Reactive Power Redeclarations

Reactive Power describes the background energy movement in an Alternating Current (AC) system arising from the production of electric and magnetic fields. Devices which store energy through a magnetic field produced by a flow of current are said to absorb Reactive Power. Those which store energy through electric fields are said to generate reactive power.

The flows of reactive pwer on the system will affect voltage levels. NG must manage voltage levels on a local level to meet the varying needs of the system. Without the appropriate injections of reactive power at correct locations, the voltage profile of the transmission system will exceed statutory planning and operational limits.

EDFE has to comply with grid code which requires power generators to provide reactive power capability to National Grid. In the event that a station's reactive power availability canges, the grid code obliges power generators to submit redecletations. Failure to do this could breach grid code and also reduce the income recieved from providing this service.

Reactive Power is measured in Mega Volt-Amps Reactive (MVAr). A positive value is said to be "lagging" and a negative value "leading". Leading MVAr can be converted to Lagging Mvar by multiplying by -1. Eg. 70Mvar Leading is equal to -70MVar Lagging.

National Grid utilises the below services in order to manager voltage levels:

• Obligatory Reactive Power Service (ORPS) - Mandatory. At any given output, power generators may be requested to produce or absorb reactive power to help manage the sytem voltages close to its point of connection.
• Enhanced Recactive Power Services (ERPS) - Any provision on voltage support that isnt covered by ORPS. The ERPS is procured via a market tender.