Electrical Interference

Not only do we have the noise problem described earlier, but when the turbine is running slowly, it produces stray voltages at high frequencies. This is having bizarre effects on some electrical equipment in the farmhouse. Fluorescent light tubes buzz like mad, the hi fi buzzes, our super new electronic bread maker won’t work, strangely the interior light in one of the fridges won’t come on. Apparently it is to do with one of the inverters that convert the variable frequency AC voltage from the turbine to DC, and then back to AC again at 50 hz to match the mains. We are waiting for some filtration equipment to be fitted which should cure the problem.

Turbine Noise

The turbine is noisier than it should be. It produces two quite separate sounds, a whooshing noise as the blades rotate, and a humming or ringing noise. The whooshing is fine, no problem and as expected. It is only audible in high winds, and then you have to listen out for it to hear it. It also depends on the wind direction. The farmhouse is about 450 metres away from the turbine. The humming noise is more serious, in that it is more intrusive, and can be heard in a wider range of wind conditions. It appears that the fairly quiet noise from the generator and gearbox is resonating with the column of air inside the tower, and thus the tower is amplifying and broadcasting the noise. The solution is to put foam in the top of the tower, both to prevent the sound travelling down into the tower, and also to change the length of the air column in the tower and therefore reduce the resonance. This will be tried when the engineers come back to do the 6 month service. Watch this space for a resolution.

Unintended Shut-Down

We do seem to be getting more than our share of problems with this turbine. The latest issue is that the turbine’s control mechanism is detecting high voltage spikes in the mains grid. It thinks that this is an alarm situation and shuts itself down. You then have to go into the control panel, tell the turbine that there is nothing wrong, and off it will go again. Mains voltage is supposed to be 230 volts, plus 10%, minus 6%. This is a range of 216 V to 253 V. We are seeing voltages at the turbine well in excess of 253 V, the highest being 294 V. There are two potential causes for this, one is that the grid voltage is high, the other that the length of the cable from turbine to distribution board (approx 450 m) is causing higher resistance which in turn is lifting the voltage. This may all be made worse by the lack of tolerance in the time setting of the G59 relay. Manweb have so far insisted that the delay be set at zero seconds so the briefest voltage spike will trip it out. Manweb have agreed to come and put a data logger on the mains input to see what the incoming voltages are.

More G59 Issues

We still haven’t got this DNO G59 issue resolved yet. It seems that the interface relay between the turbine and grid as fitted by the Dutch manufacturers is absolutely fine for some DNOs but not for Manweb. We have tried in vain to explain this, but each DNO has their own rule book probably dating back to when they were established as independent entities even pre-dating the National Grid. We now have to change the relay, which will hopefully satisfy Manweb and allow the G59 test to be performed.

This has not involved me in any extra cost, other than stress, but I do think that the manufacturers should have done their homework a little more thoroughly before selling turbines into the Manweb area. But they will know for the next one!