Power quality observations at a light industrial site

Abstract

Abstract-This paper deals with observations of events that occur in the power system and could effect power quality at a winery. Power system incidents recorded at the site are presented. The impact of the equipment, which includes large induction motors, power factor correction capacitors and halfwave rectifier induction motor heaters on the supply system is described. The disturbance to equipment operation caused by system events such as sags are also detailed. In order to gauge the effect of the power events at the site the opinions of the customer and the supply company on the power quality were sought. These opinions are reported and in general, the events recorded and described caused little detriment to the customers power quality.

Characterization of Switching Transients in Low Voltage Power Systems of Tea Factories in Sri Lanka

“…The time in between this mechanical jump happens in magnetic contactors, which is approximately 0.25 seconds as stated in the study [1] is sufficient to establish a voltage sag in the start of motor. [5,7]. However, it is observed at this point, a significant transient pulse also generated by contactor switching, as Figure 8.…”

“…At the same time, transient nature at the starting period of a power system has also gained great attention as they tend to make associated devices in to accelerated ageing. Whenever a load turned on or off through a switching action in the system, voltage transients possibly pierce to the specific electrical environment [3][4][5]. Therefore, a retrofit to equipment safety in an environmentally harsh situation can only succeed if sufficient attention is given to protecting associated electronic control gear or drivers against overvoltage conditions.…”

“…As reported in scientific literature [3,[5][6][7][8][9][10][11][12][13][14], on every occasion where the circuit conditions suddenly change, a transient is prone to be initiated, often follows with switching operations or owing to lightning. This can either be a change loading condition of the equipment or current demand predominantly.…”

The transient and steady state performance of a shunt active filter using measured site data

“…Figure 11 A large oscillation occurs in both the current and voltage and the transient oscillation causes the induction motor heater unit to produce the 1300A peak after the capacitor switching. The heater units are the cause of the spiked current [5]. In order to filter this transient the shunt active filter must produce a compensating current with a peak of 1300 Amps and the maximum rate of change of current is 6.3 Amps/µs.…”

“…The use of this type of heater is common in New Zealand dairy factories where induction motors operate in wet environments. A more complete description of the site and measurements is given in [5]. The shunt active filter system considered in this paper is a load side active filter and is shown schematically in Figure 2.…”