MAJOR collapses of developed world electricity grid systems are not uncommon. The rise in renewables increases the probability.

Being able to rapidly “Black Start” the country is a public health priority and, rightly, a public expectation. In Scotland it is presently an unrealisable imperative.

Industry expectation for Scotland to Black Start has now risen to five days and the replacement of large-scale dispatchable on-demand generation with weather-dependent intermittent distributed renewables is the cause.

The PM088: Scottish Black Start Restoration Working Group reviewed its procedures in September. These are based upon Local Joint Restoration Plans from transmission operators to first power up and stabilise “local transmission islands” . Thereafter these islands/areas can be electrically synchronised and interconnected progressively to rebuild the onshore grid.

The report prefix expresses concern that restart practice post-Longannet will result in “severe delays” to restoration – highlighting oil refineries.

Previously the 53-year-old Cruachan pumped storage station was to be used to restart Longannet providing up to 440MW for a maximum of 22 hours and this plan was successfully “tested” in the 1980s. Peterhead gas-fired station is now Scotland’s only high-powered and high-inertia (essential to stabilise frequency) dispatchable power station and is seeking planning permission to install 32 diesel generators capable of running at full power for seven days to secure its restart. It will be unable to restart all of Scotland, being half the capacity of Longannet, without input from Foyers pumped storage/Cruachan and from England, which is an untested scenario.

Wind farms will be unable to Black Start the grid for several reasons. Both principal generator types in national deployment need external power to start generating. Whilst some latest devices have self-start capabilities, connecting to a dead grid via long offshore cable interconnections remains an unsolved problem as the turbines cannot provide enough reactive (wattless) power to energise them. They would also be unable to meet National Grid requirements for block loading, grid voltage or frequency control if asked to support grid reloading.

The first grid restoration activity therefore under PM088 is to disconnect all offshore generation networks.

Similarly, onshore windfarms will be progressively reintroduced to the grid only once it is restabilised providing they are not frozen and there is wind.

Critical restart power will arrive from England only once the north of England grid is re-established.

Scotland’s two nuclear stations can only be reconnected into a stable grid, this taking several more days post-Longannet increasing their diesel back-up reactor cooling demand.

The new £2.4bn plus HVDC interlinks from Wales to Hunterston area and from Moray Firth to Spittal south of Thurso have not been engineered to support Black Start as their inverters are not of the latest design.

London has a similar Black Start problem for differing reasons and I understand the Black Start issue has recently attracted the attention of Cobra, the UK Government's civil contingencies committee.

Parallels with the Titanic disaster are obvious. The grid is assuredly sinkable and the lifeboats, rather than being too few, won’t even appear in Scotland for five days.

DB Watson,

Saviskaill, Langdales Avenue, Cumbernauld.

THE Scottish Government and its quangos love to boast about Scotland “leading the world”. For example, apparently we lead the world on CO2 emissions reduction, LGBT rights and are planning to lead the world on third gender recognition and human rights.

Reality suggests that where we really lead the world are in areas such as obesity, child poverty, state dependency, hospital waiting times and potholes per mile of road.

GM Lindsay,

Whinfield Gardens, Kinross.