When the arrester is activated by overvoltage, will the residual magnetism of the lightning arrester wound core affect its recovery performance?
Publish Time: 2025-05-07
In the power system, the arrester, as a key protection device, bears the important responsibility of limiting overvoltage and protecting electrical equipment from damage by lightning or operating overvoltage. As one of the core components of the arrester, the magnetic properties of the wound core have a direct impact on the overall performance of the arrester. When the arrester is activated by overvoltage, residual magnetism may remain in the wound core. Whether this phenomenon will affect the recovery performance of the arrester is worth further discussion.
The arrester is in a high-resistance state under normal operating voltage, with only microampere current flowing through it, which is equivalent to an insulator. When subjected to an overvoltage shock, the resistance of the internal components of the arrester (such as the zinc oxide valve plate) drops sharply, and the current increases instantly, releasing the overvoltage energy through the grounding wire. After the action is completed, the arrester needs to return to a high-resistance state to maintain the normal operation of the system. However, the wound core may produce residual magnetism due to magnetization during the overvoltage action, resulting in irreversible changes in its magnetic properties.
The presence of residual magnetism will change the hysteresis loop characteristics of the wound core, causing it to deviate from the initial symmetric state. In subsequent operation, this asymmetry may cause the arrester to deviate from the response of the arrester at the same voltage. For example, when the system voltage returns to normal levels, the residual magnetism may cause the magnetic permeability of the wound core to decrease, thereby increasing the excitation current of the arrester. This change will not only reduce the energy absorption efficiency of the arrester, but may also cause local overheating and accelerate the aging of the insulating material.
The impact of residual magnetism on the recovery performance of the arrester is also reflected in the dynamic response. After the overvoltage action, the arrester needs to quickly recover to a high-resistance state to cope with the next impact. If residual magnetism remains in the wound core, its magnetization process may be disturbed, resulting in a longer recovery time. This delay is particularly critical in high-frequency overvoltage scenarios, which may prevent the arrester from limiting subsequent overvoltages in time, thereby threatening system safety.
Experimental studies have shown that the degree of influence of residual magnetism on the performance of the arrester is closely related to the size and direction of residual magnetism. When the direction of residual magnetism is consistent with the direction of subsequent magnetization field, it may accelerate the saturation of magnetic flux, causing the arrester to enter the nonlinear region in advance; on the contrary, if the direction is opposite, it may induce hysteresis effect and increase energy loss. In addition, residual magnetism may also change the volt-ampere characteristic curve of the arrester, increase its leakage current at low voltage, and affect the accuracy of insulation monitoring.
In order to reduce the impact of residual magnetism on the recovery performance of the arrester, measures can be taken from both design and operation and maintenance. In the design stage, the material and structure of the wound core can be optimized, magnetic materials with low residual magnetism coefficient can be selected, or the magnetic flux concentration can be reduced by layered winding process. In the operation and maintenance stage, it is recommended to demagnetize the arrester regularly and use AC demagnetization method to gradually reduce the residual magnetism level. At the same time, the online monitoring of the arrester should be strengthened, and the residual magnetism accumulation problem should be discovered and dealt with in time by analyzing the changes in parameters such as leakage current and resistive current.
The residual magnetism of the lightning arrester wound core may indeed affect its recovery performance. In order to ensure the reliable operation of lightning arresters in complex electromagnetic environments, comprehensive measures must be taken from multiple dimensions such as material selection, structural design, and operation and maintenance management to minimize the negative impact of residual magnetism.
