Dear all , 

I wont to clarify something regarding the settings on Digsi Protection Relay type 7SJ622.

This protection is used for a Slip Ring Induction Motor with parameters described as below:

Nominal Voltage 6000 V

Nominal Power 4000 Kw

Nominal Current  464 A

Nominal frequency 50 Hz

When there is a power fluctuation on the grid, the protection relay trip I2 [46 Negative Sequence (Time Overcurrent ) - Settings Group A]   

The settings are as described below : 

No.                   Settings                                                    Primary value         

4001             46 Negative Sequence Protection         ON 

4012A           46 Drop-Out Time Delay                          0.0 sec

4002               46-1 Pickup                                               60 A

4003               46-1 Time Delay                                      1.5 sec

4004               46-2  Pickup                                              94  A

4005                46-2 Time Delay                                     0.2 sec

What do you suggest to avoid the trip of the motor when there are power fluctuations on grid. 

Best Regards,

Mentor Toma

Hello Mentor,

we would recommend to contact the customer support for this issue:

I think the problem need coordination and clear data between relay - grid char. - motor

1. to make sure that the relay work properly, relay calibration should be done. make sure that 46 work properly as per setting

2. if the calibration pass, the problem no longer in relay. please send the fault report (trending) to the motor manufacturer when the problem come. then ask for their solution

3. about the grid? i don't think we could make any change related to grid fluctuation. (except the grid dispatcher)

Mentor

Dear all , 

I wont to clarify something regarding the settings on Digsi Protection Relay type 7SJ622.

This protection is used for a Slip Ring Induction Motor with parameters described as below:

Nominal Voltage 6000 V

Nominal Power 4000 Kw

Nominal Current  464 A

Nominal frequency 50 Hz

When there is a power fluctuation on the grid, the protection relay trip I2 [46 Negative Sequence (Time Overcurrent ) - Settings Group A]   

The settings are as described below : 

No.                   Settings                                                    Primary value         

4001             46 Negative Sequence Protection         ON 

4012A           46 Drop-Out Time Delay                          0.0 sec

4002               46-1 Pickup                                               60 A

4003               46-1 Time Delay                                      1.5 sec

4004               46-2  Pickup                                              94  A

4005                46-2 Time Delay                                     0.2 sec

What do you suggest to avoid the trip of the motor when there are power fluctuations on grid. 

Best Regards,

Mentor Toma