Perfecting performance of distance protective relays and it´s associated pilot protection schemes in extra high voltage (EHV) transmission line applications

The fundamentals of protective relaying of EHV transmission lines such as 345 kV is to ensure secure protection for all line s internal faults, and stable operation for all foresee-able external faults during system contingencies. This paper provides an overview of how utilities have traditionally applied distance protection relays and its associated pilot protection schemes for protecting EHV transmission lines. These traditional methods cover most aspects of the protection and control of EHV lines, however these methods lack in performance when they are subjected to actual power system and fault conditions. This paper highlights the needs in perfecting distance protection relays and its associated pilot protection schemes for EHV transmission lines ensuring reliable performance during all foresee-able system load and fault conditions. This paper also compares the findings of a real time closed loop study against with traditional methods of protecting and controlling a 345 kV EHV transmission line, and provides guidelines to ensure dependable performance of distance protective relays during dynamic system conditions