As all ferry users across Argyll and the Isles today know well, the winds are blowing.
For Argyll’s main newsroom has a generator to protect internal systems from power supply problems. It cuts in automatically when there is a variation beyond the limits in the power coming in from the mains – and cuts out again, handing back to the mains supply when it has returned to normality.
We had only ever envisaged this as a protection against power cuts – but the experience of this morning has thrown up a different problem.
Our system switched to generator, then after an hour or so, switched briefly back to mains and almost immediately back to the generator.
No one else in the area had any power failures and Scottish Hydro had had none reported to it, so the problem was site specific.
It emerged that the generator protects the internal power system from both too low voltages and too high ones, taking over the supply in either case.
Since each of the blips and switchovers we had experienced had been accompanied by stronger swells of wind – heavy but not extreme, the wind farm in the hills was generating over capacity, creating ‘high volts’ voltages over the legal upper limit.
No one else in the vicinity had a problem because the over-limit voltages experienced in our system were modest enough not to create serious safety rick in well wired properties – whereas, with us, the generator is obviously set to respond to any variation outside the legal limits.
The setting of legal voltage limits is, of course, a necessary safety-first system – but will already have sensible tolerances built into it at the low and high ends of the allowed scale.
The question raised now is that there is an apparent disparity between the legal limits set to govern the supply to customers premises and the legal limits set to which wind turbines may generate before they are required to switch off for over production – and at which point another subsidy [for enforced non-production] kicks in. This requirement is not about an inability of the turbines to operate in strong winds but in the ability of our feeble power grid to cope with the additional power.
The legal voltage limits for the supply side and the demand side in this situation clearly ought, for the sake of safety, to marry. One is obviously currently incorrect. But which one?