Schneider SEPAM M20 Protection relay

[graovacb]

Good day to All,

This is first time I'dealing with this type of relay (I've met ABB, Areva, Siemens) and we have problem during the motor start-up. Since that start time is longer than definite time set for 50/51 the protection trips due to 50/51 during start-up. The real motor start current is greater than threshold of 50/51.
My question is there any possibility to disable 50/51 (or to double like for ABB REM610) during start-up?

Thanks

 

[veritas]

My first question is why have an OC element set faster than the start-up time? If you wish to have fast trip for say locker rotor condition, then you would either need to use a speed switch or alternatively have the CB/contactor auxilairy contact wired to the relay. Thus on closure program in a delay of x seconds to ensure the OC function is only enabled after the x seconds delay. x seconds needs to be longer than the longest starting time + safety margin.

 

[graovacb]

Thanks for replay.
I was not in the project from the beginning and I'm not the one who made configuration file for the relay parameters. In the moment I came 3 out of 4 MV motors have been already running and when we wanted to start the fourth one we faced the issue. And guess what, in those three OC protection is disabled even in the design is mentioned to be enabled . I don't know who did it and why for 4th is not done the same. OK, I can do the same for the last one but in this moment I'm wondering whether is possible to do something in the relay itself. As I already said in ABB protection it's possible to set that protection recognizes start and double the setting for OC.
I agree with you that rewiring the panel would help but it'll be the last option.
Regards,

 

[jghrist]

The normal procedure is to set the instantaneous (50) pickup higher than the motor starting current. Disabling the instantaneous prevents fast protection for faults.

 

[graovacb]

jghrist
I agree with you absolutely regarding disabling the protection. In order to set OC higher than the motor start current I need to increase the OC setting at list 50%, that's why I'be been seeking for some other solution.

 

[jghrist]

If the overcurrent pickup is lower than the fault current, then it will provide the necessary fault protection. If the fault current is less than the motor starting current, you have a major motor starting problem.