Hello You Clever People
We run a 150kw wind turbine (415v 3 phase 50 hz induction generator-see schematic attached) which fortunately still runs but the status bar on the computer shows an output reading in KW of approx 30% of the actual "true" power being produced. ie if its saying 30kw on the status bar I know the "actual" reading of power being produced is around 90kw as confirmed by two independent power meters (and by using a clamp meter to measure the amps,) one in the turbine and one at the POC. Any pointers for me to follow? I'm thinking AC/DC convertor faulty ? CT's faulty? Thanks in advance.

 

Welcome to AAC!
Are the voltage and current outputs measured at the terminals of the transformer board what you expect them to be, or only 30% of expectations ?

 

Welcome to AAC!
Are the voltage and current outputs measured at the terminals of the transformer board what you expect them to be, or only 30% of expectations ?

Hi Alec. Many thanks for your response. Funnily enough today I put on a new transformer board thinking that it might be that.........but restarted the turbine and its still reading the same power output ie approx 30% of actual

 

Welcome to AAC!
Are the voltage and current outputs measured at the terminals of the transformer board what you expect them to be, or only 30% of expectations ?

Hi again Alec.........or are you thinking its a problem BEFORE the voltage actually gets to the transformer board ?

 

If it is three-phase maybe it is only measuring one phase? Does it show how much power is on each phase?

 

If it is three-phase maybe it is only measuring one phase? Does it show how much power is on each phase?

Hi Ian
Many thanks for your response.
Yes the computer board shows voltages (via a different display to the one thats only showing 30%)) on all 3 phases and they are all correct, another display also shows the current on all 3 phases, and that is correct as well.

 

Are all the measurement transformers connected to the correct terminals?
If you have two CTs swapped, then the calculation of power will multiply the voltage by a current that is 120° out of phase, and get an answer that is far too low.

 

are you thinking its a problem BEFORE the voltage actually gets to the transformer board ?

It was one possibility which needed to be eliminated. Your post #6 does that. So the fault lies somewhere downstream of the transformer board.

 

Are all the measurement transformers connected to the correct terminals?
If you have two CTs swapped, then the calculation of power will multiply the voltage by a current that is 120° out of phase, and get an answer that is far too low.

Hi Ian
Thanks for that.
I'll check that on T phase S1 goes to No 13 and S2 to No 12, S phase S1 goes to No 11 and S2 to No 10, R phase S1 to No 9 and S2 to No 8 as per page 18 on the schematic and recheck the KW reading on restart.

 

If the computer readings for each phase voltage and current are correct – then I would suspect that Ian0 is correct that the currents are out of phase (for some reason); even that the wrong current phases have been paired with each phase voltage. The reason for the low power reading being the low power factor due to the mismatch of voltage and current phases

Does the computer have to option to display apparent power (VA)?

 

Are all the measurement transformers connected to the correct terminals?
If you have two CTs swapped, then the calculation of power will multiply the voltage by a current that is 120° out of phase, and get an answer that is far too low.

Preliminary check Ian shows that R,S and T PHASE wires are all on the correct phases (colour coded as 2 black wires are T phase and are on 13 and 12, S phase has two white wires and are on 11 and 10 and R phase has 2 red wires on 8 and 9) but I haven't checked if the S1 and S2's on each phase are the correct way round. Would that make any difference if S1 were on S2 and vice versa on any phase ?

 

Preliminary check Ian shows that R,S and T PHASE wires are all on the correct phases (colour coded as 2 black wires are T phase and are on 13 and 12, S phase has two white wires and are on 11 and 10 and R phase has 2 red wires on 8 and 9) but I haven't checked if the S1 and S2's on each phase are the correct way round. Would that make any difference if S1 were on S2 and vice versa on any phase ?

Yes. It would calculate a negative power, and when it adds up three phases it would get a low reading. Probably about a third of what it should be reading!

 

If the computer readings for each phase voltage and current are correct – then I would suspect that Ian0 is correct that the currents are out of phase (for some reason); even that the wrong current phases have been paired with each phase voltage. The reason for the low power reading being the low power factor due to the mismatch of voltage and current phases

Does the computer have to option to display apparent power (VA)?

Hi Hymie
No there is no option for VA just current on each phase (which shows (on the computer) around 65-70 amps per phase when idling at 1500rpm with no wind/no slip which corresponds with the clamp meter at the POCC) and a voltage display for each phase, which all show around 238 volts. There is also a power factor display which varies enormously due to it being a wind turbine with constantly varying windspeeds rather than a motor under constant load.

 

You have not shown your current sensors, but if they are toroidal or anything that goes over a wire, one of them must be rotated 180 degrees. This is not speculation, I personally have seen it. More than once.

Remember, AC power calculation use vectors, they require the magnitude and angle.

 

With a generator, you have to take into account the POWER FACTOR of the load. With a switching power supply, the power factor will be far less than the ideal 1.0 of a purely resistive load.

Power factor = (real load) / (apparent load)

I'll leave this for those with a better grasp to explain, but I found this out the last hard way powering a furnace blower from an inverter.

 

Yes. It would calculate a negative power, and when it adds up three phases it would get a low reading. Probably about a third of what it should be reading!

Thanks Ian
The wind is dying down shortly so I can turn off the turbine and I'll do a check to see that all 6 of the S1 and S2's are on their correct terminal points.
Thankyou all for your excellent help so far - top guys

 

Yes. It would calculate a negative power, and when it adds up three phases it would get a low reading. Probably about a third of what it should be reading!

Fag packet maths Ian........10kw + 10kw +10kw = 30kw OR 10kw + 10kw minus 10kw = 10kw 33% of normal. Could it be that simple ?? I'll find out tomorrow........thanks Ian !

 

Is the 3-phase Delta or Wye configured?

 

Is the 3-phase Delta or Wye configured?

Hi Alec

Its delta configured.

 

I've been playing with simulations of both delta and wye circuits and can't get the total VA to drop more than 50% below the highest total VA by just swapping wires/phases around. So I'd be surprised if miswiring is the cause of your problem.