Assuring Continuous Operation at CONVEX Control Center
By Mike Meagher, SL Corp.
The key to understanding the operations of the Connecticut Valley Electric Exchange (CONVEX) is the word “exchange.” An operations center of Northeast Utilities, United Illuminating and several smaller utilities, CONVEX operates a control center that links the systems of several operating companies into a single efficient grid, serving approximately more than two million customers in Connecticut and western Massachusetts. One control room governs the movement of power at 69,000 V and above and the generation of nearly 10,100 MW of electricity, including four nuclear power plants. CONVEX can never close. Operators at the facility continually monitor the status of every device in this vast power grid–from individual circuit breakers to telemetry data from more than 200 substations–more than 120,000 supervisory control and data acquision (SCADA) and state estimated data points in all. It is the CONVEX mission to use this complex system to assure a continuous flow of high quality, efficient power for customers and the safety of the maintenance workers in the field.
An energy management system (EMS) based on VAX computers monitors and controls the substations, transmission lines and power plants under the charge of CONVEX. However, the EMS had two major drawbacks–lack of high quality graphics and real-time mapboard capability. First, status information was reported to operators in the form of overwhelming displays of character-based graphics and tabular data. The operator had to wade through many displays in order to conduct any analysis and initiate action.
Operators also reviewed a 50-foot static pegboard, which covered an entire wall in the control room, carrying summary status information. The wall was also an important safety device, holding the safety tags which showed where parts of the system had been temporarily shut down by maintenance workers. The static mapboard was cumbersome, it was difficult to update in a timely manner, and it had the potential for error.
Recently, the static pegboard was replaced by a 10-foot-high by 52-foot-wide video wall employing SL Corp.`s graphic modeling system software to display a dynamic, interactive, near real-time view of the system.
Hardware and Software Protects Workers, Enhances Customer Service
The video wall presents a dynamic schematic of the CONVEX transmission system. The objects in the schematic are linked to variables in the real-time EMS database so the graphical objects change with the values in the database in near real-time. This allows an operator to determine the status of a device or any entire area at a glance. For example, graphic modeling system objects that represent lines and transformers include limited information. In that way, if limits are exceeded, the object changes color to inform operators of the problem and its severity (such as turning red as a warning). Objects representing circuit breakers have the ability to open or close to match the state of the field device.
Operators also open windows on the video display with detailed data on a single substation, or a window with several stations in a subsystem.
The display also employs path function of the graphic modeling system software to animate other components in the system. When a line is overloaded, an icon begins traveling from one end of the line to the other until an operator resolves the situation. Safety is always a key concern and the graphic modeling system software objects include special tagging palettes used to mark devices when people are working in the field. Information on the video display is easy to understand and reliable, and it is presented as soon as an event occurs.
The display is an inventive combination of modified X technology, a UNIX workstation, a new video projection system and the graphic modeling system software. The workstation is linked to the EMS database via a fiber-optic network. The video display system utilizes four high-resolution and luminosity projectors, driven by video cards in the workstation`s Sbus. An extended X-Server combines the output of the four video cards into a single 10-by-52 foot X-Window. In this way, the graphic modeling system software, which is also X-based, provides a dynamic display of more than 100,000 graphical objects, updated every four seconds. The operators interact with the EMS and the video image via their VAXstations in front of the video wall.
It is the high performance nature of the graphic modeling system that allows for such a large amount of graphical data to be displayed in a single X-Window. In addition, multiple instances of the same application can be run off of the same workstation. This allows multiple users access to the same workstation with excellent performance benchmarks.
Operators can now easily share information and assist each other with troubleshooting. An operator on one end of the screen (dynamic mapboard) can open a detail window, ask a colleague at the other end of the room to review the data, and then use a mouse to drag the window to the opposite end of the display. The mapboard application can also be displayed across the network onto an inexpensive PC-based X-Server.
On each operator`s VAXstation there is a small portal window. When the operator moves the cursor into the portal window, the mouse and keyboard input are directed to the workstation driving the projection screen. In addition to the graphic modeling system-based application, the VAX EMS displays are also integrated with the video display. Now the comparison of numeric from the EMS to graphical state data is straightforward, requiring only mouse movements, resulting in better analysis by operators and smoother operations.
Graphical Drawing Editor Used to Build Realistic, Animated Display
Each of the 100,000 objects on the display was created using the graphic modeling system software`s graphical modeling editor application. The graphical drawing editor was used to create each object, and also to specify its dynamic properties and link it to one of the 120,000 variables in the EMS database. All of the substation models were initially generated in software, automatically providing all needed attributes and database binding information.
The editor proved to be an easy-to-use, intuitive tool. A team consisting of an engineer, a CAD designer and an assistant built the entire display in less than four months. The short development cycle was possible due to the object-oriented approach of the graphical modeling system software. Once an object is created, it can be instanced as many times as needed, and each new instance retains all of the properties of the original. Also, complex portions of the display, such as substations, were generated by grouping collections of devices. Each device retains its individual dynamic properties, and properties can also be assigned to the group object. Finally, objects can be tested using simulated data without leaving the drawing tool, further cutting development time without sacrificing quality.
As soon as the video display was installed, CONVEX began plans to extend the application and capitalize on the flexibility of the graphic modeling system software. The first is the use of Motif widgets that can be seamlessly integrated with graphic modeling system generated displays. Beyond that, data visualization tools (graphs, charts and other trending information) are now being developed to provide the operator with a better way to analyze power flows over time. In addition, the graphic modeling system application will be fitted with artificial intelligence software that will suggest a course of action to the operator. The graphic-modeling-system-generated objects will display these suggestions in an animated format.
Mike Meagher is a software engineer for SL Corp., working in various engineering, training and support capacities. Prior experience includes time at NASA`s Ames Research Center, concentrating on graphics applications for computational fluid dynamics.
Dispatch operators view a dynamic schematic of the CONVEX transmission system.