Protection of electrical energy distribution infrastructures – The example of EDP
The protection of the electrical energy distribution infrastructure is a key task for any operator of such an infrastructure. Securing the main infrastructure components through the deployment of secure wireless sensor and actuator networks (WSAN) that provide remote monitoring and alarm capabilities is an attractive option for achieving this objective.
The European research project WSAN4CIP is searching for innovative solutions for enhancing the reliability and security of critical infrastructures by providing self-healing and dependability modules for WSANs. One of the WSAN4CIP demonstrators is built in the electrical energy distribution network of EDP, the main Portuguese electricity distribution company.
Electricity distribution network
The electrical energy distribution network mainly consists of a set of substations, medium voltage (MV) / low voltage (LV) power transformers, MV power lines connecting substations to MV/LV power transformers and LV power lines from the power transformers to customers. Some industrial customers may also get direct MV power lines. This is illustrated in figure 1. Associated to this network we also consider the Supervisory Control and Data Acquisition (SCADA) system, which is centralized for the whole distribution infrastructure.
Safety and security improvements
For safety reasons, remote surveillance of the electrical energy distribution network is already established to some extent based on wired sensors. The use of WSAN can lead, however, to a more efficient protection of the infrastructure. The higher deployment flexibility allows wireless sensors to capture more status parameters than the existing fixed sensors and can contribute to avoid critical points of failure. Specific actuators can also be included in the infrastructure as part of the WSAN.
For safety improvement, with a direct result in regard to better infrastructure reliability, solutions have been identified for the remote active monitoring of: i) substation circuit breaker trip coil status; ii) substation power transformer oil temperature; iii) substation neutral reactance and neutral resistor coil temperatures; iv) MV power line activity in all three phases to detect location of power line failures; v) remote MV/LV power transformer hotspot detection to detect a likely near future malfunction. All the monitored parameters will be visualized at the SCADA system through a special-purpose interface and a graphical user interface.
Security improvements are focussed on: i) substation perimeter unauthorized intrusion detection by using a combination of cameras, motion detectors and WSAN; ii) intrusion detection in remote MV/LV power transformer installations via deployment of video cameras integrated with the WSAN for image transmission, which get activated by a motion detection sensor.
The WSAN uses Wi-Fi as data link layer communication protocol and includes security features in the network and transport protocols.
Interaction with SCADA
The electricity network devices are nowadays monitored and controlled through the SCADA system. The WSAN will be integrated with this existing system to provide a unified electricity distribution infrastructure interface to the human operators. A high level view is shown in figure 2.
From the supervisor point of view, the SCADA/WSAN gateway behaves as a database that responds to queries about the status of WSAN devices. The application interface for these queries is based on Web Services. From the point of view
of the WSAN, the gateway takes the role of the sink node, i.e. it is the destination of all sensed sensor data and the source of queries and configuration/command requests. It also includes a database of sensing and management data.
The electrical energy distribution network constitutes a critical infrastructure in industrially developed societies, which requires protection regarding safety and security threats. The fact that this infrastructure is geographically spread across large areas puts challenges to real-time prevention, detection and precise localization of anomalies and security breaches, which can be significantly improved through the appropriate deployment of secure wireless sensor and actuator networks.
Further information is available at www.wsan4cip.eu/demonstrators/demonstrator-1-power-distribution.html