Disabling the over current protection on a relay

[mbrooke]

Does anyone know how to program an over current disabling input into an SEL501/SEL551 or similar relay? Something that can be activated by either an external switch or pressing a designated button on the relay.

 

[ptonsparky]

Does anyone know how to program an over current disabling input into an SEL501/SEL551 or similar relay? Something that can be activated by either an external switch or pressing a designated button on the relay.

I know nothing about these, but dare I ask why you want to?

 

[mbrooke]

I know nothing about these, but dare I ask why you want to?

Sometimes you just want to stop nuisance or hard to find faults from tripping the OCPD. Keeps everything online, as is a few sparks never hurt nothing




In all seriousness, when the transfer buss breaker is being used for substitution you want to disable it from having any over current response. That way any faults (or even normal load) outside the protection boundary will not inadvertently trip it.

 

[SG-1]

Program an alternate protection Group, then program an input to select that Group.

 

[mbrooke]

Program an alternate protection Group, then program an input to select that Group.

But can this alternate protection be made to have absolutely no response?

 

[JoeStillman]

I would use a set of ABB Flexitest shorting terminal blocks to disable the input CT's and take the relay out of the circuit.

Probably want to report some kind of trouble condition somewhere if you do.

 

[jim dungar]

I would use a set of ABB Flexitest shorting terminal blocks to disable the input CT's and take the relay out of the circuit.

Unless they want to use the CTs as part of their troubleshooting. So some type of selector switch on the output or to an alternate function group may be more appropriate.

In any situation, annunciation of the 'non-routine' state of performance should be mandatory.

 

[Bugman1400]

There are other methods that can apply a temporary higher setpoint without disabling the protection. Neither relay has buttons that can easily be used to provide a temp setting. The 501 is really two relays in one (501-X & 501-Y). The 551 is just one relay but, both have limited inputs. Is one of these relays already in service? You may need to go with a relay that has more features (like pushbuttons) but, is still economical (ie 751A). Also, I would take a good look at the existing protection scheme before I would implement a workaround. The scheme may just need to be reviewed and a slight adjustment made.

Would like to see the existing scheme (w/relay settings) first.

 

[mbrooke]

I would use a set of ABB Flexitest shorting terminal blocks to disable the input CT's and take the relay out of the circuit.

yup, I use/spec these:


http://www.statesproducts.com/product-test-switches.php

Probably want to report some kind of trouble condition somewhere if you do.

:?

 

[mbrooke]

There are other methods that can apply a temporary higher setpoint without disabling the protection. Neither relay has buttons that can easily be used to provide a temp setting. The 501 is really two relays in one (501-X & 501-Y). The 551 is just one relay but, both have limited inputs. Is one of these relays already in service? You may need to go with a relay that has more features (like pushbuttons) but, is still economical (ie 751A). Also, I would take a good look at the existing protection scheme before I would implement a workaround. The scheme may just need to be reviewed and a slight adjustment made.

Would like to see the existing scheme (w/relay settings) first.

Its main and transfer. The outgoing lines are protected via an SEL411L and the transformers via SEL487E. The normal breakers are wired as breaker 2 while the buss tie as breaker 1. Normally the buss tie VT and CTs are ignored in the SEL4xxxx relays and the transformer bus is protected via an SEL 501 or SEL551. When a normal breaker is taken out of service the SEL4xxx relay uses the transfer buss breaker and the transfer buss over current relay must then be disabled.


Let me know if this makes sense.

 

[mivey]

Set pickups off, or set trip outputs to none, or block the elements with "IN" using a switch, or use a switch to block output trip signal.

 

[mbrooke]

Set pickups off, or set trip outputs to none, or block the elements with "IN" using a switch, or use a switch to block output trip signal.

Most likely blocking via a programmed input initiated via switch. Blocking the output trip signal is not enough as that would initiate the BF contacts which would clear the whole buss. Unless of course I blocked that to but never considered what would happen with a relay in a perpetual trip state.