NOJA Power’s single-phase Automatic Circuit Recloser offers rail companies safer, less expensive solution for electrified track isolation

Electrical switchgear engineers NOJA Power today announces that Aurizon, Australia’s largest rail freight operator and a top-50 ASX (Australian Stock Exchange) company, has selected the OSM38 Single Phase Automatic Circuit Recloser (ACR or “auto recloser”) for switching operations at its Callemondah, Queensland shunting yard. This is the first time an Australian rail company has selected medium voltage electrical switchgear for a safer and more cost effective track isolation solution.

The OSM38 Single Phase ACR is rated for 30,000 full-load switching operations on a live medium-voltage feeder. The unit is fully type tested by independent laboratory KEMA in the Netherlands and is capable of a rated maximum voltage of 38 kV, rated continuous current of 800 A and a full break capacity of 12.5 kA. The unit is type tested to an impulse withstand (BIL) phase-to-earth and phase-to-phase of 195 kV but passed further testing to a BIL of 200 kV to meet Aurizon’s requirements for the shunting yard application. Aurizon has issued the OSM38 Single Phase ACR with a Provisional Type Approval Certificate for this application.

Electrification of the Callemondah shunting yard is achieved via single overhead cables supplying 25 kV with one of the rails forming the return path. The train picks up the power via a roof-mounted pantograph. Part of the work at the Aurizon shunting yard includes electric train maintenance; trains are moved to a designated section of track up to six times a day and the track is then isolated and earthed to ensure maintenance personnel safety while they work on the unit.

Currently, isolation and earthing is achieved by remote-controlled circuit breakers at switching stations and by manually-operated switches. Use of the OSM38 Single Phase ACR has enabled Aurizon to introduce a semi-automated process controlled by interlocks. The ACR works in conjunction with two mechanical isolation switches and an earthing switch which remain locked until the ACR opens.

The process starts with the ACR’s RC-10 or RC-15 control and communication cubicle receiving a signal from the track controller confirming the train has fully entered the designated section of track. A technician then operates the ACR to isolate the line and when the voltage on the load side drops below a set threshold, an LED lights and a Fortress Interlock Key is released. This key is then used to operate the first isolation switch which in turn releases a second key for the next switch in the sequence until finally the earthing switch is operated to ensure no residual voltage remains. To re-energize the line, the sequence is reversed and the ACR closed. Safety is assured at each stage because each switch is interlocked until the previous device is operated.

An additional advantage of the ACR in this application is its ability to measure voltages on both bushings - allowing both supply and load feeders to be monitored. The parallel feeders in a shunting yard can induce high voltages on adjacent lines, including the isolated section prior to it being earthed. The ACR can be set to retain the Fortress Interlock Key until the voltage on the isolated section drops below a safety threshold, thereby taking into account induced voltages.

“NOJA Power auto reclosers are a proven solution for medium-voltage electricity distribution switching across the world, but this is the first application of the technology in a rail operation and underlines the flexibility of our technology,” says Neil O’Sullivan, NOJA Power’s Managing Director.

“We hope that the first application of the auto recloser in the rail industry could open other rail operators’ eyes to the equipment’s versatility because not only is cost effective for shunting yard operations but also other rail switching applications such as isolating ‘balloon loops’ where defective trains are moved off the main line for inspection and repair.”

NOJA Power’s OSM series ACRs provide a comprehensive suite of automation features. The units perform voltage measurement on all bushings, current measurement on all phases, bidirectional protection and extensive power quality and data logging capability. The OSM series has been fully type-tested by independent laboratory KEMA in the Netherlands to ensure long life and reliability under the harshest environmental conditions. Since their introduction, the OSM series ACRs have been installed by utilities in over 84 countries around the world.