May 2013
Electricity Transmission
Reactive Power Exchange Application Capability Transfer (REACT)
May 2013
May 2015
National Grid Electricity System Operator, Western Power Distribution, National Grid Electricity Transmission, Scottish and Southern Electricity Networks, SP Energy Networks, Northern Powergrid, Electricity North West Limited and UK Power Networks
Ben Marshall
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Network Innovation Allowance
Low Carbon Generation
The proposed project will form the first building block required to answer the following two questions.

  • How can voltages at 400kV & 275 kV be kept within statutory limits?

  • What factors and trends are there that could be making transmission voltage control increasingly more problematic and/or costly under low load conditions and how do these influence reactive power?

In addition, it will crucially allow DNOs to understand the technical aspects to be tackled in order to comply with the European Demand Connection Code that will in a few years limit GSP exchanges to 0MVAr for load up to 25% of the GSP capacity.

The key objectives are to determine:

  • The key factors behind the significant decline in reactive power demand and the corresponding increase in the DNO system reactive power gain as observed at the Transmission/DNO interface (i.e., Grid Supply Point). During periods of minimum loading the reactive power demand has reduced from circa 7500 MVAr in 2005 to 2100 MVAr in 2013.
  • The key factors behind the significant decline of the reactive to active power ratio (Q/P ratio) during periods of minimum demand. During the last 5 years, there has been a fall of 50% of the reactive power demand followed by a corresponding non-proportional fall of 15% of the active power demand.
  • The relationship of all factors affecting the decline in reactive power demand at these interfaces during the same periods.
  • The link to the upcoming requirements from the European Demand Connection Code changes expected in Demand Connection Code.

The project will develop key learning relating to the interaction between active and reactive power demand while establishing an understanding of why reactive power is reducing across the country.