Illinois Case Study: How to Increase Critical Customer Load Reliability

By Steven Allen, City of Batavia Municipal Electric Utility

Rubicon Technology recently sent the city of Batavia, Ill., a few special requests. The Midwest manufacturer of industrial sapphire used in LEDs needed to expand manufacturing capacity to accommodate a substantial increase in product demand. Because the company had filled two existing Illinois plants to capacity, it elected to build a new facility. The where would be determined by the location’s ability to meet those special requests.

Viper-ST recloser with SEL-651R controls installed on the two overhead lines.

Rubicon Technology had several demanding requirements for this new facility: 18 MW peak demand, an outage duration of less than 5 seconds (required to avoid substantial product loss), and the desire to have the project running in less than seven months. After a thorough search for real estate with adequate power requirements, Rubicon Technology located an existing building within the city of Batavia, located 40 miles west of Chicago.

The city of Batavia owns and operates a municipal electric utility with the flexibility needed to meet Rubicon’s challenging requirements. The city of Batavia Municipal Electric Utility is connected to the 138 kV transmission system and uses both a 35 kV and 12 kV distribution system, with a 2010 summer peak demand of 89 MW.

Rubicon Technology began construction in April 2011 with the desire to have the full 18 MW of capacity installed and available in a short time. The city of Batavia Municipal Electric Utility elected to serve this customer at 35 kV, using both an existing line and new lines installed near the facility. The utility soon determined a restoration system that could automatically sense and isolate an electrical problem without the need for crew dispatch. The utility researched the industry’s better known suppliers of distribution automation equipment, finally choosing G&W’s Lazer distribution automation system.

System Configuration

Two 35 kV overhead lines from different sources were extended to the facility during construction. The 35 kV line was then transitioned underground to feed the facility through four padmount switches. The new facility was sectioned into 10 separate services, with up to three services being fed through each switch. The design allows half of the load to be carried on each of the two 35 kV source lines, with each line being able to carry the entire load. Reclosers (G&W Viper-ST style with SEL-651R controls) were installed at the 35 kV downfeed points on the overhead lines. Each feeds two switches. (See photo, Page 52.)

The switches (G&W PNI style) incorporate two automated source (line) ways and three three-phase load ways. (See photo, Page 54.) Each source-way switch is controlled with an SEL-451 relay and incorporates a stored energy mechanism for high-speed switching. A Schweitzer Engineering Laboratories RTAC (SEL-3530) located in one of the padmount switch control enclosures serves as the master control for reconfiguration after a fault occurrence or voltage loss. Each switch has an additional way to protect the potential transformers (PTs) located in a custom side-mount enclosure. This design allows accessibility to the PTs without opening the main switch compartment. (The PTs provide the ability to monitor power for each individual service way and voltage to the SEL relays for power metering and harmonic analysis.) A battery backup system was also included to provide control power and the ability to operate the switches in the event of a widespread, extended power outage.

Operation

The automated system operates as an open loop with fault interruption occurring at the pole-mounted reclosers. When a fault or a voltage loss is detected, the line recloser opens to isolate the system from the 35 kV source line. Fault indicators on the padmount switches’ line ways are tied through the relays and back to the controller utilizing multimode fiber-optic communication paths. The controller then determines the fault’s location. Once located, the controller opens the closest switches to quickly isolate the faulted section and closes the midpoint switch, if necessary, to allow power flow to all of the services. Finally the recloser closes back into the reconfigured circuit to restore power. This allows all of the loads to be re-energized while the faulted line section is isolated.

After an operation, the system can lock out and provide notice of an event through SCADA and on the front panel of each relay with a “Fault Detected” message on the rotating display. This allows the utility to send a repair crew to the site without the added stress of knowing this critical customer is without power. When the crew arrives onsite, they can determine the fault location from any of the controls. The circuit is broken up into five zones corresponding to the line sections (L1-L5) between switching devices. All of the relays contain five programmed LEDs that indicate the fault’s location zone. The controls also indicate whether the fault is instantaneous overcurrent (ANSI device number 50) or time overcurrent (ANSI device number 51). This feature saves time for the operators; they can determine fault location by opening any relay cabinet.

At the request of the utility, the system was set up for manual reconfiguration. When the faulted line section is repaired, all of the switches can be manually returned to their original configuration. Once in the normal configuration and the “Remote Enable” is activated on all of the switches and reclosers, an LED on each relay will change to “Normal Configuration.” From there, the reconfiguration logic is activated by pressing the “Automation Enable” push button at any relay. The rotating display on all relays show “Lazer Automation Ready” when the system is activated.

Results

The system was programmed and factory acceptance tested at G&W prior to shipment. All reconfiguration scenarios were confirmed, and the reconfiguration time was verified as less than 2 seconds. The switches and reclosers were installed onsite by city of Batavia Municipal Electric Utility personnel and are fully operational.

 PNI style switch with two automated source ways, three load ways and an additional way for PT protection only.

Five months after commissioning, one of the sources lost power, but the system operated as designed. The customer saw only a brief interruption in power while the recloser opened to isolate the source and the tie switch closed to restore power. The sequence of events information was uploaded from the controller afterward which showed the system had completely reconfigured in 1.6 seconds saving the customer from a “substantial loss.”

The system was called on again during a storm in July 2011 that was one of the most destructive on record in the Chicago area. One of the sources to Rubicon was lost following a lightning strike at the substation and the system reconfigured in less than 2 seconds. This allowed Rubicon to maintain operations while more than 868,000 customers lost power in and around the Chicago area because of the storm. Thanks to the city of Batavia’s well-designed electric infrastructure and the G&W Lazer Distribution Automation system, Rubicon continued production.

Steven Allen, P.E., is the senior project engineer for the City of Batavia Municipal Electric Utility in Batavia, Ill. He has more than 12 years of utility engineering experience with investor-owned utilities and independent power producers.

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