Case study 3

In this case the voltage stability is analyzed in a long term point of view. The system study is shown in Fig. 5, where a control exchange area exists between the transmission and  load area. 

Although the problem of the voltage stability is a dynamic phenomenon you can use a simple technique based on succesives power flows, what is specially appropriate if the load nature is not rotative. 

In this case the previous technique is used, carrying out a succesive power flows to obtain the  P-V curves that describe the system behavior for different operation conditions (line outages and demand increments) and the  Q-V curves to quantify the amount of reactive power necessary to maintain a certain voltage level. 

To include the time variable in the problem, several load flows are carried out to discretice the system temporal evolution in different instants of time.

Fig. 5.- Study network for case 3

Problem Solution : 

Fig. 6.- Voltage stability long-term static analysis for the network of Fig. 5:

 P-V curves considering a residential load increments

Fig. 7.- Voltage stability long-term static analysis for the network of Fig. 5:

 Q-V curves considering the outage of one line of the transmision area 

Fig. 8.- Voltage stability long-term static analysis for the network of Fig. 5:

 Q-V comparative curves considering the outage of  lines of the transmision area 

Theoretical details:

The full theoretical details of the proposed solution are free available in a pdf file

Software developed:

The problem was solved using a classical power flow program