GEE Multilin 489 Relay Failures 1

[cairnhill]

Hope someone can help - I have recently been on a couple of offshore drilling units that were fitted with GE Multilin 489 generator protection relays. The units are about ten years old (old version). They previously worked for around 9 years on one rig and 3 years on the other (but rig construction was delayed so the two rigs were contemporary). Unit powers up and all output start flashing - this has happened on about six relays. New replacements seem to work but we don't want this problem later. Any suggestions

 

[DTR2011]

A couple of questions and suggestions.

#1 Were the relays ordered with conformal coating? Does the relay room have positive pressure? Are these failures related to the harsh environment?

#2 Did you ask GE to provide a failure analysis? What did they say? If the relays were alarming (flashing ?), what do the event reports on the relay indicate as far as the failure goes?

I don't recall exactly on the 489, but do recall that GE relays are in an alarm state until programmed, or commissioned in GE speak. Are the failures related to lack of programming? Have you had the relays tested independent of GE?

 

[Drivesrock]

Hi Cairnhill.

What is the supply voltage? If 24Vdc read on!

I have had this - all the front LEDs flashing at power up or after a while ON - and it's because of components of the internal power supply ageing. Whereas the input supply range is 18-30 odd volts and you may have a +24Vdc supply that is now no longer enough. You can prove this with an external variable power supply - increase above the usual supply value by a few volts and they work! When lowering the voltage again they may well work fine at 24V - for a while or you power cycle again.

Now, if you have a fixed 24V supply from a UPS and this also supplies other relays and circuits you probably won't be able to up the voltage.

I've not attempted a field repair to the units preferring to send to GE so as to not have an important piece of plant protection messed with by a field hand.

If you can supply them at a higher voltage they will continue to work fine. Consider a rotating program to get them sent to GE for servicing.

I hope this helps!

 

[cairnhill]

Drivesrock

Yes they were both 24VDC supplies and they are operating exactly as you describe. Both systems failed after putting the 24VDC UPS power supplies off for installtion of new generator control gear. The rigs had them powered up almost constantly for years because even after blackouts they were still energised. Sometimes if you left them on they would "come back to life" after a few hours.

Thanks for answering so quickly and it is certainly given me food for thought about using the same voltage range for standard 24V DC UPS systems

Look forward to helping you in the future if I can

Cairnhill

 

[Drivesrock]

Where is your offshore drilling rigs location? If South America way, we should meet up!

 

[cairnhill]

UK sector North Sea and Caspian Sea. Maybe down Brazil sometime next year but will mostly be on a shipyard job here. Would be glad to meet up sometime and again thanks for your help - I've passed on your information to the rig chief electrician and I did not take all the crerdit!

 

[Chapssa]

Hi CrainHill,

After approximately 10 years in service, the relay may need to be serviced. I suggest you contact the GE Multilin support team to have the relay serviced or replaced with the new one (what ever cost effective for you).
Cheers

 

[cairnhill]

Thanks Chapssa - the guys got all the units up and running by increasing the UPS voltage from the information given to me by Driverocks and they are now going through a rotation back to GE for servicing. The other rig replaced them all so they don't have a problem.

Funny thing is GE don't mention that the relays will self destruct after prolonged use and with breathtakingly simultaneous synchronisation - now thats what you call MTBF!