Moeller advances wind turbine product range.
Moeller has refined three of its products to meet the component requirements of engineers working towards higher wind turbine generator outputs.
Vacuum technology has been incorporated into selected Moeller contactors, and the company has designed space-saving circuit-breakers to protect against overload and short circuit. Improved arc fault protection systems have also been introduced.
Vacuum technology makes Moeller’s contactors well suited to wind turbine switching voltages up to 1000 V because of the absence of arcs and escaping gases during switching. It has also allowed the components to become smaller, releasing more working space for other purposes. In addition, the necessary mechanical forces and drive outputs are smaller compared with conventional air contactors, allowing the use of intelligent electronic control units.
Contactor lifespan is good for wind turbine operation over several decades, with a rated current of 1600 A being distributed on two vacuum tubes per pole. Integrated electronics ensure the synchronous switching of all contactors, relieving the user of otherwise unavoidable control routines in the PLC program.
With Moeller contactors available for rated operational currents of 2200 A (and soon 2500 A), high-cost medium-voltage switchboard systems can now be replaced with less expensive low-voltage power distribution systems in wind turbines of 2 MW and more.
Moeller’s second contribution to wind turbine development is the new NZMH4 VE2000 circuit-breaker, suitable not only for connecting wind turbines to the grid power supply, but also sized at a compact 280 x 400 x 210 mm rated for operation at ambient up to 50°C.
Breaking capacity is 35 kA at 690 V, allowing the NZMH4-VE2000 to disconnect a wind turbine from the grid in complete safety. The short-circuit release itself can be adjusted to between two and eight times rated current range, offering the generator excellent protection against overloads.
The combination of the NZMH4-VE2000 with DILH1400 or DILH2000 vacuum contactors is approved for Type-1 coordination. Contactors execute the connection and disconnection of the wind turbine during normal operation, and the circuit-breaker provides the protective function. The DILH2000 enables users to implement direct grid connections, with a star-delta combination being used to extend the operating range in weak wind zones.
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, however, 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 ready for service without any restriction.
For more information contact Jose Ruivo, CBI-electric, +27 (0)11 977 0700, ruivo@moeller.co.za, www.cbi-electric.com
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