New Ekhuruleni power problems

Well, we have just gotten past our sixth outage this week so far.

Of course, it is only Thursday.
 
As to why the transformers blow up?

It's dire lack of maintenance folks. They didn't know the oil had to be changed including the air drying unit needed regular maintenance.

The calcium chloride gets used up and the moist air from outside permeates into the oil, and at 66kV the oil becomes a conductive sludge. The substation draws more and more power and people's lights get dimmer but the chops think its "increased demand" until eventually the oil becomes conductive enough and BANG!!! it causes a short on the 66kV side with a bright flash, tripping the line and usually igniting the oil and they have a fire on their hands.

THEY HAVE THE ABILITY TO DETECT AN IMPENDING FAILURE LONG BEFORE THE THING BLOWS UP FOLKS!!!! They are clearly ignoring the problems.

A partial short or overload causes the oil to gasify, this phenomenon is what is used in the operation of a Buccholtz relay which is a nifty way of detecting a fault by checking out the oil.
 
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Interesting stuff JTech.
Buchholz relay
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In the field of electric power distribution and transmission, a Buchholz relay, also called a gas relay or a sudden pressure relay, is a safety device mounted on some oil-filled power transformers and reactors, equipped with an external overhead oil reservoir called a conservator. The Buchholz Relay is used on conservator type oil preservation systems as a protective device sensitive to events which occurs during dielectric failure inside the equipment.

When an electric arc or overheating develops inside the coils, gas is generated. The relay has two different detection modes. On a slow accumulation of gas, due perhaps to slight overload, gas accumulates in the top of the relay and forces the oil level down. A float operated switch in the relay is used to initiate an alarm signal. This same switch will also operate on low oil level, such as a slow oil leak. If an arc forms, gas accumulation is rapid, and oil flows rapidly into the conservator. This flow of oil operates a switch attached to a vane located in the path of the moving oil. This switch normally will operate a circuit breaker to shut down (isolate) the apparatus before the fault causes additional damage. Buchholz relays have a test port to allow accumulated gas to be withdrawn for testing. Flammable gas found in the relay indicates some internal fault such as overheating or arcing, whereas air found in the relay may only indicate low oil level or a leak. Buchholz relays have been applied to large power transformers at least since the 1940's.
Click to expand...
http://en.wikipedia.org/wiki/Buchholz_relay
 
The best warning system in the world is useless if not attended to, though.
There lies my frustration.

EDIT:

I can see it now:
"Engineer" #1: I cant sleep with that noise
"Engineer" #2: Switch it off.
E1: much better.
 
Moederloos said:
govt is probably right now forming a sub commitee to debate the need for a full commitee to organise the commitee to commission a report on the situation, and in the end all parties to the original discussion will deny ever having had any discussions and that the report was "never given to them".
Click to expand...

That is so sad, especially since it is true.
 
JTech said:
As to why the transformers blow up?

It's dire lack of maintenance folks. They didn't know the oil had to be changed including the air drying unit needed regular maintenance.

The calcium chloride gets used up and the moist air from outside permeates into the oil, and at 66kV the oil becomes a conductive sludge. The substation draws more and more power and people's lights get dimmer but the chops think its "increased demand" until eventually the oil becomes conductive enough and BANG!!! it causes a short on the 66kV side with a bright flash, tripping the line and usually igniting the oil and they have a fire on their hands.

THEY HAVE THE ABILITY TO DETECT AN IMPENDING FAILURE LONG BEFORE THE THING BLOWS UP FOLKS!!!! They are clearly ignoring the problems.

A partial short or overload causes the oil to gasify, this phenomenon is what is used in the operation of a Buccholtz relay which is a nifty way of detecting a fault by checking out the oil.
Click to expand...


To ADD I wonder when last was any of the transformers oil recycled and filtered for carbon and moisture removal. Gradual Build up of moisture and carbon in the oil could occur over time which is aggravated when wide temperature fluctuations is eminent like now during the winter.

From experience (Eskom)

oil-insulated switchgear that undergoes routine maintenance every three years (minimum).
Note that the assumed maintenance frequency and average cost of maintenance were
based upon Eskom experience with the installed base of oil-insulated compact switchgear;
Click to expand...

Thus each transformer should have had the oil cleaned (Recycled/filtered) or replace 3 times by now. The steaks probably did not do any. Boom!!
 
Out of interest sake - if the explosion of the two transformers in Boksburg was due to bad/no maintenance...

How much did the 2 replacement transformers cost again (was about R5mil each?)

How much would a oil change have cost?
 
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