A comparison of the operational performance of different types of distance protection in new energy power transmission lines

Abstract

Following a fault on an AC transmission line for new energy， the fault response of the new energy power supply can influence the operation of distance protection. Therefore， leveraging the control strategy of the new energy power supply， this study delves into alternations in impedance， system power angle， and faulty electrical quantity prior to and post-fault. It also contrasts the performance of three distance protection mechanisms： phase polarization voltage， positive-sequence polarization voltage， and sudden magnitude variation. Given that the phase voltage drops to zero when faults occur at the line outlet， a non-responsive zone is inherent in the action area of phase polarization voltage distance protection mechanism. After a fault， the phase of the positive sequence voltage is influenced by control and shifts. This presents risks of refusal to trip during an internal fault and false tripping during an external fault for positive-sequence polarization voltage phase-sequence distance protection mechanism. Regarding the sudden magnitude variation distance protection mechanism， a fault can compel a shift in the compensated voltage phase due to control influences， which could result in protection refusal or false tripping. Using the real-time digital simulator （RTDS）， a system model demonstrating the transmission of new energy via AC lines is established. A simulation analysis of the performance of the three mechanisms is performed. The findings from the simulation align seamlessly with the theoretical scrutiny.

Keywords

• new energy control response
• transmission line
• distance protection
• equivalent impedance of power supply
• system power angle
• polarization voltage