The case we present concerns reactive energy compensation in a factory producing semi-finished plastic products with a continuous 5/7 work cycle.
The factory is powered by two 15kV/400V transformers. The types of loads are mainly inverters that control new and old generation extrusion motors and other automatic machines. There is a photovoltaic system connected directly to the distribution panel.
The system experienced inadequate reactive power compensation due to the instability of the photovoltaic energy production, which is sized for almost the whole power absorbed by the loads.
Note: PV systems are “variable generators” that may change also drastically the functionality of the electrical system.
There were penalties for capacitive reactive energy consumption, as well as penalties for reactive energy input (existing in some country) during the F3 night-time period which is associated with the photovoltaic system and the new LED lighting system. The target was to compensate the reactive energy to ensure a cosφ close to 1 even in the presence of capacitive load, and to balance the three phases affected by imbalance.
To achieve this result, the existing conventional power factor correction systems were removed and replaced with a hybrid HSVG-AAR/100 system, consisting of capacitor banks and an electronic power compensator in a three-phase+neutral configuration.
The proposed system is characterised by high compensation speed, in the order of 20 milliseconds, and extreme precision in maintaining the desired cosfi. The hybrid system was the only configuration that allowed real-time compensation of the capacitive cosfi and balancing of the currents on the three phases, in a single machine and smart HMI.
For a complete compensation, a set of three 800A CTs was placed on the input line of the distribution panel, in order to have real-time knowledge of the electrical variables and act in the most effective way on each single phase.
For the sizing of the automatic equipment, we carried out a series of measurements with a network analyser at the main switch..
