Effects of unsymmetrical power transmission system on the voltage balance and power flow capacity of the lines

Transmission lines transposition and balance loading in all phases are the initial criteria for analyzing a power system with a symmetrical model. Untransposed transmission lines have different effects on the power system like voltage unbalance, reduced power-transmission capacity of the lines and increased losses in the lines. In this paper, the effects of unsymmetrical transmission lines on the performance quality of the power system will be studied. First, the effects of asymmetry of the power system on the balance of grid voltage will be discussed as an important power quality parameter. Then, its effects on decrease of power-transmission capacity of the lines will be analyzed. Line coupling and problems such as divergence of calculations would face the use of advanced existing software for analyzing unsymmetrical networks with some difficulties. In this paper, the amount of voltage unbalance in transmission and 132kV network of a case study power system located in Khorasan province in Iran will be calculated. After calculating unused capacity of transmission lines in this system, the financial consequences of this problem will be discussed at the end.

[1]  A. Abur,et al.  Effects of nontransposed lines and unbalanced loads on state estimation , 2002, 2002 IEEE Power Engineering Society Winter Meeting. Conference Proceedings (Cat. No.02CH37309).

[2]  A.L.A. Vilaca,et al.  An analysis of costs related to the loss of power quality , 1998, 8th International Conference on Harmonics and Quality of Power. Proceedings (Cat. No.98EX227).

[3]  B. Banerjee,et al.  Assessment of Voltage Unbalance , 2001, IEEE Power Engineering Review.

[4]  M. Chindris,et al.  Propagation of unbalance in electric power systems , 2007, 2007 9th International Conference on Electrical Power Quality and Utilisation.

[5]  A.K. Singh,et al.  Some Observations on Definitions of Voltage Unbalance , 2007, 2007 39th North American Power Symposium.

[6]  B. Singh,et al.  Effects of voltage unbalance on induction motors , 2004, Conference Record of the 2004 IEEE International Symposium on Electrical Insulation.

[7]  M. Dargahi,et al.  Derating of transformers under non-sinusoidal loads , 2008, 2008 11th International Conference on Optimization of Electrical and Electronic Equipment.