Substation Automation–the Next Generation of Solutions
By Gordon van Welie, Siemens Energy & Automation
Deregulation and increased competition have had, and are continuing to have, dramatic effects on the way electric utilities do business. Companies are downsizing, right-sizing and resizing. Dramatic re-arrangements are occurring as a result of deregulation and competitive forces. Technology is exploding; microprocessors are finding their way into what were once the simplest electro-mechanical devices. All of these and other phenomena are putting a great deal of pressure on today`s utility personnel who must react more quickly to a rapidly changing environment.
In the past, many of the hardware and software products and systems used within the electric utility were custom designed and built, requiring long lead times, lots of engineering work and resulting in complex maintenance and upgrade procedures. This mode of operation limits the utility`s ability to react quickly and adapt to new market conditions. In addition, it requires more people with more training. In terms of substations, utilities are responding to these business pressures by insisting on an open systems approach for substation automation. Such an approach relies on industry standard hardware and software products using industry standard communications technologies and protocols. The Electric Power Research Institute is acting as a catalyst for this open systems approach with its RP3599 project, which aims to standardize the data object model and the communications protocol for the LAN within the substation.
The new focus on an open systems approach has resulted in a new generation of substation automation solutions consisting of PC- and PLC-based substation integration, automation and communications products. These systems provide control, automation and monitoring and allow various intelligent electronic devices (IED) to be integrated into one system. This will introduce an era of “shrink wrapped” substation automation systems and solutions to the utility industry. Products are being designed to enable personnel to install and configure them with a minimum of training. User interfaces are intuitive and have a look and feel consistent with commercial PC products bought at the local computer superstore. Components which use standard, open communications protocols permit a “building block” approach to substation construction and upgrade. Simple gateway products allow legacy devices to be easily incorporated. In short, shrink wrapped solutions permit the wide-scale introduction of cost-effective substation automation applications.
What is Driving Substation Automation?
In terms of positioning a product within a rapidly evolving marketplace, it is important to understand what is driving the market. The following are key factors: changes in the substation environment and the technology used in primary and secondary substation equipment; evolving power system control requirements within the control center; the utility business environment, both internal and external; and enabling technologies, including technologies which have lowered the “barrier to entry” for providing cost-effective and reliable substation automation solutions.
Substations are Changing
The amount of change in the substation has been substantial over recent years. These changes include the following:
RTUs and IEDs are currently based on microprocessor technology. This has been a significant change for utilities over the past decade, particularly in more conservative areas such as protective relaying and metering. This will have an enormous impact on utilities over time in terms of the complexity of the substation secondary systems they are building and the expected economic lifecycle of the technology installed today. Substation secondary equipment was for many years based primarily on electromechanical technology. The equipment gradually moved through a solid-state digital environment during the 1970s and the early 1980s and entered the numerical age during the late 1980s and early 1990s.
The explosion of microprocessor-based devices in the substation will dramatically increase the availability of data. Presently, data is still largely “trapped” due to the lack of effective mechanisms to retrieve and present it in a form which is consistent with that required by the utility information systems. It is possible to access individual devices within a substation, but due to the lack (until very recently) of standard communications protocols, it was necessary to install a separate master station application for each device. Unfortunately, the introduction of standard protocols has not overcome the lack of common data structures between the various devices, which further inhibits providing a consistent data access mechanism into the substation.
The designers of primary plant equipment such as switchgear, current, voltage and power transformers are including digital interfaces in their equipment in order to facilitate the automation of the substation and hence increase the attractiveness of their equipment. The introduction of microprocessor-based devices, computer-based control systems and advanced communications architectures into the substation has increased available functionality and has also dramatically increased the complexity of managing and configuring this equipment.
The increase in functionality in the various RTU, PLC and IED devices has resulted in an overlap in functionality between these devices: RTUs can now provide simple protection and measurement functions; protection relays can provide both measurement and control functions; intelligent meters can be configured as simple RTUs; RTUs have made stand-alone sequence of event recorders obsolete; protection relays are able to do disturbance recording (normally the domain of stand-alone devices); and PLCs offer RTU functionality and RTUs offer PLC functionality.
Utilities are also under constant cost pressure, particularly in the new deregulated and competitive environments which are being thrust upon them. Thus they are now, more than ever, open to new ways of designing and refurbishing substations. Substation automation offers reductions in the capital cost of designing and building a substation.
Not only does it offer the advantage of decentralizing data acquisition into the switching yard–thus obviating the need for long runs of copper cable–but it also offers advantages in the area of application engineering, as there is less cabling and interfacing to do within the substation control room. The capital cost reduction implications also apply to existing substations, many of which were built 40 more more years ago.
Evolving Power System Control Requirements
The technological advances have moved even more rapidly within the control center. The network control systems of today and tomorrow will require enhanced functionality from the substation control system.
Multiple control center access to the substation is particularly important in terms of changing network boundaries and responsibilities within a utility. This will also be important in the context of utility acquisitions, where there is a need to integrate two or more different systems into one system. More sophisticated EMS applications will require more data. A good example is on-line reconfiguration of protection relay settings to enable system protection to be optimized to the prevailing environmental and operating conditions of the network.
The cost and environmental pressures on utilities will cause utilities to run their networks and substation plant closer to the design limits of the equipment. This will require more sophisticated monitoring of plants and equipment and faster operational response times. The need by utilities to increase their level of customer service will also drive a need for faster restoration and reconfiguration of the power network. In addition, the need to increase the quality of supply will drive a need for accurate, on-line monitoring of the quality of supply, which can only be achieved be employing more sophisticated measurement devices in the substation, which are in turn linked back to the control center.
The increase in complexity within the control center environment, both from an operational and technological point of view, will require that the suppliers of EMS systems build intelligence into their systems to shield the operators from some of that complexity. An increase in intelligence at the control center level will be matched with a requirement for an increase in intelligence at the substation level.
Dramatic Changes in the Utility Business Environment …
Utilities are facing a dramatically different environment today. There is enormous pressure on utilities to “do more with less” as they strive to become more efficient in a growing competitive market. Utilities are facing many issues, including:
reduction in operating costs which has been translated into “reengineer the business,” which in turn has driven the need for an “enterprise data model” which supports an overall enterprise information systems strategy for supporting the reengineered business;
reduction in tariffs coupled with a requirement for flexible, time-of-use based tariffs. Often this is linked to demand-side management initiatives. These business initiatives require sophisticated metering systems linked into energy management systems;
generally increasing the level of customer service. This includes response times to customers, coupled with faster restoration times, reduced outages and an improved quality of supply. It is not enough for the utilities to say that they will improve customer service and improve the quality of supply, it must be measured. This creates a demand for technological solutions to measure these variables. Utilities also want to differentiate themselves on the basis of value added services. This in turn is causing them to explore communications paths from the substations all the way down to the home.
Reduction in maintenance costs is linked back to the pressure to reduce operating costs. G2 Research Inc. of Mountain View, Calif, a market research company, and Computer Sciences Corp. of Boston, Mass., an industry information technology outsourcing/consulting firm, recently stated that one of the fastest growing areas within a utility was in the area of work management systems.
The utility has a limited pool of resources to do maintenance, and one of the first budgets to be cut is normally the maintenance budget. Having a limited amount of resources, the question raised is, “How to deploy these resources for maximum return?” A topic currently under discussion within utilities is the concept of condition-based maintenance. The idea is simple –only maintain the plant and equipment when it needs maintaining. As an example, utilities have a largely time-based, mechanistic approach to maintenance of switchgear, based on the number of trips counted.
Although the trip counter, as an indicator, is better than nothing, it gives the maintenance personnel no indication as to whether the breaker opened under load or not and whether it tripped under fault conditions or not, both of which will dramatically affect the amount of wear on the breaker contacts. It is in areas such as this where the data available in the substation control/automation system and the control center can be utilized to achieve predictive maintenance mechanisms for individual plant items, which in turn can be used as a valuable input to work management systems.
Gordon van Welie is the business unit manager responsible for Siemens` substation automation business. van Welie was with Eskom, the national utility of South Africa, for 11 years both as chief engineer, measurements and control, and corporate measurement and control consultant. He received a bachelor`s of science degree in electrical engineering and a master`s of business administration degree from the University of the Witwatersrand, Johannesburg, South Africa.
If you would like to see more articles on this topic, circle R.S. 107.
For more information on this article, circle R.S. 108.