Switchbay Control Units

[nraju]

We have ABB's Switchbay Control Units (SCUs) installed in 4.16 kV and 34.5 kV switchgear. Since the past 7 months, we have had a series of failures on some of these SCUs. The display becomes totally blank. Upon inspection, we found that the capacitor in the power supply card had failed. The failures occurred in different switchboards in different locations, so voltage spike is ruled out as a cause. Also, the ambient temperature in the room is around 25 degrees, well below the allowed 55 degrees C by the manufacturer. Could you please help me diagnose the reason for the failures?

 

[DanDel]

First step is to contact the manufacturer, even though they may not help you(for free), especially if the equipment is not new.
You may want to check for power quality issues like harmonics and spikes(you can have them at more than one location), though this type of equipment should not be overly sensitive to them.

 

[nraju]

Dandel,

We already contacted the manufacturer, but the response from them is not so encouraging as it is well-past the warranty period. So, we are left to fend for ourselves. The installation is 5 years old. The manufacturer's catalog specifically says that the average life of the capacitor is over 35 years! What puzzles us is that in all the failures, the pattern is the same, i.e., failure of the capacitors, even though they are located in different switchboards in different locations. Does anyone have a similar experience / suggestions?

 

[DanDel]

Have you been replacing the defective capacitors? What have you been using, ABB-supplied replacements or off-the-shelf? Have there been any subsequent failures with the new capacitors?

 

[nraju]

We have been replacing the entire card with spare ones (supplied by ABB), but we have now ran out of all spares and have reached a critical stage. We have lost about 7 SCUs until now, all of them with the same problem. (This is a big company with about 200 such SCUs installed all over the complex). Obviously, there is no point in replacing the cards without knowing the root cause of the failure of the capacitors. We tried measuring for any possible spikes by fixing recorders, but the failures seem to happen at random at various locations (unfortunately not in the feeders where the recorders were fixed).

 

[DanDel]

200 units and no response from the manufacturer? Do you have 200 ABB substation/switchboards? That would represent quite an investment, and significant future income for ABB for parts and service. If they don't see that, you may be forced to replace all the ABB SCUs with another, more friendly manufacturer, and not purchase any new equipment from ABB.
Perhaps you can also send a failed unit out for forensic analysis and determine more about the failures.

 

[nraju]

Dandel,

Each of the outgoing feeders from the switchgear has one of these SCUs installed and there over 200 such outgoing feeders from various switchboards. You are right, we are seriously considering blacklisting the manufacturer. But for the moment we are stuck with this problem.

 

[jbartos]

Suggestion: Have the power supply card analyzed/troubleshoot by the electronic specialist. It may not be that serious problem. Recently, there were some leaking capacitors observed on PC motherboards due to improper electrolyte. The tech support mentioned that this type of failure is better to fix without submitting the PC motherboard for repairs.