THE EVOLUTION OF DISTRIBUTION MANAGEMENT SYSTEMS

Transmission & Distribution World June 1996

By Chuck Newton, Automation Editor

The use of one or more types of control systems in modern electric utilities is extensive, if not pervasive. Often, overlapping applications capabilities can be found between and among energy management, supervisory control and data acquisition/AGC, distribution management systems (DMS) and distribution automation systems (DAS).

The worldwide application of SCADA systems technology has been developing and maturing for the past 30 years or so. By now, most of the larger distribution utilities in industrialized nations have implemented distribution SCADA systems. Most larger utilities, having power generation plants and transmissions networks to manage, have implemented at least one generation of energy management systems. Within the power plant itself, other plant and unit-level control systems have been implemented for about the same length of time.

These initial waves of automation during the late 1960s through the late 1980s helped resolve many of the issues related to the management, monitoring and control of electric power generation and transmission processes, such as unit cost, network security, interchange transactions and transmission load flow studies.

Since the mid 1980s, the term distribution management systems has come into popular use, primarily to herald the arrival of a new generations of "SCADA-plus" systems, extending monitoring and control capabilities beyond the sbustation, down the feeder lines and in a few cases, into the customer premises.

Suppliers of distribution SCADA systems, typified by Advanced Control Systems (ACS), CAE Electronics and Valmet in North America and Landis & Gyr, AEG and ABB in Europe, were early providers of DMS capabilities. In fact, ACS pioneered the use of the term in the United States via its advertisements as early as 1986. Studies conducted by Newton-Evans as early as 1984 found strong evidence of substantial systems of distribution network management and control implemented at mid-size and smaller public power utilities and electric cooperatives throughout the country.

By the mid-to-late 1980s, the term distribution automation systems began to be used interchangeably with distribution management systems.

Thus, the second major wave of utility automation initiatives is clearly coming from the distribution side of the electric power business with two major but distinct developments, namely distribution automation systems, subsystems, components and applications and secondly, distribution management systems, or, more accurately, distribution operations managements systems.

The distribution operations-oriented SCADAs are part of the DMS equation if they acquire real-time data beyond the substation and down into the primary and secondary distribution network ... from the feeders to the fuse to the transformers to customer-premise devices.

DMSs differ from traditional SCADAs in two ways: operator interaction levels (ability to call up detail level distribution network diagrams and GIS-based maps) and level of data and file integration with other utility systems, especially customer information systems, outage management systems, trouble call applications, work management and the like. In doing so, DMS is taking advantage of technology leaps, including availability of third party distribution applications, advances in software development tools and a new generation of intelligent electronic field devices.

In the DMS environment, operators not only monitor points and devices throughout the distribution network but they can effect control over power distribution down to the residential level. Effectively, this is an expanded view of the concept of control room operations.

The power of an analytical DMS software to assist in rerouting power by automatic line sectionalizing in both planned and unplanned outage conditions is part of the DMS environment. The intrinsic nature of these systems to concurrently update closely related applications and to allow operators to simulate actions and effective reactions before taking final decisions, are valuable capabilities of a DMS.

Commercial DMS packages have become available from two important sources: the "traditional" SCADA systems firms and a new breed of DMS firms, stressing the data/file integration aspects of DMS with concurrent updating of related files. Companies such as Configured Energy Systems and M3i are leaders here. Several electric utilities comprise a third group of DMS developers.

Unlike most DA applications, which tend to have fewer requirements for human decision making and are more apt to be "closed loop" in design and more directly involved with field equipment, distribution management systems must have strong MMI designs, given their more "open-loop" design with more operators interaction or intervention.

The market for distribution management functions, if not separate systems, will grow dramatically over the next decade. Given the number of distribution utilities versus the number of generation and/or transmission utilities, spending for DMS functions will likely outgrow spending for basic SCADA applications before too long.

Newton-Evans Research Co. forecasts that spending on distribution management systems (including separate DMS masters, portions of SCADA systems allocated to distribution management functions, DMS applications software and related services) will amount to about US$76 million worldwide in 1996. About 45% of these expenditures will be with the SCADA systems companies and about 55% will be spent with DMS specialist software and consulting firms.