Hello everyone !!

I am facing the tripping problem of 6RA8086-6KS22-0AA0 DC drive when DC motor starts to reach 

above 50 rpm to 60 rpm. Meanwhile, 11000V substation also tripped with tmr ground relay fault is on. There is no fault or alarm number displayed on DCM & all system just blackout above 55rpm of DC motor. 

Help me out to find the fault either in the substation or DCM parameters setting issue

Thanks

Assuming a "tmr ground relay" is checking/monitoring the isolation/earthing status:

I see no reason, why the DCM should cause this kind of error (isolation problem).
Habe a detailed look on the motor. Maybe the centrifugal forces cause the problem when you reach the 55rpm . E.g. something is moving a bit inside the motor and causes a short curcit to ground/earth.

To contact your local Siemens office to get support use the contact database .

Hello,

Here I presume, your 11KV sub-stn earth relay trips when DC motor runs above 55 rpm.

What type of protections provided at drive AC input side?

Have you checked DC motor earth resistance?

Do you observed any type of sparking/arcing in motor or at motor supply cables?

I guess, you have MCCB at AC input side for short circuit protection. In motor wiring or inside motor any short ciruit could causes sensetive earth relay triping at 11KV sub-stn since MCCB at drive input side response time is much slower or there is no any earth short sircuit protection at drive AC input side.

Please check above points. I also suggest you to provide MCCB or ACB with overload, shortcircuit & ground fault protection of adequate capacity at drive AC input side.

HTH

PISCEAN 2010

Hello,

Here I presume, your 11KV sub-stn earth relay trips when DC motor runs above 55 rpm.

What type of protections provided at drive AC input side?

Have you checked DC motor earth resistance?

Do you observed any type of sparking/arcing in motor or at motor supply cables?

I guess, you have MCCB at AC input side for short circuit protection. In motor wiring or inside motor any short ciruit could causes sensetive earth relay triping at 11KV sub-stn since MCCB at drive input side response time is much slower or there is no any earth short sircuit protection at drive AC input side.

Please check above points. I also suggest you to provide MCCB or ACB with overload, shortcircuit & ground fault protection of adequate capacity at drive AC input side.

HTH

Thank you for your valuable suggestions. here are some my submissions regarding your suggestions.

1. There is no spark in the DC motor input cable. 

2. One year ago this motor has been tested at 170 rpm then there was no such fault or 11kv substation tripping. After one year this motor is being re starting but this time above explained fault is occurring ar different speed i.e sometime at 50 rpm and sometime 55 no regular pattern

3. Yes you are right there is no protection at the AC drive end. Two DC drives one is operating on star and onther is operating on Delta 660V. But it is worth mentioning that star connection neutral is not being used in DCM it is layed out only from transformer to 660V electric panel. this panel does not trip instead 11kv sub station gets tripped.

gabbas@abbas1234

 

PISCEAN 2010

Hello,

Please check above points. I also suggest you to provide MCCB or ACB with overload, shortcircuit & ground fault protection of adequate capacity at drive AC input side.

HTH

3. Yes you are right there is no protection at the AC drive end. Two DC drives one is operating on star and onther is operating on Delta 660V. But it is worth mentioning that star connection neutral is not being used in DCM it is layed out only from transformer to 660V electric panel. this panel does not trip instead 11kv sub station gets tripped.

Install MCCB with earth/ground short circuit protection at drive AC input side, but before it confirm sub stn earth relay only trips when this suspecious drive is in operation. 

PISCEAN 2010

 

gabbas@abbas1234

 

PISCEAN 2010

Install MCCB with earth/ground short circuit protection at drive AC input side, but before it confirm sub stn earth relay only trips when this suspecious drive is in operation. 

OK thank you i am also in doubt that there is a problem with substation earth fault tripping setting but it is totally annoyed. 

Thanks again