The Convergence of Distribution Networks and Smart Grid Technologies

 

By Marina Ohrn and Hormoz Kazemzadeh, ABB

During the past decade, the electric power industry has seen unprecedented technological advancements and industry restructurings, creating innovation and automation in utility control systems where there was little throughout the 20th century.

Moreover, the business realities of today’s utility industry combined with the growing demands of modern society and the sustainability requirements of the environment in which we live is driving the development and implementation of a new power delivery system. This newer, smarter network will use the same basic infrastructure we know today but also will draw on advanced monitoring, control and communications technology that is only beginning to develop.

The result for the distribution operation center and distribution network will be a grid that is largely automated, applying greater intelligence to operate, monitor and even heal itself. This smart grid will be more flexible, more reliable and better able to serve the needs of today’s digital world.

Today’s quickly evolving environment is ripe for innovation. Today’s integrated supervisory control and data acquisition and distribution management system (SCADA/DMS) is enabling smart distribution systems that are increasingly a key component of the emerging smart grid.

DMS Continues to Evolve

As distribution systems continue to move rapidly toward becoming smarter and more secure, the operations centers that control them also are taking on new roles to manage such grids. The separate information technology systems operating in these control centers are becoming more streamlined, communicating seamlessly to provide an integrated monitoring and management system. More advanced applications and analytical software are providing more sophisticated analyses and automated operations. The control systems of operations centers are helping make the grid smarter to improve support for decision-makers responsible for operations, maintenance and planning. Such integrated operations centers are helping distribution organizations meet their goals despite ever-increasing challenges.

Within the past few years, external drivers have accelerated the development and expansion of applications for smart grid technology. Drivers for change include society and government, the business environment of distribution organizations and technology. From a business perspective, however, distribution organizations are looking to smart grids to help them maintain or improve reliability, increase asset utilization, deal with aging infrastructure and reduce knowledge loss as employees retire.

Technology has been a great driver in smart grid development. Communication technology has developed strongly in the past decade. Distribution companies have a choice among many solutions. The communication can be based on a dedicated network owned by the distribution organization (e.g., SCADA radio networks) or on third-party infrastructure (e.g., cellular communications provider networks). Depending on factors such as required availability and bandwidth, the distribution organization can select the appropriate technology. Whatever the choice, availability of two-way communication in distribution networks will increase.

There are increasing numbers of distribution equipment with sensing, data processing, control and communications on the feeder. Automation systems are becoming more common, with smart devices and appliances within a home network. The deployment of this technology will depend upon the development and unification of interoperability standards.

Systems Integration Benefits

As the emerging smart grid continues to develop and as companies have invested time and resources to create operations center systems, three areas of system integration have arisen in recent years: integration of DMS, outage management systems (OMS), and SCADA; advance metering infrastructure (AMI) integration with the DMS; and the integration of data from substation gateways and intelligent electronic devices (IEDs).

The integration of SCADA at the distribution level with DMS and OMS applications has been increasingly advocated in recent times. With the smart grid driving more distribution companies to install additional SCADA on the distribution system, power solution providers continue to improve this integration. Available functionality now includes the transfer of status points, analog points or both from SCADA to the DMS; the sending of supervisory control and manual override commands from the DMS to the SCADA system; and an integrated user interface running on the same personal computer operator console with integrated single sign-on for users.

Utility grid operators are seeing tangible benefits from implementation of integrated SCADA/DMS/OMS systems. This includes increased operator efficiency within one system, thus eliminating the need to go to multiple systems with potentially different data. It also includes integrated security analysis for substation and circuit operations to check for tags in one area affecting operations in another and streamlined login and authority management within one system. Operators also have noted improved, consolidated system support for DMS, OMS and distribution SCADA.

Much of the discussion about developing the modern-day smart grid has revolved around the potential of advanced metering infrastructure (AMI)and emerging advanced metering technologies. As a result, installations of AMI systems are rapidly growing in number. ABB and other network management solutions providers are developing ways distribution grid operators can best leverage AMI data. Interfaces among AMI, meter data management (MDM) and SCADA/DMS/OMS have been created and improved for outage notifications, meter status queries and restoration notifications.

Resulting benefits include reduced customer outage times and a more efficient use of resources in the field. The use of other AMI data in DMS applications, such as voltage indications and interval demand data, also has been explored. This will provide additional benefits, such as better voltage profiles throughout the system and an improved understanding of system loading.

In addition, many distribution organizations are increasing the number of substation gateways and distribution automation on their systems. This provides increased access to information in IEDs that are installed in substations and distribution systems. Many of these IEDs have advanced communications capabilities. These include more intelligent recloser controls, switch controls and voltage regulator controls. Integration of these systems with the DMS allows for model-based centralized automation and system optimization while supporting decentralized local control at the substation level, feeder level or both. Integrating SCADA/DMS/OMS with other utility systems provides an integrated operations center for managing the smart grid.

Advanced Network Applications

Today’s leading network management platforms provide advanced applications that use the network model along with the measurements of network operating conditions to provide recommendations for optimal network operation. These platforms typically include built-in, advanced DMS applications for distribution network power flow analysis, optimal capacitor and regulator operation, and fault and restoration switching analysis (RSA) of the network in response to faults or outages.

The distribution power flow (DPF) application is an integrated application that provides unbalanced power flow solutions for online analysis of the real-time network, on-demand analysis of what-if scenarios in simulation mode and automatic analysis of service restoration switching plans. The DPF application is designed to accommodate large scale distribution models extracted from GIS and provide fast solutions for real time. The application can support distribution networks meshed or paralleled including multiple swing sources, electrical loops and underground phase loops.

Today’s leading volt/VAR optimization (VVO) applications enable a distribution company to minimize peak demand and reduce real power losses. This defers the need for additional generation, transmission and substation capacity; reduces fuel and power purchase costs; and reduces greenhouse emissions. The VVO application monitors the distribution network and computes the optimal distribution control settings to minimize a weighted objective function of megawatt demand, megawatt energy loss, and voltage and current violations in three-phase, unbalanced and meshed distribution systems. The VVO application computes the optimal control settings for switchable capacitors and tap changers of voltage-regulating transformers.

Fault location (FL) applications use short-circuit analysis and can help significantly reduce Customer Average Interruption Duration Index (CAIDI) and System Average Interruption Duration Index (SAIDI) values by reducing the time required for troubleshooters or crews to locate faults. The application computes the possible locations of faults on distribution circuits based on fault current measurements and the real-time network connectivity.

Finally, RSA applications provide the operator with a quick method to identify switching options to isolate a faulted area and restore power to as many customers as possible without creating new overloads. The RSA application computes and analyzes switching plans to isolate a specific fault location and restore power to customers isolated from the fault zone.

These types of applications provide decision support to operators in manual mode and support fully automated operation without operator intervention in automated mode. As utilities move more and more toward smart grids and use better data and more advanced technologies, advanced applications will be used in automated modes to improve reliability and efficiency of the distribution operations.

Smart Distribution Centers’ Future

The integrated operations center is a vital component of the smart distribution grid.

In general, the operation of distribution systems will become more complex. Additional amounts of distributed generation and energy storage will impact the magnitudes and directions of power flows on the system and might vary. Demand response, either controlled by the electricity provider or the consumer, also will impact power flows and voltage profiles. In addition, there is already an increasing trend to place additional intelligence in devices on the distribution system, such as IEDs, substation computers and gateways, sensors and advanced meters. These devices will result in additional local control actions, further increasing the complexity of distribution systems’ operation.

In the presence of increasing amounts of decentralized intelligence and control, the integrated operations center will be a centralized way of overseeing and coordinating the entire system.

The smart distribution grids of the 21st century will require innovative operations centers for effective system management. Smart grid operations will provide a comprehensive view of the distribution system, including system status and monitoring, control, outage response, planned work and optimal equipment loading, as well as improved control over distributed generation, energy storage and demand response resources. The integrated distribution operations center will help distribution companies meet the goals of customers, owners, employees and society.

Marina Ohrn is director of marketing and sales for ABB Power Systems, Network Management and is based in Zurich, Switzerland. Reach her at marina.ohrn@ch.abb.com.

Hormoz Kazemzadeh is director of marketing for ABB Power Systems, Network Management in North America and is based in Sugar Land, Texas. Reach him at hormoz.kazemzadeh@us.abb.com.

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