MICOM P542 Secondary Injection 2

[bdf5526]

Hi All,

I have been trying to inject current for Micom P542 and the setting of the relay is:

Is1= 0.2 pu
Ki= 30%
Is2= 2.0 pu

I was checking the low set of the cable differential protection function.

I did exactly the same like in the manual and the monitoring Bit in the Commissioning Test menu and nothing change for Bit 1 or Bit 2. What could be the problem? The relay tripped but the monitoring 'bit' did not change.

Pleas find attached doc for the respective page from the manual.

Thanks for the hints. Meanwhile I will be keep checking what went wrong.

Thanks in advance guys.

 

[DiscoP]

Check that you have assigned the correct DDB numbers to the monitor bits.

The numbers given in the manual are sometimes for a different firmware version.

You can check the DDB numbers in the Commision Tests menu.

 

[bdf5526]

Hi DiscoP,
Thanks for the feedback. Yes. You are correct the DDB was wrong. I was looking at the manual for Micom P543. After assign the correct DDB the relay tripped for Diff B,C and later A as expected.

The thing I tried to understand is when I inject in Phase A, the relay tripped (Idiff A). In the manual they said when I inject in phase A, this will be used as I bias. This part I am not really clear.

I injected 1 pu (0.66 amp) in phase A and injected 0.2 Amp (as per the setting in phase B). The relay 'Idiff B' tripped exactly at 200mA.

Any explanation?

Thanks.

 

[DiscoP]

The bias current is 0.5*(I local + I remote).

Because this is a loop back test, I local = I remote.

Therefore what you inject locally is also the bias current, and the relay uses the highest bias qty for all 3 phases.

In a loop back test, the differential current is twice the current injected.

The required diff current follows the formula for a line (y=mx+c)

The formula given on the bottom page is based on the line equation.

Are you sure that 0.66 A is 1 pu. In line diff protection normally the injected and pu values are the same. If you inject 0.66 pu in Ia, the expected op current is 0.199 Amps using that formula - which is what you are getting

 

[bdf5526]

Hi DiscoP,

Thanks for the clarification.

The transformer rated current current is 794 Amp.
CT ratio is: 1200/1 Amp
CT secondary rated current 794/1200= 0.66 pu
Is1 setting is 0.3xIrated = 0.3x0.66= 0.198 pu

I was mixed up. 0.66 amp is the transformer secondary rated current.

In the test loop mode there is no alarm and secondary injection was ok. I was trying to communicate with the remote Micom relay which has same model and software version. I could not communicate. We were suspicious about the fibre optic and we check the fible optic cable it was ok. We do not have access to the remote relay side sice it is under 3rd party control.

I wanted to check the relay and made a fibre optic loop from Tx to Rx at the back of the micom relay at my side. And I activate the parameter for 'test loop -->external' I observe the 'C diff fail' and 'signal fail' alarm become not active. when I remove the fibre optic cable from the Tx,I observe the 'C diff fail' and 'signal fail' alarm active again. As per the manual there cuild be some setting/fibre optic or hardware problem. What could be wrong? I do not think this could be PSL or setting problem. Am I wrong? is some thing I need to change in the setting ?

Thanks guys..

 

[DiscoP]

The only thing that I can think of to check is the channel ID ( that may not be its correct name ).
With Micom relays you have one end set to 1a, the other as 1b ( or 2a-2b etc ).
If it not that, then it could be any number of things.

 

[bdf5526]

Hi DiscoP,

Thanks for the feedback. The relay address were wrong. We established connection and we did as well send trip to the remote relay. Thanks for the tips.

 

[bdf5526]

Hello Guys,



Now the client have new request about the tripping sent via fibre optic. They wanted the trip to be latched.

From ourside we made the trip send to be latched (intertrip CH 1) is active until we reset at ourside.

I am trying to figure it out how to make the trip via Fibre Optic to be latched. I can make the trip inputput always active.

When I make the trip active all time am I sending the trip FLAG always active? I tried to figured it out.

At the moment they are claiming they receive trip only for few milliseconds.

I proposed to them, once they receive the intertrip signal from my side they have make it latch at their side with PSL. It think this is possible. But until now no decision.

Any suggestion?

Thanks guys.

 

[ZapSib]

Hi Bdf,
the trip itself will not be latched but the output contact ( RLxx, blue color in PSL) shall be latched.
On the remote end, received signal shall be routed to RL, this one being latched.
regards,

 

[bdf5526]

Hi ZabSib,

Sorry for very late reply. Yes, it is as what you said. Modification on PSL has solved the problem. Further mode we have also Lorck Our Relay. We also make use of this contact as an Input to give have the trip active.

Thanks for the feedback.