Under the Visualization of Real-time System Dynamics using Enhanced Monitoring (VISOR) project led by ScottishPower Energy Networks, a flexible wide area monitoring solution is to be deployed across Britain to strengthen the stability in the electricity network.
The solution will be supplied by Alstom, based on its e-terraphasorpoint wide area monitoring technology, and will extend and integrate the existing GB wide area monitoring systems. This will improve visibility of system voltage and stability limits across the entire national electricity network.
Other participants in the project include Scottish Hydro Electric Transmission, National Grid and the University of Manchester.
Phasor measurement units (PMUs)
In Britain’s transmission network, the primary and most costly network constraint is the Cheviot boundary between Scotland and England, although now other boundaries are becoming increasingly constrained as well. This boundary is now constrained about 50% of the time, with an operational cost currently running between £80 million and £130 million per year.
This large operational cost is being progressively addressed through bootstrap high-voltage direct current (HVDC) and series compensation. However, these reinforcements also introduce additional complexity that needs to be managed. For example, the introduction of series compensation introduces the risk of sub-synchronous oscillation (SSO), which can result in plant damage and network outage if not addressed.
The VISOR project is intended as a complementary wider solution. The aim is to improve transmission operation through enhanced risk mitigation and boundary transfer management, using real-time synchrophasor and waveform data with advanced analysis and presentation.
The project will deploy new phasor measurement units (PMUs) and innovative applications for using the phasor data to understand and analyze real-time dynamics of the transmission network. These will supplement the existing PMUs, and eventually leading to a GB-wide PMU-based wide area monitoring system. Alongside this a new central server will be implemented to receive and store data from the three transmission operators.
The VISOR trial aims to demonstrate a potentially avoided investment benefit of £45 million for every 100MW capacity realized. It is also aimed to provide the system operator with the ability and confidence to utilize the full capacity of the network where increasing volumes of wind generation lead to more volatile system flows, resulting in greater operating margins to maintain and manage network security. A conservative estimate of operational savings is £4 million per annum.
The WAM system will also provide transmission network owners with a risk-mitigating measure in a period of uncertainty to help safeguard the network against low probability high-impact events that may result in partial or widespread system failure. An estimate of the financial impact of a GB wide blackout is in the order of £30 billion.
“We believe that the collaboration between ScottishPower Energy Networks, Alstom-Psymetrix and the VISOR partners will deliver valuable insights and tools for improving the efficiency and security of transmission in the Great Britain system, and contribute to international experience and knowledge,” commented David Campbell, manager of Future Networks at ScottishPower.
SSO monitoring of Scotland’s grid
This contract follows another recent award to Alstom from ScottishPower to strengthen the Scottish grid with the provision of SSO monitoring and detection capabilities. The contract includes a grid monitoring and detection system for real-time early warning of SSOs and off-line analysis of system behaviour related to the physical effects of series compensation and HVDC systems on nearby generation units.
ScottishPower is installing series compensation at four locations on key transmission lines to reduce impedance and increase power transfer capability, releasing capacity for more generation where renewable energy resources are plentiful.
The solution also will be based on the e-terraphasorpoint technology. In addition, Reason RPV311 multifunction PMUs will be installed at a number of ScottishPower substations, including series capacitor and power station sites.
Since the power plants most exposed to SSO are large nuclear and thermal units, the potential benefit is significant.