Solid-Dielectric ACR Installation Improves Distribution Network Reliability

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With the increase in demand for high reliability power supply to Fiji Electricity Authority's customer base , FEA purchased an initial 20 OSM Recloser units for installation mainly on the rural spurs of several distribution feeders.

Offering a circuit exposure of more than 1000 kilometres, these feeders supply approximately 20% of the FEA's customer base.

Recloser & Control Cubicle Installation

In the 12-18 months since the commissioning, over 500 network faults have been registered and successfully restored beyond the recloser installation, with two recloser units accounting for more than 150 of these alone. Previously, an oil circuit breaker rated for 50 operations was used to protect the nearby substation and distribution feeders. The two NOJA Power OSM Recloser units now installed at the location of the circuit breaker are rated for over 30,000 operations and have performed 150+ operations in the 18 month period since commissioning, representing a substantial decrease in maintenance time and an increase in customer power supply.

The installations in this division have substantially increased the mean time between network power outages and helped the maintenance teams identify feeder inadequacies by highlighting spurs with high fault incidences. By calculating the theoretical impact of a fault without the recloser installed, it has been estimated that the 20 units have saved over 350 minutes in SAIDI, and have enabled a 30% reduction in SAIDI for the FEA Network Division. Plans have been drawn up to accordingly address these network defects and their impact on the SAIDI performance of the feeders.

The success of this strategy is particularly evident through an approximate 70% improvement in annual SAIDI performance in one of FEA's distribution feeders.

To ensure future reliability of this network division, the recloser's provide functionality extending beyond the current standard for ACR's. The OSM Recloser utilises voltage sensing technology on all six bushings to allow automatic operations to be performed in response to network conditions. Functionality includes Automatic Backfeed Resoration (ABR), where the device automatically closes if supply is interrupted on one side of a normally open recloser and supply on another side is present. Advanced communication capabilities of the recloser are being utilised by the FEA to integrate the devices into their SCADA system. This will have additional benefits in fault locating and supply restoration.

Due to the measureable success of the OSM automatic circuit recloser installation on the FEA Distribution Network, the utility purchased a further 30 OSM Recloser units from NOJA Power in 2007, with the intention of continuing the implementation of Distribution System Automation. This is expected to further reduce SAIDI and improve customer confidence in the reliability of power supply from the FEA.

By Kitione Valili (FEA) and Oleg Samarski (NOJA Power)