While the Seeds of Automation Innovations are being Sown Across the Country, some of the most intriguing projects are coming from independent municipal utilities in search of solutions to their unique situations. In Orangeburg, South Carolina, U.S., a picturesque town of around 14,000, the Orangeburg Department of Public Utilities (Orangeburg DPU) began a project to deliver top-notch customer service. Soon, the project grew to include the integration of self-healing feeders and a distribution automation system.

The project began with an effort to increase customer satisfaction by reducing the utility's system average interruption duration index (SAIDI). Orangeburg DPU set a goal to cut the number and duration of its customer outages. The first step was simple: implement a tree-trimming program. This lowered the utility's SAIDI from 3.6 to 2.6. But Orangeburg DPU wanted to do more. With a goal of reducing SAIDI to 1.0, the public utility decided to implement a self-healing feeder solution.

REQUIREMENTS OF SELF-HEALING OPTIONS

Orangeburg DPU launched an extensive study of the available self-healing options. While all promised to reduce the number and duration of outages on unfaulted sections, not every solution could integrate well with other technologies or applications. Ultimately, the utility decided the solution it would choose must have the flexibility to work with other technologies and applications, be cost justifiable and be capable of being deployed across the entire service area.

A multiservice utility, Orangeburg DPU is the largest municipal electric utility in the state of South Carolina. Orangeburg DPU owns and operates 22 electric substations, with service available at 115 kV, 46 kV, 25 V, 8.32 kV and 480 V for large customers. Its distribution system operates 60 feeders on 800 miles (1287 km) of line. The largest circuit has 1600 customers, but most feeders operate with 500 to 800 customers per circuit.

To avoid costly mistakes down the road, Orangeburg DPU used a phased approach in the build-out of its strategy. The utility identified its top-four priorities for system architecture and feeder application:

1. Cost

   The solution had to be cost effective. For Orangeburg DPU, this would mean reusing the common infrastructure shared by all its applications. By using common infrastructure such as platforms, sensors and communications, the utility prepared to reduce ongoing maintenance costs.

2. Scalability

   Orangeburg DPU needed a technology that would be scalable across the entire system, with the potential to expand from a pilot system to serving customers across 340 sq miles (881 sq km). Orangeburg DPU's ongoing objective is that all new technology be fully expandable and easy to add incrementally.

3. Interoperability

   The utility required applications that would operate smoothly across a suite of applications, in which each application would be adaptive to the current state of the system, whether the network state was normal or abnormal.

4. Daily accountability

   Orangeburg DPU needed a system that would deliver daily updates and maintenance of the distribution network to be performed from a single data source to all applicable functions.

CENTRALIZED OPERATION

The Orangeburg DPU selected these priorities to work within its architecture, through which system functions perform from a centralized distribution control center. The dispatch center monitors and controls the electric system under 24/7 operations. A state-of-the-art fiber-optic communications network supports the distribution management system (DMS), which provides advanced visualization of the distribution network.

All applications use the distribution network topology model to provide and display the real-time network status. The network map supports dynamic features such as a direction of power flow indicator, network tracing to find key network elements, color by phase, loop detection and coloring line segments with violations. All of these features help to improve situational awareness for Orangeburg DPU operators.

Orangeburg DPU has 30 Cooper Power Systems (Waukesha, Wisconsin, U.S.) NOVA reclosers on its network and 12 S&C Electric Co. (Chicago, Illinois, U.S.) Scada-Mate switches. During a recent outage, Orangeburg DPU operators were able to visually identify the location of the break through the dynamic network colorization features.

The system provides operator switching support with a 3-phase dynamic, unbalanced load flow by supporting the operator's ad hoc analysis. Before an operator closes a switch, a click on the device can run a load flow from a pop-up menu. Any violations that may result from the operation will display in a pop-up box (for example, “operation will cause 109% overload” or “operation will cause a 32% phase imbalance.”)