基于通道级联高频并采的配电终端高速采样方案设计与实现

Design and Implementation of a High Speed Sampling Scheme for DTU Based on Channel Cascade High Frequency Parallel Acquisition

目前国网配电终端的招标量越来越大,且对配电终端产品的功能要求也越来越多,除了要保证基本的三遥与历史数据记录功能外,还需要具有小电流接地判断能力。对于小电流接地算法,需要大采样率作为支撑,以便于抓取接地瞬间的暂态特征波形并计算高次谐波。常规装置硬件设计都是采用高性能的CPU处理器,比如PowerPC加FPGA实现高速采样与计算,但是这样的方案设计使得装置硬件成本直线上升。为此,设计一种配电终端用的低成本高速高性能解决方案,该方案能够提供每周波160点(8 kHz)的高采样率和低中断计算负荷率(1 kHz)来满足小电流接地功能的需求。通过实际测试,该方案可以在普通的低端平台CPU上实现高采样率,并以低中断负荷率进行算法计算;通过继电保护测试仪加量测试,能够正确识别接地波形,且对接地波形能够正常进行故障录波,对降低配电终端产品成本起到了促进作用。

At present,the bidding volume of distribution terminals of State Grid is increasing,and there are more and more functional requirements for distribution terminal product.In addition to ensuring the basic three remote and historical data recording functions,it also needs to have the ability to judge small current grounding.For the small current grounding algorithm,a large sampling rate is needed to capture the transient characteristic waveform at the grounding moment and calculate the high-order harmonic.Conventional device hardware design adopts high-performance CPU processor,such as PowerPC and FPGA to realize high-speed sampling and calculation.However,such scheme design makes the hardware cost of the device rise sharply.Therefore,a low cost high speed and high performance solution for power distribution terminal is designed,which can provide high sampling rate of 160 points per week(8 kHz)and low interrupt calculation load rate of 1 kHz to meet the requirement of low current grounding function.Through the actual test,the scheme can achieve high speed sampling rate on the common low-end platform CPU and calculate the algorithm with low interrupt load rate.Through the dosing test of relay protection tester,the scheme can correctly identify the grounding waveform,and the fault waveform can be recorded normally,which can reduce the cost of distribution terminal products.