Trip coil supervision

[pukar12345]

I saw a 132kV capacitor beaker with three individual pole operating mecanism.
obiviously the breaker has three separate individual trip coil for three poles.
Now for supervison of trip coils, In my opinion, we need three separete coil relay (could be a one reay with three coils)
I saw single coil supervision relay in the circuit for supervision of three trip coils that are in parallel.

I believe the circuit is not good.

Do anyone have experience of supervising three parallel trip coils with one coil relay.



Thanks in advance for advice.

Pukar

 

[rcw retired EE]

Some trip coil supervison devices monitor the milliamp current to the trip coils with enough accuracy to detect the difference between 2 or 3 coils in parallel.

Some relays can be specified with several trip output contacts with built-in coil monitoring so single pole tripping and monitoring are possible. Most relay designs still look for a single trip coil.

Other systems depend on the pole diagreement alarm to alert the operator action or initiate a breker failure action.

In my limited experience, the primary cause of trip coil failure was loss of trip circuit power. A single monitor will alarm for this condition.

The expense and complication of monitoring three coils oer breaker createw a lot of complexity which can lead to reduced reliability. Except for very critical circuts, the added benefit is not worth the cost and complexity.

 

[pukar12345]

RC wilson,

Thank you for the nice explanation.


Pukar

 

[slavag]

Hi.
We use one TCS per coil.
Possible use a one device for the 3 coils, for example TSG 930:

http://www.seags.ch/ses/tsg/.

Importnat point: monitoring of trip coil of openeed CB

Good Luck
Slava

 

[jghrist]

Importnat point: monitoring of trip coil of openeed CB

How is this done if the trip coil is isolated by 52a contacts as is normal?

 

[rasevskii]

For monitoring the trip coil of an open CB, a high resistance relay coil is connected in parallel to the trip contact, bypassing the 52a of the breaker. This relay is therefore energized continuously as long as the trip coil is intact, and the DC supply is intact. A NC contact on this relay is connected to the alarm.

Disadvantages:

1. The alarm will sound when a trip is activated.

2. A shorted trip coil cannot be detected.

rasevskii

 

[mirilovic]

Siemens 7PA30, three phase and single phase trip circuit supervision.

Go to:
7PA30

 

[slavag]

jghrist, isnt problem, we dont use additional relay, as
rasevskii said.
Some resisitor about 30kOhm for 220V DC across a 52a contact.
current about 3-7mA, enough for supervision, voltage about 60V.
Isnt exactly, usually used NC contact of CB, etc...
This is a idea.
Used for decades.
Best Regards.
Slava

 

[ScottyUK]

jghrist,

Here's one of the more common British trip circuit supervision relays, the GEC MVAX, which has some explanation of operation and some typical application circuits.


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If we learn from our mistakes I'm getting a great education!

 

[cranky108]

Be careful of single pole devices. In one case I've seen where each pole had a monitor, and someone plugged in an AC powered relay for one of these. When it failed it only tripped one phase.

The new single pole capacitor breakers, that I know of, have an electronic module which monitors the trip coils, as well as manages the close functions. The second trip coils, are not controled by the module, and each coil should be monitored.

 

[rcw retired EE]

With three trip coils, all trip contacts should be in triplicate to prevent shorting out the monitoring function with a single relay trip contact feedign three trip coils in parallel. Diode isolation of the three circuits can keep the monitoring in operation.

 

[SMB1]

Yes,

you have to have three 74/TC trip coil supervision.