CN108387824B - A method for evaluating the state of oil-paper insulation with improved recovery voltage measurement - Google Patents
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Abstract
Description
技术领域technical field
本发明涉及变压器油纸绝缘老化与寿命预测技术领域,尤其是基于一种改进回复电压测量方式的油纸绝缘状态评估方法。The invention relates to the technical field of transformer oil-paper insulation aging and life prediction, in particular to an oil-paper insulation state evaluation method based on an improved recovery voltage measurement method.
背景技术Background technique
油浸式电力变压器具有较高的绝缘强度、较长的使用寿命等优点因而被广泛用于电力系统中,然而变压器在运行过程中,不可避免地会受到电、热、机械应力以及其它环境因素的影响,导致介质的绝缘性能不断劣化,因此,研究变压器油纸绝缘状态的诊断方法,并正确地评估变压器的绝缘状态,对确保整个电网的安全、稳定和可靠运行具有重大理论和实际意义。Oil-immersed power transformers have the advantages of high dielectric strength and long service life, so they are widely used in power systems. However, during the operation of transformers, they will inevitably be subjected to electrical, thermal, mechanical stress and other environmental factors. Therefore, it is of great theoretical and practical significance to study the diagnosis method of the transformer oil-paper insulation state and correctly evaluate the insulation state of the transformer to ensure the safe, stable and reliable operation of the entire power grid.
目前,针对变压器油纸绝缘状态的诊断方法均是以介电响应为理论基础的无损诊断方法,其中,回复电压法得益于其敏感度高、信息量大,抗干扰能力强,且便于现场测试,因而得到广泛关注。然而传统的回复电压法测量时间长是一大缺陷,重复充放电多次本就需要耗费大量时间,在每次循环中还需要测得回复电压峰值,更加延长了测量时间,整个实验过程需耗费3~5小时,效率低下;现有的一些改进方法也大都是在充一次电放一次电,重复测量多个周期的基础上进行的,只是为了通过改变充放电时间研究其对特征量的影响规律,并没有从缩短实验时间的角度考虑对测量方式进行改进;此外,传统的回复电压测量法用测量的特征量直接对变压器油纸绝缘状态进行评估,实验误差对结果的影响很大,而主时间常数是回复电压测量法中最常用的绝缘诊断特征量,主时间常数的确定直接影响到最终的诊断结果,因此需要尽量准确确定极化谱中的峰值对应的时间。At present, the diagnostic methods for the transformer oil-paper insulation state are all non-destructive diagnostic methods based on the dielectric response. Among them, the recovery voltage method benefits from its high sensitivity, large amount of information, strong anti-interference ability, and easy on-site testing. , and thus received widespread attention. However, the long measurement time of the traditional recovery voltage method is a major drawback. Repeated charging and discharging many times takes a lot of time. In each cycle, the peak recovery voltage needs to be measured, which further prolongs the measurement time. 3 to 5 hours, the efficiency is low; some of the existing improvement methods are mostly carried out on the basis of one charge and one discharge, and repeated measurement for multiple cycles, just to study its influence on the characteristic quantity by changing the charge and discharge time. In addition, the traditional recovery voltage measurement method uses the measured characteristic quantities to directly evaluate the transformer oil-paper insulation state, and the experimental error has a great influence on the results, while the main The time constant is the most commonly used insulation diagnostic feature in the recovery voltage measurement method. The determination of the main time constant directly affects the final diagnosis result. Therefore, it is necessary to determine the time corresponding to the peak value in the polarization spectrum as accurately as possible.
发明内容SUMMARY OF THE INVENTION
为了解决这些问题,本发明的目的在于提供一种改进回复电压测量方式的油纸绝缘状态评估方法,在同样极化时间下,将实验时间缩短至传统方法的三分之一以下。同时,对辨识出参数的等效电路进行仿真,还原的回复电压极化谱的峰值时间与绝缘纸中水分含量之间存在对应关系,能够对油纸绝缘的状态进行评估。In order to solve these problems, the purpose of the present invention is to provide an oil-paper insulation state evaluation method with an improved recovery voltage measurement method, and under the same polarization time, the experiment time is shortened to less than one third of the traditional method. At the same time, the equivalent circuit of the identified parameters is simulated, and there is a corresponding relationship between the peak time of the restored voltage polarization spectrum and the moisture content in the insulating paper, which can evaluate the state of the oil-paper insulation.
本发明采取的技术方案为:The technical scheme adopted in the present invention is:
一种改进回复电压测量方式的油纸绝缘状态评估方法,包括以下步骤:A method for evaluating the state of oil-paper insulation with an improved recovery voltage measurement method, comprising the following steps:
步骤1:在实验室中将干燥的绝缘纸暴露在空气中自然吸潮,然后将其充分浸泡于新变压器绝缘油中,得到不同水分含量的实验样本;Step 1: Expose the dry insulating paper to the air to absorb moisture naturally in the laboratory, and then fully immerse it in the new transformer insulating oil to obtain experimental samples with different moisture contents;
步骤2:变压器油纸绝缘回复电压自动采集系统主要通过对6517B静电仪写入VB程序,控制其中的高压直流电源模块和电表测量模块的自动投切,实现充放电及测量流程的循环控制,以及对变压器油纸绝缘回复电压的自动采集;Step 2: The transformer oil-paper insulation recovery voltage automatic acquisition system mainly controls the automatic switching of the high-voltage DC power supply module and the meter measurement module by writing the VB program to the 6517B electrostatic meter, realizing the cyclic control of the charging and discharging and measurement process, as well as the Automatic collection of transformer oil-paper insulation recovery voltage;
步骤3:将样品置于三电极装置并接入系统中,打开回复电压测量系统,在参数设置界面对充电电压、充电时间、放电循环次数、各放电时间进行设置,启动静电仪,将其初始化,开始采集后系统将自动执行充电环节,然后按照逐渐递增的步长进行循环放电、测量的过程,每个测量环节初始时刻回复电压在采样间隔内的增量即为该环节的初始斜率;Step 3: Place the sample in the three-electrode device and connect it to the system, open the recovery voltage measurement system, set the charging voltage, charging time, number of discharge cycles, and each discharge time on the parameter setting interface, start the electrostatic meter, and initialize it , after the collection starts, the system will automatically perform the charging link, and then perform the process of cyclic discharge and measurement according to the gradually increasing step size. The increment of the recovery voltage at the initial moment of each measurement link within the sampling interval is the initial slope of the link;
步骤4:将获得的持续放电过程中每次放电环节的初始斜率对扩展德拜等效电路中各支路的参数进行辨识;Step 4: Identify the parameters of each branch in the extended Debye equivalent circuit with the obtained initial slope of each discharge link in the continuous discharge process;
步骤5:辨识出各支路参数后,通过网络函数对等值电路进行分析,利用线性电路的叠加定理,可计算出多放电过程中各放电环节的回复电压及其初始斜率;将初始斜率计算值与测量值进行对比,调整优化算法的参数,使得持续放电过程中各放电环节的初始斜率计算值与测量值重合度尽可能高,即辨识出的参数尽可能精确。Step 5: After identifying the parameters of each branch, analyze the equivalent circuit through the network function, and use the superposition theorem of linear circuits to calculate the recovery voltage and initial slope of each discharge link in the multi-discharge process; calculate the initial slope. Compare the value with the measured value, and adjust the parameters of the optimization algorithm so that the calculated value of the initial slope of each discharge link in the continuous discharge process coincides with the measured value as high as possible, that is, the identified parameters are as accurate as possible.
步骤6:将辨识出参数的等效电路,在matlab中模拟重复多次充放电的传统回复电压测量方式,编程仿真出回复电压极化谱,观察不同水分含量的样本还原出的回复电压极化谱所呈现的规律,根据极化谱中峰值时间与水分含量的对应关系对油纸绝缘状态进行评估,峰值时间越大,则绝缘纸中水分含量越多,绝缘状态越差。Step 6: The equivalent circuit of the identified parameters, simulate the traditional recovery voltage measurement method of repeated charging and discharging in matlab, program and simulate the recovery voltage polarization spectrum, and observe the recovery voltage polarization restored by samples with different moisture contents According to the law presented by the spectrum, the insulation state of the oil-paper is evaluated according to the corresponding relationship between the peak time and the moisture content in the polarization spectrum. The greater the peak time, the more moisture content in the insulating paper and the worse the insulation state.
所述步骤4中,辨识过程如下:In the step 4, the identification process is as follows:
经过第j次放电后支路i上电容电压为:After the jth discharge, the capacitor voltage on branch i is:
其中,i代表各支路,j代表各放电环节,U0为测量前设置的充电电压,tc为充电时间,tdcj为各放电时间,τi表示各支路的时间常数,由对应支路RC参数的乘积表示。Among them, i represents each branch, j represents each discharge link, U 0 is the charging voltage set before measurement, t c is the charging time, t dcj is each discharging time, τ i represents the time constant of each branch, and is determined by the corresponding branch The product representation of the road RC parameters.
根据电路特性对等效电路进行分析,结合换路定理,利用测得的初始斜率可构建关于等效电路中各支路RC参数以及变压器几何电容Cg的目标函数,通过优化算法求得最优解,带入到式The equivalent circuit is analyzed according to the circuit characteristics, combined with the switching theorem, the objective function about the RC parameters of each branch in the equivalent circuit and the geometric capacitance C g of the transformer can be constructed by using the measured initial slope, and the optimal value can be obtained through the optimization algorithm. solution, bring into the formula
中解出绝缘电阻Rg,此时,Urj(t)为第j个放电环节后测得的第二个回复电压值,表示对应采样点的斜率。Insulation resistance R g can be solved in the middle, at this time, U rj (t) is the second recovery voltage value measured after the jth discharge link, Indicates the slope of the corresponding sampling point.
所述步骤5中,回复电压及其初始斜率计算如下:In the
第j次放电后,支路i上的电容单独作用时产生的回复电压通式如下:After the jth discharge, the recovery voltage generated when the capacitor on branch i acts alone is as follows:
其中,ucpij(0-)为开路测量瞬间电容电压值,多项式Nij(s)和Dij(s)通过分析等效电路方程的运算形式得出,系数a0,ij、a1,ij、…、an-1,ij以及b0,ij、b1,ij、…、bn+1,ij与等值电路中的参数有关,是Rpi、Cpi、Cg、Rg组合的结果,分析过程复杂,可利用matlab编程分析得出,并求出零点z1、z2、…、zn-1和极点p1、p2、…、pn+1。Among them, u cpij (0 - ) is the instantaneous capacitor voltage value of the open circuit measurement, the polynomials N ij (s) and D ij (s) are obtained by analyzing the operation form of the equivalent circuit equation, the coefficients a 0,ij , a 1,ij , ..., a n-1,ij and b 0,ij , b 1,ij , ..., b n+1,ij are related to the parameters in the equivalent circuit, and are combinations of R pi , C pi , C g , and R g . The result of , the analysis process is complicated, which can be obtained by using matlab programming analysis, and find out the zero points z 1 , z 2 , ..., z n-1 and the poles p 1 , p 2 , ..., pn+1 .
通过拉氏逆变换可得,第j次放电后,支路i电容电压单独作用产生的回复电压为:Through the inverse Laplace transform, it can be obtained that after the jth discharge, the recovery voltage generated by the independent action of the branch i capacitor voltage is:
其中,Kr,ij代表在对Nij(s)/Dij(s)中的分母多项式做因式分解时对应的每项系数,个数与Dij(s)多项式的阶数有关,运用极限法确定Kr,ij的值,公式如下:Among them, K r,ij represents each coefficient corresponding to the factorization of the denominator polynomial in N ij (s)/D ij (s), and the number is related to the order of the D ij (s) polynomial. The limit method determines the value of K r,ij , the formula is as follows:
Dij’(s)为Dij(s)的一阶导,pr,ij为极点。 Di ij '(s) is the first derivative of Di ij (s), and pr,ij is the pole.
根据叠加定理,即可得出第j次放电后,n条支路上的电容电压共同作用时,在电路两端产生的回复电压及其初始斜率。According to the superposition theorem, after the jth discharge, when the capacitor voltages on the n branches act together, the recovery voltage and its initial slope are generated at both ends of the circuit.
本发明一种改进回复电压测量方式的油纸绝缘状态评估方法,优点在于:An oil-paper insulation state evaluation method for improving the recovery voltage measurement method of the present invention has the advantages of:
改进后的方法除了在测量方式上作了突破性的改进,极大地缩短了实验时间之外,根据该方法测得的数据辨识出的等值电路还原的回复电压极化谱,同样可以对不同水分含量的变压器油纸绝缘样品的绝缘状态进行评估,且该极化谱是通过较精确的等效电路计算出来的,测量过程中引入的误差大大减小,提取出的峰值时间特征量评估的结果也更可靠。In addition to making breakthrough improvements in the measurement method, the improved method greatly shortens the experimental time. The recovery voltage polarization spectrum restored by the equivalent circuit identified according to the data measured by this method can also be used for different measurements. The insulation state of the transformer oil-paper insulation sample with moisture content is evaluated, and the polarization spectrum is calculated by a relatively accurate equivalent circuit, the error introduced in the measurement process is greatly reduced, and the extracted peak time characteristic value is evaluated. Also more reliable.
附图说明Description of drawings
图1为本发明实验的流程示意图。FIG. 1 is a schematic flow chart of the experiment of the present invention.
图2为三电极系统结构图;Figure 2 is a structural diagram of a three-electrode system;
其中:V:电压表,1-变压器油,2-上极板,3-油浸纸板,4-下极板。Among them: V: voltmeter, 1-transformer oil, 2-upper plate, 3-oil-impregnated cardboard, 4-lower plate.
图3为回复电压测量原理接线图。Figure 3 is a wiring diagram of the principle of measuring the recovery voltage.
图4为常规回复电压法的测量过程图。FIG. 4 is a measurement process diagram of the conventional recovery voltage method.
图5为改进回复电压法的测量过程图。Figure 5 is a measurement process diagram of the improved recovery voltage method.
图6为扩展德拜等效电路图。Figure 6 is an extended Debye equivalent circuit diagram.
图7为第j个放电环节支路1电容电压单独作用对应的运算电路。FIG. 7 is an operation circuit corresponding to the independent action of the capacitor voltage of
图8为0.7%水分含量的样本在0.1s、1s、10s、100s放电时间后的计算回复电压曲线图。Fig. 8 is a graph showing the calculated recovery voltage of samples with 0.7% moisture content after 0.1s, 1s, 10s, and 100s of discharge time.
图9为持续放电过程中各放电环节初始斜率的测量值与计算值对比图。FIG. 9 is a comparison diagram of the measured value and the calculated value of the initial slope of each discharge link during the continuous discharge process.
图10为还原的各水分含量样品的回复电压极化谱图。FIG. 10 is the recovery voltage polarization spectra of the reduced samples with various moisture contents.
具体实施方式Detailed ways
一种改进回复电压测量方式的油纸绝缘状态评估方法,A method for evaluating the state of oil-paper insulation with an improved recovery voltage measurement method,
1)、在测量方式方面:通过一个长时间的充电和多个短时间连续的放电过程实现,相比于传统的以充放电时间比2:1重复多个周期的回复电压测量方法,在同样极化时间下实验时间缩短为原来的三分之一以下,提高了实验效率;1) In terms of measurement methods: it is realized through a long-term charging and multiple short-term continuous discharging processes. Compared with the traditional recovery voltage measurement method that repeats multiple cycles with a charge-discharge time ratio of 2:1, in the same Under the polarization time, the experimental time is shortened to less than one third of the original, which improves the experimental efficiency;
2)、在支路电容电压描述方面:测量方式的改变后,采用累乘衰减指数的形式对每次放电过程后的支路电容电压进行描述,每放一次电即在前一次电容电压的基础上乘一个衰减指数,层层递进;2) In the description of the branch capacitor voltage: after the measurement method is changed, the branch capacitor voltage after each discharge process is described in the form of a cumulative attenuation index. Each discharge is based on the previous capacitor voltage. Multiply by a decay exponent, progressive layer by layer;
3)、在参数辨识方面:利用测得的整个持续放电过程中各放电环节的初始斜率,以及第二个采样点的斜率对扩展德拜等效电路的参数进行辨识;3) In the aspect of parameter identification: use the measured initial slope of each discharge link in the entire continuous discharge process and the slope of the second sampling point to identify the parameters of the extended Debye equivalent circuit;
4)、在绝缘评估特征量方面:利用辨识出的等值电路参数计算回复电压极化谱的峰值时间作为评估变压器油纸绝缘状态的特征量,而不是直接通过测量数据获得的极化谱中的主时间常数特征量进行评估。4) In terms of insulation evaluation characteristics: use the identified equivalent circuit parameters to calculate the peak time of the polarization spectrum of the recovery voltage as a characteristic quantity for evaluating the insulation state of the transformer oil-paper, rather than the polarization spectrum obtained directly from the measurement data. The main time constant characteristic quantity is evaluated.
所述1)中:一次长时间充电多次短时间连续放电的过程,在同样极化时间下本就能够将实验时间缩短至传统方法的三分之一,同时,每次测量环节仅需测得前三个回复电压值即可,无需一直测到该环节的回复电压峰值才结束,更加提高了实验效率。In the above 1): the process of charging for a long time and discharging continuously for a short period of time can reduce the experimental time to one third of the traditional method under the same polarization time. At the same time, each measurement link only needs to measure It is enough to obtain the first three recovery voltage values, and it is not necessary to measure the recovery voltage peak value of this link until the end, which further improves the experimental efficiency.
所述2)中:由于改进后的方法的放电过程是多次连续进行的,因此,采用累乘衰减指数的形式对每次放电过程后各支路电容的电压进行描述如式(1)。In the above 2): since the discharge process of the improved method is carried out continuously for many times, the voltage of each branch capacitor after each discharge process is described as formula (1) in the form of cumulative decay index.
所述3)中:根据测得的整个持续放电过程中每次放电环节后的初始斜率,求出等效电路中各支路的RC参数及变压器几何电容后,将其带入到式(2)中解出绝缘电阻Rg,此时,Urj(t)为第j个放电环节后测得的第二个回复电压值,表示对应采样点的斜率。In the above 3): According to the measured initial slope after each discharge link in the whole continuous discharge process, after obtaining the RC parameters of each branch in the equivalent circuit and the geometric capacitance of the transformer, bring it into the formula (2) ) to solve the insulation resistance R g , at this time, U rj (t) is the second recovery voltage value measured after the jth discharge link, Indicates the slope of the corresponding sampling point.
所述4)中:实验结果表明,改进后的方法还原的回复电压极化谱中的峰值时间随绝缘纸中水分含量的增加而增大,即通过该方法还原的回复电压极化谱的峰值时间越大,油纸绝缘状态就越差。In the above 4): the experimental results show that the peak time in the recovery voltage polarization spectrum reduced by the improved method increases with the increase of the moisture content in the insulating paper, that is, the peak value of the recovery voltage polarization spectrum reduced by this method. The longer the time, the worse the oil-paper insulation state.
如图1所示,本发明通过一次长时间充电多次连续放电的测量方式,在同样极化时间下将测量时间缩短至传统方法的三分之一以下,提高了实验效率,且测得的数据能够较精确地辨识出扩展德拜等效电路中的参数,根据该等效电路可计算出改进测量方式后的回复电压及其初始斜率,同时,在该等效电路上模拟常规回复电压测量方法仿真出回复电压极化谱,利用该极化谱的峰值时间可对油纸绝缘样品的绝缘状态进行评估。具体实施步骤如下:As shown in Figure 1, the present invention shortens the measurement time to less than one third of the traditional method under the same polarization time through the measurement method of one long charge and multiple continuous discharges, which improves the experimental efficiency, and the measured The data can accurately identify the parameters in the extended Debye equivalent circuit. According to the equivalent circuit, the recovery voltage and its initial slope after the improved measurement method can be calculated. At the same time, the conventional recovery voltage measurement is simulated on the equivalent circuit. The method simulates the polarization spectrum of the recovery voltage, and uses the peak time of the polarization spectrum to evaluate the insulation state of the oil-paper insulation sample. The specific implementation steps are as follows:
1)在实验室中制备绝缘纸中水分含量分别为0.7%、1.3%、3.4%的实验样品,将样品放置于图2所示的用于模拟实验变压器的三电极装置中;1) Prepare experimental samples with moisture contents of 0.7%, 1.3%, and 3.4% in the insulating paper in the laboratory, and place the samples in the three-electrode device for simulating the experimental transformer shown in Figure 2;
2)按照图3测量系统的原理接线图将实验变压器接入系统中,打开回复电压测量系统,在参数设置界面对充电电压1000V、充电时间2000s、放电循环次数13次、各放电时间分别设置为0.1s、0.2s、0.5s、1s、2s、5s、10s、20s、50s、100s、200s、500s、1000s,启动静电计,将其初始化,点击开始采集后系统将自动执行充电环节,并根据设置的放电时间进行放电、测量的循环过程,示意图如图5,常规回复电压测量过程示意图如图4。2) Connect the experimental transformer to the system according to the principle wiring diagram of the measurement system in Figure 3, open the recovery voltage measurement system, and set the charging voltage 1000V, charging time 2000s, discharge cycle times 13 times, and each discharge time in the parameter setting interface as 0.1s, 0.2s, 0.5s, 1s, 2s, 5s, 10s, 20s, 50s, 100s, 200s, 500s, 1000s, start the electrometer and initialize it. The cycle process of discharge and measurement at the set discharge time is shown in Figure 5, and the schematic diagram of the conventional recovery voltage measurement process is shown in Figure 4.
根据每个测量环节初始时刻回复电压增量与采样间隔的比值即可得出该环节的初始斜率值,不同水分含量样品在各放电环节后测得的初始斜率数据如下:According to the ratio of the recovery voltage increment and the sampling interval at the initial moment of each measurement link, the initial slope value of the link can be obtained. The initial slope data of samples with different moisture contents measured after each discharge link are as follows:
表1不同水分含量样品在各放电环节后测得的初始斜率Table 1 Initial slopes of samples with different moisture contents measured after each discharge cycle
3)扩展德拜等效电路由多条RC支路并联构成,如图6所示,能够在理论上很直观地描述不同程度的介质驰豫过程,一般采用6条支路就能较准确地反映真实状态,即n=6。用上述初始斜率结合优化算法能够辨识出等效电路中各支路的参数,具体分析过程如下:3) The extended Debye equivalent circuit is composed of multiple RC branches in parallel, as shown in Figure 6, which can theoretically describe different degrees of medium relaxation process intuitively. Generally, 6 branches can be used to more accurately Reflect the real state, ie n=6. The parameters of each branch in the equivalent circuit can be identified by using the above initial slope combined with the optimization algorithm. The specific analysis process is as follows:
经过第j次放电后支路i上电容电压如式(1),根据电路特性对等效电路进行分析,结合换路定理,利用测得的初始斜率可构建关于等效电路中各支路RC参数以及变压器几何电容Cg的目标函数,通过优化算法求得最优解,带入到式(2)中解出绝缘电阻Rg,此时,Urj(t)为第j个放电环节后测得的第二个回复电压值,表示对应采样点的斜率。After the jth discharge, the capacitor voltage on branch i is shown in formula (1). According to the circuit characteristics, the equivalent circuit is analyzed. Combined with the switching theorem, the measured initial slope can be used to construct the RC of each branch in the equivalent circuit. parameters and the objective function of the geometric capacitance C g of the transformer, the optimal solution is obtained through the optimization algorithm, and is brought into the formula (2) to solve the insulation resistance R g , at this time, U rj (t) is the jth discharge link after The second measured recovery voltage value, Indicates the slope of the corresponding sampling point.
通过混合蛙跳算法对扩展德拜等效电路中的参数进行辨识,以绝缘纸中水分含量0.7%为例,辨识结果如下表:The parameters in the extended Debye equivalent circuit are identified by the hybrid leapfrog algorithm. Taking the moisture content of the insulating paper as an example of 0.7%, the identification results are as follows:
表2水分含量0.7%时的辨识结果Table 2 Identification results when the moisture content is 0.7%
4)辨识出各支路参数后,通过网络函数对等值电路进行分析,可计算出回复电压及其初始斜率:4) After identifying the parameters of each branch, analyze the equivalent circuit through the network function, and calculate the recovery voltage and its initial slope:
当支路1的电容电压单独作用时,对应的运算电路如图7所示,其它支路单独作用时只需将电压源移到相应的支路上即可。When the capacitor voltage of
当n=6时,第j次放电后,支路i上的电容单独作用时产生的回复电压可化简为如下形式:When n=6, after the jth discharge, the recovery voltage generated when the capacitor on branch i acts alone can be simplified to the following form:
其中,ucpij(0-)为开路测量瞬间电容电压值,多项式Nij(s)和Dij(s)通过分析等效电路方程的运算形式得出,系数a0,ij、a1,ij、…、a5,ij以及b0,ij、b1,ij、…、b7,ij与等值电路中的参数有关,是Rpi、Cpi、Cg、Rg组合的结果,可利用matlab得到求出零点z和极点p。Among them, u cpij (0 - ) is the instantaneous capacitor voltage value of the open circuit measurement, the polynomials N ij (s) and D ij (s) are obtained by analyzing the operation form of the equivalent circuit equation, the coefficients a 0,ij , a 1,ij , ..., a 5,ij and b 0,ij , b 1,ij , ..., b 7,ij are related to the parameters in the equivalent circuit and are the result of the combination of R pi , C pi , C g , and R g , which can be Use matlab to find the zero point z and the pole point p.
通过拉氏逆变换可得,第j次放电后,支路i电容电压单独作用产生的回复电压为:Through the inverse Laplace transform, it can be obtained that after the jth discharge, the recovery voltage generated by the independent action of the branch i capacitor voltage is:
其中,Kr,ij代表在对Nij(s)/Dij(s)中的分母多项式做因式分解时对应的每项系数,个数与Dij(s)多项式的阶数有关。运用极限法确定Kr,ij的值,公式如下:Among them, K r,ij represents each coefficient corresponding to the factorization of the denominator polynomial in N ij (s)/D ij (s), and the number is related to the order of the Di ij (s) polynomial. Using the limit method to determine the value of K r,ij , the formula is as follows:
Dij’(s)为Dij(s)的一阶导,pr,ij为极点。 Di ij '(s) is the first derivative of Di ij (s), and pr,ij is the pole.
根据叠加定理,即可得出第j次放电后,6条支路上的电容电压共同作用时,在电路两端产生的回复电压及其初始斜率。According to the superposition theorem, after the jth discharge, when the capacitor voltages on the six branches act together, the recovery voltage and its initial slope are generated at both ends of the circuit.
0.7%水分含量的样本在0.1s、1s、10s、100s放电时间后的计算回复电压曲线如图8,计算出的持续放电过程中各放电环节的初始斜率与测量获得的初始斜率对比如图9,两者重合度为92.52%,说明通过改进后的方法测得的各放电环节的回复电压初始斜率值辨识出的等值电路的参数是有效的,通过该等值电路能够较好地反映出多次放电过程中绝缘介质内部的极化、去极化过程,从理论上验证了该实验方法的可行性。还可进一步调整算法的参数,使得辨识出的参数尽可能精确。The calculated recovery voltage curves of samples with 0.7% moisture content after 0.1s, 1s, 10s, and 100s of discharge time are shown in Figure 8. The calculated initial slope of each discharge link during the continuous discharge process is compared with the initial slope obtained by measurement. Figure 9 , the coincidence degree of the two is 92.52%, indicating that the parameters of the equivalent circuit identified by the initial slope value of the recovery voltage of each discharge link measured by the improved method are effective, and the equivalent circuit can better reflect the The polarization and depolarization processes inside the insulating medium during multiple discharges have theoretically verified the feasibility of the experimental method. The parameters of the algorithm can be further adjusted to make the identified parameters as accurate as possible.
在辨识出参数的等值电路上按充放电比2:1循环多次模拟常规回复电压测量法,可通过matlab仿真出各水分含量样品的回复电压极化谱如图10,可以看出,通过等值电路还原的回复电压极化谱的峰值时间随绝缘纸中水分含量的增大而增加,而水分含量与油纸绝缘状态之间存在着很好的对应关系,更加验证了改进后的测量方法获得的数据的有效性,以及用这种测量方法实现后续油纸绝缘状态评估的可行性。On the equivalent circuit of the identified parameters, the conventional recovery voltage measurement method is simulated for many times according to the charge-discharge ratio of 2:1, and the recovery voltage polarization spectrum of each moisture content sample can be simulated by matlab as shown in Figure 10. It can be seen that by The peak time of the recovery voltage polarization spectrum restored by the equivalent circuit increases with the increase of the moisture content in the insulating paper, and there is a good correspondence between the moisture content and the insulation state of the oil-paper, which further verifies the improved measurement method. The validity of the data obtained and the feasibility of implementing subsequent oil-paper insulation condition assessments with this measurement method.
综上所述,改进后的方法除了在测量方式上作了突破性的改进,极大地缩短了实验时间之外,根据该方法测得的数据辨识出的等值电路还原的回复电压极化谱,同样可以对不同水分含量的变压器油纸绝缘样品的绝缘状态进行评估,且该极化谱是通过较精确的等效电路计算出来的,测量过程中引入的误差大大减小,提取出的峰值时间特征量评估的结果也更可靠。To sum up, the improved method not only made a breakthrough improvement in the measurement method and greatly shortened the experiment time, but also identified the recovery voltage polarization spectrum restored by the equivalent circuit according to the data measured by this method. , the insulation state of transformer oil-paper insulation samples with different moisture content can also be evaluated, and the polarization spectrum is calculated by a more accurate equivalent circuit, the error introduced in the measurement process is greatly reduced, and the peak time extracted The result of feature quantity evaluation is also more reliable.
本发明的应用仅用于说明本发明,但不限于上述举例,在此基础上进行的改进和等同变换都应属于本发明所附权利要求的保护范围。The application of the present invention is only used to illustrate the present invention, but is not limited to the above examples, and improvements and equivalent transformations made on this basis shall fall within the protection scope of the appended claims of the present invention.
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