A Fast Directional Protection Method for DC Distribution Network Based on Current/Voltage High Frequency Traveling Wave Ratio

Abstract

The invention discloses a fast direction protection method for a DC distribution network based on current / voltage high-frequency traveling-wave ratio. After the protection is started, high-pass filtering is performed on the measured voltage and current signals to obtain high-frequency components; according to |u Sb_hf |and|u Sc_hf The ratio of | determines whether it is a DC fault, if max|u Sb_hf | / max|u Sc_hf |>k set1 , it is determined to be a DC cable fault; step 4, after determining the DC fault, further distinguish faulty cables from non-faulty cables in the case of a DC bus connected to multiple DC cables. Compared with the prior art, the present invention is based on an accurate line model, takes into account the impact of line geometric parameters on protection, avoids the threat of large line wave impedance differences to protection reliability, and is suitable for DC power distribution systems, especially MVDC power distribution system.

Description

technical field [0001] The invention relates to the field of relay protection of a DC power distribution system, in particular to a fast direction longitudinal protection method for a DC power distribution network based on the current / voltage high-frequency reverse traveling wave amplitude ratio. Background technique [0002] DC line protection is one of the key technologies in the development of DC systems, and fast and reliable judgment of the fault direction is an indispensable key link for the rapid protection of DC lines. [0003] The existing DC distribution level longitudinal protection part considers the influence of line distribution parameters and frequency variable parameters on protection, but does not consider the influence of parameter differences of different lines on protection. In different types of transmission conductors (conductors and overhead lines), different Geometric parameters (cable inner diameter, insulation type, thickness, buried depth, and rela...

AI Technical Summary

Problems solved by technology

This means that conventional current differential protection cannot reliably distinguish between internal and external faults

Similarly, the directional protection based on Δi or di / dt is also seriously affected by the distributed capacitive current due to its oscillation characteristics

To sum up, for MVDC power distribution system, when designing DC protection, it is unreasonable to ignore the influence of distributed capacitive current and line wave impedance difference, and rely on line terminal boundaries

Images