Digital Lockout Relay?
Digital Lockout Relay?
(OP)
I apologize if I am a little bit outdated but one of our client's suggested us to use a digital lockout relay.
I used to specify electromechanical lockout relays (i.e. Electroswitch, GE HEA etc.).
I never encountered a "digital" lockout relay as a separate device. At first, I was thinking an 86 function logic programmed in a multifunction digital protection relay. If one exists as a discrete digital relay, I'll be happy to be informed.
Thanks..
I used to specify electromechanical lockout relays (i.e. Electroswitch, GE HEA etc.).
I never encountered a "digital" lockout relay as a separate device. At first, I was thinking an 86 function logic programmed in a multifunction digital protection relay. If one exists as a discrete digital relay, I'll be happy to be informed.
Thanks..






RE: Digital Lockout Relay?
RE: Digital Lockout Relay?
RE: Digital Lockout Relay?
Yes, the current rating/reliability of the output contacts directly tripping the breaker trip coil may also be an issue.
Are there any technical papers that relates to this? I appreciate if you can share one.
Many thanks.
RE: Digital Lockout Relay?
Large number of dry contacts with relatively high current ratings that can be used for breaker tripping, control, etc.
Hand-reset function to prevent remote operation after the relay has tripped.
Electrically-reset LOR are available, but not often used.
Your application doesn't sound like a typical use a LOR. They are generally used for tripping a lot of equipment after something bad happens.
David Castor
www.cvoes.com
RE: Digital Lockout Relay?
However, an electromechinical lockout is intented to not only increase the number of contacts, but is also intended to make people think before they reset them.
We always felt it was a good idea to make someone go to the site, and hopefully look at what could have caused the lockout to operate.
However we have used electrinic reset lockouts for 81 functions where the dispatcher should have control.
RE: Digital Lockout Relay?
In the industrial venues in which I work, I train operators that if the lockout device is rolled then they are NOT to reset and retry, the difference being that between a rewind of a motor or transformer, and a catastrophic failure and total replacement.
The electricians know that there are specific steps that must be taken to determine and isolate the cause of the operation.
old field guy
RE: Digital Lockout Relay?
What cranky108 saied.
Digital LOR, it the LATCH function in the digital relays.
In the newer digital relays possible two options:
LATCH of contact or protection function with same push button RESET or deenergizing of relay and
classical LOR with hand reset only, into digital relay
Best Regards.
Slava
RE: Digital Lockout Relay?
Yes, i had a discussion with some of our design folk about using latched outputs of digital relays in place of an actual and discrete electromechanical lockout relay.
I stood my ground FOR the old hand-reset, big ol' knob, separate from the reset button on the digital device because I wanted to make sure that the person responding to the trip had a substantial indication that THIS was more serious event and required more attention that "push the 'reset' button and let's try it again."
old field guy
RE: Digital Lockout Relay?
RE: Digital Lockout Relay?
OFG, David, I agree with your reasons, its right.
But, its a rules of operation personal.
We stop design/used LORs before a 10 ( or more ) years.
Only special request for transfromer or generator bays, from time to time for capacitor banks.
And... I prefered somthing chepaer and small sized then Electroswitch LOR
Some bistable relay, for example.
Best Regards.
Slava
RE: Digital Lockout Relay?
We both don't like Electroswitch LOR for diametrically opposite reasons. I like the open contacts of the older designs.
But then, I'm pretty much a dinosaur among power people as the days pass...
old field guy
RE: Digital Lockout Relay?
Have I mentioned that they need to be torqued correctly every few years.
After some thinking, I have used an electronic lockout for a capacitor bank unbalance. Not as big a deal as an over current operation.
RE: Digital Lockout Relay?
Just an aside regarding Electroswitch Series 24 lockout relays - I have used these for over 35 years and never heard of or experienced any failures. I have seen failures in the GE and Westinghouse designs - although not often. The old electric reset HEA relays were definitely problematic.
One advantage of the Electroswitch design is the smaller depth for the same number of contacts.
I'd be interested in knowing what sort of problems you've experienced.
Dave
David Castor
www.cvoes.com
RE: Digital Lockout Relay?
I also have seen that when non-inusulated lugs were used, they can become bent into the next terminal.
However I've seen more problems with the GE lockouts (the old ones, the new ones look like the Electroswitch lockouts).
RE: Digital Lockout Relay?
I agree with David and OFG - lockouts should not be used for "recoverable" faults. We have seen designs where the generator's reverse power protection tripped a lockout that tripped the turbine and breaker. Operators would take a unit off line by backing down the steam until the breaker tripped, which is a good practice in itself. But they had to reset the lockout evey time they started the unit. This taught them that resetting 86 devices is a normal daily operating function. That led to another problem. ( Fortunately, no one was hurt.)
We roll lockouts on MV motor ground faults and short circuit trips but not over-temperature or over load trips. We do latch the relay trip output so the operator has to at least go to the relay where he might see the trip alarm before resetting.
RE: Digital Lockout Relay?
Other than that, I'll add my voice to those insisting that 86 devices have mechanical contacts. I see the lockout as "end of the world" protection: Maybe the protective relay is on fire; maybe an arcing primary fault has migrated to a CT secondary... I'm simply more comfortable with last-ditch protection relying on large contacts and big conductors.