IEEE 67 directional overcurrent protective relay issue

[vetlover]

Greetings forum misters!
Wanted to see if somebody might ponder an issue I am seeing at a customer's data center. I am getting an occasional and inconsistent target 67 trip of a Basler BE-951 protective relay that is tripping a 3000amp 480v main breaker. We initially saw the target when the data center UPS systems were bypassed(have concerns that the bypass procedure may not be synchronized), but now the system is getting the 67 when it is really cold outside. (Only event that we feel is re-occurring and common to the failure) At first we thought the Basler was bad, now we feel the anomaly may be real. Possible transient? Some kind of inrush from the transformer? Some kind of issue between the transformer, a static switch that is incorporated or the UPS system? Any thoughts on 67 common results would be much appreciated.

 

[dpc]

Your UPS feeding a utility-side fault? Without more information, it's hard to say. A directional overcurrent relay can be configured to look in either direction, so I'm not clear on the purpose of this 67 device.

Was this relay properly tested during commissioning? It's fairly common for the directional element to be looking in the wrong direction.

 

[DTR2011]

the relay has the ability to create an event report for such things. use it

 

[vetlover]

The site is 7 years old and this has been occurring for only about 3 months. The Basler has been removed and tested. Unfortunately, the reporting on this relay only logs about 18 events and when we download it, they are all either 27s for the undervoltage which starts the gens or else they are the 67's. What is odd is that each 67 log will also indicate the legs the fault is on and that changes each time. It will be a 67a then 67b then 67abc. The utility mandated the relay, which looks at reverse power (since we have gens and use softloading/unloading), obviously overcurrent(directional) and low votage which starts the gens for emergency power. We have yet to see reverse power target.

 

[ScottyUK]

Obliquely related, perhaps:

We experienced a long series of rogue trip events on an ST generator where the only common factor appeared to be low ambient temperature. It was, to say the least, an absolute pig of a fault to track down because there were a number of signals all connected in to a customer trip input and no means of distinguishing one from another. The cause turned out to be a PCB screw terminal which had been over-tightened, fracturing the solder joint but with sufficient contact to stay conductive across the damaged joint. When it got cold the metals contracted slightly and the joint went high resistance, initiating a trip.

Look at any joints in trip and command circuits where a poor joint could cause similar problems. Protection relays and tripping units are obvious candidates, especially if your switch house sees large swings in temperature.

 

[dpc]

Scotty,

That sounds like an absolute nightmare to track down.

 

[ScottyUK]

Hi dpc,

It plagued us for months - the STG racked up more trips in that winter than in the previous ten years. We were getting called out almost every night, chasing ghosts in the trip system.

 

[Vincentb1298]

What is the normal feeder load ?
And what is the pickup of the protection?
Is the problem occured when transformers are energized ?

 

[Vincentb1298]

Sorry i didnt see that youd find the problem