Transmission & Distribution
Early warning system1 November 2006
In response to increasing concerns about blackout risk, AREVA T&D has developed e-terravision, designed to be a reliable, user-friendly system that can anticipate powerline problems and enable operators to react in real time.
Launched at the Cigré 2006 technical exhibition in Paris, ‘e-terravision’ is Areva’s response to the perceived need to increase the system operators’ ability to reduce occurrences of power blackouts and brownouts, at a time when huge demands for electricity are projected for public, commercial and private sectors and in which electricity’s critical role will make more intolerable still the consequences of blackouts.
The company has designed and developed the software system in partnership with a group of its prominent customers, including American Electric Power, Northeast Utilities and Ameren.
The system, an addition to the ‘e-terraplatform’ of system tools and controls, is designed to help operators monitor, predict, anticipate and prevent potential problems that can lead to major power outages, enabling them to fully visualise their networks in real time. It also provides tools to assist them in taking corrective action through pro-active decision-making. The key to this is the ability to obtain a more comprehensive view of the network, then having the means to analyse that view and act to forestall problems.
The project’s utility partners working together defined what they felt they needed to meet control centre operational challenges. Significantly the operative question was "what problems does an operator have to solve?" rather than "what data needs to be displayed?" Areva helped the process by conducting workshops and conference calls on a regular basis, and iteratively presented prototypes that addressed various goals. Some of the key tasks were to identify voltage and related VAR reserves, to prepare for unplanned contingencies and to validate remedial scenarios, among others.
e-terravision sits on top of the energy management system and is fed data by it. It is designed to be integrated with the existing EMS at the control centre. All displays are automatically generated and real-time data is automatically transferred from the EMS. But it doesn’t make decisions. Rather, it is a decision support system, meaning it does not automate the response but provides recommendations as well as simulations of ‘what-if’ scenarios to validate an operator decision. It is intended to reduce human error and improve the speed of response in an emergency.
Areva says that the business case for installating the system lies in the value of better decision making for safe and reliable operation, and a faster learning curve for new operators, or existing operators facing new power flow patterns within the transmission grid. A typical project installation should take from 3 to 9 months.
Operators and dispatchers work with and rely on new technologies. The power industry is being challenged by the realities of an ageing T&D infrastructure combined with the operational complexity of very large T&D networks. There is a need for new tools and easier ways to assist operators perform these critical tasks and enable them to make quick, accurate decisions.
The system should significantly improve transmission system operations and control by helping to eliminate the kind of instant-response decisions that are routinely being made in control centres. Systems are growing more complex and data flow is increasing hand over fist. New operational methods are needed to deal with the new situation. e-terravision is intended to supplement control room capabilities with support capability using visualisation, "smart applications" and simulation, the central object being to improve the view of the grid – to enable power dispatchers to visualise their networks well enough and with enough advance notice to take the necessary real-time corrective actions.
The system’s ability to give early warnings is based on gathering more information from more sensors and by making better use of the information it receives. The software was developed in conjunction with Microsoft and its high performance level is achieved by bringing more computing power to bear and employing better algorithms to interpret the information gathered. Central to this are new programming techniques capable of handling the vast quantities of data available, and which can quickly separate out the information from the noise.
The watchword is wide vision. Operators are used to having an incomplete view of the system they control. The objective with e-terravision was to widen that view (in particular where systems interconnect and produce fault conditions that travel into neighbouring networks) thereby giving early warning of developing situations and their progress towards fault conditions. This improves the odds of heading off a potential trip or at least limiting its knock-on effect.
Analysis of violations
One of the main tasks of security or reliability co-ordinators is to maintain compliance with N-1 operating principles for contingencies. e-terravision is delivered with a tool to analyse base case and post contingency violations based on industry best practices. Existing network applications provide the analytical results which are efficiently and intuitively presented to operators.
The system also monitors the health of applications and visually indicates whether the computed results are current and valid.
The main issues that e-terravision helps resolve through graphical aids are:
• voltage limit violations and remedial VAR compensation;
• thermal limit violation and remedial switching actions;
• preventative contingency analysis;
• overall assessment of network reliability with constant monitoring of past, present and future situations.
Direct access to vital data
The system architecture is designed to fetch real-time data directly from the EMS database and present it as key vital signs in a concise form. A single panel organised with logical tabs brings relevant data to the unique main window. What is considered ‘vital’ is defined by the user (Figure 2). For example, a substation can be associated with MW, MVAR interface flow towards connected substations as well as generation and load connected. A transmission line can be associated with vital signs such as MW and MVAR flows and respective limits.
Displaying voltage contours
Voltage contours are generated for each kV level from the voltages at the buses. The voltage magnitude at each bus is determined by the state estimator. Contours are overlaid on the overview display. Animations of MW and MVAR flows on transmission lines can be displayed on both system overview and regional schematic displays.
The software allows users to build their own dashboard displays to assist in the assessment of a situation, to create a display context that best fits the monitoring and resolution of a specific problem. Displays can be built ‘on the fly’ (Figure 3) by combining subsets of different displays onto a dashboard area. For example, the user may want to monitor a particular problem in the network and will need information from a number of different displays to do this. He is able to ‘rubber band’ the areas of existing displays that are of interest and drag the selected portion onto the dashboard. These dropped displays continue to be updated in real-time. Dashboards once created can be saved and recalled later just as any other display in the system and be refreshed with live data.
A unique feature of the system is the ability to access fly-outs and pods (Figure 4) containing context sensitive information. The aim is to present additional information to help with the assessment of a given operating condition. For example, one can call an online diagram of a substation into a flyout display originating from the substation node on the overview diagram. Another example is selecting an area and displaying voltage values for all nodes in this area within a pod.
Overview and drill down analysis
The overview feature allows the user to send overall views of the power grid to display boards. He can also display drill-down views in some detail, to operators and analysts at their workstations, updated in real time so that all workstations see the same view. Extensive use of rubber banding and drag and drop allows efficient access to associated data for all workstations and wallboards in the loop.
Overviews are presented either geographically or schematically and each view carries with it its own set of data and associated graphics, to be pulled up as required.
Figure 1. A typical wallboard display Figure 2. Access to user definable data Figure 3. Display created 'on the fly' Figure 4. Substation diagram shown in a 'flyout', grid voltages shown in a 'pod'