STATCOM AHF Reduces Flicker
Due to an increased usage of the local grid, a stricter limit of flicker emission became a necessity. One of the largest steel wire producers in Europe managed the problem by installing a STATCOM solution and lowering their flicker emissions.
The processing plant is the largest steel wire producer in Europe, part of a German industry group founded in 1856. The company produces steel reinforcement mesh grids. The production line is made up of various welding equipment, including spot welders from Schlatter AG. As is the case with all powerful spot welders, the abrupt current consumption causes voltage variations, which in turn produces flicker.
Due to expansion of the area and increased amount of renewable energy sources, it became necessary to lower flicker contribution. Early reference measurements showed flicker levels up to Pst 2 and Plt 1.4. A futher
complication the the case was caused by a lot of switching activity in the surrounding electrical grid. This contributed to higher background flicker and making measurements more difficult. Finally, depending on the production type currently running, the flicker will vary.
STATCOM by AHF – the Solution
The solution was offered in cooperation with Schlatter AG, who also delivered the welding lines.
A STATCOM solution consisting of 7 300/690W water cooled active harmonic filters was installed. The nominal installed power is 2.5 MVAr. The fully water cooled STATCOM follows the load dynamically. Neither changes in the production nor newly installed equipment leads to any need for adjustment of the compensation system. The AHF units were installed via a dedicated transformer and use their own medium voltage measurement point.
The STATCOM solution reduced the flicker level to Plt 0.6. Reduced reactive power lowered current consumption 25-40%. Voltage dips on the 20 kV rail were lowered from around 500V to around 100V.
AHF Reduces Flicker from Radiator Production
Today’s industry constantly faces new challenges. As the local community grows, large businesses with energy intensive production processes are faced with the challenge of reducing their effects on the grid. High flicker emission levels can potentially disturb other industries on the public grid.
The plant is a 55000 square meter radiator factory in Belgium, It consists of six production lines that in total can produce about 5000 radiators a day. The production process consists of presses, seam welding and spot welding. The process is inherently very energy demanding and so puts great demands on the power grid. These processes combined to create large voltage drops in the feeding substation with the result of too high Pst values. The problems at the plant caused flashing lights when the local utility company would connect other consumers to the same transformer.
The local utility company demanded that the Pst 95% value could not exceed 0,7. Measured values during 2009 showed tops in the Pst equivalent to 1,6. Achieving this goal was no small feat due to the rapidly fluctuating load, and the many different load patterns that could occur with such a high number of welding machines.
Active Harmonic Filters – the Solution
The market leading response time for the active harmonic filter was a necessity for the customer to reach the values that the utility company demanded. The system consists of six units, making it a total of 2,1 MVAr continous power to compensate for the voltage drops.
Installation of Active Harmonic Filters Creates Results
After installing the active harmonic filters, the plant has managed to keep their Pst value below 0,63, regardless of how many welding lines are run simultaneously. The reference values have been measured by external consultants and approved by the local utility. As a side effect of the lowered flicker value, the plant now also enjoys stabilized production environment.
Harmonics Mitigation Increases Output with 30%
The water treatment process involves a large number of variable-speed pumps to process large amounts of fluids. By using Active Harmonic Filtering technology to optimize the electrical behaviour of their variable frequency drives, a major water processing plant in Sweden managed to increase the maximum output capacity of their systems by 30%.
Thanks to Active Harmonic Filtering we can now process 30% more fluids during periods of peak demand. We also save energy.
– Project Manager
The treatment plant is part of the sewage works in Gothenburg. It is one of the largest in all of Scandinavia and central to saving the environment from pollution. With heavy demands, the two basic requirements on this critical regional infrastructure are constant operation and sufficient treatment capacity. UPS power backup systems are crucial to ensure a secure and stable power supply.
To increase plant capacity, 17 new VFD-controlled pumps were installed at the processing plant. This increased harmonic distortion on the electrical system significantly and the resulting overcurrents caused the UPS fuses to melt. To avoid this, the pumps were run at reduced speed. This was however a temporary solution as it reduced treatment capacity below demand. Frequency converters are a well-known source of potentially damaging harmonics.
Harmonics Elimination – the Challenge
After consulting a premier Swedish consulting firm, the processing plant announced a public procurement process seeking the implementation of active harmonic elimination technology. The target was to retrieve full treatment capacity by eliminating the harmonics.
Solution – Active Filter Units
The result was the installation of two 600 kVA Active Harmonic Filter units to manage two transformers supplying 2160 kVA. There were a number of characteristics of the specific harmonic filter solution that led to the plant’s choice:
- Flexible connection and system dimensioning
- Reduced maintenance costs to other connected equipment
- Disturbance free electrical environment
- Reduced energy consumption through decreased transformer losses
Harmonics Eliminated – the Result
Eliminating the harmonics in the system resulted in an increased max output capacity of 30%.
In addition, the processing plant now manages to operate below the threshold value for harmonic distortion (SS 421 1811). The plant now enjoys further benefits with a reduced energy consumption and improved environmental performance.
Harmonics Case Study:
Secure Food Production by Mitigating Harmonics
Highly automized processes often contain VFDs, which cause harmonics in the power supply. This can affect machinery and can cause downtime in production lines. This was the case at a major food processing plant in Dortmund, Germany.
The food processing plant is part of a federation of over 300 independent retail dealers and suppliers to approximately 540 grocery stores. The center is a 100.000 m² warehouse and distribution center with affiliated butcher. After the butcher was destroyed in a fire in 2009, it had been rebuilt and expanded in 2011 into an 18.000 m² large butcher shop. Since completion at the end of 2011, the new processing plant produces 250 tons of meat for the grocery stores and up to 25 tons of sausages every day. The new butcher shop contains state of the art logistics and meat processing systems.
The VFDs connected to the new meat cutter created typical current harmonics of a six-pulse-converter (5th, 7th, 11th, 13th, etc). These harmonics resulted in commutation notches in the voltage, which influenced the whole production process. The harmonics caused blackouts and disturbances to the lighting. It also influenced the sausage stuffing and caused long production stops disturbing the process flow. Occasionally up to half of the employees had to be sent home for the day due to disturbances in the process.
Solution – Active Harmonic Filter with Harmonics Compensation
The food processing plant decided to use an Active Harmonic Filter to eliminate the problems in the power supply. The installed system consists of one filter with a capacity of 300 A harmonics compensation to provide the needed harmonic power for the meat cutter.
After the installation and a short commissioning, all disturbing harmonics were cancelled and the commutation notches disappeared. All meat cutters could now, for the first time, be started at the same time, without any effect on lighting or the sausage stuffing process.