基于SHF信号采集和下混频技术的方波下局部放电测试方法

Partial Discharge Test Method Under Square Wave Based on SHF Signal Acquisition and Down-mixing Technology

方波上升和下降沿处电场快速变化引起的位移电流和空间电磁波对局部放电(partial discharge,PD)的测量造成较大干扰。为此设计并检验了一种基于超高频(super high frequency,SHF,3~30 GHz)信号采集和下混频技术,适用于方波电场下绝缘系统的PD检测方法。系统性能测试验证了SHF混频法能有效抑制方波电源的干扰,混频信号在降低频率的同时也保留了原SHF信号幅值和相位信息,且系统可检测到视在放电量20 pC左右的PD,灵敏度较好。SHF混频法与脉冲电流法和UHF法的对比实验结果表明,SHF混频法适于检测发生在绝缘强度较高材料中放电速度较快的PD。所设计系统在方波下,对环氧树脂和灌封硅胶两种绝缘封装材料进行了PD对比实验,验证了其实用性。

The displacement current and space electromagnetic waves induced by the rapid changes in the electric field at the rising and falling edges of the square wave can cause considerable interference to the measurement of partial discharge(PD).Therefore,we designed and verified a PD detection method based on super high frequency(SHF)signal acquisition and down-mixing technology,which is appliable to the insulation system under square wave.The system performance tests verify that the SHF mixing method can suppress the interference from the square wave effectively.The mixed-signal retains the SHF signal amplitude and phase while lowering the frequency.It is also verified that the designed system can detect the PD with an apparent discharge level of about 20 pC.The experimental results of PD detection show that,compared with pulsed current method and UHF method,the SHF mixing method has better performance for the PD with a faster discharge rate occurring in the material with higher dielectric strength.Furthermore,the PD experiment was performed on epoxy resin and potting silicone under square wave,verifying the feasibility of SHF-mixing method.