Voltage too high
Voltage too high
(OP)
Hi everybody,
After installing modern lighting, in a school, the lamps flickered all the time, I measured the voltages:
L1=230V, L2=260V, L3=230V
Load is basically evenly distributed over the phases. In the Substation the transformer occasionally makes a bubbling sound suggesting gases rising in the oil.Any ideas as to possible causes of the over-voltage?
After installing modern lighting, in a school, the lamps flickered all the time, I measured the voltages:
L1=230V, L2=260V, L3=230V
Load is basically evenly distributed over the phases. In the Substation the transformer occasionally makes a bubbling sound suggesting gases rising in the oil.Any ideas as to possible causes of the over-voltage?






RE: Voltage too high
I don't think overvoltage would cause flicker though. And the bubbling transformer sounds like a third problem.
K2ofKeyLargo
RE: Voltage too high
It will probably stop doing this soon, dramatically. I would start enquiries as to the location of a possible replacement transformer.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Voltage too high
Keith Cress
kcress - http://www.flaminsystems.com
RE: Voltage too high
If your interpretation is correct, you may want to go ahead and shut it down before it shuts itself down, possibly violently. Then start looking for the problem. As the others have eluded, this should not wait until it's convenient or even until a replacement is located.
RE: Voltage too high
RE: Voltage too high
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Voltage too high
Keith Cress
kcress - http://www.flaminsystems.com
RE: Voltage too high
Keith Cress
kcress - http://www.flaminsystems.com
RE: Voltage too high
Take shut down and conduct a single phase low voltage excitation test - it will reveal any turn shortings.
Measure resistances of windings - for loose contacts.
RE: Voltage too high
Video of substation fire : http://au.youtube.com/watch?v=qvoDNKJX7SU
Although I cannot confirm the cause of THIS specific fire one could expect that this is the way most oil-filled transformer which have 'small' internal arcing fault problems would fail : internal arcing faults cause overpressure inside the transformer, an oil leak may develop (unless there is overpressure protection), oil will start spreading outside the transformer until an explosion occurs (catastrophic internal arcing fault), causing hot oil to ignite, and the fire to burn out of control.
RE: Voltage too high
Earth calling roemer.
Earth calling roemer.
COME IN roemer!
Do you copy?
Perhaps he's been occupied with the fire..
Keith Cress
kcress - http://www.flaminsystems.com
RE: Voltage too high
http://www.youtube.com/watch?v=fzbQjd_Oo4Q
RE: Voltage too high
RE: Voltage too high
Thanks for all the comments, seems everybody would like an explosion. The higher voltage 260V on L2 seems to have been present for at least 6 months. The electricity supplier says primary voltage is OK 10KV. The engineer from the electricity board reckoned that sometimes transformers do bubble and it doesn't necessarily mean there is a problem. Suppose the transformer isn't at fault, what could it then be ?
RE: Voltage too high
I've been reading in this forum for quite a number of years & those folks that have commented have been around the block quite a bit. Based on their comments, I'd get everyone in authority that said everythings OK, to sign off on their opinion.
Then, you'll have a bit of recourse when that over-voltage transient comes down your line and trashes all manners of things.
Ed
RE: Voltage too high
For what it's worth, I've never heard of a transformer bubbling being normal.
RE: Voltage too high
RE: Voltage too high
One more thing, you never mentioned what was done to the supply transformer prior to installing your "modern lighting". We are not wishing for an explosion, but possibilities are enormous in your case.
RE: Voltage too high
RE: Voltage too high
I've spent a bunch of years installing, caring for and repairing oil-filled transformers and it's been my goal to PREVENT bubbles. That's ONE reason we vacuum fill transformers. Once a transformer is filled, there is NO reason for bubbles under normal operation.
I recommend that you get a testing company to come in, do an on-site TCG (total combustible gas) test AND draw a sample for the dissolved gas analysis. Most testing companies can do the TCG within minutes. The equipment is relatively cheap and very portable.
The TCG test is quick and non-specific. If the results are high, there's reason enough right there to shut down the transformer without waiting several hours for the dissolved gas results to show up. I've had TCG results with elevated readings within a few minutes of a bubble/trip episode.
old field guy