pisimatza,
Do you believe that it could be justa reset button (afterall it is not called Reset relay)?
Lockout relay is what its name truly suggests - relay meant to lock the functioning of the circuit breaker out (after the breaker opens on a fault).
The lockout relay needs to be reset (through reset push button on the relay panel, through remote reset from the SCADA/SCS or through mechanical lever attached to the relay) by the operator/engineer before he can go ahead and energise the circuit. This is a time tested way of checking that the operator / engineer has consciously made the decision (after duly investigating the cause of trip) to energise the circuit.
The lockout relay is a latching device that, besides mutplying contacts, is intended to make it difficult to reset. Our intent was always to make someone go to the substation, and look at things. The operator in the bunker could not restore what was locked out without sending someone to the substation.(86LO)
However, this is different from a reclose lockout, which only latches so that there can be no more recloses. The operator in the bunker can restore the circuit remotely. (79LO)
WE use lockout relays for the operation of protected devices that indicate serious electrical faults.
For instance, in the case of a large motor, the time-overcurrent or thermal (RTD) elements do NOT trip the 86 relay. The operator (this is an industrial facility) is allowed to attempt a restart after determining the cause of the problem.
Instantaneous overcurrent or motor differential operations operate the lockout relay. The operators are specifically instructed that they cannot reset the lockout relay. Resetting the lockout relay is ONLY done after a qualified electrician has investigated the operation and cleared the unit for restart.
We still specify a discrete electromechanical lockout relay as opposed to a separate reset button on a microprocessor-based multifunction relay, specifically because there is no doubt in the mind of the operator that if that big handle is turned, they MUST call an electrician to investigate.
Hi.
Raghun, it's second time when I see "through remote reset from the SCADA/SCS".
Lot of companies (99.99%) work according to Cranky108 and Oldfieldguy.
It's intresting point, where are you use this option?
Best Regards.
Slava
Thank you all
Oldfieldguy, good explanation. The RTD or Thermal relay does not trip on a serious fault(just on heating), so the big handle from lockout relay will not turn.
It seems to be a not expensive relay, isn't it? I mean cannot cost more then 2-300 $?
Hi.
It's depend: how contacts you need and what is a make/break current is request.
Siemens have a good relay ( Areva and ABB too).
Please don't forgot, if you need a simple solution ( not a handele reset or bistable relay) you can build this fron every relay with N.O contact and some push button in series to coil).
Good Luck.
Slava
pisimatza, if your thermal relay NO contact is wired in series with the lockout relay coil, then that "big handle" will definitley turn.
For temperature protection, it is customary to have 1st and 2nd stage overtemperature. The 1st stage will send off an alarm and the 2nd stage can be wired either to directly trip the breaker or trip via lockout relay.
The lockout relay should also be supervised by a 74 relay (similar to AREVA MVAX 12) to monitor lockout relay coil either in the trip or closed position.
I guess I've never seen a reset pushbutton, other than one set up on a protective relay. Most of the lockouts I've seen are either GE or Electroswitch where ther have a handle for a reset (And lights for coil monitor).
What you are describing sounds like a latching relay.
The main thing we accomplish with the 86 relay in our protection circuits is to differentiate between serious faults and less serious overloads.
In addition to tripping contacts it is customary to use a set of contacts from the 86 relay to block the close circuit also, making sure that the breaker or contactor will not close until the 86 is reset. This is especially needed where starting or closing can be initiated from a remote location.
Also, another set of contacts from the 86 can be used to signal that it has operated.
My recent US projects have used Electroswitch and GE devices. I personally prefer the old-style GE "HEA" series, mainly because I like the hefty, visible (if you remove the cover) contacts.
Hi.
Yes, true LOR is Electroswitch and GE .
Big and expensive.
Today many companies prefered bistable relays--latching relay with reset button, possible install on the DIN rail, easier change.
Regards.
Slava
I have wondered about the 86 relay functionas well. Sadly I never get to see the actual equipment I am engineering for.
I understand the 86 keeps the breaker from being closed, thereby ensuring (hopefully) it is not being closed into a fault. My question would be, HOW does it do this? Is it a physical block to the breaker closing mechanism? Is it a set of contacts within the breaker in the closing scheme? How does it block the closing of the breaker?
Hi.
Usually it's "CB block close" contact is wiried in series to close coil.
As saied above, not all trip is pick block close function.
For example: thermal, undervoltage, etc.
Best Regards.
Slava
I am back with this:
One 86 relay can be used for more than one circuit?
Let's asume 5 circuits.
I mean, if 1 trip is detected, all output contacts will open, and circuits of all 5 closing coils of circuit breakers will be open?
This will not be a problem, i guess.
Thanks.
No problem,
For example generator 86 relay send open command
to CB, field breaker, turbine, boiler, etc.
Trafo with multi breakers- same.
Best Regards.
Slava
