Wireless Control System Reduces Start Time at Gen-Set Farm

Diesel Progress North American Edition, Nov, 2001

A new wireless remote control system has reduced the time to start and parallel peak shaving generator farms owned by CMS Distributed Power LLC, a CMS Energy Co., Dearborn, Mich., from about 1 hour to 10 minutes. These time savings have dramatically reduced the manpower required to operate the generator sets, which supply power during peak periods to the local electrical grid and a large automotive plant.

CMS Energy, Jackson, Mich., through its principal subsidiary, Consumers Energy, is the fifth-largest investor-owned electric and natural gas company in the U.S. and its electric business is the nation's 12th largest. In 1999, the utility delivered 41 billion kW/hr of electricity through 68,000 miles of electric lines to 1.7 million customers in Michigan's Lower Peninsula. It generates power at over 70 plants located throughout its 27,800 sq.mi. service area.

The 39 generators installed with the remote control system at the two Michigan sites would previously take minutes each to start and synchronize to the grid manually, while the wireless system starts them simultaneously in response to a signal provided by an engineer in the company's headquarters. "This application saves us a considerable amount of time," said Felipe Mazzini, project development engineer for CMS. "We can get these units up and running immediately from a remote site, thus reducing the number of operators on call at each site."

Every utility has a base power demand as well as fluctuations caused by changing conditions, such as a rise in temperatures that increases the use of air conditioning. The two CMS generator installations are designed to meet peak power requirements, avoiding the need to build additional generating plants. One is located at the Ford Rouge plant in Dearborn and occupies a space that is approximately as large as two football fields. It consists of 26 Caterpillar 3516 diesel generators, with a total capacity of 37.7 MW. The other site is in Zilwaukee, Mich., and consists of 20 Cat 3516 and 12 Cat 3512 diesel gen-sets with a capacity of 40 MW. The units are designed to be regularly cycled on and off in response to fluctuations in demand and can be started one at a time or in groups.

In the past, CMS has used human operators to cycle similar generators. It takes an operator an average of five minutes to turn each generator on and synchronize it to the grid. The large number of generators at each of these two locations means that a considerable staff would be required at each in order to provide the cycling speed needed to respond efficiently to market conditions. Using the traditional manual approach, the company would have been faced with a difficult trade-off. Increasing the number of operators would reduce the time needed to respond to the market but also raise operating costs of both generator farms.

CMS engineers also considered automated control systems for the generators. One approach is to build a command center with a hard-wired control system, but that was considered cost prohibitive, partly because of the far-flung nature of the generator farm. Another approach would have been to use control systems that communicate with a central control system through a modem connection. This type of system would have been less expensive to install but would have required that the company install telephone lines to each of the generator sets. This would have involved a recurring monthly cost of $50 or so for each generator set in addition to the cost of operating and maintaining the control systems.

Mazzini said that CMS had decided from an early stage in the project that it wanted to control the operation of the generator sets remotely from its corporate headquarters. "The whole point of installing these generators was to be able to react quickly to the market, so it didn't make any sense for each cycling decision to have to go through a chain of command," he said. "Of course, we need to keep our costs to a minimum because we are heading for a competitive deregulated environment where the low-cost producer is the one that will prosper."

Mazzini said that Energy International, a Caterpillar distributor, evaluated the various systems on the market and recommended the G-Series control from OmniMetrix, Atlanta, Ga., "because it provides the lowest cost alternative while providing functionality that meets our needs."

According to Harold Jarrett, president of OmniMetrix, the G-Series is designed specifically to control emergency power generators. It turns the generator on and off and also monitors its operation, such as fuel level, oil pressure, coolant temperature, etc. The device generates an alert message whenever a failure mode is detected. Normal run and stop events are archived and reported in regularly scheduled summaries that are e-mailed to the service manager.

The control system takes 10 minutes to install and includes an internal battery that will operate the unit for two days in the event of a power failure.

Since it uses the overhead control channels of the existing cellular network, the G-Series control eliminates the need for dedicated wireline connections and also avoids the expense of bard-wired or satellite service by using Cellemetry Data Service technology from Numerex Corp., Atlanta, Ga. Numerex is a technology company comprised of operating subsidiaries that develop and market a wide range of communications and information products and services. The company's Cellemetry technology is designed to reduce the cost of monitoring and control operations to a minimum by taking advantage of an underutilized portion of the existing cellular telephone network.