It is crucial for cast resin transformer to detect void and delamination existing in the cast resin because these defects reduce insulation performance of cast resin equipment. Furthermore, defects are likely to be mixed in cast resin because of several surface boundaries between resin and conductor. It is considered that detecting partial discharge (PD) is effective to diagnose equipment of power equipment. However, it is reported that withstand lightning impulse voltage test may give influence on AC partial discharge test, especially partial discharge inception voltage. This paper deals with accumulated charge in a void under AC voltage to investigate the effect of the impulse voltage prestress on subsequent AC PD characteristics in cast resin transformer. AC PD characteristics were compared before and after impulse application. In addition, recovery of PD characteristics was measured to investigate charge decay. As a result, the mechanism of prestress effect is revealed and surface charge density is estimated quantitatively in cast resin transformer.

中文翻译：

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雷电预应力对浇铸树脂变压器交流局部放电特性的影响

铸造树脂变压器检测铸造树脂中存在的空隙和分层至关重要，因为这些缺陷会降低铸造树脂设备的绝缘性能。此外，由于树脂和导体之间的多个表面边界，缺陷可能混入铸塑树脂中。认为检测局部放电（PD）对于诊断电力设备的设备是有效的。然而，据报道，雷电冲击电压测试可能会影响交流局部放电测试，特别是局部放电起始电压。本文针对交流电压下空隙中的累积电荷进行研究，以研究脉冲电压预应力对浇铸树脂变压器中后续交流电局部放电特性的影响。在脉冲施加之前和之后比较AC PD特性。此外，测量PD特性的恢复以研究电荷衰减。结果，揭示了预应力作用的机理，并定量估计了铸塑树脂变压器中的表面电荷密度。