Abstract:
The distribution power lines have some power quality problems such as voltage drop voltage
sag, voltage fluctuation, voltage flicker, transient voltages etc. Those are some common
problems in the distribution systems all over the world. Those problems are occurred due to
reasons such as loading pattern, length of the line, consumer behavior in the feeder etc.
Considering Sri Lanka, in recent history there was no much power requirement and the
demand of the electricity supply is less. At present distribution system is expanded to the
whole country and provides the electricity to each house hold. Additionally due to growing
of economy in the country the industries, factories are also established and the demand
growth is occurred very fast. Therefore the Power quality problems were raised in the
distribution system rapidly in past few years.
To minimize the voltage violation of the regulation, the several temporary solutions were
adopted to the system in time to time by implementing the short term planning proposals.
But they were not much suitable solutions to mitigate the voltage violation of the system
permanently.
This research was done to enhance the system voltage by applying the reactive power
compensators along the distribution feeders. Analysis of the whole network of Sri Lanka by
simulating is a very difficult task and therefore the most critical feeder of the down south
network of the electricity is selected as a case study of the research. The same procedure is
followed by another feeder also as derivation of the results.
For this drastic problem, this study is carried out to find the solution by placing of reactive
compensators in the distribution feeder to improve the voltage level within the required limit
of ± 6% of 33 kV as the CEB planning guide lines.
The Synergee software is used to prepare a model and to analyze the feeder. Loading data of
the transformers and conductor data in the feeder is required to prepare the model. This
model is a mathematical model and by using load flow technique the model is analyzed. In
this analysis, a range of voltage drops were recorded by adding capacitor banks to the line
and there by the required sizes and locations of the capacitor banks were recorded as in the
relevant voltage drop. Study about the capacitor bank types and installation methods were
carried out to get the most effective solution. The results obtain from the study is to install
one switching capacitor bank of 3600 kVar ,and two fixed capacitor banks of 150 kVar and
one 300 kVar fixed capacitor bank in the feeder which improve the voltage level within the
required level of the regulation of CEB.
As a Conclusion of this study, the voltage level improvement can be carried out with reactive
power compensator placement to the medium voltage distribution line economically. The
total capacitor bank sizes installed in the distribution feeder should be less than the required
reactive power in that feeder. The Fixed capacitor banks should be installed at the most
affected load ends with validation of off peak loads also. After selecting the fixed capacitor
banks sizes the rest of the reactive power requirement should be installed with capacitor
banks having switching facility and the harmonic damping reactors should be installed at the
load center. The power utilities can implement the capacitor bank installation techniques to
improve the voltage level up to regulated level in the distribution network. It is an
economically viable solution where thoes capacitor banks can be used with any other feeder
enhancement in the future and they will provide the additional benefits of improving power
factor, reducing feeder losses etc.