Busbar Diffrential protection for 2 Incomer & 1 Buscoupler logic ( 2 out of 3)

[pal]

In system of 6.6kv there is busbar differential protection is provided.
The operating philosophy is of 2 incomer & 1 buscoulpers ( With TWO incomers ON & Buscopler OFF). The differential scheme is of 2X87 type ( respective bus has its differential protection)

Case -1 TWO incomers ON & Buscopler OFF

Any fault happens say at Bus A in switchboard at the outgoing feeders of boards - The Incomer-1 Trips & also the Outgoing feeder trips

Case -2 Incomers-1 ON , Incomer -2 OFF & Buscopler -ON

1) what will happen if the fault occur at BUS -B ( which is now fed from Incomer -1)

2)what will happen if the fault occur at BUS -A

what should be ideal design

Rgeards
Pal

 

[Engineer54]

To answer your question, we need to first of all know if the 2 incomers are fed from the same source, or from 2 different sources as this will change the way your 87's are connected?? You can have a fully functioning auto control using the 87 relay's coupled in with the other protection control relay's.

It would be far easier to give you a definitive answer if you can post your switchboard single line drawing and if possible your control schematic.

 

[Knobhead]

Homework! Sent packing from CR4 and now he's here.

 

[Engineer54]

Homework! Sent packing from CR4 and now he's here.

Shame, that could of been an interesting thread.... lol!!

 

[Knobhead]

Shame, that could of been an interesting thread.... lol!!

I know, that's why I looked! Oh well....

 

[pal]

To answer your question, we need to first of all know if the 2 incomers are fed from the same source, or from 2 different sources as this will change the way your 87's are connected?? You can have a fully functioning auto control using the 87 relay's coupled in with the other protection control relay's.

It would be far easier to give you a definitive answer if you can post your switchboard single line drawing and if possible your control schematic.

Hi...

As you stated please find below the details required by you
1) The Two incomer are having their separate incoming supply from 33KV/6.6KV Power Transformer 30MVA. (2 Nos) from upstream.
2)There Automatic Change-over & Momentarily parelleing facilities in the switchboard.
3) The Protection relays are numerical relays of ABB make REF series ( high end numerical Relays ) .
4) Relays are interconnected trough Cat 5 cable to one another & further to Ethernet switches to facilitates ECS & SCADA system. (For Remote Monitoring & Controls)
5)Shortly i will try to send you the SLD. Sending control schematic is not possible.

regards
Pal

 

[Knobhead]

Pal, if this was in a genuine problem, you would simply pick up the

and call ABB, you would not be trawling the internet asking random people.

If you want help, give the findings you have so far.
This is not a homework service!

 

[pal]

Pal, if this was in a genuine problem, you would simply pick up the
View attachment 15512
and call ABB, you would not be trawling the internet asking random people.

If you want help, give the findings you have so far.
This is not a homework service!

Dear, Tony

1)Look i have just given the input required to another person (Engineer54 )who is trying to resovle the issue.

2)I don't understand what do mean by homework service.I am just antipcated the situation which can occur during normal operation of MV switchgear.

3) And calling ABB person doesn't resolve my query.Since being the designer i have to give operation logic ( control & protection) to ABB who can just implement the same in relay block logic.

Before giving final operation logic to ABB i want to just ensure that i have considered all the wort situation during which the all protection are covered.

I hope it is clear .

regards
Pal

 

[Knobhead]

As designer you should know the basics of what you require. You have chosen not to share them.

Do you’re employers know you go on the internet to get complete strangers to do you’re work? Please do not tell me you are a freelance consultant designer, I’ve just come out of hospital and it hurts to laugh.

 

[pal]

Dear, Tony

I don't know what is your problem!

As i can seen you are Appreciated Member of this forum but it doesn't mean that
the new members or any member of this forum has to seek your permission for discussion on any point.

I didn't expect this from appreciated Member of this forum.

Note that i know the basics please don't take pain to teach the same to me.
Also please don't be so concern about my employers.

And at last i will resolve my issue don't you worry about that.

The forums are made for the discussion i am just doing that.
Note If you are not interested than simply ignore.

And i will end up with quote of Albert Einstein“Any fool can know. The point is to understand.”

regards
Pal

 

[pal]

Dear ( Engineer 54)

I found about Busbar differential protection- for MV switchbaords for 2 incomer & 1 buscoupler scheme .Just i want to share with you.

1) For Bus A Differential relay there shall be input from 3 C.Ts
a. From Incomer -1
b. From Outgoing feeders
c. Buscoupler - C.T located after the Buscoupler at Bus B

Similarly for Bus B differential relay there shall be input from 3 C.Ts
a. From Incomer -2
b. From Outgoing feeders located at Bus B
c. Buscoupler - C.T located before the Buscoupler at Bus A

Case-1

So under Normal operation i.e Buscoupler is OFF & both the Incomers are charged & healthy. & if fault occur at Bus A than the Total Current from Incomer-1 C.T & summation current of Outgoing feeder sense by C.T . There shall be diffrence & hence differential relay at Bus A shall operate & it will trip Incomer -1 & Outgoing feeders. Note that the current of 3rd C.T located at Bus B shall have zero current.

Case-2

When Buscopleer is ON ,Incomer-1 is OFF & Bus A is charged through Bus B
Under this condition if the fault Occur at Bus A than ,C.T at buscopler located at BUS B shall be act as Source Current & summation current of Outgoing feeder sense by C.T . There shall be difference & hence differential relay at Bus A shall operate & shall trip Buscopler & Outgoing feeders. Note that the current of C.T located at Incomers -1 shall have zero current.
Under this condition Bus B differential relay shall not operate since the Current sense i.e summation current of Buscoupler C.T current located before the Buscoupler at Bus A & C.T current out outgoing feeders shall be equal to C.T current of Incomer -2 .
I hope it is clear to you.

Regards
Pal