Download a voltage dip - Electrical and Computer Systems Engineering

LOAD BEHAVIOUR DURING VOLTAGE DIPS
Ignatius Rendroyoko, Prof. R.E. Morrison and Peter K.C. Wong
VOLTAGE DIPS are one of the important
power quality problems affecting all electricity
customers.
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 DIP CHARACTERISTICS
Characteristics of Voltage dips : Magnitude,
Duration, Phase angle jump and Post-fault
dip
Effect of load on voltage dip characteristics
Vdip
ZF

E
ZS  ZF
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.
Voltage dips cause serious problems to industrial
customers.
Results :
SUMMER AND WINTER LOADS
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
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.
SYNCHRONOUS SERIES
COMPENSATOR
There is a difference between summer and
winter loads. The electricity load in summer is
higher than in winter
DISTRIBUTION SYSTEM UNDER
STUDY
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
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.
The difference of load between summer and
winter in this subsystem is due to the operation
of air conditioners.
Typical voltage dip in winter
Electrical and Computer Systems Engineering
Postgraduate Student Research Forum 2001
Flywheel Energy Storage