Abstract
Voltage sags are caused by faults which cause equipment trips. Different equipment
have voltage sensitivity thresholds, and when voltage sags are below that specific
threshold, they can lead to interruption of supply, and as a result, they will result in
financial losses.
In this dissertation, the impact of distributed generation (DG) on voltage sag
performance is investigated. Using a stochastic approach, voltage sag performance is
assessed by using a method of fault position to determine profiles of magnitudes of
remaining voltages at a monitoring point. From these, the expected number of critical
voltage sags at a monitoring point are calculated, and the expected cost of these sags is
derived for various voltage sensitivity threshold limits. An illustrative study is carried
out comparing the voltage sag performance and expected costs of voltage sags for a
network without DG and a DG Case for various mixes of customers.
It was shown that in the presence of DG, the expected number of critical voltage sags
was lower for all voltage sensitivity criteria assumed and for all customer mixes. In
addition, the expected costs of voltage sags were fewer for all voltage sensitivity
criteria. This study has shown the positive impact of DG in improving the voltage sag
performance and the expected cost of voltage sags.
M.Sc.