Large MV Motor Diferential Protection 87 3

[JuanGomez]

Hi.

There any recommendations or guidelines for knowing when to install the differential protection 87 (87M "motor" or 87S "stator" according to the manufacter) in MV motors, with 1 or 2 set of CT´s for this function, i mean from xxxx KW?

For example from 1500kW? motor up to 1200kW/2000kW?

I am looking for a guide or recommendation of a standard IEC / IEEE / UNE indicate where this information.

A recomendation of GE is (but not show kW values):

http://www.gedigitalenergy.com/multilin/family/motors/app_guide_lm1.htm

Thanks in advance.
Juan Gomez

 

[slavag]

Hi Juan.
NO recommendation, no rules, no standarts.
According to local rules only.
I tried found this recommendation few times...:-(.
Best Regards.
Slava.

PS, but, if you'll found something, please back with this information

 

[VTer]

ABBs Protective Relaying book recommends diff. protection for motors 1500hp and above.

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

 

[jraef]

I have seen individual specifications enforcing it at 2500HP and above. So as you can see, there are no standards as was previously mentioned.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[JuanGomez]

Thanks for the comments.

But i´m still searching for a GUIDE o SOME PAPERS example IEEE Guide/papers or other international standar.

Maybe we can find a document or study indicating this subjet, if any one knows of have access to a technical information about this, i would be grateful to receive.

VTER, can you send me the web link, to the "ABBs Protective Relaying book"

Thanks in advance.

 

[RRaghunath]

IEEE C37.96 AC Motor protection recommends use of motor differential protection in case the motor kVA happens to be greater than half of the transformer kVA rating.
However, many utilities seem to have motor kW based norms for stipulating differential protection for motors.
In PDO, 3.5MW and above require differential protection if they are connected direct to motor MCC. If connected through unit transformers, the motor-unit transformer combination is provided differential protection irrespective of the motor kW rating.

 

[JuanGomez]

Thanks for the posts to Raghun, Jraef, Vter and Slavag...

regards.