Lockout Relay
Lockout Relay
(OP)
I am wondering why sometimes a separate relay is used for 86-lockout, whereas 86-lockout can be integrated into other relays (for example in GE F35 relay), thanks for help...
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
Download nowINTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
|
RE: Lockout Relay
RE: Lockout Relay
In other words, I employ them as a measure of fault classification.
In pre-microprocessor relay days, the lockout relay was also a common 'contact multiplier' so that one protective device could trip several breakers.
Further, it was typically employed to block reclosure on serious faults, ostensibly to make sure that a thorough investigation took place before throwing power back into faulted equipment.
Yes, you can program microprocessor relays to require manual reset, but in my admittedly archaic mind, nothing says 'NO!' quite like a rolled lockout relay.
old field guy
RE: Lockout Relay
RE: Lockout Relay
RE: Lockout Relay
On the other hand, all those protective functions you listed should be implemented in a single microprocessor relay and duplicated in its redundant companion.
RE: Lockout Relay
RE: Lockout Relay
You could theoretically have 27/59 & 50/51 all mapped to the same output contact on the microprocessor protection and have it trip an electromechanical 86 device.
Depending on what you are protecting, 27/59 may not suggest serious faults and as such may not need the 'block close' (normally closed contacts of lock out in the breaker close circuit). Remember that a traditional lock out relay has (2) sets of contacts, the normally open, which trip several devices when the 86 operates and normally closed, which open up when the 86 operates and blocks the close. I have seen devices that trip only (and look nearly identical to West/GE/Electroswitch) and are generally referred to as a 94 device (Aux relay)
Although the GE F35 does have a big configurable display and many programmable push buttons available, which could make for an intelligent lockout scheme without a separate lock out device, the rolled lockout does have the history of being a device that means something serious has occurred and requires further investigation.
RE: Lockout Relay
I'm aware that redundant relaying has ceased to be the normal condition in industrial installations and that's a matter of being penny wise and pound foolish. Back when it was one relay per phase plus a ground relay you could almost always count on two relays seeing any fault so that one failure wouldn't result in a fail to trip.
RE: Lockout Relay
There is now and again pressure from operators to make these remotley resetable, and we can make an excuse of cost, or outage time. But the answer is always we can't without consiterable work.
RE: Lockout Relay
Remembering that this comes from "old fashioned" electromechanical relay practice.
I think that the use of what we call in the UK a Master Trip Relay comes from the fact that most protection relays are self reset. So after the fault has cleared, the relays reset and remove the trip signal.
In order to lock out the system, a separate 86 relay is used, which stays in the trip position after the breaker has tripped, isolating the fault.
So there is clear and simple logic after a fault:
Go to site
Acess the HV switch room (Authorised Person in Uk)
Investigate fault
Reset 86
Close breaker
As davidbeach said, all sites are the same and the devices even from different manufacturers are much the same.
Also, during commissioning and testing, the system can be tested and each device trips the master trip relay, but not the breaker. Then one device is selected to trip the 86 and the breaker AND the plant it feeds - eg a steam turbine.
The use of the 86 system in LV plant was not used for reasons of cost not logic.
PLC systems have their place, but you have to consider the benefits of the above old fashioned system, when Plc systems have hidden logic and can be susceptible to uncontrolled modification (design drift I call it)