Research on Lightning Flashover Path Constraints of Compact Multi-Chamber Parallel Gap

The multi-chamber parallel gap (MCPG) has the advantages of simple configuration, prominent arc extinguishing performance and self-arc extinguishing function, and is widely used in lightning protection of distribution lines as a new lightning protection device. However, due to the particular configuration of the MCPG, it is different from the conventional parallel gap, and its flashover path is complex under lightning impulse. When the discharge gap is set improperly, it may cause an uncontrolled flash path and arc damage to the insulator string. In view of the deficiencies of the whole structure analysis of the existing multi-chamber arc-extinguishing structure, in this paper, the lightning impulse test of the multi-chamber arc-extinguishing structure is carried out, and the equivalent relationship between this structure and the air gap of the rod-rod electrode is calculated and analyzed. The flashover channel is confined in the multi-chamber body and the arc is quenched. It ensures the safety and stability of the transmission line, which provides a reference for the engineering design of the MCPG of the distribution line. Firstly, the constraint principle of the flashover path is analyzed, and the lightning impulse test is carried out, which obtains the lightning impulse 50% breakdown voltage of the multi-chamber arc extinguishing structure. Then, because the MCPG and the rod-rod electrode parallel gap both are in extremely non-uniform electric fields, the length of the multi-chamber arc extinguishing structure is converted into the equivalent rod-rod electrode air gap length. According to the U50% curve of the air gap of the rod-rod electrode, it is given the calculation formula of the equivalent number of chambers in a multi-chamber arc extinguishing structure. According to the equivalent calculation formula, the length of the serial outer gap can be calculated, and the multi-chamber parallel gaps with different structures can be designed. Besides, the voltage-time characteristics test is carried out to verify the feasibility of the equivalent calculation formula, and determine the length of the outer series gap of MCPG under 35 kV. Finally, the test platform of MCPG is built, and the arc quenching test is carried out, and the quenching time difference of MCPG with different structures is compared. The following conclusions can be drawn from the test result and analysis: According to the equivalent gap formula, the outer serial gap length of the MCPG with different chamber numbers is calculated. The test results show that the voltage-time characteristic curve of the composite insulator is higher than that of the multi-chamber parallel gap. Under the same amplitude of lightning impulse voltage, with the decrease of the length of the outer series gap, the MCPG is easier to break down, and the test results are consistent with the theoretical analysis. Compared with the insulator string, the MCPG is more likely to break down under the lightning impulse voltage and has the ability to constrain the flashover path and accelerate the arc extinction. It has been applied in the 35 kV distribution lines, and the line operation and maintenance records show that the protection effect is noteworthy. © 2023 Chinese Machine Press. All rights reserved.