Abstract:
Voltage instability is a problem of overloaded systems. The main factor causing
voltage instability is the inability of the power system to meet the demand for
reactive power. The Nairobi Area Power distribution network supplies over 50% of
Kenya’s national load demand. The increase in load demand in the network, over the
years has generated interest to the network’s voltage stability status. This research
assessed the voltage stability of Nairobi Area Power distribution network using static
analyses methods. The objectives of the study were to identify the voltage weak
buses and overloaded branches in the network, and to assess the network proximity
to voltage collapse point. The network power flow problem was formulated, and
solution attained using Newton Raphson method to determine the base operating
voltages and angles, the power flows, and to compute the full Jacobian matrix.
Sensitivity and modal analyses methods were then used to investigate the network
weak buses and overloaded branches. Further P-V and Q-V curves analysis methods
were used to compute the active and reactive power margins respectively of the
identified weak buses.The peak load conditions of June, 2012 were used in the case
study. The study established that the network isoperating closer to
voltagestabilitylimit at peak load conditions. Further analysis is recommended on
thebuses identified as weak to investigate the impact of reactive power
compensation, and contingency analysis for the network branches identified as
overload to study the impact of loss of any of those branches. Finally, since the
loading and network topology of the distribution networks are known to change
relatively fast, it is recommended that voltage stability analysis be conducted at
regulartime intervals to determine the stability status of the network as the topology
and loadings change.
