We first raised the issue of high voltage peaks with Manweb back in July, and we do now have some further information. When we first contacted Manweb, they did react very speedily, and an engineer was here fitting a recording device the following day. However it turned out that it wasn’t a particularly sophisticated device, and the guy whose job it was to learn about the connection of small generators to the grid was on holiday, so the whole thing got moved back a couple of weeks.
But to cut a long story short, the right man has now had the right equipment connected to the supply for the right period of time, and he has been kind enough to let us have a copy of the data. What it shows is that the voltage levels are within the accepted parameters nearly all the time, though there are a few peaks over the 253 volt maximum. However the data is based on 5 minute averages, so we still don’t really know how high these voltage peaks are. Bearing in mind that the G59 mains interface relay is still set to zero time tolerance, it is not surprising that we are still getting problems. The problems only occur however in high wind conditions, when the turbine is trying to pump out its maximum power. This does suggest that it is the length of the cable from the turbine to the transformer that is actually causing the final bit of the voltage spike which is in turn causing the turbine to shut down.
Looking at the mains voltage data, we think that the output from the transformer can be stepped down without causing the voltage to fall below its minimum limit. This would give a bit of slack to the system, allowing it to cope with cable-induced voltage spikes without shutting down. If Manweb can be convinced of this, we will be well on the way to curing our main problem.
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