Digital relay push button functions
Digital relay push button functions
(OP)
We are designing a relay upgrade for a client. I was reviewing existing and reference schematics and was looking for controls for functions like 79 and POTT (comm), which made me consider that this utility may be utilizing relay push buttons for these functions.
In our region, for whatever reason, we still prefer cut out or control switches for reclose enable (79CO), trip/close (101), local/supervisory and comm disable (85CO) on the transmission system. We have HMI's in the station but they are for indication only. Our local disco has moved to all soft points (via HMI) for similar functions. Our SEL 400 series do not utilize any programmable push buttons. This approach obviously ups the parts count, wiring & real estate on a panel.
I'm curious what others do any why. I'm also curious to what extent others integrate SCADA functions into relays. We use SEL relays for metering and I see others using a dedicated meter.
In our region, for whatever reason, we still prefer cut out or control switches for reclose enable (79CO), trip/close (101), local/supervisory and comm disable (85CO) on the transmission system. We have HMI's in the station but they are for indication only. Our local disco has moved to all soft points (via HMI) for similar functions. Our SEL 400 series do not utilize any programmable push buttons. This approach obviously ups the parts count, wiring & real estate on a panel.
I'm curious what others do any why. I'm also curious to what extent others integrate SCADA functions into relays. We use SEL relays for metering and I see others using a dedicated meter.
RE: Digital relay push button functions
For metering: I prefer to have an analog ammeter on the transformer secondary or primary just as a sanity check. And an analog voltmeter. But I'm old. Otherwise we use the relays for metering. If you're talking about revenue metering, that's a different story - separate CTs and PTs. Not many relaying CTs are revenue accuracy.
RE: Digital relay push button functions
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If you can't explain it to a six year old, you don't understand it yourself.
RE: Digital relay push button functions
-We have also moved to using relays for both displaying analog values locally and for sending analog values back to SCADA. Many transformer relays have only CT inputs, so we need a separate meter
Though there have definitely been lessons learned along the way, the reduction in hardware and wiring costs is quite dramatic.
RE: Digital relay push button functions
RE: Digital relay push button functions
We had some problems with it. Duty personal forgot to enable functions of protection after an immobilization and when there was a short-circuit, backup protections worked.
RE: Digital relay push button functions
Trip/close should not be depend on relay health. Same with local/scada. Reclosing already depends on relay health, so it's game.
Microprocessor lockouts are not a good idea, when the old type work well, and can be seen that it is locked out.
RE: Digital relay push button functions
RE: Digital relay push button functions
RE: Digital relay push button functions
The outdoor switch can not access the sync-check, local/supervisory switch and lockout block closes, so it is a risk to allow it to be used.
Besides, do not operate tags only need to be applied to one location.
In many of our applications, we use two protective relays, so we can keep a line in service even with a failed primary relay.
We would not put trip and close on the secondary relay, as this would be confusing.
RE: Digital relay push button functions
I don't really agree, but there are a lot of considerations, obviously.
I spent 8 years developing logic schemes using SB-1 switches and I really have a lot of affection for them. But I think it's really hard to justify using them in the large majority of breaker control applications at this point. YMMV.
RE: Digital relay push button functions
The next challenge is that the TT function comes through the SEL relay via MB fiber. The relay already trips both line breakers and blocks reclose. Why are we then using the same SEL to hit an Aux relay to do the same thing???
The customer is always right and they don't want to hear when they are not :)
I feel that some control switches are useful, beyond their intended function. For example a Local/Supv switch , while in Supervisory, can save someone from bumping the 101 (Trip Close) switch. It's also convenient when doing any physical wiring on the Trip/Close Aux relays or I/O units. Additionally, it's nice to be able to place the station, or parts of, in local when doing function tests related to SCADA upgrades. I just recently heard a horror story of a station being dumped, feeder by feeder, due to incorrect SCADA RTU to EMS mapping.
RE: Digital relay push button functions
It also could be a testing thing, or an operational procedure.
You can also hang a tag on a physical 43 switch, and it is difficult to do that on a soft switch.
I have had problems with 'cutoff' switches, as people are confused by 'ON' and "OFF'.