IntelliTEAM II® Improves Reliability When Conventional Source Transfer Can’t.

Background

A southeastern U.S. electric cooperative needed to improve their service reliability for a growing commercial area . . . or face the possibility that other retailers, who were evaluating the commercial development for new stores, might elect to locate elsewhere. The co-op wanted to take a proactive stance — to prepare for future growth and improve reliability for the existing stores too.

The problem was perplexing. Alternate power circuits in the vicinity of the commercial area either lacked sufficient capacity or were not reliable enough to allow implementation of a traditional source-transfer scheme. Also, traffic congestion made line repair difficult; it typically took hours to repair faults in the area.

What did they do?

The utility discussed these challenges and goals with S&C. A solution was proposed employing the S&C IntelliTEAM II Automatic Restoration System. S&C developed a simulation demonstrating how the system would function.

S&C’s proposal was accepted. The co-op purchased and installed five S&C Omni-Rupter® Automated Switching Systems (NOTE: S&C has subsequently retired this product from our product offering and replaced it with our new Scada-Mate CX™ Switching Systems), with S&C 5801 Automatic Switch Controls equipped with the IntelliTEAM II Automatic Restoration System. Figure 1 shows a single-line diagram of the automated circuit in its normal configuration.

Figure 1. Single-line diagram of automated circuit in normal configuration.

The commercial district consists of three loads, all normally fed by Source B. Source B is capable of supporting the maximum combined area load of 2.5 MVA. Source C supports residential load and can be used as an alternate source, but can only supply 2 MVA. Source A is outdated and has long stretches of exposed line. It can be used as a secondary alternate source, but can only pick up a portion of the load. Load LD1 is a new large retailer.

How does IntelliTEAM II work?

With IntelliTEAM II, the automated circuit is partitioned into sections called “teams”—in this case, Teams T1 through T6. If a team loses power, either because of a source outage or a fault, IntelliTEAM II uses the excess capacity of an adjacent team to supply the load. IntelliTEAM II typically completes service restoration in under a minute.

Consider, for example, a fault occurring upstream of Switch S3, in Team T4, while the area is operating at peak load, 2.5 MVA. See Figure 2. The circuit breaker on Source B trips, causing loss of voltage to Loads LD1, LD2, and LD3.

Figure 2. Single-line diagram of automated circuit after
isolating a fault upstream of Switch S3. Service has been
restored to all but the faulted line segment.

IntelliTEAM II now goes to work to restore service to as much of the load as possible. After sensing an extended loss of voltage, IntelliTEAM II opens Switch S3 to isolate the fault. IntelliTEAM II then opens Switches S2 and S5 in preparation for the intelligent load restoration.

Since Source C cannot serve the entire load, IntelliTEAM II closes Switch S1, restoring service to Load LD1 through Source A. IntelliTEAM II then closes Switches S4 and S5, restoring service to Loads LD2 and LD3 through Source C. All team operations are completed in less than 60 seconds.

Results

As expected, performance of the IntelliTEAM II Automatic Restoration System has been very successful. The excellent reliability statistics provided an incentive to a hotel and several other large retail and drug stores to locate in this commercial district.