Difference between Newton Raphson and Fast Decoupled

Difference between Newton Raphson and Fast Decoupled Load flow methods

Contents

The Key Difference between Newton Raphson and Fast Decoupled are in the below 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