LOAD BEHAVIOUR DURING VOLTAGE DIPS Ignatius Rendroyoko, Prof. R.E. Morrison and Peter K.C. Wong VOLTAGE DIP CHARACTERISTICS VOLTAGE DIPS are one of the important power quality problems affecting all electricity customers. Characteristics of Voltage dips : Magnitude, Duration, Phase angle jump and Post-fault dip Effect of load on voltage dip characteristics A VOLTAGE DIP is a reduction of voltage at a customer position with a duration between one cycle and a few seconds. Voltage dips are caused by faults, switching of circuit breakers and motor starting Voltage divider model for a voltage dip in radial distribution system Typical voltage dip in summer It is shown above that the typical voltage dip characteristics in summer and winter time are different. The voltage dip in summer needs longer time to recover. Results : In a system with rotating machine loads, the voltage does not directly drop to its minimum level when a fault occurs, but it decays until reaching a steady state condition before the fault is cleared. This decay is caused by the contribution of each motor to the fault. After the fault is cleared, the voltage does not directly return, but recovers slowly until reaching its original level. This phenomena is also caused by motor loads which take large current when accelerating from the initial speed. Voltage dips cause serious problems to industrial customers. Industrial equipment such as process controllers, PLCs, ASDs and other computer based equipment are actually sensitive to voltage dips. Most of these sensitive items will be shutdown or tripped out during voltage dips SUMMER AND WINTER LOADS SYNCHRONOUS SERIES COMPENSATOR There is a difference between summer and winter loads. The electricity load in summer is higher than in winter One of the solutions for mitigating Voltage dip problems is synchronous series compensator using flywheel energy storage. This device is currently being studied as a part of this project. DISTRIBUTION SYSTEM UNDER STUDY The difference of load between summer and winter in this subsystem is due to the operation of air conditioners. The subsystem under study is The White Horse Springvalle 22kV system, owned by United Energy. The system supplies commercial, residential, and light industrial customers. The System Under Study Flywheel Energy Storage Typical voltage dip in winter Electrical and Computer Systems Engineering Postgraduate Student Research Forum 2001