Fault protection uses fibre-optics
3rd Quarter 2009
Electrical switching & drive systems & components
Electrical engineering specialist Moeller has been developing new products to meet the requirements of engineers working towards increased wind turbine generator outputs.
In the field of arc fault protection systems Moeller has introduced its second generation ARCON unit, confirmed by the IPH testing laboratory in Berlin as fully suitable for wind turbines.
The effects of arc faults are serious, ranging from personal injury to extensive switchboard damage. Damaged power distribution systems must be exchanged, and the operator further loses weeks of downtime.
ARCON is able to quench an arc fault in only two milliseconds – long before any serious damage to persons or to the switchboard can occur. It operates by detecting two variables: the light emitted from the arc fault, and the short-circuit current.
For the first, special light sensors connected to fibre-optic cables are laid along the active switchboard sections to transfer some of the extremely bright light of the arc fault to an evaluation device. ARCON uses the current transformers present in the incomers to detect the short-circuit current.
When both detection variables exceed certain specified threshold values at the same time, the evaluation unit triggers a quenching device which produces a three-phase bolted short-circuit as close as possible to the incoming supply and parallel to the location of the fault.
The current takes the path of least resistance and the arc fault is quenched. The entire process – consisting of detection, evaluation and quenching – is completed within two milliseconds. Once the causes of the fault have been rectified and the quenching device replaced, the switchboard is once more ready for service.
For more information contact José Ruivo, CBI-electric: industrial controls, +27 (0)11 977 0700, [email protected], www.moeller.co.za
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