Power Systems
Load Flow Analysis
Practice questions from Load Flow Analysis.
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IncorrectDuring a power failure, a domestic household uninterruptible power supply (UPS) supplies AC power to a limited number of lights and fans in various rooms. As per a Newton-Raphson load-flow formulation, the UPS would be represented as a
During a power failure, the only power source is UPS. Since for convergence of load flow solution we need to declare one bus as Slack Bus and that bus needs to have power source. In our case only one bus has power source i.e. UPS and hence that bus needs to be treated as Slack Bus.
The bus admittance matrix of a 3-bus power system is given below.
Considering that there is no shunt inductor connected to any of the buses, which of the following can NOT be true?
Sum of the elements in a row of YBUS matrix represents the admittance b/w particular bus & ground.
Based on values above the system can be represented as,
π-model of a transmission line can be shown as
That is the line has equal capacitances at both ends.
So, we can consider line connecting bus-2 & 3 only has line charging capacitance of j0.5
Bus-3 has shunt capacitor of j0.5
∴ Statement b & d are correct & statement a & c are incorrect.
The three-bus power system shown in the figure has one alternator connected to bus 2 which supplies 200 MW and 40 MVAr power. Bus 3 is infinite bus having a voltage of magnitude p.u. and angle of . A variable current source, is connected at bus 1 and controlled such that the magnitude of the bus 1 voltage is maintained at
1.05 p.u. and the phase angle of the source current, , where is the phase angle of the bus 1 voltage. The three buses can be categorized for load flow analysis as
Bus 1 Slack Bus
Bus Bus
Bus Bus
Bus Bus
Bus Bus
Bus Bus
Bus 3 Slack Bus
Bus Bus
Bus Bus
Bus 3 Slack Bus
Bus Bus
Bus 3 Slack Bus
Since voltage magnitude is given at bus 1 & angle of current source
∴ Phase shift b/w V & I across current source =
∴ P = 0, Hence Bus – 1 is PV bus
Bus-2 has real & reactive power specified ∴ it can be characterized as PQ bus.
Bus-3 has voltage magnitude & phase angle specified
∴ It can be characterized as slack bus.