NOJA Power News

Issue 10

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Reliable Power At Western Australian Mine Thanks To NOJA Power Reclosers

Kimberley Nickel's Sally Malay mine in Western Australia have dramatically improved their power quality after installing two NOJA Power reclosers in their distribution network. This eliminated frequent and lengthy power outages from affecting their entire network. These conditions are now reduced to short outages in isolated areas of the network allowing the mine to operate efficiently with minimum interruptions.

The central cause of all this fuss is the extremely large population of bats living in the immediate vicinity. The electrical coordinator for the Sally Malay mine, Mr Peter Jensen, said the bats often swarm around the 11kV aerials causing faults.

“Some of them touch the metal crossarms creating a 300 Amp phase to ground fault”, he said.

“This would be picked up by the 11kV breaker at the power station which would open on an earth fault shutting down our underground and camp services”, he said.

The cost of running feeders underground for any significant length cannot be justified when a mine has an expected 5 - 10 year lifespan. On the other hand, the bats are protected and cannot simply be culled to reduce the problem. Kimberley Nickel Mines looked into the problem and decided to install two reclosers on the sections most affected by the bat strike problem.

“A bat strike downstream of the recloser opens on that particular aerial only, avoiding a complete outage, but also giving us an idea as to where to look for the offending bat”, said Peter.

Bats are usually incinerated when they come into contact with voltages of this level (11kV). When the recloser detects the fault it opens and lets the bat fall to the ground. This removes the fault and the reclose operation is generally successful.

The worst case now is that a small portion of the network may lose power while the fault is restored. In most cases, however, the interruption will only last a few seconds. A definite improvement by any measure.

Installation of the reclosers were undertaken by an electrical contractor. Peter Jensen, then contacted NOJA Power directly to help with commissioning. Although reclosers are a common sight in electrical utility networks, they are not so common in small privately owned networks.

NOJA Power pride themselves on superior service and support and are always ready to help customers who need to properly commission their new recloser. Due to the remote location of the mine, all training and commissioning advice was delivered over the phone and online using email.

NOJA Power's service manager. Oleg Samarski, was supplied information on the substation circuit breaker settings, transformer sizes and other network information. From this he calculated appropriate settings that accounted for proper protection coordination and transformer inrush currents.

"Commissioning a recloser as flexible as ours can be difficult if you have never worked with one before", said Oleg.

"We are always happy to help customers get the most out of our reclosers for their particular situation. In this situation we were able to solve a technical issue without the need to visit the site ourselves", he said.

After the recloser had been in service for a while the data log was downloaded and analysed. It was discovered that the recloser had cleared many temporary faults due to bat-strike. In order to reduce the number of interruptions, it was decided to further fine-tune the protection settings in order to coordinate the protection as close as possible with the main substation circuit breaker.

Reviewing the protection coordination based on actual in service data proved to be invaluable in improving the overall reliability of the power supply. The settings have now been adjusted so finely that interruptions have been reduced to the absolute minimum possible given the circumstances.

Peter Jensen also used the flexibility of the recloser to implement a fuse saving scheme and limit the effects of lightning and line slap.

“We set the reclosers so they will now open before we blow the Expulsion Drop Out fuses located on each aerial. We also have the recloser open and reclose in the event of a lightning strike or line slap”, he said.

“All this has helped us greatly and NOJA Power have been excellent with their backup service” he said.

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