ogEn FIGURE 63.1 The one line diagram of a power system is often the starting point for many other types of power system analyses. In addition, power flow analysis and many of its extensions are an essential ingredient of the studies performed in power system operations. In this latter case, it is at the heart of contingency analysis and the implementation of real-time monitoring systems The power flow problem(popularly known as the load flow problem) can be stated as follows For a given power network, with known complex power loads and some set of specifications or restrictions on power generations and voltages, solve for any unknown bus voltages and unspecified generation and finally for the complex power flow in the network Additionally, the losses in individual components and the total network as a whole are usually calculated. Furthermore, the system is often checked for component overloads and voltages outside allowable tolerances Balanced operation is assumed for most power flow studies and will be assumed in this chapter. Consequently the positive sequence network is used for the analysis. In the solution of the power flow problem, the network element values are almost always taken to be in per unit. Likewise, the calculations within the power flow analysis are typically in per unit. However, the solution is usually expressed in a mixed format. Solution voltages are usually expressed in per unit; powers are most often given in kVA or MVA The " given network " may be in the form of a system map and accompanying data tables for the network components. More often, however, the network structure is given in the form of a one-line diagran Regardless of the form of the given network and how the network data are given, the steps to be followed in a power flow study can be summarized as follows 1. Determine element values for passive network components 2. Determine locations and values of all complex power loads. 3. Determine generation specifications and constraints. 4. Develop a mathematical model describing power flow in the network. 5. Solve for the voltage profile of the network. e 2000 by CRC Press LLC© 2000 by CRC Press LLC is often the starting point for many other types of power system analyses. In addition, power flow analysis and many of its extensions are an essential ingredient of the studies performed in power system operations. In this latter case, it is at the heart of contingency analysis and the implementation of real-time monitoring systems. The power flow problem (popularly known as the load flow problem) can be stated as follows: For a given power network, with known complex power loads and some set of specifications or restrictions on power generations and voltages, solve for any unknown bus voltages and unspecified generation and finally for the complex power flow in the network components. Additionally, the losses in individual components and the total network as a whole are usually calculated. Furthermore, the system is often checked for component overloads and voltages outside allowable tolerances. Balanced operation is assumed for most power flow studies and will be assumed in this chapter. Consequently, the positive sequence network is used for the analysis. In the solution of the power flow problem, the network element values are almost always taken to be in per unit. Likewise, the calculations within the power flow analysis are typically in per unit. However, the solution is usually expressed in a mixed format. Solution voltages are usually expressed in per unit; powers are most often given in kVA or MVA. The “given network” may be in the form of a system map and accompanying data tables for the network components. More often, however, the network structure is given in the form of a one-line diagram (such as shown in Fig. 63.1). Regardless of the form of the given network and how the network data are given, the steps to be followed in a power flow study can be summarized as follows: 1. Determine element values for passive network components. 2. Determine locations and values of all complex power loads. 3. Determine generation specifications and constraints. 4. Develop a mathematical model describing power flow in the network. 5. Solve for the voltage profile of the network. FIGURE 63.1 The one line diagram of a power system