1 Introduction
Background
1. In December 2011 and January 2012, Scotland was
subject to numerous storms that caused damage to homes, road and
rail infrastructure, as well as leaving tens of thousands of residents
without a power supply. In some cases it took more than three
days before power was restored. Although all of Scotland was affected,
it appears that the most severe damage occurred in the Highlands
and Islands.
2. We decided to conduct a brief inquiry in relation
to the power cuts which occurred as a result, focussing on:
- The frequency and severity of weather-related
power cuts in Scotland;
- The consequences of such power cuts to individuals,
businesses and public sector services;
- The current condition and technological state
of Scotland's electricity transmission network, and what conditions
it is built to withstand;
- The advantages and disadvantages of using an
alternative electricity transmission infrastructure, particularly
regarding its vulnerability to weather-related damage, but including
all significant consequences;
- Whether the response provided by the energy companies
was satisfactory (On terms of notification, restoration and compensation);
and
- How the regulation of transmission network operators
and distribution network Operators impacts upon investment in
Scotland's electricity transmission network.[1]
3. We received a number of written submissions and
took oral evidence from representatives of local communities,
Argyll and Bute Council, Scottish and Southern Energy, Scottish
Power, Scottish Renewables, The Energy Networks Association and
Ofgem. We are grateful to all those who submitted evidence and
helped us in our inquiry.
THE ENERGY TRANSMISSION AND DISTRIBUTION
INDUSTRY IN SCOTLAND
4. The electricity transmission system (the high
voltage grid) is operated by National Grid Plc, who balances supply
and demand across Great Britain. National Grid does not own any
electricity transmission infrastructure in Scotland, the responsibility
for these assets, with regards to ownership and investment, lies
with the two transmission network operators (TNOs), Scottish Power
Transmission and Scottish Hydro Electric Transmission Ltd.
5. The lower voltage local network, is made up of
14 electricity distribution networks in Great Britain, owned and
operated by seven distribution network operators (DNOs). These
correspond to the old regional boards and are therefore regional
monopolies. DNOs are responsible for the local distribution of
electricity to homes and businesses, transporting electricity
along overhead power lines and through underground cables. This
means that regulation, rather than competition, has to ensure
customer protection. There are two electricity DNOs in Scotland.
They are Scottish Hydro Electric Power Distribution in the North[2]
and Scottish Power Distribution in Central and Southern Scotland.
6. Scottish and Southern Energy (SSE) is the parent
company to Scottish Hydro Electric Power Distribution and Scottish
Hydro Electric Transmission. The parent company to Scottish Power
Distribution and Scottish Power Transmission is Scottish Power,
itself now owned by Iberdrola.
7. The DNOs have a responsibility to ensure that
their customers have a reliable supply of electricity and must
restore customers' electricity supply promptly in the event of
an interruption. Where these responsibilities are not met, Guaranteed
Standards operate to ensure payment to affected customers. There
is no statutory requirement for the DNOs to have their Guaranteed
Standards data independently audited. However, Ofgem has made
an informal request to the DNOs to have their data audited externally,
as part of the Best Practice guidelines.
8. Nearly all overhead lines in the UK are constructed
using wooden poles or steel towers. The overhead line structures
are fitted with insulators that support wire conductors to carry
an electrical current. However, they are more likely to be disrupted
by severe weather events. Underground cables are not susceptible
to storm damage apart from water and are far less likely to cause
death or injury due to accidental contact.[3]
When considering whether to 'underground' an overhead line, a
balance needs to be drawn between cost, impact and benefits.
9. In evidence, Alistair Redman (Postmaster from
Portnahaven on Islay) stated that:
Over the last 18 months, after many years of good
electricity supply, the area [Islay, in the constituency of Argyll
and Bute] was subject to many power cuts and power surges. These
ranged from many small multiple cuts in a day to very lengthy
ones lasting over 24 hours. Such events put stress on electrical
equipment and either damages them or shortens their life. We have
also had to invest in expensive surge protectors for each piece
of equipment. A significant number of these cuts were not weather
related. Scottish and Southern Energy operatives tell us that
the infrastructure on this part of Islay is old, outdated and
very corroded. This has caused the unacceptable number of faults
on the line as it has started to fail.[4]
10. According to SSE, wind gusts of up to about 90
mph may cause one or two faults on a circuit and when a repair
is carried out, supplies are generally restored.[5]
When wind gusts exceed 90mph, there are generally multiple damages
per circuit. Any particular repair may well not restore supplies
as there will be multiple repairs required per circuit. SSE submitted
that the policy for refurbishment of overhead lines had been in
place since 1995. In that time, the performance of the lines had
improved consistently. Excluding exceptional events, they had
seen a continued reduction in the number of customer interruptions
and duration of events.[6]
11. In this report, we examine the events that occurred
during December 2011 and January 2012, and consider the implications
for the consumer, company and overall robustness of the electricity
network in Scotland.
1 'A Robust Grid for 21st Century Scotland,
terms of reference', SAC Press release 12 January 2012 Back
2
Owned by SSE who also run a DNO in England, SSE Southern Back
3
ICF Consulting Ltd, Overview of the Potential for Undergrounding
the Electricity Networks in Europe, 28 February 2003 Back
4
Ev 40 Back
5
Ev 44 Back
6
Ev 61 Back
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