Effect of commutation failure on the distance protection and the countermeasures

Abstract

Commutation failure (CF) may be caused by AC fault in AC/DC interconnected system, and it will affect the performance of distance protection. The transient characteristic of equivalent current of power-frequency of the dc-ac inverter is first analysed by introducing the concept of quadrant. Then, the effect of CF on distance protection is studied in detail with consideration of the connection mode of distance relay. The analysis results show that both the fault position and fault resistance contribute to the effect of CF on the performance of distance protection significantly. Furthermore, a novel countermeasure based on the amplitude of second harmonic is put forward, and a concept of 'successive trip' by using the change of measured reactance is also presented. Simulation results based on PSCAD/ EMTDC prove the correctness of these conclusions.

Reduction of Commutation Failure Frequency in HVDC Transmission Systems by Means of an Improved Solid-State Fault Current Limiter

“…Such an AC voltage reduction leads to the decrease of the DC voltage. However, since the transmitted power in an HVDC system is controlled to be constant, the DC voltage drop leads to the sudden increase of the DC current which is proportional to according to (3). Therefore, according to Fig.…”

“…In VSCs, Insulated gate bipolar transistor (IGBT) switches are used which have superior controllability, while the switching of LCCs is performed by thyristors with only turn-off capability. Therefore, LCCs are vulnerable to commutation failure which is mainly caused by the voltage drop at the inverter AC system [3].…”

A novel AC line distance protection scheme for AC/DC hybrid system based on fault likeness factor

“…When in-zone fault occurs on AC line M-N, there is not fault point in DC system, thus (1), ( 2), ( 5), ( 6) are satisfied, and currents i ma , i mb and i mc calculated according to (16)…”

“…Compared to current protection and voltage protection, the protection range and sensitivity of distance protection based on power-frequency variables is less affected by the variation of operation mode of AC system. However, when DC system is integrated to AC system, AC-side fault may cause commutation failure in DC system, which will cause the equivalent feed-in current from DC system to AC system to change suddenly [13][14][15], thus the measured impedance will fluctuate, resulting in narrowed protection range or over-reach operation [16][17][18]. Time-domain distance protection is usually based on the assumption that the current distribution coefficients are constant, and uses parameter estimation method to calculate the fault distance [19].…”

Prevention and mitigation of high‐voltage direct current commutation failures: a review and future directions

“…A single CF can lead to consecutive or recurrent CFs and cause stability problems throughout the entire grid, such as angle stability issues at the sending end and voltage stability issues at the receiving end. In addition, CFs can decrease the reliability and sensitivity of relay protection systems or further initiate power shortages [3–5]. In heavy‐load areas, such as northeastern Brazil and those served by the China Southern Power Grid and East China Power Grid, multiple LCC‐HVDC links feed the system.…”