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摘要: 为探讨脉冲方波电压频率对局部放电特性的影响,基于超高频(UHF)检测方法和IEEE 488.2传输协议,构建了宽频、高速数据采集局部放电测试系统.利用该系统,研究了变频电机耐电晕漆包线的局部放电脉冲幅值、相位和时频特性.研究结果表明:频率200 Hz以上的高频脉冲电压使空间电荷扩散效应减小,增大了局部放电初始电子产生的概率,使得局部放电瞬时电压降低,出现幅值小于200 mV的局部放电脉冲.在高频脉冲电压下,当局部放电发生在电压上升时段时,快速变化的电压幅值将改变局部放电特性,使得局部放电脉冲在1~2 GHz高频能量的比重增大.因此,根据相关标准检测变频电机局部放电时,为易于激发绝缘薄弱点处局部放电,宜采用频率低于200 Hz的低频脉冲方波电压,且局部放电超高频传感器在1.2 GHz及以上频率处应具有较好的增益特性,并采用500 MHz的高通滤波器,以提高测试系统的信噪比.
关键词: 变频电机;局部放电;脉冲方波电压;超高频;时频分析;数据采集
中图分类号: TM344.6文献标志码: A Influence of Frequency of Impulsive Square Wave Voltage on
可见,在快速上升的脉冲电压下,放电发生在脉冲上升时间时,放电过程中的电压变化会改变局部放电脉冲特性[1012],这可能是导致局部放电高频能量成分增加的原因.4测试电源频率选取及传感器设计基于以上试验结果及机理分析,在较高频率的脉冲电压下,由于初始电子更易产生,导致放电延迟减小,局部放电脉冲距离电源干扰脉冲(脉冲方波电源逆变产生的干扰[4,9])时间间隔较短(见图2(b)),因此可能导致电源干扰和局部放电脉冲的叠加.此时如果不采取合适的滤波策略,局部放电信号将被淹没在电源干扰中,给放电测试带来一定困难.
值得指出的是,当脉冲频率继续增加时,电压极性翻转后放电处电压虽超过了起始放电电压,但在下次电压极性反转时可能没有初始电子产生,此时局部放电就不会在每个周期出现,需要更高的外部激发电压以增大初始电子产生概率,因此,在实际测试中可能得到比低频脉冲电压偏小的PDIV和RPDIV测试结果.
由于高电源频率导致局部放电高频能量增加,且电源干扰和局部放电时间间隔减小,为提高信噪比,必须设计高频响应较好的超高频传感器,配合后端高通滤波器,才能提取到局部放电,从而得到较为准确的PDIV和RPDIV测试结果.
综上所述,在变频电机局部放电检测中,为确保局部放电初始电子产生,激发绝缘缺陷或薄弱点的局部放电,应优先考虑采用低频(如<200 Hz)脉冲电压,以促使相对高幅值的局部放电发生在脉冲电源干扰之后,从而提高测试灵敏度.在进行较高频率下的局部放电测试时,应提高超高频传感器的高频响应性能,从而有效提取出局部放电脉冲.5结论通过所设计的检测系统及对不同频率下的单点接触试样局部放电测试,可得到以下结论:
(1) 根据IEC标准进行变频电机的局部放电测试时,应根据电源干扰脉冲和局部放电的频域能量特性,选取合适超高频传感器和滤波方案,从而提高信噪比.本研究中,局部放电能量主要集中在1.2 GHz处,采用500 MHz高通滤波器可有效抑制陡脉冲电源下的干扰.
(2) 脉冲电源频率对放电相位和幅值具有较大影响,高频下初始电子产生概率的增加使得放电延迟减小并导致放电时的瞬时激发电压降低,促使较低幅值的局部放电脉冲产生.
(3) 在脉冲电压下的变频电机局部放电检测中,为确保激发绝缘缺陷或薄弱点的局部放电,应优先考虑采用较低频率的脉冲电压.
当在高频电压下测试时,应提高超高频传感器的高频(>1.2 GHz)响应性能,并结合高通滤波模块,才可有效从强电源干扰中提取局部放电信号.
参考文献:
[1]CAVALLINI A, FABIANI D, MONTANARI G C. Power electronics and electrical insulation systemspart 1:phenomenlogy overview[J]. IEEE Electrical Insulation Magazine, 2010, 26(3): 715.
[2]KAUFHOLD M, BORNER G, EBERHARDT M, et al.Failure mechanism of the interturn insulation of low voltage electric machines fed by pulsecontrolled inverters[J]. IEEE Electrical Insulation Magazine, 1996, 12(5): 916.
[3]YIN Weijun. Failure mechanism of winding insulation in inverterfed motors[J]. IEEE Electrical Insulation Magazine, 1997, 13(6): 1823.
[4]TOZZI M, CAVALLINI A, MONTANARI G C. Monitoring offline and online PD under impulsive voltage on induction motorspart 1:standard procedure[J]. IEEE Electrical Insulation Magazine, 2010, 26(4): 1626.
[5]CAVALLINI A, LINDELL E, MONTANARI G C. Offline PD testing of converterfed wirewound motors: when IEC TS 600341841 may fail[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2010, 17(5): 13851395. (下转第270页)[6]FORSSEN C, EDIN H. Partial discharges in a cavity at variable A[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2008, 15(6): 10611069.
[7]CAVALLINI A, MONTANARI G C. Effect of supply voltage frequency on testing of insulation system[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2006, 13(1): 111121.
[8]HAZLEEI A, CHEN G, LEVWIN P L. Partial discharge behavior within a spherical cavity in a solid dielectric material as a function of frequency and amplitude of the applied voltage[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2011, 18(2): 432443.
[9]LINDELL E, BENGTSSON T, BLENNOW J, et al. Influence of rise time on partial discharge extinction voltage at semisquare voltage waveforms[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2010, 17(1): 141148.
[10]HAMMARSTROM T, BENGTSSON T, BLENNOW J, et al. Evidence for changing PD properties at short voltage rise times[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2011, 18(5): 16861692.
[11]WU Kai, PAN Cheng, GAO Minggang, et al. Effects of rising rate of square voltage on PD characteristics in aging process[C]∥International Conference on Condition Monitoring and Diagnosis. Tokyo: [s.n.], 2010: 573576.
[12]CAVALLINI A, LINDELL E, MONTANARI G C, et al. Inception of partial discharge under repetitive square voltages: effect of voltage waveform and repetition rate on PDIV and RPDIV[C]∥Annual Report Conference on Electrical Insulation and Dielectric Phenomena. West Lafayette: [s.n.], 2010: 14.
[13]FABIANI D, CAVALLINI A, MONTANARI G C. A UHF technique for advanced PD measurements on inverterfed motors[J]. IEEE Transactions on Power Electronics, 2008, 23(5): 25462556.
[14]LUTZ N. A generalized approach to partial discharge modeling[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 1995, 2(4): 729743.
[15]GUTFLEISCH F, NIEMEYER L. Measurement and simulation of PD in epoxy voids[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 1995, 2(5): 510528.
[16]KIMURK K, OKADA S, HIKITA M. Electromagnetic wave in GHz region of PD pulses under short rise time repetitive voltage impulses[C]//International Symposium on Electrical Insulating Materials. Yokkaichi: [s.n.], 2008: 633636.
[17]KEN K, SOJIRO U, TAKAHIRO, et al. PDIV characteristics of twistedpair of magnet wires with repetitive impulse voltage[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2007, 14(3): 744750.
(中文编辑:唐晴英文编辑:付国彬)删a.表明,高频下局部放电延迟时间缩短,使得局部放电激发电压降低,从而产生低幅值的局部放电脉冲.通过不同频率下局部放电频域分析,发现高频电压下的局部放电在高频范围内(1.6 GHz)具有较高能量成分周凯,吴广宁,何景彦,等. 脉冲电压下局部放电信号的提取和统计[J]. 西南交通大学学报,2008,43(03): 320325.
ZHOU Kai, WU Guangning, HE Jingyan, et al. Extraction and counting of partial discharges under pulse voltage[J]. Journal of Southwest Jiaotong University, 2008, 43(03): 320325.
关键词: 变频电机;局部放电;脉冲方波电压;超高频;时频分析;数据采集
中图分类号: TM344.6文献标志码: A Influence of Frequency of Impulsive Square Wave Voltage on
可见,在快速上升的脉冲电压下,放电发生在脉冲上升时间时,放电过程中的电压变化会改变局部放电脉冲特性[1012],这可能是导致局部放电高频能量成分增加的原因.4测试电源频率选取及传感器设计基于以上试验结果及机理分析,在较高频率的脉冲电压下,由于初始电子更易产生,导致放电延迟减小,局部放电脉冲距离电源干扰脉冲(脉冲方波电源逆变产生的干扰[4,9])时间间隔较短(见图2(b)),因此可能导致电源干扰和局部放电脉冲的叠加.此时如果不采取合适的滤波策略,局部放电信号将被淹没在电源干扰中,给放电测试带来一定困难.
值得指出的是,当脉冲频率继续增加时,电压极性翻转后放电处电压虽超过了起始放电电压,但在下次电压极性反转时可能没有初始电子产生,此时局部放电就不会在每个周期出现,需要更高的外部激发电压以增大初始电子产生概率,因此,在实际测试中可能得到比低频脉冲电压偏小的PDIV和RPDIV测试结果.
由于高电源频率导致局部放电高频能量增加,且电源干扰和局部放电时间间隔减小,为提高信噪比,必须设计高频响应较好的超高频传感器,配合后端高通滤波器,才能提取到局部放电,从而得到较为准确的PDIV和RPDIV测试结果.
综上所述,在变频电机局部放电检测中,为确保局部放电初始电子产生,激发绝缘缺陷或薄弱点的局部放电,应优先考虑采用低频(如<200 Hz)脉冲电压,以促使相对高幅值的局部放电发生在脉冲电源干扰之后,从而提高测试灵敏度.在进行较高频率下的局部放电测试时,应提高超高频传感器的高频响应性能,从而有效提取出局部放电脉冲.5结论通过所设计的检测系统及对不同频率下的单点接触试样局部放电测试,可得到以下结论:
(1) 根据IEC标准进行变频电机的局部放电测试时,应根据电源干扰脉冲和局部放电的频域能量特性,选取合适超高频传感器和滤波方案,从而提高信噪比.本研究中,局部放电能量主要集中在1.2 GHz处,采用500 MHz高通滤波器可有效抑制陡脉冲电源下的干扰.
(2) 脉冲电源频率对放电相位和幅值具有较大影响,高频下初始电子产生概率的增加使得放电延迟减小并导致放电时的瞬时激发电压降低,促使较低幅值的局部放电脉冲产生.
(3) 在脉冲电压下的变频电机局部放电检测中,为确保激发绝缘缺陷或薄弱点的局部放电,应优先考虑采用较低频率的脉冲电压.
当在高频电压下测试时,应提高超高频传感器的高频(>1.2 GHz)响应性能,并结合高通滤波模块,才可有效从强电源干扰中提取局部放电信号.
参考文献:
[1]CAVALLINI A, FABIANI D, MONTANARI G C. Power electronics and electrical insulation systemspart 1:phenomenlogy overview[J]. IEEE Electrical Insulation Magazine, 2010, 26(3): 715.
[2]KAUFHOLD M, BORNER G, EBERHARDT M, et al.Failure mechanism of the interturn insulation of low voltage electric machines fed by pulsecontrolled inverters[J]. IEEE Electrical Insulation Magazine, 1996, 12(5): 916.
[3]YIN Weijun. Failure mechanism of winding insulation in inverterfed motors[J]. IEEE Electrical Insulation Magazine, 1997, 13(6): 1823.
[4]TOZZI M, CAVALLINI A, MONTANARI G C. Monitoring offline and online PD under impulsive voltage on induction motorspart 1:standard procedure[J]. IEEE Electrical Insulation Magazine, 2010, 26(4): 1626.
[5]CAVALLINI A, LINDELL E, MONTANARI G C. Offline PD testing of converterfed wirewound motors: when IEC TS 600341841 may fail[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2010, 17(5): 13851395. (下转第270页)[6]FORSSEN C, EDIN H. Partial discharges in a cavity at variable A[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2008, 15(6): 10611069.
[7]CAVALLINI A, MONTANARI G C. Effect of supply voltage frequency on testing of insulation system[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2006, 13(1): 111121.
[8]HAZLEEI A, CHEN G, LEVWIN P L. Partial discharge behavior within a spherical cavity in a solid dielectric material as a function of frequency and amplitude of the applied voltage[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2011, 18(2): 432443.
[9]LINDELL E, BENGTSSON T, BLENNOW J, et al. Influence of rise time on partial discharge extinction voltage at semisquare voltage waveforms[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2010, 17(1): 141148.
[10]HAMMARSTROM T, BENGTSSON T, BLENNOW J, et al. Evidence for changing PD properties at short voltage rise times[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 2011, 18(5): 16861692.
[11]WU Kai, PAN Cheng, GAO Minggang, et al. Effects of rising rate of square voltage on PD characteristics in aging process[C]∥International Conference on Condition Monitoring and Diagnosis. Tokyo: [s.n.], 2010: 573576.
[12]CAVALLINI A, LINDELL E, MONTANARI G C, et al. Inception of partial discharge under repetitive square voltages: effect of voltage waveform and repetition rate on PDIV and RPDIV[C]∥Annual Report Conference on Electrical Insulation and Dielectric Phenomena. West Lafayette: [s.n.], 2010: 14.
[13]FABIANI D, CAVALLINI A, MONTANARI G C. A UHF technique for advanced PD measurements on inverterfed motors[J]. IEEE Transactions on Power Electronics, 2008, 23(5): 25462556.
[14]LUTZ N. A generalized approach to partial discharge modeling[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 1995, 2(4): 729743.
[15]GUTFLEISCH F, NIEMEYER L. Measurement and simulation of PD in epoxy voids[J]. IEEE Transaction on Dielectrics and Electrical Insulation, 1995, 2(5): 510528.
[16]KIMURK K, OKADA S, HIKITA M. Electromagnetic wave in GHz region of PD pulses under short rise time repetitive voltage impulses[C]//International Symposium on Electrical Insulating Materials. Yokkaichi: [s.n.], 2008: 633636.
[17]KEN K, SOJIRO U, TAKAHIRO, et al. PDIV characteristics of twistedpair of magnet wires with repetitive impulse voltage[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2007, 14(3): 744750.
(中文编辑:唐晴英文编辑:付国彬)删a.表明,高频下局部放电延迟时间缩短,使得局部放电激发电压降低,从而产生低幅值的局部放电脉冲.通过不同频率下局部放电频域分析,发现高频电压下的局部放电在高频范围内(1.6 GHz)具有较高能量成分周凯,吴广宁,何景彦,等. 脉冲电压下局部放电信号的提取和统计[J]. 西南交通大学学报,2008,43(03): 320325.
ZHOU Kai, WU Guangning, HE Jingyan, et al. Extraction and counting of partial discharges under pulse voltage[J]. Journal of Southwest Jiaotong University, 2008, 43(03): 320325.