Load-Flow-Studies.8177219.powerpoint.pptx

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1. Topic : L oad F low S tudies Presented By : Arshdeep Kaur Department of Electrical Engineering GNDEC ,Ludhiana

2. What is a Load Flow Study??? It is a steady-state analysis whose target is to determine the Voltages Currents Real and Reactive power flows in a system under a given load conditions A load flow study also known as power-flow study

3. A load flow study is done on a power system to ensure that Generation supplies the demand (load) plus losses. Bus voltage magnitudes remain close to rated values Generation operates within specified real and reactive power limits Transmission lines and transformers are not overloaded.

4. A Load Flow Study Specifically Investigates the Following Bus bar voltages Effect of rearranging circuits and incorporating new circuits on system loading. Effect of injecting in-phase and quadrature boost voltages on system loading. Optimum system running conditions and load distribution. Optimum system losses. Optimum rating and tap range of transformers.

5. Power-flow Analysis Equations The basic equation for power-flow analysis is derived from the nodal analysis equations for the power system. For example, for a 4-bus system where Yij are the elements of the bus admittance matrix, Vi are the bus voltages Ii are the currents injected at each node. The node equation at bus i can be written as

6. Power-flow Analysis Equations Relationship between per-unit real and reactive power supplied to the system at bus i and the per-unit current injected into the system at that bus: where Vi is the per-unit voltage at the bus; Ii* - complex conjugate of the per-unit current injected at the bus; Pi and Qi are per-unit real and reactive powers. Therefore,

7. Power-flow Analysis Equations

8. The Load Flow Problem The starting point of a load flow problem is a single line diagram of the power system, from which input data for computer solutions can be obtained. Input data consist of bus data, transmission line data and transformer data. A bus is a node at which one or many lines, one or many loads and generators are connected.

9. Formulation of load-flow study In a power system each node or bus is associated with 4 quantities, such as 1. Magnitude of voltage V 2. Phage angle of voltage δ 3. Active power P 4. Reactive power Q In load flow problem two out of these 4 quantities are specified and remaining 2 are required to be determined through the solution of equation.

10. Depending on the quantities that have been specified, the buses are classified into 3 categories. Bus Classification

11. Each bus is categorized into one of the following bus types : Swing bus / slack bus Bus Defined To Defined Application Slack bus V and δ usually V 1= 1 d 1 =0 o P and Q There is only one bus of this type in given power system This is numbered as one for convenience

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