WO2023072174A1 - 抽水蓄能发电电动机vpi线棒绝缘热机械劣化的判定方法 - Google Patents

抽水蓄能发电电动机vpi线棒绝缘热机械劣化的判定方法 Download PDF

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WO2023072174A1
WO2023072174A1 PCT/CN2022/127843 CN2022127843W WO2023072174A1 WO 2023072174 A1 WO2023072174 A1 WO 2023072174A1 CN 2022127843 W CN2022127843 W CN 2022127843W WO 2023072174 A1 WO2023072174 A1 WO 2023072174A1
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wire rod
insulation
vpi
determining
data
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PCT/CN2022/127843
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English (en)
French (fr)
Inventor
刘向东
聂靓靓
李青
黄明浩
凌鹏
贾亚琳
赵亚康
蒋军
陶诗迪
黄文汉
陈绪滨
肖畅
谢旋
陈皓南
齐鹏超
胡冬阳
杨海霞
胡德江
柳艳红
张娜
黄译锋
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南方电网调峰调频发电有限公司检修试验分公司
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Priority to US18/273,892 priority Critical patent/US11892496B1/en
Publication of WO2023072174A1 publication Critical patent/WO2023072174A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/045—Analysing solids by imparting shocks to the workpiece and detecting the vibrations or the acoustic waves caused by the shocks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
    • G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
    • G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
    • G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/46—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by spectral analysis, e.g. Fourier analysis or wavelet analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/025—Change of phase or condition
    • G01N2291/0258—Structural degradation, e.g. fatigue of composites, ageing of oils

Definitions

  • the present application relates to the technical field of thermal-mechanical degradation determination of wire rod insulation, for example, to a method for determining thermal-mechanical degradation of VPI wire rod insulation of a pumped-storage generator motor.
  • the main functions of pumped-storage generator motors include power grid peak-shaving functions and valley-filling functions, so the units need to be started and stopped frequently.
  • the current of the copper conductor of the fixed-speed pumped-storage generator motor rod and the variable-speed pumped-storage generator motor's stator and rotor rod will change drastically, resulting in a sudden change in temperature. Due to the difference in thermal expansion coefficient between the copper conductor and the epoxy mica insulation, internal shear stress is generated, which will cause thermal mechanical deterioration of the insulation and generate partial discharge. run.
  • Thermomechanical degradation is a unique characteristic of insulation degradation of pumped storage units.
  • the cold and hot cycle test method for testing this feature is also formulated based on the insulation failure characteristics of pumped storage units that have been in operation for many years at home and abroad.
  • the cold and hot cycle test is a method recognized at home and abroad to cause insulation mechanical deterioration.
  • the mechanical deterioration state can be judged by the insulation electrical diagnostic test.
  • the copper hammer percussion method is a simple and suitable method for detecting the insulation state of the power station site.
  • "Empty” means that there is an air gap in the insulation, and partial discharge is easy to occur during operation.
  • the disadvantage is that the type of insulation deterioration and the severity of the discharge cannot be determined. Therefore, up to now, there is no solution for on-site water pumping in power stations. Appropriate method for judging thermal-mechanical degradation of insulation of energy-storage units.
  • the embodiment of the present application provides a method for judging the thermomechanical degradation of wire rod insulation in vacuum pressure impregnation (Vacuum Pressure Impregnating, VPI) for pumped storage generator motors.
  • This application provides a method for determining thermal-mechanical deterioration of VPI wire rod insulation of pumped storage generator motors, including:
  • the wire rod is hit with a copper hammer, and the sound acquisition and analysis system is used for signal processing to determine the spectrum characteristics under the thermomechanical degradation state as a degradation criterion.
  • Fig. 1 is the method block diagram of the present application
  • Fig. 2 is a schematic block diagram of sound measurement and analysis in this application.
  • the method for judging thermal-mechanical deterioration of VPI wire rod insulation of pumped storage generator motors includes the following steps:
  • the result of the interpretation is that the data is unqualified, hit the wire rod with a copper hammer, and use the sound acquisition and analysis system for signal processing to determine the spectrum characteristics under the state of thermomechanical degradation as the degradation criterion.
  • thermomechanical degradation of the VPI wire rod of the pumped storage generator motor is judged, and the thermal cycle test is carried out according to the variation amplitude of the insulation operating temperature of the air-cooled pumped storage generator motor.
  • the relationship between the thermal mechanical degradation of the insulation and the change trend of the dielectric loss factor is determined.
  • a widely used copper hammer is used to strike
  • the wire rod percussion test was carried out by the percussion method.
  • the sound acquisition and analysis system is used to collect and analyze the knocking sound signal to determine the acoustic criterion of thermomechanical degradation.
  • the insulation of wire rods will be subjected to electrical stress, thermal stress, mechanical stress and environmental factors during operation. As the operating time of the generator set increases, the insulation will gradually deteriorate; different stresses and factors will produce different gases. The characteristics of gap discharge and the change characteristics of electrical parameters of insulation degradation are also different. Pumped storage generator motors have frequent start and stop operating conditions, which lead to thermomechanical stress between the insulation and the copper conductor, and between the insulation layers. Continuously distributed air gaps are generated, and the distribution is ellipsoidal.
  • the size of the air gap along the long axis of the bar is much larger than the size along the cross section of the bar;
  • the characteristics of insulation degradation are discontinuously distributed air gaps, showing an approximately spherical distribution, and the size of the air gap along the long axis of the wire rod is approximately equal to the size along the cross-sectional direction of the wire rod; the variation trend of the dielectric loss factor is different due to different discharge characteristics, and the characteristics The trend can determine the insulation thermomechanical degradation state; the copper hammer percussion method is a simple method to test the integrity of the insulation and has been used for many years. Criteria for judging thermomechanical degradation of insulation.
  • the wire rod uses a rectangular copper conductor as the inner core, and several through holes are set on the two end faces of the copper conductor.
  • the through holes are used to connect with the lead wires of the high-current transformer, and the middle part of the copper conductor is wrapped with less rubber mica tape.
  • a low-resistance tape is wrapped on the surface of the mica tape with less glue
  • a high-resistance anti-halation tape is wrapped on both sides of the low-resistance tape
  • the whole wire rod is vacuum pressure impregnated and solidified.
  • four through holes are provided on both end faces of the copper conductor.
  • the insulating surface of the low-resistance area of the wire rod is struck with a copper hammer; the position of the low-resistance band wrapped on the copper conductor forms the low-resistance area of the wire rod.
  • the sound collection and analysis system includes a sound sensor, a sound amplifier and a data collection and analysis system, and the sound collection and analysis system is externally connected to a computer.
  • the sound collection and analysis system transmits the data to the computer, and the computer performs Fourier transform on the data.
  • a copper hammer is used to strike an insulating surface containing a low-resistance area, and an acoustic sensor is used to collect the response signal of the copper hammer.
  • Lie analysis determines the distribution characteristics of the acoustic parameters, as a deterioration criterion.
  • thermomechanical degradation occurs:
  • the temperature of the cold and hot cycle test is determined according to the insulation operating temperature of the air-cooled pumped storage generator set at home and abroad.
  • the heating method is internal heating and forced ventilation cooling to ensure a reasonable temperature from the inside to the outside along the insulation section of the wire rod during the cold and hot cycle test. gradient.
  • each cycle is 50 cycles, the temperature of each cycle is 40-130, and the heating and cooling rate is 2.5 ⁇ 1/min.
  • the insulation dielectric loss factor test is carried out before and after each cycle. When the test data reaches the maximum value at 0.6U N , it starts when it increases from 0.2U N to 0.6U N and decreases from 0.6U N to 1.2U N When there is a significant negative increase from 1.0U N to 1.0 U, it is judged that the insulation has experienced relatively obvious thermal-mechanical degradation.
  • the test voltage is 0.2U N , 0.4U N , 0.6U N , 0.8U N , 1.0U N , 1.2U N , where U N is the rated line voltage, measured at multiple voltage points
  • U N is the rated line voltage, measured at multiple voltage points
  • Quantity (0.2U N ) ⁇ quantity (0.4U N ) ⁇ quantity (0.6U N );
  • Quantity (1.2U N ) ⁇ quantity (1.0U N ) ⁇ quantity (0.8U N ) ⁇ quantity (0.6U N );
  • the rectangular copper conductor is used as the inner core of the test wire rod, the cross-sectional size is 100mm*22mm, the total length of the copper conductor is 4500mm, and four through holes of ⁇ 14 are respectively drilled on the two ends of the copper conductor , for the connection with the lead wire of the large current transformer.
  • the middle part of the copper conductor is wrapped with less rubber mica tape, the length is 4100mm, after the VPI (vacuum pressure impregnation) process, the semiconductor low resistance anti-corona tape is wrapped on the insulating surface within the range of 3200mm in the middle, which is low resistance and anti-corona Both sides of the tape are wrapped with semiconductor high-resistance anti-halation tapes.
  • the overlapping distance of the two tapes is 20mm, and the total length of the high-resistance anti-halation structure is 140mm. Put it into an oven for heating and curing.
  • Insulation dielectric loss factor test is carried out before and after each cycle.
  • the electrode structure is a three-electrode structure, and the test voltage is 0.2U N , 0.4U N , 0.6U N , 0.8U N , 1.0U N , 1.2U N , where U N is rated Line-to-line voltage, unlike conventional hydropower units, where electrical stress degradation is the main aging type, thermal-mechanical degradation will lead to significant delamination between insulation and copper conductors, and insulation layers, and the change law of dielectric loss factor with voltage rise shows significant differences , on the basis of summarizing the change law of a large number of thermomechanical degradation characteristic parameters, determine the degradation criterion, when the values measured at multiple voltage points meet the following conditions at the same time, it is judged as unqualified, and other conditions are judged as qualified:
  • Quantity (0.2U N ) ⁇ quantity (0.4U N ) ⁇ quantity (0.6U N );
  • Quantity (1.2U N ) ⁇ quantity (1.0U N ) ⁇ quantity (0.8U N ) ⁇ quantity (0.6U N );
  • the magnitude (0.2U N ) is greater than 1%.
  • thermomechanical degradation occurs:
  • thermomechanical deterioration unique to the pumped storage generator motor and the acoustic characteristics of the copper hammer percussion method are established to correspond, which is suitable for the fixed-speed pumped storage generator motor stator winding and Wire rods, as well as the thermo-mechanical degradation state evaluation of variable-speed pumped storage generator motor stator and rotor windings and wire rod insulation, can effectively test the thermal-mechanical degradation state of insulation, and help to take preventive measures early, which is to ensure the safety and reliability of pumped storage units Important and necessary detection means of operation.
  • the insulation and anti-corona coating state at the end of the wire rod will greatly affect the test results of the overall dielectric loss factor, and the electrical parameters cannot be used to determine the insulation Criterion for thermomechanical degradation; the method of copper hammer percussion combined with acoustic judgment is simple and does not require external high-voltage power. The criterion is clear, and it can quickly confirm whether the insulation has thermal mechanical degradation. It is an important and necessary means to characterize the insulation degradation of the pumped storage generator set under working conditions.

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Abstract

本申请提供一种抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，包括：周期性地对线棒进行冷热循环试验，每个周期前后进行绝缘介质损耗因数试验及结果判读，并获得对应数据；响应于确定判读结果为数据合格，进行冷热循环试验；响应于确定判读结果为数据不合格，用铜锤敲打线棒，并用声音采集与分析系统进行信号处理，确定热机械劣化状态下的频谱特征，作为劣化判据。

Description

抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法
本申请要求在2021年11月1日提交中国专利局、申请号为202111284651.4的中国专利申请的优先权，该申请的全部内容通过引用结合在本申请中。
技术领域
本申请涉及线棒绝缘热机械劣化判定技术领域，例如涉及一种抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法。
背景技术
当前我国正处于能源绿色低碳转型发展的关键时期，风力发电、光伏发电等新能源大规模高质量发展对调节电源的需求更加迫切；抽水蓄能发电作为当前技术最成熟、全生命周期碳减排效益最显著、经济性最好且最具大规模开发的可调节电源，将迎来大发展的阶段。
与常规水轮发电机组起提供基础电力负荷不同，抽水蓄能发电电动机的主要作用包括电网调峰功能和填谷功能，因而需要机组频繁启停。在频繁启停的过程中定速抽水蓄能发电电动机线棒和变速抽水蓄能发电电动机定转子线棒铜导体的电流将发生剧烈变化而导致温度的突变。由于铜导体和环氧云母绝缘的热膨胀系数不同而产生内剪切应力，使绝缘发生热机械劣化，产生局部放电，严重时将导致绝缘产生贯穿性放电，引发严重事故的发生，威胁电网的安全运行。
热机械劣化是抽水蓄能机组特有的绝缘劣化特征，检验该特征的冷热循环试验方法也是基于国内外运行多年的抽水蓄能机组绝缘失效故障特性而制定。冷热循环试验是国内外公认的产生绝缘机械劣化的方法，可通过绝缘电气诊断试验判定机械劣化状态，由于电站现场条件的限制(无法对单支线棒进行“三电极”介质损耗因数试验)，而不能通过电气诊断试验判定运行机组绝缘的热机械劣化状态；铜锤敲击法是简便的、适用于电站现场的绝缘状态检测方法，该方法通过“人耳”识别的方式判定绝缘是否“发空”，其中发空意味着绝缘内存在气隙，在运行过程中容易产生局部放电，其缺点是不能确定绝缘劣化的类型和放电的严重程度，因而到目前位置，尚未找到适用于电站现场抽水蓄能 机组绝缘热机械劣化判定的合适方法。
发明内容
本申请实施例提供了抽水蓄能发电电动机真空压力浸渍工艺(Vacuum Pressure Impregnating，VPI)线棒绝缘热机械劣化的判定方法。
本申请提供一种抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，包括：
周期性地对线棒进行冷热循环试验，每个周期前后进行绝缘介质损耗因数试验及结果判读，并获得对应数据；
响应于确定判读结果为数据合格，继续进行冷热循环试验；
响应于确定判读结果为数据不合格，用铜锤敲打线棒，并用声音采集与分析系统进行信号处理，确定热机械劣化状态下的频谱特征，作为劣化判据。
附图说明
图1为本申请的方法原理框图；
图2为本申请中声音测量与分析原理框图。
具体实施方式
如图1所示，抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，包括有以下步骤：
周期性地对线棒进行冷热循环试验，每个周期前后进行绝缘介质损耗因数试验及结果判读，并获得对应数据；
若判读结果为数据合格，继续进行冷热循环试验；
若判读结果为数据不合格，用铜锤敲打线棒，并用声音采集与分析系统进行信号处理，确定热机械劣化状态下的频谱特征，作为劣化判据。
本申请抽水蓄能发电电动机VPI线棒进行绝缘热机械劣化的判定，根据空冷抽水蓄能发电电动机绝缘运行温度变化幅值进行冷热循环试验。在冷热循环试验的过程中热机械劣化特性的介质损耗因数变化规律的基础上，确定绝缘热机械劣化与介质损耗因数变化趋势的关系，针对绝缘热机械劣化状态，使用广泛应用的铜锤敲击法进行线棒敲击试验。与此同时，使用声音采集与分析系统对敲击声音信号进行采集与分析，确定热机械劣化的声学判据。
例如，线棒绝缘在运行过程中将承受电应力、热应力、机械应力和环境因素的作用，随着发电机组运行时间的增加，绝缘将逐渐劣化；不同应力和因素将产生各不相同的气隙放电特征，绝缘劣化的电气参数变化特征也不尽相同。抽水蓄能发电电动机具有频繁启停机的运行工况，由此导致绝缘与铜导体之间、绝缘层之间产生热机械应力的作用，当绝缘发生严重的热机械劣化时，表现为绝缘层间产生连续分布的气隙，且呈现椭球形分布，沿线棒长轴方向的气隙尺寸远大于沿线棒截面方向的尺寸；常规发电机组在持续的以电应力为主导的多种应力的作用下的绝缘劣化特征表现为不连续分布的气隙，呈现近似球形分布，沿线棒长轴方向的气隙尺寸近似等于沿线棒截面方向的尺寸；由于放电特性不同导致介质损耗因数的变化趋势不同，通过特征趋势可确定绝缘热机械劣化状态；铜锤敲击法是检验绝缘整体性的简易手段并已应用多年，绝缘热机械劣化状态下的铜锤敲击声学响应具有独有的声学特征，可作为现场判定绝缘热机械劣化的判据。
例如，线棒采用矩形铜导体作为内芯，在铜导体的两个末端面上设置若干个通孔，通孔用于与大电流变压器引出线的连接，且铜导体中部包绕少胶云母带，且少胶云母带的表面上包绕有低阻带，低阻带的两侧上包绕高阻防晕带，线棒整体真空压力浸渍固化成型。例如，铜导体的两个末端面上设置4个通孔。
在确定劣化判据的过程中，用铜锤敲击线棒低阻区域绝缘表面；铜导体上包套有低阻带的位置形成线棒低阻区域。
声音采集与分析系统包括有声音传感器、声音放大器和数据采集分析系统，且声音采集与分析系统外部连接有计算机。声音采集与分析系统把数据传送到计算机，计算机对数据进行傅里叶变换，当满足如下条件之一时，判定线棒发生热机械劣化：
在3000Hz±500Hz频率范围内出现2次及以上幅值大于背景噪声水平10倍的脉冲；在5000Hz±500Hz频率范围内出现2次及以上幅值大于背景噪声水平10倍的脉冲；在9000Hz±1000Hz频率范围内出现1次及以上幅值大于背景噪声水平15倍的脉冲。
例如，用铜锤敲击包含低阻区域的绝缘表面，同时用声学传感器采集铜锤敲击的响应信号，经放大后将信号传递到数据采集系统上，再通过网络传输到计算机上，通过傅里叶分析确定声学参量的分布特征，作为劣化判据。
例如，在用铜锤敲击线棒低阻区域绝缘表面时，用声音传感器采集铜锤敲 击绝缘产生的声学信号，输入到声音放大器中，放大的声学信号传递到数据采集分析系统上，通过工业以太网将数据传送到远程计算机，对信号进行傅里叶变换，确定热机械劣化特征，当满足如下条件之一时判定发生热机械劣化：
在3000Hz±500Hz频率范围内出现2次及以上幅值大于背景噪声水平10倍的脉冲；在5000Hz±500Hz频率范围内出现2次及以上幅值大于背景噪声水平10倍的脉冲；在9000Hz±1000Hz频率范围内出现1次及以上幅值大于背景噪声水平15倍的脉冲。
根据国内外空冷抽水蓄能发电机组的绝缘运行温度确定冷热循环试验的温度，加热方式为内加热、强制通风冷却，保证冷热循环试验过程中沿线棒绝缘截面由内到外产生合理的温度梯度。
在冷热循环试验中采用铜导体电流加热、通风冷却的方式，每个周期为50次循环，每次循环的温度为40-130，升降温速率为2.5±1/min。以50次循环为一个周期，每个周期前后进行绝缘介质损耗因数试验，当测试数据在0.6U N下达到最大值，0.2U N-0.6U N递增、0.6U N-1.2U N递减时起至1.0U N至出现显著负增量时，判定绝缘发生较为明显的热机械劣化。
在绝缘介质损耗因数试验中，试验电压为0.2U N、0.4U N、0.6U N、0.8U N、1.0U N、1.2U N，其中U N为额定线电压，在多个电压点测得的量值同时满足下列条件时判定为数据不合格，其他情况判定为数据合格；
量值(0.2U N)＜量值(0.4U N)＜量值(0.6U N)；
量值(1.2U N)＜量值(1.0U N)＜量值(0.8U N)＜量值(0.6U N)；
量值(0.6U N)与量值(0.2U N)的差值＞1％；
量值(0.2UN)大于1％。
在本申请中，以50次循环为一个周期进行冷热循环试验，每个周期前后进行绝缘介质损耗因数试验及结果判读，如数据合格继续进行冷热循环试验，如数据不合格用铜锤敲击线棒表面，同时用声音采集与分析系统进行信号处理，确定热机械劣化状态下的频谱特征，作为劣化判据，用于机组运行后阶段性检测与拆除线棒的绝缘热机械劣化评估。
其中，作为本申请的一种实施例，矩形铜导体作为试验线棒的内芯，截面尺寸为100mm*22mm，铜导体总长为4500mm，在铜导体两末端大面分别钻4个φ14的通孔，用于与大电流变压器引出线的连接。
铜导体中间部分包绕少胶云母带，长度为4100mm，经过VPI(真空压力浸 渍)工艺处理后，在中间3200mm的范围内的绝缘表面上包绕半导体低阻防电晕带，低阻防晕带两侧包绕半导体高阻防晕带，两种带子的搭接距离为20mm，高阻防晕结构的总长为140mm，放入烘箱内加热固化成型。
每个周期前后进行绝缘介质损耗因数试验，电极结构为三电极结构，试验电压为0.2U N、0.4U N、0.6U N、0.8U N、1.0U N、1.2U N，其中U N为额定线电压，不同于常规水电机组以电应力劣化为主要的老化型式，热机械劣化将导致绝缘与铜导体、绝缘层间出现显著分层，介质损耗因数随电压上升的变化规律表现出显著的不同，在总结大量热机械劣化特征参数变化规律的基础上，确定劣化判据，在多个电压点下测得的量值同时满足如下条件时判定为不合格，其他情况判定为合格：
量值(0.2U N)＜量值(0.4U N)＜量值(0.6U N)；
量值(1.2U N)＜量值(1.0U N)＜量值(0.8U N)＜量值(0.6U N)；
量值(0.6U N)与量值(0.2U N)的差值＞1％；
量值(0.2U N)大于1％。
如图2所示，当数据不合格时，用实心铜锤敲击线棒低阻防晕区绝缘表面，与此同时将B&K声学传感器安装在被测部位附近，对主绝缘进行敲击，产生频率响应，将测量到的声学响应信号传递到B&K-1704声学放大器上，根据现场噪声环境设置放大增益后，将放大后的声学信号传递到NI-9185数据采集分析系统上，通过工业以太网将数据传送到计算机上，对信号进行傅里叶变换，确定热机械劣化特征，当满足如下条件之一时判定发生热机械劣化：
在3000Hz±500Hz频率范围内出现2次及以上幅值大于背景噪声水平10倍的脉冲；在5000Hz±500Hz频率范围内出现2次及以上幅值大于背景噪声水平10倍的脉冲；在9000Hz±1000Hz频率范围内出现1次及以上幅值大于背景噪声水平15倍的脉冲。
在本申请实施例中，将抽水蓄能发电电动机特有的绝缘热机械劣化的电气特征与铜锤敲击法的声学特征建立对应的关系，适用于电站现场定速抽水蓄能发电电动机定子绕组及线棒，以及变速抽水蓄能发电电动机定转子绕组及线棒绝缘的热机械劣化状态评估，可有效检验绝缘的热机械劣化状态，有助于及早采取预防措施，是保证抽水蓄能机组安全可靠运行的重要和必要的检测手段。在对机组进行检查时，由于不能应用三电极系统进行介质损耗因数试验，线棒端部的绝缘和防晕涂层状态将极大的影响整体介质损耗因数的试验结果，电气 参数不能作为判定绝缘热机械劣化的判据；通过铜锤敲击结合声学判定的方式方法简单，不需外接高压电，判据明确，可快速确认绝缘是否发生热机械劣化，是检验具有调峰、填谷运行工况的抽水蓄能发电机组绝缘劣化特征的重要的和必要的手段。

Claims (8)

  1. 一种抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，，包括：
    周期性地对所述线棒进行冷热循环试验，每个周期前后进行绝缘介质损耗因数试验及结果判读，并获得对应数据；
    响应于确定判读结果为数据合格，继续进行冷热循环试验；
    响应于确定判读结果为数据不合格，用铜锤敲打所述线棒，并用声音采集与分析系统进行信号处理，确定热机械劣化状态下的频谱特征，作为劣化判据。
  2. 根据权利要求1所述的抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，其中，所述线棒采用矩形铜导体作为内芯，在所述铜导体的两个末端面上设置多个通孔，且所述铜导体中部包绕少胶云母带，且所述少胶云母带的表面上包绕有低阻带，所述低阻带的两侧上包绕高阻防晕带，所述线棒整体真空压力浸渍固化成型。
  3. 根据权利要求2所述的抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，其中，在确定劣化判据的过程中，用铜锤敲击所述线棒低阻区域绝缘表面；所述铜导体上包套有低阻带的位置形成所述线棒低阻区域。
  4. 根据权利要求3所述的抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，其中，所述铜导体的两个末端面上设置4个所述通孔，所述通孔用于与大电流变压器引出线的连接。
  5. 根据权利要求1所述的抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，其中，所述声音采集与分析系统包括声音传感器、声音放大器和数据采集分析系统，且所述声音采集与分析系统外部连接有计算机。
  6. 根据权利要求5所述的抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，其中，所述声音采集与分析系统把数据传送到所述计算机，所述计算机对数据进行傅里叶变换，响应于确定满足如下条件之一，判定所述线棒发生热机械劣化：
    在3000Hz±500Hz频率范围内出现2次及以上幅值大于背景噪声水平10倍的脉冲；
    在5000Hz±500Hz频率范围内出现2次及以上幅值大于背景噪声水平10倍的脉冲；以及
    在9000Hz±1000Hz频率范围内出现1次及以上幅值大于背景噪声水平15倍的脉冲。
  7. 根据权利要求1所述的抽水蓄能发电电动机VPI线棒绝缘热机械劣化 的判定方法，其中，所述冷热循环试验采用铜导体电流加热、通风冷却的方式，每个周期为50次循环，每次循环的温度为40℃-130℃，升降温速率为2.5℃±1℃/min。
  8. 根据权利要求1所述的抽水蓄能发电电动机VPI线棒绝缘热机械劣化的判定方法，其中，在所述绝缘介质损耗因数试验中，试验电压为0.2U N、0.4U N、0.6U N、0.8U N、1.0U N、1.2U N，其中U N为额定线电压，响应于确定在多个电压点测得的量值同时满足下列条件判定为数据不合格，其他情况判定为数据合格：
    量值(0.2U N)＜量值(0.4U N)＜量值(0.6U N)；
    量值(1.2U N)＜量值(1.0U N)＜量值(0.8U N)＜量值(0.6U N)；
    量值(0.6U N)与量值(0.2U N)的差值＞1％；以及
    量值(0.2U N)大于1％。
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