Positive Metered Powerflow from Open Breaker?
Positive Metered Powerflow from Open Breaker?
(OP)
Hi,
We have a windfarm that has recently energized. It currently has its breaker open, so the grid trafo 110/20kV is energized from the HV side only.
Both metering and SCADA are showing a few kW flowing from the trafo into the grid. It isn't constant, but doesn't look random or noisy either.
Does anyone have any idea where this power could be coming from??! Could it be due to poor earthing / broken CT?
The fact that two independent systems are giving the same results would suggest the power is real, rather than a measurement error, but any suggestion on what to look at would be welcome!
We have a windfarm that has recently energized. It currently has its breaker open, so the grid trafo 110/20kV is energized from the HV side only.
Both metering and SCADA are showing a few kW flowing from the trafo into the grid. It isn't constant, but doesn't look random or noisy either.
Does anyone have any idea where this power could be coming from??! Could it be due to poor earthing / broken CT?
The fact that two independent systems are giving the same results would suggest the power is real, rather than a measurement error, but any suggestion on what to look at would be welcome!






RE: Positive Metered Powerflow from Open Breaker?
Can you post a single line diagram?
Regards
Marmite
RE: Positive Metered Powerflow from Open Breaker?
RE: Positive Metered Powerflow from Open Breaker?
The default setting on many electronic meters is to sum positive and negative power flow. If that is the case I hope that the utility plans to reprogram the meter to report positive power flow and negative power flow separately.
Bill
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"Why not the best?"
Jimmy Carter
RE: Positive Metered Powerflow from Open Breaker?
RE: Positive Metered Powerflow from Open Breaker?
I've attached an SLD of the relevant bit - the CB at the bottom is open.
The chap who does the metering insists that something fishy is going on! Will let you know if we find out the problem - hopefully it is something as simple as incorrect wiring.
RE: Positive Metered Powerflow from Open Breaker?
The utility meter shop has to reprogram the meter defaults before the meter will report positive power separately from negative power.
Once the wind farm goes online it will be obvious whether or not the meter has been programed properly.
These may be customer owned meters rather than utility meters. In that case the customer may need to spend $5000 or $6000 on the cable and software package to reprogram their meter defaults.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Positive Metered Powerflow from Open Breaker?
I suspect that your problem may be confusion as to positive power flow versus negative power flow. Back to what David said.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Positive Metered Powerflow from Open Breaker?
RE: Positive Metered Powerflow from Open Breaker?
If the 110kV phase voltages are unbalanced the delta winding will transfer real power from the higher voltage phase(s) to the lower voltage phase(s). The amount of power transferred will vary as the primary voltage unbalance varies.
Bill
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"Why not the best?"
Jimmy Carter