Introduction: This programme of work consists of the following projects:

• Review of Voltage Dependency of Load

• Impact of series capacitors on transmission system performance

• Review of low voltage demand disconnection schemes

• Assessment of SVCs for use in Constant MVAr mode (CMM).

This programme addresses issues relating to system stability by ensuring assets such as SVCs are utilised effectively and that policy regarding demand disconnection and the use of series capacitors is up to date.

Objectives: This programme of work investigates National Grid’s policy and asset capability in order to better understand and ensure optimum network design and operation. The programme is made up of several projects. A review of the voltage dependency of load will review current assumptions regarding composite load models at GSP and BSP locations based on an updated breakdown of load classes. It will also investigate the impact of distributed generation or other voltage control schemes/devices connected at voltages below that of the GSP and investigate the potential impact of new load types such as energy efficient lighting and the further use of switched mode power supplies. National Grid is involved in a project with manufacturers to explore the use of series capacitors to maximise the transfer capability of the available transmission system. An assessment of the effectiveness of low voltage demand disconnection schemes to minimise the spread of voltage collapse under severe system disturbance conditions is also being carried out. The final project in the programme looks at the use of SVCs in an alternative control mode that potentially reduces the noise generated and the amount of control room action needed.