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为研究直流电场下的局部放电特性，开发了直流电场下局部放电的超高频信号测量系统，设计了针板、悬浮、沿面和气隙四种放电模型，通过对不同放电模型中局部放电产生的超高频信号进行测量和特性分析，研究了不同放电模型中超高频信号的频谱特性。结果表明：直流电场下不同放电模型中的局部放电可产生几百纳秒的超高频信号，其频谱分布中幅值较高的频段并不相同；在不同极性直流电场下，针板放电模型中超高频信号都存在300～500 MHz的超高频段，且负极性时还存在600～700 MHz的超高频段，除针板放电模型外的其他模型在不同极性直流电场作用下局部放电产生的超高频信号频谱较为相似；当外施直流电场升高时，局部放电产生的局部放电超高频信号的频谱幅值明显增大，但主要峰值的频率位置和频段并未发生明显变化，该特点可作为区分放电模式的有效依据。

To study the discharge characteristic under DC electric filed, we established an ultra high frequency (UHF) signal detection system of PD under DC electric filed, and designed four typical PD models including needle-plate, suspended particle, surface discharge, and cavity discharge model. The UHF signals generated by PD in different discharge models were tested, and their spectrum characteris-tics were studied. The results show that the PD in different discharge models under DC electric filed can generate UHF signals lasting for hundreds of ns, and their frequency bandwidths with high spectrum am-plitude were different. The frequency bandwidth with high spectrum amplitude of UHF signals in needle-plate discharge model under different polarities of DC electric field is between 300 MHz and 500 MHz, and the frequency bandwidth with high spectrum amplitude under negative DC is between 600 MHz and 700 MHz. The frequency spectra of UHF signals in other discahrge models except needle-plate discharge model are similar under different polarities of DC electric field. When the applied voltage increase, the spectrum amplitude of UHF signals increase obviously, and the frequency bandwidth with high spectrum amplitude and the frequency position of main peak do not change significantly, which can be used as an effective proof to distinguish discharge pattern.