System voltages – time for change?

Do the rise of renewables and distributed generation mean that deeply ingrained statutory voltage limits are no longer fit for purpose? Can they be changed? Philip Bale is exploring the possibility and is keen for insight.

Western Power Distribution, WPD, like all UK DNOs, operate and design 11kV and 33kV networks within the ±6% statutory voltage limits set out in the Electricity Supply Quality and Continuity Regulations (ESQCR).  

These statutory voltage limits for 33kV and 11kV electricity networks were specified for passive operation and have remained unchanged since the introduction of the Electricity Supply Regulations, back in 1937.

But now WPD are working with Parsons Brinkerhoff, to investigate both steady state and step change voltage limits for 11kV and 33kV network as part of the Low Carbon Network Fund project Network Equilibrium.

This theoretical investigation into whether steady state statutory voltage limits (±6%) and step change limits for the 11kV and 33kV networks could and should be amended, to potentially unlock further capacity for the connection of distributed generation, electric vehicles and heat pumps. 

We will be assessing whether the rationale for the present-day standards are still valid and consider both the technical and commercial barriers that could restrict an amendment to specified voltage limits.

Our initial investigative work has looked back to the start of the 20^th Century including the 1904 equipment standards to comprehensively understand the foundations of the existing standards. Work is continuing to further determine what the voltages limitations are based on, how standards are interpreted and if working outside of the present-day limits would affect network and customers’ equipment.

We expect to be able to make a recommendation for future amendments to 11kV and 33kV voltage limits, specifically if the ESQCR statutory voltage limits and the Engineering Recommendation P28 step change limits could be amended.

We are keen to hear from Utility weekly readers who may have information to contribute towards this exciting review, especially historic knowledge of the reasoning behind the standards. So, if you have experience and or a special interest in this area please get in touch: Philip Bale, Innovation and Low Carbon Networks Engineer pbale@westernpower.co.uk