Electrical switchgear engineers NOJA Power today announces that one of its OSM38 Automatic Circuit Reclosers (ACR) has been selected by Victorian electricity distribution company SP AusNet to connect Melbourne Water’s 8 MW induction generation plant at Thomson Reservoir to the utility’s distribution grid.
NOJA Power’s OSM38 ACR was selected by SP AusNet to connect the co-generation capacity for three main reasons: The ACR exceeded the customer’s specification for basic insulation level (BIL) with a rating of 170 kV; second, uniquely, the unit offered superior protection, isolation and eventual power restoration in the event of a fault on either side, and third, the unit’s proven reliability assured the customer that its valuable assets would be safeguarded for the long term.
The ACR enables Melbourne Water to take power from the grid or switch to co-generation when its induction generation plant is operational and excess capacity is available. SP AusNet also has the option to switch in or out the additional capacity depending on demand because the device integrates seamlessly with the company’s advanced grid control systems.
Conventional ACRs normally protect distribution grids downstream of a fault by monitoring the upstream line and isolating in the event of a fault. This operational characteristic has proved satisfactory for traditional distribution networks where power always flowed in one direction from a centralised generation facility to industrial and domestic consumers. But the advent of bidirectional distribution lines to facilitate co-generation capacity requires ACRs that can monitor and protect such lines in both directions.
The OSM38 ACR at Thomson Reservoir offers this bidirectional protection capability and more; not only can it monitor and protect the distribution line in both directions but it can also be set to trip at different current levels depending on the direction of electricity flow. At Thomson Reservoir, the ACR trips at a lower current for power being generated than for power being supplied. This arrangement allows SP AusNet precise control of the peak current fed into its grid––to protect voltage-sensitive devices among other requirements––while permitting Melbourne Water to draw as much current as it needs from the grid during times of peak demand.
“The unique point of difference for the NOJA Power OSM38 ACR is its bidirectional protection capability,” explains Shane Gorman, NOJA Power’s Australia-Pacific Sales Manager. “The ACR is normally closed so provides a continuous flow whether supplying power to Thomson Dam or feeding generated power the other way. But when a fault occurs the recloser is able to detect which side is affected and applies the protection criteria specifically for that condition. Normally, one protection setting would suit, but in this case the customer wanted different protection levels for supply and generation. Demand for these flexible protection systems is on the increase to enhance smart grids here and overseas.
“Within one month of commissioning NOJA Power’s ACR successfully opened and cleared two faults on the Melbourne Water network,” adds Gorman. “Without the recloser, these faults would have caused customer outages further upstream on the SP AusNet feeder to the reservoir.”
Historically, co-generation was rare because of the complexities of connecting such sources to distribution grids. But utilities now encourage co-generation because it helps them deal with demand peaks without having to invest in additional centralised power stations. Furthermore, modern ACRs have simplified the engineering required to connect conventional or renewable energy sources such as hydro, solar, wind, geothermal, wave and tidal. Greater generation diversification helps assure utilities that when one resource is unavailable due to, for example, lack of wind, another will be readily available to take its place.
Units from NOJA Power's OSM range of medium-voltage (15, 27 and 38 kV) ACRs (see “About the NOJA Power OSM range” below) have been installed by utilities in over 80 countries around the world. The ACRs have been subjected to full type testing by independent test laboratories such as KEMA in the Netherlands to the latest standards - underscoring the superior safety and performance of NOJA Power’s protection solutions.
Melbourne Water’s Thomson Reservoir is the largest of all of Melbourne’s water catchments and the third largest in the country, with a capacity of 1,068,000 ML. The reservoir contributes approximately 60 percent of Melbourne's total storage capacity.
About Melbourne Water