Fault Isolation Reconfiguration

An expanding military base needed to install a new, automated loop system operating at 25kV (150kV BIL) with the ability to interrupt up to 25kA. The required configuration was a closed loop, communication assisted protection system using POTT and DCB schemes. In addition to the supplied system, the provider had to communicate with existing substation breakers.

G&W supplied the most economical solution using TNI gas insulated switchgear with internal potential transformers and a custom control package that integrated SEL-351S relays and fiber optic transceivers. Each switch also contained three internal power transformers to monitor voltage. The system was programmed and fully tested to provide minimal isolation time by tripping only the two interrupters closest to the fault.

For more information: Application Guide.

A capital improvement project was approved to upgrade the electrical system of a critical coastal evacuation bridge. The system was originally a 5 kV manual reconfiguration system and was to be changed to a 25 kV automated fault isolation system. This project presented several challenges including meeting tight space limitations, no disturbances on the changeover from manual to automatic, working with separate utilities at either side of the bridge and complete reconfiguration within 30 seconds.

G&W, along with Canada Power Products (CPP), supplied a solution that included 11 fully automated 27kV, RFI type switches connected in an open loop. Each switch had one or two SEL-351S relays that were used for protection and to act as an RTU for the included Survalent Master Station. Nine of the vault style switches were installed on the bridge structure with the other two acting as utility feeders on either shore. The system was set up in the factory and tested to verify operation.

For more information: Application Guide.

A US military base was interested in improving the reliability of their underground distribution system. They wanted to install the project in two phases to allow for new substations to be built that would feed the distribution system. All switches would need to be automated and capable of detecting and isolating faults.

G&W worked with the military facility to provide a flexible system that used automated TNI style, fault interrupting switches. All switches were protected and monitored by SEL-451 relays. The first phase of the project was to install the switches into radial feeds and the second phase connected them into two open loops. All switches in each loop were connected to an SEL-2100 logic processor that controlled the reconfiguration. During a fault the closest switch would interrupt to protect the troubled line section. The logic processor would then open the switch on the other side of the faulted line section to isolate it and close the open point switch to restore power to the healthy line sections.

A municipal power provider needed to provide a new, key, industrial customer with reliable power during a circuit outage or fault. The solution had to interrupt faults and reconfigure in the shortest time possible because even brief outages could affect the customers’ processes. Two independent 38kV circuits were available.

G&W provided a solution pairing two Viper-ST reclosers, one on each 38kV circuit, and four 6-way PNI style switches with stored energy mechanisms. The reclosers were protected by SEL 651R relays and each switch had one SEL-451 relay and one SEL-751A relay. All relays were communicating with an SEL RTAC controller that was built into one of the switches and acted as the reconfiguration brains of the system. A fault on the system caused the recloser to trip, the RTAC to determine the location of the fault, open and close the correct switches to isolate the faulted line section, and finally close the recloser to energize the reconfigured circuit in less than one second. This operation was fully tested at the factory.

For more information: Application Guide.

A utility was interested in improving service reliability by installing an underground fault detection, isolation, and restoration circuit to feed several important residential and commercial customers. They were interested in a solution that could be scalable from an individual switch to a full circuit of switches capable of performing an open loop restoration.

G&W Electric provided a system based on four-way, back to back Trident-SR solid dielectric switches. SEL-451 relays were used for the automation logic and source protection with SEL-751A relays on the load ways. Communication was through fiber optic cables. The relay logic was designed to be extremely flexible so the same program could be used in multiple scenarios without modification. By activating different parts of the program, it could be configured as a standard automatic transfer switch, as a through point automated loop switch where both line ways are normally closed, or an open point automated loop switch where one line way is normally open.

For more information: Application Guide.