capacitor problem..help appreciated
capacitor problem..help appreciated
(OP)
we have been experiencing some weird issues concerning exported energy into the distribution grid ..the meters show readings for exported active energy at customers having capcitors installed for power factor correction
when the capacitors are disconnected the meters show 0 KW exported
i m struggling finding a logical explanation..i checked the polarities of the CT's connected to the meters and they seem to be connected as the should
many thanks in advance
when the capacitors are disconnected the meters show 0 KW exported
i m struggling finding a logical explanation..i checked the polarities of the CT's connected to the meters and they seem to be connected as the should
many thanks in advance






RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
You probably need to go up to the primary CT and PT connections and work your way back, assuming, as you go, that everything is hooked up wrong. A donut CT installed "backwards" will flip the polarity, even when the secondary wiring looks fine.
RE: capacitor problem..help appreciated
thanks for the suggestions
RE: capacitor problem..help appreciated
Gunnar Englund
www.gke.org
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
Can the meter be configured for either positive or negative phase sequence?
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
and they only display the magnitudes or the phase votages and currents...they also show a warning when the phase sequences are not respected.. so my guess is that it s not a sequence problem ..unfortunately :(
that was my first guess also but doesnt seem to be a wiring problem and we dont have meters available to see the angles of each phase
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
i m new on the job ..yet none of the senior engineers seem to find the solution to this issue either
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
Donut style CT's are known to be 'flipped over' in their packaging. There would be no way to tell unless you opened up the packaging. Without a piece of equipment to tell you this, your kind of out of luck. If this is the case, the only thing to do is start flipping them over (one at a time) or pull out three new ones and install again. I had this happen to me twice in the last ten years.
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
Good suggestion. Flipped packeging or incorrect labelling is something we all have seen at one time or another.
As for checking. It doesn't require much equipment.
a 75:5 CT will have 15 turns on the secondary. If you hand wind 5 more turns in the proper direction you should have a 100:5 CT.
If the CT is reversed internally, the new turns will subtract and the effective ratio will be 50:5. You can check the ratio with a clamp-on ammeter.
yours
RE: capacitor problem..help appreciated
When was the last time the meters were tested?
When was the last time the test set was calibrated.
then you may want to go to the where the ct's are at disconnect all the inputs to the meter and test the metering circuit from the start by injecting known voltage and current from a certified test set.
RE: capacitor problem..help appreciated
THis phenom happens only with customers equipped with capacitor banks
i know he reqding on the meter is related to the capacitors banks just cannot find a logical explanation
all the wiring have been checked and double checked down from the secondary or the PT and so was the calibration of the meter and also the windings on the CT's
RE: capacitor problem..help appreciated
Do the meters appear to accurately indicate real power flowing into loads that do not have capacitors?
And how many meters do you have that are showing this behavior?
RE: capacitor problem..help appreciated
Try using a protable clip on meter and see if the readigns stack up with the installed meter.
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: capacitor problem..help appreciated
The electronic meter is connected to 3 CT's one per phase the voltages are taken from the secondary of the transformer (240V L-N) and connected to the meter with the phase sequence being respected the neutral is taken also from the secondary of the transformer so the meter connectors go something like this
I1 V1 I2 V2 I3 V3 N G
althought all the connected were veriefiedmany time all all levers from the transformar down
the Index for energy export in KWh is quited substantial for customers with a big PF corrective capacitors or with those who have ne of the poles (for one phase) of the capacitors dead
i have spoken to a profeesor in the distribution and have done a lot of research but i havent been able to find a convincing explanation let alone solution
any further help wll be greatly appreciated
RE: capacitor problem..help appreciated
One assumption we have made is that the meters are ok. Rather than challenge that assumption directly perhaps we could substitute another type of meter and see if the problem is meter specific. Also try one of these meters in another circuit that does not have problems (yet?). Try putting three simple single phase meters in the system, one per phase.
Just for fun, try reversing all the ct connections on the test bench in the meter shop and applying a leading PF load.
Another assumption we are making that may possible be in error is that the connection diagram is correct. Is it possible that part of the diagram is a front view that should be a back view? I know these sound like silly questions, but at this point I start wondering if the answer is so simple that i will be embarrased when it's found.
Is it possible that the meters are internally programed to meter the current/voltage phase displacement in a delta system?
RE: capacitor problem..help appreciated
"The electronic meter is connected to 3 CT's one per phase the voltages are taken from the secondary of the transformer (240V L-N)"
What exactly is your PT ratio? This 240 to N looks unusual?
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
What does the manufacturer say about the problem?
RE: capacitor problem..help appreciated
delta to wye
22kv-400v
the meter expects a wye connection thus the neutral connection in the meter
thank you guys for ur suggestions
RE: capacitor problem..help appreciated
RE: capacitor problem..help appreciated
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: capacitor problem..help appreciated