Optimum phasing for high voltage power lines

Recommendations for the introduction of optimum phasing for power lines operating at voltages at 132KV or above including the introduction of codes of practice.

Codes of practice

In 2004 the Stakeholders Advisory Group on extremely low frequency electric and magnetic fields (SAGE) was set up to examine what possible precautionary measures were needed to limit exposure to the public from electromagnetic fields (EMF's) produced by electric power lines. Its remit was to provide advice to the UK Government.

SAGE recommended the introduction of optimum phasing for power lines operating at voltages at 132KV or above

In their response, the UK Government supported the SAGE recommendation to introduce the optimum phasing of all new double-circuit high voltage overhead power lines of 132kV and above and to convert existing power lines where practicable in those circumstances where this would significantly reduce public exposure to EMF's and would be cost effective to do so.

Two UK wide voluntary codes of practice were developed and agreed with the industry. These codes have been endorsed by the Northern Ireland Executive.

First voluntary code

The first voluntary code is intended to provide information to the general public and other interested parties about how the optimal phasing of high voltage double circuit overhead lines can help reduce public exposure to EMFs. The Code also sets out clearly what the electricity industry is agreeing to undertake and also how the UK Government will monitor compliance with the Code.

Second voluntary code

A second voluntary code of practice has also been developed “Power Lines: Demonstrating compliance with EMF public exposure guidelines”. This Code of Practice implements current UK Government policy in relation to public exposure to EMFs and is intended to introduce clarity to the important process by which industry will demonstrate compliance. It sets out the measures the electricity industry will utilise to calculate and demonstrate compliance with assessment field levels in accordance with International exposure limits to protect public health.

The Energy Networks Association will also maintain a publicly available list on its website of types of equipment where the design is such that it is not capable of exceeding the International exposure guidelines with evidence as to why this is the case. It will also detail equipment that normally complies with public exposure limits but also where this will need to be demonstrated on a case-by-case basis when required, for example when applying for consent or a wayleave for a line or cable.

Companion code

A companion Code has been produced to explain what measures can be used to reduce the risk to the public of indirect effects of electricity fields, including microshocks.  Microshocks are similar to the static discharges commonly experienced in dry atmospheric conditions after frictional contact with a nylon carpet or car seat.  The Code is:

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