Difference between Newton Raphson and Fast Decoupled

Difference between Newton Raphson and Fast Decoupled Load flow methods

Comparison between Newton Raphson and Fast Decoupled

  • The Key Difference between Newton Raphson and Fast Decoupled are in the below comparison chart.

Comparison Chart

Fast Decoupled Newton Raphson
Co-ordinates Polar coordinates Polar co-ordinates are preferred as rectangular coordinates occupy more memory.
Arithmetical operations Less than Newton Raphson. Elements of jacobian to be calculated in each iteration .
Time Less time compared to NR and GS methods. Time/iteration is 7 times of GS and increases with an increase in the number of buses.
Convergence Geometric convergence Quadratic convergence
No. of iterations Only 2 to 5 iterations for practical accuracies. Very less (3 to 5 only) for large system and is practically constant.
Slack bus selection Moderate Sensitivity to this is minimal
Accuracy Moderate More accurate
Memory Only 60% of memory when compared to NR method. Large memory even with compact storage scheme
Usage/application Optimization studies, multi-load flow studies, contingency evaluation for security assessment and enhancement. A large system, ill-conditioned problems, optimal load flow studies.
Programming Logic Moderate Very difficult
Reliability More reliable than NR method. Also, Reliable for large system

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