ABB TPU 2000R (Differencial Protection)

[mntg]

Any comments on ABB TPU 2000R application, problems or anything. ( Had a problem whith TPU 2000R operated on the feeder fault, tripped the transformer (230KV/27.6KV, 125MVA), dual winding.
there is also SEL 387 as a backup which did not operate.

Thanks,

 

[jimmymac2]

The only problems I know of related to the TPU are software bugs and I believe these problems have been addressed in v4.3 of the WinECP software.

If you're relay tripped on the differential element for a fault outside the zone of protection then I would re-evaluate your CTs. Make sure that they are properly matched, they are of sufficient accuracy class to supply the burden, and will provide appropriate saturation to prevent nuisance trips. If you have waveform capture set up in your TPU then you should be able to look at the oscillography and compare the CT contributions to the relay during the fault.

If the relay tripped on an overcurrent element then you may need to re-evaluate your protective device coordination. The relay may have been set to operate too quickly causing the overtrip. If everything checks out then the downstream control circuit and relay may have failed to operate properly to open the breaker.

I'd be interested in hearing what you find out. Please post the result.

 

[Plinko]

I have one TPU2000R in service and have had no problems...going on three years. We've had some pretty nasty thru faults too.

 

[dpc]

There was a firmware upgrade a year or so ago that ABB was very anxious to install on a relay that one of our clients had in service. ABB came out and did the upgrade (while the relay was in service).

I would check your firmware version with ABB just to be sure. I don't know the nature of the problem.

 

[peterb]

Four years in service at a client's plant, no real problems.
There was a case of tripping on through fault (these are quite frequent on this system) - turned out to be harmonic restraint setting problem. I managed to reproduce the fault from the recording (on a Pulsar test set) and proved the corrective action, which was a setting adjustment. No recurrence after correction.

 

[jghrist]

Are the TPU 2000R and the SEL 387 on the same CT circuits? Most false trips on differential relays are caused by CT wiring errors. Oscillography should show this if available.

 

[jbartos]

Suggestion: As any other relay connected to communication network based on a certain topology, it is dependent on advantages and disadvantages of the communication bus and associated communication network topology.

 

[mntg]

Thank you for your comments,
For your information the 87T (Harmonic restrained percentage differencial function) operated on the feeder fault.
We are still looking at this problem.
I will post the result when we figure out this problem.

 

[peterb]

Sounds similar to the case I mentioned above.
In my case, the harmonic restraint was set too high and we could see from the fault oscillogram that the trip command was issued at the same time that the harmonic restraint reset.
I played back the fault recording Comtrade file on a Pulsar test set and was able to accurately reproduce the false trip (including the waveform record). After that, it was a matter of adjusting the restraint to confirm correct operation. The relay has been back in satisfactory service for over a year, with many through faults.

 

[jbartos]

Suggestion/comment: The harmonic content is on 27.6kV level is supposed to follow industry standards, e.g. IEEE 519. There should not be much of harmonic set point adjustment deviating from the industry standards set limit. Some relays have an automatic reduction of harmonic restraint, which is used during faults or equipment startup.

 

[peterb]

I fully agree that the system should conform to established standards for harmonic content for normal operation. However, what we are discussing here is abnormal operation with faults on the system - harmonics here are a more random function, depending on the type of fault or system abnormal condition. For example, transformer inrush current is high in second harmonics - a feature that has been used for many years in the design of differential relays.

 

[alehman]

Some other common problems are incorrect programming of the CT configuration on the relay, % slope setting to low, incorrect grounding of CT circuits or incorrect phasing of CT circuits.

 

[jnims]

I have used ABB's DPU2000R and TPU2000R in many substations. The TPUs are relatively problem free, but the DPUs have been a nightmare. That's not to say the TPU2000Rs are without problems. We had a false differential trip at a substation a few years ago that ABB indentified as poor quality control from their power supply provider. I have also recently had a through fault trip at a different substation earlier this year. The diagnosis was the same as peterb's. The 2nd harmonic restraint was set to 15 percent. I have since lowered the restraint to 10 percent. To ABB's defense, they did spend a significant amount of time reviewing the problem. Their conclusion was residual CT saturation. This is a little hard to accept since the CTs are 1200:5 C400, no other devices are in the CT circuit and the fault current that caused the trip was 6400A.

Because of our problems with the DPU (not the TPU), we have stopped using the ABB products.