Protective Relay Usage Trends

By Charles W. Newton, Newton-Evans Research Co.

Between the blackout of last August, and the potential for sabotage by those who would do us harm, electric power systems protection and control activities have taken on a renewed sense of urgency. Information collected during the mid-2004 Newton-Evans Research Company’s study of protective relay usage points to a number of distinct trends in the use of digital relays, maintenance issues, approaches to security enhancements, the need for relays to be IP addressable, the communications media requirements, and more.

The 102 North American utilities participating in the mid-2004 Newton-Evans study account for more than 30 percent of all customers served in North America and for about the same percentage of total industry revenues, far exceeding the participation levels in earlier studies conducted in 1996, 1999 and 2002.

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The mid-2004 Newton-Evans study found that from 23 percent (for bus differential relays) on up to 43 percent (for large generator relays) of the installed base of relays now consists of digital units. As a percent of new purchases, the 2004 study has found that from 79 percent (for bus differential units) to 96 percent (transmission line differential units) are likely to be digital units (see Figure 1).

Earlier, depending upon application, from 12 percent to 23 percent of the installed base of relays were digital by mid-1999. By mid-2002, this had increased from a range of 15 percent to 43 percent, depending on application.

Importantly, just as the study results in 1999 first indicated, investor-owned utilities (IOUs) continue to lag a bit with regards to their installed base of digital units in several categories. However, investor-owned plans for digital units in new applications for several categories of relay products are now on a par with the plans of public power and cooperative utilities.

Despite the dominance of digital relays in current and planned relay procurements as of mid-2004, there continues to be a viable opportunity for established suppliers of electromechanical relay products. For domestic North American producers such as GE, ABB and a few other smaller suppliers, there remains a viable $30 million to $40 million market niche for electromechanical relays in the North American electric utility market.

Budgets Increase for Relay Hardware

The mid-2004 Newton-Evans study has found increases in utility budget allocations for relay hardware, compared with earlier studies. While about 60 percent of all respondents plan to spend less than $250,000 annually for relay hardware, more than one-third plan to spend at least $250,000, and about one in six plan to spend $500,000 or more. IOUs and other very large utilities plan to spend at the higher levels, including several with multi-million dollar budgets.

It seems that IOUs have to spend significantly higher relative percentages of each relay budget dollar for unit installation and for engineering. IOUs indicate that only about 37 percent of their relay budget goes for relay hardware.

Testing Intervals and Maintenance Allocations

According to the study, the average testing interval for electro-mechanical relays was three and one-third years, shorter for public and Canadian utilities, and somewhat longer for IOUs. The average interval between solid-state relay tests was 3.85 years, with IOUs reporting longer intervals.

For digital relays, the average maintenance interval was just over five years, with IOUs stretching the interval to 5.88 years, and public power utilities tightening the interval to just under four years. There is also a correlation between utility size and the corresponding length of the interval between tests.

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Officials who responded to the Newton-Evans study also indicated that the majority of the maintenance budget goes to electromechanical units (61 percent), with digital units using about 22 percent of the budget, and solid-state units using about 17 percent of the budget. Figure 2 includes information on maintenance budget allocations.

A question on the likelihood of maintenance budget decreases was included in this year’s study at the request of report clients. The replies from 102 officials indicated that 56 percent have no plans to reduce maintenance on their installed relays, but that some of these officials indicated it depends on requirements from their regional coordinating council. One-quarter of the officials indicated that they do have plans to reduce maintenance on relay systems, and another 18 percent are uncertain about whether they will do so.

Five out of six Canadian utilities surveyed indicated plans to reduce maintenance spending. The plan to cut maintenance spending was also strong among the largest utilities, those with at least 1 million customers.

Security Enhancements to Digital Relays

The use of multiple (multi-tier) passwords for gaining remote access to installed digital relays was widely indicated by respondents to the 2004 study, with a few firms using automatic random password setting. Only one utility was using callback confirmation procedures to further enhance security (Figure 3).

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Nearly 80 percent of all utilities surveyed were making use of multiple passwords, and this high rate extended to all types and sizes of utilities, with larger utilities even more likely to be using multiple passwords to enhance relay access security.

Should Relays be IP Addressable?

Opinions on the issue of whether there is a need for relays to be IP (Internet Protocol) addressable were divided fairly evenly, according to the study (Figure 4). Fifty-three percent indicated that “Yes” there is such a need for relays to be IP addressable, while 47 percent said there was no such need. More than one-half of the rural electric cooperative respondents indicated no such need for IP addressability as did 60 percent of utilities having from 100,000 to 500,000 customers.

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Regarding the functions and features that would be required to be supportable through the unit’s IP interface, all 52 of the respondents to this part of the survey said that “event commands needed to be supported through the IP interface. Ninety-two percent cited “history command,” while 75 percent want to use the IP interface for remote settings, and 60 percent for communications configurations. Fifty-six percent indicated the IP interface could be used for the “load” command.

Communications Media for Relay Data

The mid-2004 Newton-Evans study found that fiber optics is prevalent for transmission line applications. Microwave and power line carrier were especially important supplements for transmission line distance relays.

In the 2002 study, observations centered on the overall importance of hardwired approaches used for transmission of relay information. Noted also was the growth in recent years of fiber optic communications. The use of fiber was by then prevalent for both transmission line and line differential relays.

Physical Connections for Relays: Copper wire was the predominant connection media used to physically connect relays up to transmit information. Fiber links were second in importance, and in some applications, were closing in on copper approaches (distribution feeders, small generators, transmission line distance relays). Wireless relays are being used for distribution feeder units, transmission line distance relays and current differential applications.

Relay Network Topology: The use of “star” network topologies to transmit relay information was prevalent in the 2004 study, with multi-drop approaches next. Many utilities use a combination of both approaches in their relay network arrangements.

Relay Protocols in Use: According to the Newton-Evans study, North American utilities rely extensively on DNP 3.0 for relay communications, followed by proprietary protocols for five types of relays, and by Modbus in four categories, with UCA following these three. None of the North American respondents were using IEC 60870-5-103 and only one utility was making use of IEC 61850.

Planned migrations to DNP protocol are continuing, based on the study’s findings. However, it is important to note that the new trends this year are for utilities to be planning to move also to IEC 61850 and others to UCA, both of these protocol trends noted for the first time. In Newton-Evans’ opinion, most of the changes are likely to occur at the expense of proprietary protocols, not from erosion of DNP use.

Relay Communications Access Methods: The use of real-time LANs is prevalent in six of the nine relay product categories covered in the study, while dial up modems are reportedly prevalent for use with capacitor bank relays, transmission line distance and transmission line current differential units. A significant percentage of respondents (about one quarter of the total) indicated that they use both dial-up modems and real-time LANs in their communications mix strategy.

Migration Trends

More than one-quarter of 98 respondents indicated that they were relying exclusively on digital relays to provide disturbance (fault) recording (DFR) and sequence of events (SOE) recording. Just about one-half indicated that they were moving toward such reliance on digital relays. Only 24 percent indicated that they were not continuing to rely exclusively on separate disturbance recorders and SOE recorders.

Based on the type of utility, it is clear that the investor-owned and public power utilities continue to rely on discrete fault and SOE recording units, but the plans are to move toward increasing reliance on digital relays for these functions. Among cooperatives and Canadian respondents, the move is already well underway, with almost all of these subgroups already using or planning to use digital relays in place of disturbance recorders and SOE recorders.

There is also a clear correlation between continuing use of DFRs and SOE recorders and size of utility. Only one of 32 utilities serving one-half million or more respondents was relying exclusively on digital relays to serve fault recording and SOE functions. However the movement to such reliance was evident among two-thirds of the respondents in this part of the survey.

Charles W. Newton is president of Newton-Evans Research Company. A graduate of Fordham University (BA, Economics) and Loyola College (MBA, Marketing), Chuck has been researching information technology products, markets and trends for 35 years. Since 1983, that research commitment and organizational work effort has been focused on the world’s electric utilities. Further information on the research series The World Market for Protective Relays in Electric Utilities: 2004-2006 is available from Newton-Evans Research Company, 10176 Baltimore National Pike, Suite 204, Ellicott City, Maryland 21042. Phone: 410-465-7316 or visit for additional information.

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