Background

WDI (Westfälische Drahtindustrie) is a german industry group founded in 1856 and is the margest steel wire producer in Europe. The company produces steel reinforcement mesh grids at the Salzgitter plant in Germany. The production line comprises various welding equipment, including spot welders from Schlatter AG. Like all powerful spot welders, the abrupt current consumption causes voltage variations, which in turn creates flicker.

Challenge

Due to expansion of the area and increased amount of renewable energy sources, flicker contribution needed to be lowered. Early reference measurement showed flicker levels up to Pst 2 and Plt 1.4. The case was further complicated by a lot of switching activity in the surrounding electrical grid, contributing to higher background flicker and making measurements more difficult. Finally, the flicker will vary with the production type running.

Solution – the high power ADF STATCOM

A solution was delivered to the customer in cooperation with Schlatter AG, who also delivered the welding lines.
An ADF STATCOM consisting of 7 ADF P300W-300/690 was installed. The nominal installed power is 2.5 MVAr. The fully water cooled STATCOM follows the load dynamically. Changes in the production or newly installed equipment does not lead to any adjustment of the compensation system. The ADF P300W units were installed via a dedicated transformer and uses its own medium voltage measurement point.

Result

The flicker level was reduced to Plt 0.6. Current consumption was lowered 25-40% due to reduced reactive power. Voltage dips on the 20 kV rail was lowered from around 500V to around 100V.