Wide Area Protection and Control Systems used to improve system reliability and security.

CIGRE Technical Brochure provides timely overview of Wide Area Protection and Control Systems used to improve system reliability and security.

As power grids world-wide become more complex (renewable energy integration, energy efficiency, electrical vehicles, storage, etc.) and are being operated closer to their operating limits, the application of Wide Area Protection & Control Systems (WAPCS) has become necessary to better manage the grid, prevent blackouts and ensure security of power supply.  Technical Brochure 664 has recently been produced by CIGRE Working Group B5.14 as a useful reference document on the current status of the technology, its benefits and challenges and a way forward to speed up deployment and minimise costs.  The Australian member on this working group was Chuanli Zhang. 

WG B5.14 – Wide Area Protection & Control Technologies

The trend to use secondary systems to improve reliability is clearly seen through the deployment of advanced Wide Area Protection & Control Systems (WAPCS) applications in response to the increase in world-wide disturbances and grid congestion. In addition to the world-wide proliferation of System Integrity Protection Systems (SIPS), technologies such as synchronized measurements have advanced sufficiently to support commercial WAPCS deployment. These technological advances and the changes in the nature of power grids means that the implementation of various WAPCS applications is both possible and warranted, and as such represents a prudent investment.  

As power system and telecommunication technologies have advanced, the time frame of measured and communicated synchronized information has been steadily reduced from minutes, to seconds, milliseconds, and now microseconds. At present, Phasor Measurement Units (PMUs) provide the most comprehensive time-synchronized technology available to power engineers and system operators for WAPCS applications. IEEE has published an associated standard to define the synchrophasor measurement (IEEE Std C37.118.1-2011 Synchrophasor Measurement for Power Systems) and to specify how to exchange the synchronized phasor measurement data amongst power system equipment (IEEE Std C37.118.2-2011 Synchrophasor Data Transfer for Power Systems). Commercial PMU products have been available in the market for more than 10 years.

The benefits of WAPCS applications can be grouped into four categories: 

• Data analysis and visualization

Significant benefits have already been achieved using the systems that are already deployed.

• Outage reduction and blackout prevention to improve system reliability, including real-time control and protection

The huge benefit of preventing a blackout is difficult to quantify due to the myriad of factors involved, such as damage to the economy, loss of confidence in the power system and the potential for serious accidents or even deaths.

• System operation and planning, including system modelling and restoration

This enables a paradigm shift toward actively tracking grid dynamics and system measurements vs. estimation.

• Market operations and congestion management

There will be significant potential financial benefits by enabling the utilisation of accurate and optimal margins for power transfer (instead of the worst case scenario used under current practices). 

Implementing a large-scale WAPCS presents some unique challenges due to its high criticality associated with reliability and security. Some of these challenges are technical in nature, as WAPCS needs to transmit, process and store amounts of data in real-time. As such the system architecture needs to address the following issues:- 

• Scalability – The system architecture needs to accommodate the increased number of PMUs for the long term
• Flexibility – The system architecture must be flexible enough to meet the diverse requirements of various entities for installation, operation and maintenance.
• Redundancy – The system should provide enough redundancy to avoid common failure of components including communication paths.
• Communication bandwidth and latency – There will be a high requirement for the communication bandwidth and latency for transferring real time data. 

In Australia and New Zealand there are quite a number of Wide Area Monitoring schemes. These schemes use PMUs to monitor various aspects of power system stability and power system security tasks. 

There are a few Wide Area Protection and Control schemes in service that use PMU’s for both monitoring and control. The most common application is measuring the voltage angle difference between two remote sites for synch check purposes or system stability applications.

Members can access the Technical Brochure for free at  https://e-cigre.org/ 

Non members can access the abstract here  and the full brochure can be purchased for € 290 at  https://e-cigre.org/