National Terms Of Connection – Section 3 Power Factor Clause Defect

A defect has become apparent in the drafting of the Power Factor clauses within the National Terms of Connection. This specifically applies to clause 13 of Section 3 of the National Terms of Connection, although some consideration in respect of Section 2 of the National Terms of Connection may also be required in light of the growth of power electronics and micro-generation that may cause a premises to export Reactive Energy.

The Existing wording of Clause 13 of Section 3 of the National Terms of Connection and an indicative alteration are set out on the following pages for initial discussion. The wording has been crafted to avoid the use of the words Leading or Lagging and in their place refer to the Import of Reactive Energy and the Export of Reactive Energy to better align with the BSC metering requirements and metering quantity identifiers (RI and RE) as utilised in metering data.
The National Terms of Connection, Section 3 Clause 13 currently requires a customer to not operate a leading power factor and to operate a lagging power factor and as close as unity power factor as possible but not worse than 0.95 lagging power factor. These terms derive from an era focussed on almost exclusively serving demand customers and therefore the phrasing of “no leading power factor”, pointing to a capacitive mode of consuming operation, as opposed to “shall not export
Reactive Energy”, was appropriate at the time. A customer exporting Reactive Energy at the same time as exporting Active Energy is conventionally treated as a lagging power factor.

Furthermore the written prohibition on leading power factors (of consumption) was intended to refer to capacitive load because of the damaging and potential catastrophic failures arising in the opening operation of switchgear and circuit breakers that had large quantities of capacitance connected downstream. The same problems occur with energy production with a capacitive component.

The power quadrant diagram approach to describing “power factor”, as noted in BSC Metering Codes of Practice is that an export of Active Energy that is simultaneously exporting Reactive Energy is described as “Lagging”. It is the particular use of the term “Lagging Power Factor” when describing the use of a Connection Point in a generating mode that presents a problem in terms of the application of the National Terms of Connection’s current wording which refers only to “Leading Power Factor”.

On the one hand the DNO will strive to technically minimise the existence of capacitance upon its system and separately will strive to prohibit export of Reactive Energy by customers generating power at a “Lagging” Power Factor or by customers consuming power at a “Leading” Power Factor to avoid excessive voltage rise.
The DNO needs to be able to correctly manage the usage of power, including Reactive Energy, by its customers and therefore for its own purposes alone will require a correction at the very least to Clause 13 of Section 3 of the National Terms of Connection.

More broadly the proposal will also help in the context of requirements DNOs have to manage and coordinate voltage levels with the National Electricity Transmission System Operator and to prevent undesirable effects upon the transmission system. It is a distribution licence requirement to comply
with both the CUSC and the Grid Code. It is important to emphasize that in part a change in the nature of power flows on a DNO system that causes a problem on the transmission system is by causation a DNO problem with a responsibility upon the DNO to organise its affairs to compliantly co-ordinate with the electricity transmission system operator/owners. As highlighted in the System Operability Framework (SOF), issued by National Grid in September 2014, there is currently a
rapidly emerging issue around falling Reactive Energy Import from Distribution Systems leading to high voltage levels on the National Electricity Transmission System operated by National Grid under low load conditions. In some cases the Reactive Energy Export from the distribution systems to the transmission system has occurred, particularly at times of low night time load in major conurbations. The following two diagrams, extracted from National Grid’s SOF, show the decline in Reactive Energy Import into distribution systems and the number of Grid Supply Points now having Reactive Energy Export from distribution systems.A defect has become apparent in the drafting of the Power Factor clauses within the National Terms of Connection. This specifically applies to clause 13 of Section 3 of the National Terms of Connection, although some consideration in respect of Section 2 of the National Terms of Connection may also be required.

The proposer’s Company of DIF 049 has decided to close this issue on the reactive power usage of the customer. The solution of this issue has been sufficiently considered at the DCUSA SIG to allow the proposers Company or an alternative party to raise the CP.