Smart Substations: Still a Long Way to Go
- April 15, 2009
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The substation is where power is stepped down from high voltages used in transmission to the lower voltages used in homes and businesses. They are also home to the switches, capacitors, transformers and other devices that utilities use to manipulate the grid to keep load flows balanced and routed to the correct locations. Substations are central to everything the electricity grid does, thus central to any smart grid of the future.
The inside of the substation is an interesting and dangerous place that really hasn't changed much in the last 100 years. Typically, large transformers are located outside in large metal boxes connected to various power lines. Many substations also include a building where control devices are located. These devices usually are mounted on a large, typically wooden board, insulated from one another. These control devices include capacitors and switches for rerouting power. For generations, these switches and capacitor taps had to be adjusted manually. Someone had to drive to the substation and make the necessary changes.
With modern distribution automation (DA), some utilities can now manipulate some of these devices remotely. Computer systems can now read inputs from substations and provide displays in utility control stations. Even with DA, it's still essentially a manual system. Getting from there to the smart grid is a major, very expensive step for utilities -- one that doesn't get a lot of attention amid the widespread hype about the topic. Typically, advanced metering infrastructure (AMI) and home automation are in the news much more than DA.
To get to a smart grid, utilities will need to overlay a communications system and a computer network, probably IP-based, over that network of substations. In order to get a truly smart grid, those computer and communications systems will have to include artificial intelligence. The computer system will have to be able to read sensors placed at different points on the grid that report power quality and condition. The system will need the intelligence to know which switches to throw and what capacitor taps to change to correct problems and ensure stability. To date, there are very few systems on the U.S. grid, all of which are in the pilot stage.
WE Energies has been working on a system for about five or six years that can almost do it all for one small area of its service territory. The area is called a "pod" and includes a small number of homes and businesses. This project involves a consortium of utilities working with Electric Power Research Institute (EPRI) and numerous vendors to make it work. It also includes rerouting some transmission and distribution lines in the pod area.
Pacific Gas and Electric (PG&E) started implementation of automated sectionalizing restoration last July and several of the configurations are now operational, according to Randall L. Smith, information systems and technical support for supervisory data acquisition and control (SCADA). How does sectionalized restoration work? When one part of the grid goes down, intelligent systems automatically reroute power and restore as many homes and businesses as possible without human intervention. In the new automatic systems, computer systems with built-in rules and semi-artificial intelligence determine what needs to be done and throws the switches. This allows the utility to dispatch crews to just the points where human intervention is needed. PG&E uses an automatic sectionalizing system from DC Systems.
Doug Campbell, president of DC Systems, said the RTScada system is designed to operate automatically, and is not designed to produce switching orders. It is an automated system that performs the same actions an operator would do given the circumstances. The system takes into account pre-fault load, line capacity, protections settings on feeders, and so on. Since it has access to the substation -- where it typically is located -- it also looks at bank loading so it doesn't overload the bank.
There are other examples as well. Tennessee Valley Authority (TVA) and Southwest Transmission Cooperative (SWT) have installed a collection of systems from Subnet Solutions. Designed to provide access to the 90 percent of substation data typically not available from SCADA/energy management systems (EMS), SubstationSERVER.NET utilizes a high-performance in-memory database, coupled with modular software functionality.
These types of system upgrades are what will be required to make the grid truly "smart". They also will be vitally needed as more distributed generation comes on-line involving smaller, less reliable power sources that may be generating electricity at some times of the day and drawing it at other times.
Smart grid involves a complex set of new technologies that are currently still in pilot stages. It will require a massive add expensive undertaking to get these systems installed on the grid. The substation is the center of any future smart grid -- not an advanced meter on the side of a house. And utilities still have a long way to go to get there. The vast majority of them are still sending trucks to substations carrying people with "natural" intelligence.
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Intelligent Utility magazine is the new, thought-leading publication on how to successfully deliver information-enabled energy. This article originally appeared in the March/April 2009 issue.