Building a Communications Infrastructure to Maximize SCADA/EMS Investment

Most major electric utilities in North America have made significant investments in supervisory control and data acquisition/energy management system (SCADA/EMS) technology. Utilities have spent millions, in some cases tens of millions, of dollars for fully implemented SCADA/EMS-from system design to implementation to getting all of the many advanced applications up and running. In addition to its traditional operational role, SCADA/EMS is now typically generating information that is used for metering, marketing and customer service. Indeed, the SCADA/EMS investment is becoming a critical piece of a utility’s business strategy.

One of the paradoxes of SCADA/EMS is that much of its value hinges on the reliability of its communications system, which accounts for only a small portion of the total system investment. For this reason, utilities must search for and select a communications system that will provide cost-effective reliability. Many utilities are finding this solution lies with multiple address system (MAS) radio.

Puerto Rico Electric Power Authority (PREPA) is such a utility. It is committed to building an MAS radio-based infrastructure to support its SCADA/ EMS. Having used radios from four different providers in recent years for its MAS solution, PREPA is finding that MAS is still its best value and most reliable communications alternative.

PREPA’s Communications Infrastructure Upgrade

PREPA serves more than 1.3 million electricity customers on the island if Puerto Rico and has more than 31,000 miles of transmission and distribution lines. Within the last year, the utility has upgraded its EMS master station with a system from Siemens (Brooklyn Park, Minn.) and now has a fully redundant system with control centers in two separate locations.

Being a utility that needs to provide consistent and reliable service across diverse urban and rural terrain, PREPA has made the development, implementation and maintenance of its SCADA/EMS communications infrastructure a key strategic goal. PREPA is currently in the midst of a multi-year, multi-phase effort involving changing out all of its master and remote radios. By clearly defining its needs and partnering with a communications vendor, PREPA has been able to ensure unprecedented performance levels for its customers today, and expects to be able to continue performing at such a level well into the future.

Two of the four vendors that provided radios throughout the life of PREPA’s EMS are no longer in the business and a third is in the process of an ownership and investor change. Therefore, the utility had to make a change and find a vendor that offered long-term product reliability and had an “open” protocol. Throughout the last several years, it has been installing MAS radios from Alligator Communications (Sunnyvale, Calif.). Alligator Communications was selected because it met the following PREPA criteria:

  • Maximize short and long term cost-effectiveness;
  • Keep maintenance requirements and costs at a minimum; and
  • Achieve compatibility with existing radios and future needs.

PREPA learned firsthand the importance of these three criteria during the system upgrade. The utility gained some valuable insight into selecting communications technology.

Cost Effective in the Long Run

PREPA realized that a thorough analysis of both short and long term costs is a critical requirement when selecting a communications system. Such an analysis can help a utility accurately determine how cost effective a system will be.


Diagnostic software that runs on notebook computers or desktop PCs can be used to read and change any remote radio operational or diagnostic parameter.
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An MAS radio system’s cost effectiveness can be measured several different ways. First is the initial cost. With very limited construction or implementation support needs, MAS radios are less expensive on the front end than microwave systems. Another alternative, leased telephone line systems, are also less expensive than microwave systems, and they have relatively low start-up costs. However, the utility is held captive to the phone company’s maintenance priorities (usually not the same as the utility’s) and monthly fee increases. These disadvantages make MAS an attractive alternative to leased telephone line systems as well.

Most MAS radios offered by today’s leading manufacturers are similar in cost, with each offering different options. As is the case with many technology markets, many MAS radio vendors offer options that amount to “bells and whistles.” A thorough analysis based on system costs and the organization’s long term needs will assist in determining which vendor’s offering is most appropriate. This type of thorough analysis led PREPA to its current system vendor. In fact, the utility actually paid a slightly higher price for the radios that were selected, but those dollars were quickly returned due to savings in system maintenance.

Once the system is installed, long-term maintenance costs can wreak havoc on an otherwise affordable communications system. At PREPA, it was discovered that one of the biggest cost savings with the Alligator radios came from the ability to calibrate all remote radios with a single adjustment of the master radio’s transmission frequency. This saved the utility hundreds, if not thousands, of staff hours it otherwise would have spent calibrating radios at remote sites.

Mission Critical Ups the Reliability Ante

Another important aspect to remember when selecting a communications system is that a thorough analysis of both short and long term costs is required to make an accurate determination of how cost effective the communications systems will be.

SCADA/EMS, as a mission critical enterprise system, must have 24×7 availability, which places a high standard on its communications system. Reliability, in this case, comes in several different forms. The first is equipment reliability; in other words, will it work? PREPA has excellent system reliability, with a very small spares inventory-resulting in another cost advantage.

Reliability in terms of the radio frequency deviation and stability is also important. Two features that utility managers should look for are automatic deviation control and global frequency calibration. Both of these features are apparent at PREPA, enabling it to maximize the strength and stability of its radio signals within legal limits.

It’s Gotta Be Plug-N-Play

Another valuable lesson PREPA learned with its SCADA/EMS communications upgrade was to stay away from proprietary protocols. Potential advantages, if any, will be offset by problems with future compatibility.


Once a communications system is installed, long-term maintenance costs can wreck havoc on an otherwise affordable system. The Alligator system has saved PREPA a lot in maintenance costs by allowing all the remote radios to be calibrated with a single adjustment of the master radio’s frequency.
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One of the difficulties that many utilities face is that they may have multiple communications systems that have been implemented over a number of years, with changes in vendors necessitated by several leaders leaving the market. These changes in vendors present potential compatibility problems, particularly when proprietary communications protocols are involved. These problems can be exacerbated as the system grows or when needs change (for instance, if new regulations dictate changes in communications systems).

As the utility industry continues to evolve toward a truly open market, the use of SCADA/EMS as a tool for competitive advantage, in addition to its critical use on operations, will become more commonplace. Building a dependable, cost-effective telecommunications infrastructure will go a long way toward ensuring that this competitive advantage can be realized.

Manuel Perez has been with the Puerto Rico Electric Power Authority for 23 years and is currently an engineering supervisor in PREPA’s Telecommunications Division. He has a bachelor’s degree in electrical engineering from the University of Puerto Rico.

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