MK 30 Automatic Voltage Regulator

[ahhie]

We have 3 66/11 kV system transformers (18.8/27MVA) connected in parallel. Each transformer 11kV side have tap changer to keep the voltage at 11kV. I am wondering why some of automatic voltage regulator (MK 30) failed (indicated on it display screen), hence no automatic voltage regulation if the failed MK 30 is the MASTER? Is it due to the bandwidth setting or other things like load or noise that cause it to fail to regulate the voltage? When this happen we just reset the MK 30 and put in the setting and it function like normal again. The bandwidth setting is 1% (the transformer tap size is 1.25%), U<=80%, U>=108%, I>= 110%(not used). Anyone have similar experience??
Thank you.

 

[ScottyUK]

I have seen some really wierd behaviour from MK30s of approx 1992 vintage. Normally they suffer from memory loss and corruption - an EPROM of some kind failing, I assume - which causes almost random tap position indication and an assortment of other odd effects. One faulty MK30 unit caused the station transformer to tap down to bottom tap, dropping our 11kV bar to about 9kV and tripping most of the drives on the bar. The actual cause was never traced other than the MK30 was replaced and sent for repair.

Reinhausen's repair service is quite reasonably priced from my experience and does tend to find the fault more often than not. Send the offending item back with a detailed description of the fault, plant configuration, and any additional information you have. The more detail you send back with the unit, the better the chances of a successful fix.



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If we learn from our mistakes,
I'm getting a great education!

 

[mc5w]

That seems to be a lot better than how a I sent a faulty servo computer to Allen-Bratley twice and it came back not fixed. I had already told them that the digital to analog converter was shorting the +12 volt side of the analog power into the 5 volt digital logic. Had to change the D/A converter myself. Analog to digital converters can also fail this way with the result that the microprocessor gets toasted. Basically, these devices try to use a 12 to 15 volt version of transistor transistor logic and fudge the difference with 5 volt logic with a voltage dropping resistor.

You might want to upgrade to a newer technology voltage regulator electronics. For the size of your facility the cost is trivial compared to malfunctions.

What kind of load are you running that requires an 81 MVA bus? Usual practice at this power level is to keep each secondary bus separate except when transferring load from one bus to another.

 

[ahhie]

It is our main 11kV distribution substation which feed other remote secondary 11kV substations that are in interconnected ring network configuration.