From Today's Distribution System to Tomorrow's Smart Distribution

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Written by Georges Simard, George Larry Clark and Robert Uluski

Emerging smart grid technologies are accelerating the transformation of the distribution system into the smart distribution system of the future. New operating techniques and design practices will be developed to continue improving the reliability of the distribution system. Engineers will develop tools and applications to be integrated with today's technologies so as to ensure the resilience of the distribution system and to achieve a self-healing grid.

The growing sophistication of IT and computer technologies, along with their decreasing costs of deployment, are presenting power engineering designers with many new opportunities to give electric delivery systems much greater intelligence. However, the definition of what has come to be known as the smart grid varies significantly, depending on contexts and use. Some existing systems are by no means dumb.

Sophisticated methods to improve efficiency and reduce operating costs are well entrenched in generation and transmission systems. Some techniques, such as high-speed protection, remote control and monitoring, and automatic restoration, could not be justified for deployment in distribution. But some forms of intelligence already exist even there; for example, reclosers once activated hydraulically came to be electronically and nowadays digitally controlled. Many of the modern reclosers have some wave shape monitoring capabilities to be used in some smart distribution applications.

Most recently, many distribution systems in Europe, Asia and the Americas have adopted Advanced Metering Infrastructure. AMI systems typically anticipate integration of intermittent energy sources like wind and solar energy at medium and low voltage buses, as well as premises-based demand- response programs, whether by means of direct control or through time of day tariffs. AMI has been receiving so much attention, indeed, that some in the industry are coming to consider it as virtually synonymous with the smart grid. That is very selective and restrictive, considering that the smart grid encompasses much more than a single technology and that intelligent applications are available at all levels of the energy delivery chain.

Focusing our attention on distribution, here is a non-exhaustive list of smart grid (or smart distribution) applications:

• Distributed energy resources integration
• Demand response
• Remote controlling of feeder reclosers and switches
• Fault location, isolation and service restoration
• Adaptive distribution feeder protection
• Accurate fault location based on wave shape analysis
• Remote controlling of capacitors
• Volt and Var control and optimisation (for conservation voltage reduction and peak shaving)
• Power quality measurements (Voltage sags and surges, harmonic content, etc,)
• Distribution line monitoring (power measurements)

These applications will require technologies, such as sensors, telecommunication infrastructure, analysis, simulation software and so on, to facilitate real time decisions and to meet growing customer expectations. With the integration of different smart distribution applications, software tools are being developed to integrate information from dissimilar systems and to summarize it, so as to facilitate and enhance operational decisions for the distribution system.

A number of these applications are under consideration in several current smart grid demonstration projects. The EPRI Smart Grid demonstration project and DMS Demonstration initiative are good examples of technology development and collaboration. Generally, distribution utilities are developing such applications on a project-by-project basis. It would be better in principle if many or all the applications could be evaluated in combination, as they have mutual influence.

For example, distribution systems are combining applications to achieve improved operational efficiency. These combined applications include, but are not limited to, Volt and Var control, distributed generation that is connected to either the medium-voltage or low-voltage system, and an automatic service restoration scheme, which has the capability to change the system configuration following a fault event on the distribution system. Integration of these applications is becoming essential to guarantee continued or improved network performance for energy delivery to the customer.

Since many distribution utilities are testing technologies and advanced smart grid applications in demonstration projects and in R&D programs, there is an opportunity to share the lessons learned with each other to avoid pitfalls and to benefit from the best experiences.

Another requirement is to develop standards that promote interoperability and interchangeability of end-use devices in order to reach, at least in the long term, a plug-and-play type design. International standards committees such as IEC TC 57 are extending standards from existing transmission applications to support the goal of distribution-level interoperability.

Within the framework of IEEE, the Power and Energy Society's Smart Distribution (SD) Working Group (part of the Distribution Subcommittee) is organizing panel and paper sessions to promote knowledge sharing. Task forces on Volt and Var, and on Distribution Management Systems, were launched recently to bring together experts to share experiences and develop standards. The distribution planning working group, which is affiliated with the Power Systems Planning and Implementation committee, supports the development of new planning tools, including advanced SG applications simulations.

In conclusion, the utility's distribution system has been and is in a continuous state of change and evolution. Emerging smart grid technologies are accelerating the transformation of the distribution system into the smart distribution system of the future. New operating techniques and design practices will be developed to continue improving the reliability of the distribution system. Engineers will develop new tools and applications to be integrated with today's technologies so as to ensure the resilience of the distribution system and the achieve a self-healing grid. The new smart distribution era will be indeed an exciting time with tremendous opportunity for distribution engineers.