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Load flow study

The application of load flow study in industrial plant and supporting software ETAP.

What is the purpose of study?

“The principal information obtained from a power-flow study is the magnitude and phase angle of the voltage at each bus and the real and reactive power flowing in each line.” This is excerpted from Power System Analysis by William D. Stevenson.

In other word, power flow studies are performed to evaluate the voltage profile of buses in system and the loading of the system components such as generators, transformers, switchgear, cables and transmission lines.

Which method is best for load flow study?

There are 3 common methods to solve load flow equation, namely Gauss-Seidel, Newton-Raphson and Fast-Decoupled method. The detail pro and con is as below:

  • Gauss-Seidel Method: Low Requirements on initial values, but but slow in speed.
  • Newton-Raphson: Fast in speed, but high requirement on initial values.
  • Fast-Decoupled Method: Fast in speed, but low in solution precision. Better for radial systems and systems with long lines.

Study methods is available in ETAP software.

Load-flow-study-methods
Load-flow-study-methods

Standards and guideline

  • IEEE Std 399, IEEE Recommended Practice for Industrial and Commercial Power Systems Analysis
  • IEEE 3002.2, Recommended Practice for Conducting Load-Flow Studies and Analysis of Industrial and Commercial Power Systems

An example of load flow result from ETAP

ETAP-load-flow-result
ETAP-load-flow-result