Trip and auxiliary relays: Vibration Resistance 2

[RRaghunath]

Trip and auxiliary relays of Alstom (now GE grid solutions) conform to vibration resistance class-2 as per IEC 60255-21-1 whereas, others in the market (except Reyrolle which is now part of Siemens) seem to provide relays conforming to Class-1 only.
Any one experienced problems like spurious tripping due to relay panel vibration with Class-1 relays??
I am afraid this could be true especially when the relays are mounted on the switchgear in LV compartment, located above the breaker compartment.

 

[thermionic1]

A few years ago, I was doing some SCADA work at a large, old station. On the 345kV lines, there were ABB RXMS (Combiflex) relays installed for transfer trip receive tripping (no flag). I just checked the datasheet for the relay and there is no mention of a Class, per IEC 60255-21-1. The entire SCADA map was re-indexed, so every point had to be checked. A last minute call to install a serial cable was made.

At some point into testing, a got a call from the dispatcher. One of the 345kV breakers tripped. Several hours later, it was determined that an electrician bumped a relay panel with the ABB relay, which caused the breaker to trip. It took reviewing the security cameras to figure out what really happened. It looks like there is an option for a flag on these units, but in my case that was not there. Would have saved a lot of aggravation during the troubleshooting phase.

I make a point of placing a warning label on panels that have these relays and others known to have similar problems (GE BDD, etc).

 

[dpc]

Can't speak to IEC requirements, but misoperation of instantaneous trip elements in overcurrent relays due to vibration is definitely something I have experienced. Relays in nuclear power plants in the US have to have a seismic rating. I'm not aware of any microprocessor relays that are nuclear certified in the US. This is mainly due to the small market vs cost of testing.

I've never known vibration to be a problem in the small output relays used in the digital relays. So I don't know how susceptible they actually are.

 

[RRaghunath]

Thanks thermioninc1 for sharing the experience. ABB aux relay RXMS is Class-1 device as per IEC.
That is exactly my concern. If we use the Class-1 devices in transfer trip or other trip circuits, how can we justify the spurious trips!!
On the other hand, other than Alstom and Reyrolle, no one else seem to be having Class-2 auxiliary / Trip relays in their range.
Wonder how other utilities are overcoming this problem??
Is it common in Europe (except UK) to have contacts both on positive and negative sides in the circuit (so that one contact maloperation cannot lead to spurious trip)!!

 

[JG2828]

dpc,
ABB had the REF544N, REM544N, and RET544N Class 1E certified microprocessor relays. I'm pretty sure they were just 1E certified versions of the DPU2000R and TPU2000R. However, I don't think they sold very many and they are now obsolete. Apparently one made it into Duke Power McGuire Nuclear Station (google search) Ref page 13:

https://www.nrc.gov/docs/ML0827/ML082760400.pdf

 

[dpc]

Thanks, JG2828! I was not aware of this.

 

[HamburgerHelper]

I have a hard time imagining that the relays wouldn't be the least of your worries if the site was shaking so much to trip a microprocessor relays. I am not discounting it but I just have a hard time imagining it. So what do people do? Build separate foundations? Put building or foundations on shock absorbers?

------------------------------------------------------------------------------------------
If you can't explain it to a six year old, you don't understand it yourself.

 

[marks1080]

it **might** help, if in cases, where you are energizing a relay to close a contact, how about you de-energize the relay to open the contact. Where I am going with this, is that it's much more difficult (if not impossible) for a contact being held closed by an energized relay to change state due to vibration, vs an open contact on with a de-energized coil. You want to check that the relay coil can handle being normally picked up - I think the RXMS can, but not sure.

You obviously can't hold closed a contact in a trip circuit, but to be fair you shouldn't ever use an RXMS relay in the trip circuit, only the control circuit. Use a heavy duty relay for the actual trip circuit.

 

[dpc]

With de-energize to trip schemes, there are much higher risks for misoperation for a wide variety of causes. I don't see that as an improvement in reliability. The amount of vibration needed to cause the relay contacts to close might be a lot less than you think. Like banging your fist on the relay panel door.

 

[thermionic1]

What about mounting the relay on some kind of shock absorbing base?

 

[HamburgerHelper]

Connect your relays to a remote I/O module with fiber and put the I/O module on a nice foam bed.

https://selinc.com/products/2507/

https://selinc.com/products/2505/

------------------------------------------------------------------------------------------
If you can't explain it to a six year old, you don't understand it yourself.

 

[marks1080]

dpc - i agree with you. You do see it sometimes though in certain environments and applications.