A Methodology for Rating Electricity Transmission Lines to Assess the Most Important or Critical Lines

Abstract

The proposed method, based on three combined criteria—Sn—design capacity of the power line, LF, (line flow)—power flow in an electric transmission line, MVA, and the ratio of LF/Sn—allows for ranking electric transmission lines when calculations are performed in normal/pre-emergency modes. A combined set of criteria used to study critical/post-emergency N-k modes is developed. The simulations were performed on the real Baltic 330 kV electricity transmission system. The results reveal that when the power system operates in different load modes, most of the critical power lines determined by our method fall into the actual set of important/“critical” power transmission lines. This allows us to significantly reduce the number of simulated combinations and shorten the calculation time required for it. During the study of the Baltic electricity system, it was found that the developed method was accurate and efficient and suitable for the assessment of the reliability of real electricity transmission networks when planning operational and perspective work modes. The simulations results revealed the high reliability of the Baltic electricity system. The 330 kV electricity transmission network of the Baltic countries fully meets the N-2 criterion (usually, electricity transmission networks are designed to meet the N-1 criterion).

Keywords

• pre-contingency
• combined set
• ranking
• Baltic system