Determining the Correct Electrical Resistance of Conductors in Power Systems Analysis

The electrical resistance of a conductor varies with its material (e.g., copper or aluminum) and operating temperature. This paper discusses the importance of determining conductor resistance at the appropriate temperature for voltage drop calculations, short-circuit current assessments, and ground-fault current evaluations in power system design. To normalize conductors based on their electrical characteristics, standards specify nominal cross-sectional areas uniquely associated with specific resistance values per unit length at 20∘ C. These resistance values, considering the metal’s resistivity, can be reliably measured, eliminating the need for potentially unreliable physical measurements, especially in stranded wires. The paper highlights the need for conservative approaches in voltage drop calculations by considering maximum operating temperatures of insulation materials and outlines the methodologies for accurately determining the resistance for maximum and minimum prospective short-circuit currents calculations. Additionally, it addresses the significance of proper ground-fault currents calculations to ensure speedy protective device operation, thereby enhancing system safety and reliability. The principles and standards herein discussed are applicable across various global power systems, underscoring the universal importance of standardized practices in electrical resistance calculations.