Preffered method For Wetting Breaker Aux Contacts in Relay monitoring 2

[proznick]

I have subsation design where three hydro plants are going to tie into the sub of one of hydro plants. Between the generators and the sub, there are a total of 7 breakers and 10 protection relays.

I am trying to simplify the wiring requirements from the relay digital inputs and the breaker auxillary contacts (relays monitoring state of breakers).

I wanted to know if common practice is to run both input channel leads back to the breaker aux contacts as in Wetting Method 2 attached or if its an acceptable practice to use Wetting Method 1 also attached.

Wetting Method 1 eases up wiring requirements on the relay as well as to and from the breakers. I would like to utilize this but want to hear from experience whether this is a poor method before proceeding.

Any thoughts on this appreciated, thank you.

R Proznick

 

[proznick]

Forgot to include the attachment for my question.

RP

 

[cranky108]

I'm not finding the methods 1 & 2.

In general, you need to be sure the wetting method used won't have a common mode of failure, where you could lose all your indication at the same time.

 

[slavag]

Hi Proznick .
From my point of view ONLY methods 1.
"-" is common on the BI of relays
"+" is common on the aux contacts of CB's. DS's.
Izn't good practic disconnect "-" on the BI (binary/digital
inputs).
In additional, are less wiring.
Best Regards.
Slava

 

[slavag]

Sorry, forgot add small remark.
Isn;t critical, but is also some style of design
You connected "-" of relay power supply to "-" common of BI, but "+" you use frome other fuse/MCB, please use same "=/-" for the same loops, is safety.
Best Regards.
Slava

 

[davidbeach]

I strongly disagree, method 1 is only asking for trouble; method 2 will save your behind when things start to go wrong.

Look at the negative fuse below each relay in method 1 and trace the circuits back to the positive. You will wind up at both breaker positives and that is a disaster waiting to happen.

 

[slavag]

Sorry again.
David, you are right, I dosen't put attention on the "+" to second relay BI.
Of course NO. I would recommend in this case use only ONE dedicated fuse/MCB for the BI.
Is safety and in case of some problem in the wiring, protective relays continue work, every one with dedicated power supply.
Best Regards.
Slava

 

[bacon4life]

We would generally have the DC+ run to the relay panel terminal block, then split it to run to each 52A, then back to to the (+) relay inputs and common them on the (-) of the relay inputs. This has only 4 wires run to each breaker instead of the 6 shown in method 2.

Are these primary/backup relays? With either method you have shown, loss of either wetting voltage will result in both relays not sensing the breaker status correctly. In the attached diagram, loss of a single wetting voltage will only affect one relay.

 

[davidbeach]

bacon4life's scheme is even better than method 2. This way you have a DC for each relay with no crossing. Still missing from all of the drawings are the trip and close circuits; these should be from individual breaker DC circuits.

 

[proznick]

Thank you for your taking time out of your day to submit a response.

I love the exchange of ideas and community on ENG tips.

Thanks to all,

RProznick