/13/2011 11:36 PM

sir we have installed the a 11kv /270kw motor in our plant and also installed the 7SJ6001 Protection relay for the same. during the starting we have facing the instant tripping due to unblance load (FD I2> Fault) and Tripping due to IE>> fault, and for the that motor what should be starting time
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vijaymail_electrical
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Join Date: Jan 2011
Location: India
Posts: 98
Good Answers: 2
#1

Re: HT Motor Tripping

01/13/2011 11:48 PM

This kind of trippings occur when CT polarity is reversed for any one phase. Check out for correct polarity. When polarity reversed , it may trip on earth fault or negative phase sequence. check for tightness also..

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nesubra
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Join Date: Nov 2006
Posts: 729
Good Answers: 2
#2

Re: HT Motor Tripping

01/16/2011 9:19 AM

FD 2 i presume is a Forced draught fan.The starting current values may be high and relay may be tripping.the starting time has to be calculated using inertia values of Motor rotor,fan coupling and plat the curve of fan on Motor Torque vs speed curve (done by software now) and calculate the acceleration or starting time.I have seen a 50MW Unit fan take almost 7sec.but this cannot be taken as a rule of thumb.

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joanaphiri
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Join Date: Jan 2011
Posts: 10
#3

Re: HT Motor Tripping

01/18/2011 8:30 AM

Because of the Unbalance that is why the relay is regestering IE>> fault,which is simply an earth fault.It is simply telling you that you have a residual current on your neutral which is far much greater than Zero.You may solve your problem by changing /checking the unbalance percentage settings on your relay.Probably the setting is too sensetive.Also tell me the type of application you have subjected the motor to.Otherwise,change the motor.
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electricalexpert65
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Join Date: Oct 2009
Posts: 2061
Good Answers: 169
#4

Re: HT Motor Tripping

01/18/2011 1:18 PM

It might happen due to unbalance currents during the initial magnetising inrush conditions. Suggesting to introduce an increased time delay (about 100ms) in the Ie>> element. If this cannot be done, you may add a stabislising resistor in the current input to the Ie>> element.
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electricalexpert65 (1); joanaphiri (1); nesubra (1); vijaymail_electrical (1)

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