Selection Standard of Zinc Oxide Lightning Arrester (2)

Ensure the selection and necessity of the arrester when operating under single-phase grounding overvoltage and the power system is safe

From the perspective of safe operation, the selection of the rated voltage of the arrester should also comply with the following principles:

① The rated voltage of the zinc oxide arrester should be higher than the power frequency transient voltage that may appear at the installation site. In the neutral grounding system of 110kV and above, it can be selected according to the above method.

②In the 110kV and below neutral point indirect grounding system, the electric power department regulations stipulate that the operation is allowed for 2h in the case of single-phase grounding, and sometimes even when the arc grounding overvoltage is generated intermittently, the fault can be found after running for more than 2h. The operating characteristics of such systems pose a serious threat to the safe operation of zinc oxide arresters under rated voltage for 10s. In addition, the structure and design of the zinc oxide arrester and the SiC arrester are different (the latter has a gap to extinguish the arc, the former has no gap or only a current isolation gap), which makes the zinc oxide arrester suffer thermal collapse or even serious explosion accidents in practice. In the face of this situation, many power supply bureaus and power design institutes have proposed many types of rated voltage values (such as 14.4kV, 14.7kV, etc.) according to the power grid conditions in various regions. In many national standard discussion drafts, the rated voltage withstand 10s during the action load test is increased to 1.2-1.3 times, which improves the adaptability of the zinc oxide arrester to the operating conditions of the neutral point indirect grounding system.

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