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Electronically monitor the position of a Lockout Relay?
3

Electronically monitor the position of a Lockout Relay?

Electronically monitor the position of a Lockout Relay?

(OP)
We had a request from one of our maintenance guys to do this. Is this a common thing? These are lockout relays on large circuit breakers.  

RE: Electronically monitor the position of a Lockout Relay?

All the time.  Contact from the 86 into SCADA.

RE: Electronically monitor the position of a Lockout Relay?

If I understand correctly what you mean by electronically monitoring, it is very common.  I have never seen a lockout used that wasn't monitored.  Usually one of the contacts of the lockout relay are fed to the SCADA or DCS system.

RE: Electronically monitor the position of a Lockout Relay?

Oh, and it is best to use a contact on the last deck for the SCADA indication so that if something happens and the whole lockout doesn't actually roll (it happens) then you won't see the expected result.

RE: Electronically monitor the position of a Lockout Relay?

(OP)
We don't have a SCADA but we are planning to get one.

Right now the lockout lights up an annunciator...which I guess in a way is electronic. Sometimes I realize the stupidity of my question after I read your answers...thanks.

RE: Electronically monitor the position of a Lockout Relay?

davidbeach, I had never heard of that.  Is this with the ElectroSwitch series 24 type or other?  Which is the last deck? (closest to the handle or farthest away)

RE: Electronically monitor the position of a Lockout Relay?

I would assume the farthest away on an electroswitch, as the coil is located near the handle.
On a HFA I would assume nearest the handle, as the coil is at the back end.

But a comment: I would also monitor the condition of the coil, to be sure the circuit is intact. This would be good to see that you have DC in the whole circuit (in case of a DC fuse blowing).

RE: Electronically monitor the position of a Lockout Relay?

Farthest from the handle.  It's probably the most likely to not operate.  But these are pretty reliable devices.   

David Castor
www.cvoes.com

RE: Electronically monitor the position of a Lockout Relay?

Pretty reliable yes.  But when they don't (or when related switches like instrument transfer switches don't) the results can get really ugly.  If you're really paranoid, you monitor both the first and last decks and alarm on discrepancy.  Last deck would be furthest from the coil.  Shafts break, shafts twist.

It was long that thought that they were so reliable that one was enough for any application.  There have been some ugly incidents that resulted in an 86 that failed to roll meaning that breakers weren't tripped and breaker failure wasn't initiated.  The 86 trip coil can be monitored just the same as a breaker trip coil can be monitored.

RE: Electronically monitor the position of a Lockout Relay?

There have also been nuisance rolls of the LOR without it receiving a trip initiate.  There is a Mfg Service advisory to address this, but they are not always followed.

RE: Electronically monitor the position of a Lockout Relay?

(OP)
Can anyone provide a link that shows exactly how the 86 relay works and clearly demonstrates what you guys are referring to?  

RE: Electronically monitor the position of a Lockout Relay?

Quote:

It was long that thought that they were so reliable that one was enough for any application.  There have been some ugly incidents that resulted in an 86 that failed to roll meaning that breakers weren't tripped and breaker failure wasn't initiated.  The 86 trip coil can be monitored just the same as a breaker trip coil can be monitored.
It's also a good idea to use another relay output to directly trip the breaker in addition to tripping the lockout.

RE: Electronically monitor the position of a Lockout Relay?

(OP)
I'm looking at this lockout circuit and notice they have the normally closed lock out contact in series with the coil. This contact is in series with another normally closed contact on this same manually operated switch. I guess this is normal practice in case the contact doesn't operate?

RE: Electronically monitor the position of a Lockout Relay?

Lockout contacts usually come in pairs. I think this is more of a mechanical consideration. Think of two fixed contacts with terminals, and a center section that rotates with the shaft. The alternative would require a flexible conductor that would be subject to fatigue.

RE: Electronically monitor the position of a Lockout Relay?

bdn--

The contacts in series with the coil are to interrupt the current when the device operates, much the same as "a" contacts in series with the trip coil of a circuit breaker.  Typical "operate" currents of some 86 devices are quite high.  The 86 contacts are designed to handle interrupting this current.

We commonly use an indicator light in the lcokout relay trip circuit in much the same fashion as the indicator light in a circuit breaker coil trip circuit, i.e., a low-current indicating lamp paralleled across the trip contacts.  Presence of voltage in the 86 trip circuit will keep this lamp illuminated.  

Some modern protective relays perform a similar service.  I'm thinking of GE's UR family which has output contact voltage and current monitoring.  If you're using one of these devices, then the status of the voltage and current elements are available as data to be programmed for whatever purpose you might wish.

Simultaneously we use a contact from the 86 device as a digital input to our UR relay, giving us another piece of data for using programming the device as well as for recording in the event record.

old field guy

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