Many countries have important targets to increase the amount of electric power generated from renewable energies. Especially wind and solar energy are in the focus. Along goes a change from centralized traditional power generation to decentralized local generation, making also the conditions in the electric grids changing. The distribution grids do no more only experience voltage drop due to loads, but also rise of voltage caused by local generation. Large variation of voltage may occur. A line voltage regulator automatically adjusts the voltage to a regular level, makes the distribution grids “smarter”, and allows the infeed of higher amounts of renewable power.
The European grid code requires the voltage at the customer to stay within a range of +/-10% of the nominal voltage Un. With +/-5% the requirements in the US are even more demanding. Present grid design practices attribute only part of this voltage range to a voltage rise. In Germany this is typically +3% for low voltage and +2% for medium voltage distribution grids.
The power of local infeed of wind or photovoltaic energy is often a multiple of the maximum load for which the distribution grid was originally designed and the voltage rise quickly exceeds the limits. Although the current carrying capacity of the cable or overhead line is large enough, the infeed has to be reduced or completely stopped. Using an innovative ABB line voltage regulator, the voltage is “re-calibrated” and the capacity for infeed is increased. This is an important ABB contribution to allow to integrate renewable power generation into the existing distribution grids, without the need for costly grid extension, and with the possibility to quickly realize. Line voltage regulators are available for Medium Voltage
or for Low Voltage
Germany takes a leading role in the change towards more renewables, named “Energiewende”. By end of 2014 a total power generation capacity of about 195 GW was installed in Germany. The capacity of wind and of photovoltaic power was with 38 GW close to 20% each. During sunny and windy week-end days, up to 80% of electricity is generated from renewable resources. Germany targets to further increase the share of renewables in the electricity mix from an actual value of 27% to 50% by 2030, and to 80% by 2050. This will substantially further pronounce the problem of voltage rise and variation. And it is not only Germany, many other countries have similar ambitious targets.