NRTC promotes 220MHz for electric utility SCADA systems

The National Rural Telecommunications Cooperative

is known for its purchase of 220MHz spectrum in an FCC auction and its work with Securicor Wireless in promoting two-way radio communications systems to its more than 1,000 rural telephone and electric service utilities. The 220MHz voice, data and vehicle location equipment is made by Securicor Wireless and by SEA, a subsidiary of Datamarine International.

What may not be so widely known is NRTC’s success in helping utilities use 220MHz and other frequency bands for supervisory control and data acquisition. NRTC’s SCADA system includes wireless metering that gives utility companies more control and monitoring of the distribution feeder systems that originate at each substation. The system allows workers in the field to communicate in real time with all substations in the region.

Rural electric and independent telephone utilities have much in common. Both industries do business over networks that reach nearly all homes and businesses. They must work with local and state authorities regarding rate regulations, right-of-way approvals, tax policies and other issues. In spite of their similarities, rural telephone and electric utilities do little together, except to provide the telephone office with power and the electric office with phones.

These two industries may have a common interest in power monitoring and control technology, though. As states deregulate the power industry and electric utilities buy and sell power as a commodity, they need to measure power characteristics in every sector of the power grid. A rural electric distributor must be able to monitor power from generation and transmission to consumer use. The electric utility needs reliable telecommunications partners to gather this information.

A SCADA system monitors substation characteristics, such as kilowatt-hour use and voltage and amperage readings. Utilities can also track electric use in homes and businesses through automated meter reading units placed in strategic parts of the network.

The SCADA cost barrier

The cost of monitoring and communications technologies has dissuaded many rural utilities from deploying SCADA and AMR in the past. Traditional SCADA systems, for example, have been too expensive for rural utilities to deploy because those systems required high-cost dedicated landlines capable of maintaining an open channel at all times. Standard dial-up lines often require toll payments that are especially burdensome for rural electric utilities that cover large service areas.

The SCADA cost barrier is falling with the incorporation of “distributed intelligence” features into the latest-model utility meters. The new meters come with onboard microprocessors and memory to store readings. A utility can link to the meter through a PC interface at any time and no longer has to maintain an open telephone line. With SCADA-delivered data in hand, rural electric utilities do not have to rely on the accuracy of billing data from generation-and-transmission wholesalers.

Electric utilities can use similar meters to monitor power use by their largest commercial and industrial customers. Many businesses, especially those that operate data centers and customer service operations, need nearly flawless electric service. By load profiling their largest power consumers and setting up alarms for when the monitoring system detects “sags,” “swells,” and other power-related events, the utility can maintain the “five 9s” of reliability (equivalent to five minutes of power outage time per year) that many modern businesses demand.

Fortunately, rural independent telephone companies have a strong track record when it comes to providing the kind of reliable communications lines that SCADA and AMR systems require. However, phone lines do not reach some extremely remote substations. What does a rural utility do if the landline service cannot do the job?

Some meter users have had excellent results using wireless links, especially radios that operate below 500MHz. VHF and UHF radio signals tend to propagate over longer distances and are less susceptible to signal degradation from hills, trees and other natural barriers.

220MHz and utilities

The 220MHz band comes into play because NRTC is in a position to offer its member utilities the use of frequencies it purchased in an FCC auction. The member utilities use NRTC’s license, which means no waiting period for government license application processing. At about the same time NRTC bought spectrum, Microwave Data Systems was developing data-only radio equipment for use in the 200MHz range of frequencies.

Wade Sober, MDS’ inside sales representative for the Northeast and Southeast regions, explained the compatibility between the 220MHz equipment and the utility data requirements.

“The 220MHz band is divided into 5kHz-wide channels allowing data throughput up to 3,200 bps. This works well with most of the devices currently being used to capture data and control or monitor different parts of a SCADA system. “One advantage is that the MDS radios are optimized for use in the 220MHz band for data,” he said.

“One advantage is that the radios are optimized for use in the 220MHz band for data. The modems in them are well-designed for reliable data transactions,” he said.

Sober said that electric utilities are using 220MHz SCADA in key field locations, where in the past they may have used telephone lines for connections.

“Phone lines break, and sometimes it can take a great deal of time to have them repaired. With radio, you don’t have to worry about someone digging up a buried cable or a storm taking down an overhead line. It gives the utility the ability to be autonomous in terms of maintaining their system. When they have a problem with the radios in their system, they can replace them, in their own time,” Sober said.

Sober said that if a wired SCADA network connection is broken, the utility usually has to send someone to the substation or other remote point to make manual checks, taxing the manpower of the utility.The radio network allows the utility to avoid that problem as well as to build in redundancy in the system.

The Kansas Electric Power Cooperative, Topeka, KS, found a need for improved SCADA capability with its combination of two-thirds home-generated power and one-third purchased power under contracts with other utilities. To take advantage of the wholesale power supply market, KEPCo installed a new energy management and SCADA system with nearly 300 remote terminal units at substations across Kansas and remote operator consoles at each of its member cooperatives’ headquarters.

The EMS/SCADA system constantly monitors the metered flows of electricity to provide real-time power quality information and the actual demand of KEPCo’s 21 member cooperatives. The system also provides a common platform on which KEPCo’s members can expand automated monitoring and controls of their distribution and load management systems.

220MHz radio

The most widely deployed communications technology in the EMS/SCADA system is 220MHz radio, using frequencies purchased from NRTC. KEPCo was the first utility in North America to use 220Mhz for SCADA. Other communications technologies deployed include extensive use of telephone frame relay services, 2.4GHz microwave radio, 900MHz licensed radio, fiber optic cable and dedicated leased telephone circuits.

Workers at Lyntegar Electric Cooperative, Tahoka, TX, had been using cellphones to access data from the coop’s SCADA system. Because it took several phone calls to complete an information download from the field, the phone bills were huge. But so was Lyntegar’s 100-mile by 100-mile territory.

NRTC’s 220MHz SCADA program delivered the necessary coverage, and Lyntegar replaced its cell phones with 220MHz radios.

Lyntegar engineer Shane McMinn said that switching “from cellphones to 220MHz radios has provided us with several advantages. The radios allow us to have real-time information [on] loads, alarms, and history files.”

To retrieve information using cellphones, McMinn said, workers “had to dial up each of our 38 substations one at a time. With the radios, we have all of this information in real time for all substations. Not having to dial up each individual substation has saved approximately 30 hours of labor per month.”

Lyntegar’s 220MHz system, which uses MDS 2710 radios, allows workers to communicate in real time to all 38 substations across the coop’s entire territory. “The radios are user-friendly and are easily programmed in the field if changes are needed,” McMinn said.

The backbone system involves multiple repeaters, with the longest path independent of repeaters reaching roughly 50 miles. Bill McGinnis of Alexander Utility Engineering in San Antonio, TX, designed the system.

Lyntegar serves the rural electric needs of parts of nine counties south of Lubbock, TX. As one of the largest electric coops in the state, Lyntegar belongs to United Telecomm, a group of Texas coops that jointly purchased 220MHz rights for Texas, Arizona, New Mexico, and Oklahoma through NRTC and Cooperative Wireless.

MDS’ Sober said that with his company’s products, different types of SCADA systems can be incorporated over one wireless network. This network can include serial or ethernet devices, licensed or license free radios and different frequency bands, such as 220MHz, 400MHz or 900MHz. “Our newer products allow long range, higher speed wireless IP/Ethernet connectivity and enable many new services and applications.

“Coverage can be offered from a short distance to a longer distance. Microwave can take you to 30 miles. All of the optimum methods can be combined in a system for full coverage,” Sober said.