By-Passing Circuit Breaker trip- Is this possible
By-Passing Circuit Breaker trip- Is this possible
(OP)
Hi,
This might be more of a controls related question. I have attached a pictures which has two schematic.
1. Existing Schematic
2. Planned Schematic
My Distribution utility shares substation with the transmission utility. Bus protection and bus is owned by transmission utility but our distribution utility owns the feeders and its associated protection.
Existing Schematic shows the main trip that is from the feeder relay and Aux Trip1,Aux Trip 2, 3 & 4 show coming from the transmission utility to trip our breaker directly. These trips could be from Bus diff., bus back up or any other protection scheme. Blocking is shown to block tran.utility trip.
My objective is to determine if transmission utility issued a trip to my breaker, and that is shown in the Planned Schematic. it is like taking + ve and -Ve and then feeding to a digital controller just to detect if a trip was issued from transmission utility.
But I dont want to detect my own trip because my relay would tell me that. Would this work ? Any suggestions please.






RE: By-Passing Circuit Breaker trip- Is this possible
RE: By-Passing Circuit Breaker trip- Is this possible
RE: By-Passing Circuit Breaker trip- Is this possible
One question - if your own relay can tell you when it caused the trip, wouldn't the existence of (trip and no locked-in target from your own relay) inform you that the trip came from the utility?
xnuke
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RE: By-Passing Circuit Breaker trip- Is this possible
Alternately, if you can live with a small amount of delay in the trip signal, have the utility trip activate an interposing relay, rather than tripping the circuit breaker directly. One contact of the interposing relay trips the breaker, another gives you a trip indication.
Alternately alternately - perhaps the best solution - is to see if you can get the utility to provide you with a trip indication signal directly from their relay (fairly simple if they're using a numerical relay with some spare outputs).
RE: By-Passing Circuit Breaker trip- Is this possible
RE: By-Passing Circuit Breaker trip- Is this possible
Thanks Main relay is a SEL 351 and Aux. relays from transmission utility are old electro-mechanical relays.
mgtrp, I like your idea of using a diode, could you please be kind enough to draw a schematic and show it to me.
Thanks
RE: By-Passing Circuit Breaker trip- Is this possible
RE: By-Passing Circuit Breaker trip- Is this possible
RE: By-Passing Circuit Breaker trip- Is this possible
RE: By-Passing Circuit Breaker trip- Is this possible
RE: By-Passing Circuit Breaker trip- Is this possible
the benefit of SER reports on the SEL 351 and 3530.
This also provides a nice way to test the Aux Relay and document it.
RE: By-Passing Circuit Breaker trip- Is this possible
Using the SEL-351 as an interposing relay could also be a good solution.
RE: By-Passing Circuit Breaker trip- Is this possible
Thanks Mgtrp. I just have tweaked to reflect my situation. As the right side is auxiliary trip. Please see attached. It is a 125 V DC system, Could you please suggest me something on Diode specifications.
I was advised by one of my peers that it might be good idea to have a resistor in parallel with input. What do you think ?
Any fallback of this method, what if a diode has to fail, what would happen?
RE: By-Passing Circuit Breaker trip- Is this possible
You don't want anything parallel with the trip coil, be cautious that the "digital input" may disable your trip coil!
Also, that is 30 years old method and it does not match your data concentrator application, or you wast your money on it!
RE: By-Passing Circuit Breaker trip- Is this possible
A failure of the digital input would not disable the trip coil, only the trips on the upstream side of the diode. The two most common failure mechanisms on a modern protection system are human error (bad settings) and output contacts - routing all of the trips through a single relay hardly reduces your risks as compared to worrying about the possible failure of an input.
For all that, I don't have any issue with the suggestion of routing the trips via the SEL-351, there are a number of benefits such as event capture that can be realised. I use both methods, depending on the application.
With regards to diode rating - the reverse voltage should be well above the nominal voltage of your system, but the diode continuous current rating doesn't need to be as high as the trip coil operating current since it is momentary only. Good diodes are cheap, failures can be expensive.
RE: By-Passing Circuit Breaker trip- Is this possible
Thanks to All. Appreciat the comments. I think I will go with interposing relay option. I am trying to find interposin relay with very short operating time and which is used for breaker tripping interposing operation. I have looked at ABB RXMS1 but it canot break enough current. Any suggestions please.
RE: By-Passing Circuit Breaker trip- Is this possible
As mentioned above you can use the SEL 351 as your interposing relay. Wire each of the existing Aux relays to inputs of the SEL. You can then map those inputs to the main trip output. Set up your event reports to capture this information and there is no guessing who tripped your breaker.
RE: By-Passing Circuit Breaker trip- Is this possible
Above link shows a tripping assembly marketed by ABB.
The schematic is shown on page 18 fig. 5 . I can reduce pickup time of my interposing relay by RXMS1 and breaking by RXMH2 relay. I would appreciate your input if any body has used this before.
Thanks
RE: By-Passing Circuit Breaker trip- Is this possible
1/ Old electromechanical relays often require a certain amount of current to flow to pick up the seal-in coil, which in turn drops the trip flag - please be aware that the utility may no longer be able to tell which of their relays initiated the trip, as the auxiliary relay coil will not draw enough current.
2/ Generally, you do not need to interrupt the trip coil current with the relay contacts, that is what the 52A contact is for. You do need to make sure that the relay contact stays closed until the circuit breaker opens, however. One way that I have seen this achieved with interposing relays is to use a contact from the relay to seal in the relay coil, and then a 52A contact to drop out the relay coil.
3/ I'm not sure if you've worked with the ABB relays before, but if you're not used to them they are kind of a pain. You need special terminations for the wire and some additional tools to install/remove the wires. The relays can be installed in a Combiflex rack, which aren't too bad to access but will need to be panel mounted, or can be installed in a DIN-rail socket inside your cabinet, which from what I've seen need to be removed to work on. That being said, the ABB relays are otherwise excellent in my experience.
RE: By-Passing Circuit Breaker trip- Is this possible
I will have to ask my P&C Staff to use DIN rail arrangement at the back of panel as the front has SEL 351 and FT switches. If they need to be removed that means feeder will be down. My objective is to make sure there is no delay and RXMS1 takes care of it.
Could you please suggest me delay optimum value for RXMH2 contacts to drop out?
These contact rating is 6 amp , hope that is enough.
RE: By-Passing Circuit Breaker trip- Is this possible
RE: By-Passing Circuit Breaker trip- Is this possible