基于脉冲触发和锁峰采样的低成本特高频局部放电采样系统设计

Design of Low-Cost Ultra-High Frequency Partial Discharge Sampling System Based on Pulse Triggering and Peak-Locking Sampling

特高频(UHF)局部放电传感器的高灵敏度和优越抗干扰能力,使其成为电力设备绝缘诊断的重要局放传感器之一,在变压器、GIS等多种场合得到成功应用。传统的降频采样技术将千兆赫兹的特高频信号降频至几十兆赫兹的包络检波信号,仍需百兆赫兹级的采样电路以确保对峰值及其相位信息的准确测量,较高的硬件成本限制了该技术在配网应用领域的推广与普及。提出了一种低成本特高频局放采样电路设计方案,该方案设计了一套基于特有的脉冲触发和峰值保持技术,在与传统降频检波技术相配合的情况下,利用FPGA编写的触发及控制逻辑,实现了在几兆赫兹采样频率情况下的精确局放信号采样,并且,其中滤波器的设计不仅能够降低监测频率外的干扰,亦可以抑制特高频段内手机信号的干扰。测试结果表明,该套采样电路可实现250ns的脉冲分辨率,局放脉冲采样误差优于1.5dBm,小信号局放漏检率可低至5%,在低成本前提下完全满足监测需求,精度远高于同类产品。

The ultra-high frequency(UHF)partial discharge sensor has become one of the important local discharge sensors in the insulation diagnosis of power equipment due to its high sensitivity and superior antiinterference ability,and it has been successfully applied in transformer,GIS and so on.The traditional downgrade frequency sampling technique reduces the UHF signal of gigahertz to the envelope detection signal of tens of megahertz,but still requires the sampling circuit of hundred-megahertz to ensure the accurate measurement of the peak value and its phase information,and the high hardware cost limits the popularization and popularity of this technology in the field of distribution network application.This paper presents a design scheme of low-cost ultra-high frequency local discharge sampling circuit.The design of this scheme is based on a set of unique pulse triggering and peak-holding technology.In the case of cooperating with the traditional downgrade frequency detection technology,the trigger and control logic written by FPGA is used to realize accurate local discharge signal sampling at several megahertz sampling rate,and the filter design can not only reduce the interference outside the monitoring frequency,but also suppress the interference of the mobile phone signal in the ultra-high frequency band.The test results are shown as follows:This set of sampling circuit can achieve a pulse resolution of 250 ns;the sampling error of local discharge pulse is better than 1.5 dBm;the omission ratio of the small signal local discharge can be as low as 5%,which fully meets the monitoring requirements under the premise of low cost;the accuracy is much higher than that of similar products.