Given a balanced three phase network, positive sequence impedance models of the network elements like transmission lines, transformers, reactors etc., and steady state models for loads and generators, aim of the experiment is to compute the voltage phasors at all the busses in the system, when the terminal conditions are specified in the following format:
- Active Power injection (P) and terminal voltage magnitude (V) at the busses having a generator or synchronous condensers, also known as PV busses. Phasor voltage angle and reactive power injected at the PV bus are the unknowns.
- Active power (P) and reactive power (Q) loads at the busses having loads, also known as load busses or PQ busses. Voltage magnitude and angle at a PQ bus are the unknowns.
Once the voltage phasors at all the busses are known, active and reactive power flow in the network elements like transmission lines, transformers etc., can be calculated. By comparing these values with the steady state device limits one can infer about the health of the system i.e., whether a system is in normal, alert or emergency state. If all parameters are within acceptable range considering even one line outage, then the system is in normal state. On the other hand, if after any one outage, steady state limits are violated, it is in the alert state. Emergency state involves serious violations of the limits demanding disconnection of apparatus. Usually it also leads to loss of loads.