Georgia Power uses UtiliNet in its Distribution Efficiency Program (DEP)

Georgia Power, a unit of Southern Company, has been providing electricity to Georgia for more than a century. Georgia Power is the largest subsidiary of Southern Company, one of the largest generators of electricity. Georgia Power, an investor-owned, tax-paying utility serves customers in 57,000 of the state’s 59,000 square miles.

The challenge
In 1998, Georgia Power set out to find a solution to lower its peak demand, while at the same time maintaining reliable customer service at a reasonable cost. After running several tests, the decision was made to look at improving efficiency on the distribution side of the system.

The solution
The solution that was proposed in 1998 was called the Distribution Efficiency Program (DEP). It was approved and funded with two additional years to complete the project which would reduce the peak load by 200 MWs. This system provides for power reduction through the installation of capacitors at strategic points on the distribution system and the use of conservation voltage reduction (CVR) during peak load conditions and other critical times.

The voltage level along the feeder is held within a narrow bandwidth by switched capacitor banks control led by capacitor controllers that automatically switch the capacitor banks on and off based on preset voltage limits. Automatic voltage-sensitive switching of the capacitors eliminates the need for a sophisticated computer program to analyze conditions along the feeder and switch capacitors on and off. Georgia Power focused attention on careful upfront analysis and design work: selecting initial capacitor placement near load centers, setting correct time delays and voltage settings on capacitor controllers, and setting correct voltage levels and bandwidths on substation regulator controllers. Voltage compensation settings on regulator controllers are also a key factor in the operation of the system. All of these settings must be correct for the system to operate as designed and produce expected results.

Because of the limited time to implement and the availability of equipment already in place, they opted to use the existing distribution SCADA system. The Landis+Gyr UtiliNet radios worked well with the existing SCADA system and could be customized to communicate with all IEDs along the distribution feeders and in the substations using the Device Control Word (DCW) software tool provided with the radios.

The radios were also a good fit because they require no FCC license and they act as routers for transmitting device data to radio headend towers. Also the UtiliNet radio system installed for DEP is an excellent communication system for the Distribution Automation devices.

On each feeder, a communicating controller placed on the switched bank farthest from the substation is used to monitor voltage, especially during voltage reduction periods. Some feeders have as many as three monitoring points. The communicating capacitor banks talk to the UtiliNet radio system, which interfaces with the SCADA system. The values monitored at capacitor banks are volts, temperature, and the status of switches.

The results
After converting the test data to equations and evaluating the results with and without voltage reduction, they determined the DEP effect was statistically significant, averaging about 0.8% in load reduction per volt reduction. Simply stated, for every 1% in voltage reduction, load was reduced 1 percent. In summer 1998, additions lowered Georgia Power’s peak load about 32 MWs. With the additional 1999 – 2001 substations, the reduction totaled 264 MWs. Over 15 years the 264 MW load reduction will save GPC $25 million. In addition, $4.6 million was saved in purchased power cost in 1999 and 2000 during peak loads and extreme spot market power prices. “In return for the expectation of a fair rate of return to stockholders, a distribution company should make plans and decisions that benefit the customers. Implementing DEP is just such a decision,” said project manager Jim Bright.

The initially planned system is in place and has been used to reduce load for 85 hours during summer peaking conditions. They will continue to add DEP feeders, a round five each year, as load grows and the benefit-to-cost ratio justifies the expenditure.