RU2491561C1 - Method to determine condition and resource of insulating system of electric equipment - Google Patents

Abstract

FIELD: measurement equipment.SUBSTANCE: spectrum of dielectric absorption is generated for a controlled insulation gap, and according to the calibration characteristic, the drawn and the residual resource of insulation is defined, the insulation gap is previously discharged within a required interval of time, current value is measured in the selected time interval from 0 to 600 sec., controlling for this purpose the current value I(t) after equal time intervals, and the value of leakage current Iym. is assessed, from such produced spectrum representing a curve t*I(t)=f(t), stretching via the maximum, two main strips of absorption are identified, at the same time they monitor the value of maxima of the first and second absorption strips and their position on the time axis, information is received on condition of dielectric materials, controlled insulation gap, and the value of the resource is assessed by the value of generalised polarisation index, which represents maximum value of the function t*I(t), by means of comparison with the rated value characterising the condition of the average statistic gap, the ageing process of which is represented in the form of a mathematical model, generated on the basis of results of condition N control on the equipment actually operated for a long time, where N - integer number selected from the ratio N?70.EFFECT: higher validity of assessment of condition of insulating gaps of power equipment operating for a long time.2 dwg

Description

The invention relates to the field of measurement technology and is intended to assess the state of the insulation system of high-voltage and high-voltage power devices, such as high-power transformers of transmission and distribution networks, high-voltage cables, electrical machines, etc.

A known method for determining the state of the insulation system of an electrical installation (AC SU No. 1476406, IPC G01R 31/00, publ. 1989.04.30), which consists in the fact that the measured values under certain conditions, the values of ohmic resistance R _from. and the values of the dielectric loss tangent tanδ determine the resistance to the absorption current, absorption capacity, the absorption tangent, with the help of which an idea of the state of the insulation system is formed.

The disadvantage of this method is the low level of reliability predicting the life of the insulation system of an electrical installation.

The closest in technical essence to the present invention is a method for assessing the state of insulation and predicting its life (patent RU No. 2044326, IPC G01R 31/00, publ. 1995.09.20), which consists in the fact that the dielectric absorption spectrum is formed for the device under control in the form the dependence of the dielectric loss tangent on the frequency and find the frequency of the maximum dielectric loss, additionally determine the reference value of the frequency of the maximum dielectric loss tangent and calibration characteristics I exemplary electrical systems at various temperatures, the working temperature of the insulation, mentioned are the difference values and a calibration characteristic set generated and residual resource isolation.

The disadvantage of this method is the low level of reliability of the estimates obtained, since the calibration characteristics of the exemplary installation can differ significantly from the similar characteristics of the controlled installation, which was commissioned thirty or more years ago and manufactured using a completely different technology.

The technical result of the invention is to increase the reliability of assessing the status of long-term insulation gaps of power equipment.

This result is achieved by the fact that in the method for determining the state and life of an insulating system of electrical equipment, which consists in forming a dielectric absorption spectrum for a controlled insulating gap and using the calibration characteristic, the worked out and remaining insulation life, the insulating gap is pre-discharged for the required time interval, measure the current value in the selected time interval from 0 to 600 sec., controlling for this the current value I (t) through equal time intervals and estimate the magnitude of the leakage current Iout., from the spectrum thus obtained, which is a curve of the dependence t * I (t) = f (t) passing through the maximum, two main absorption bands are distinguished, while the maximums are monitored the first and second absorption bands and their position on the time axis, they obtain information about the state of dielectric materials, the controlled insulation gap, and the resource value is estimated by the value of the generalized polarization index, which is the maximum e is the value of the function t * I (t) by comparing with the calculated value characterizing the state of the average statistical interval, the aging process of which is presented in the form of a mathematical model formed on the basis of the results of monitoring the state of N equipment that has been in operation for a long time, where N is an integer and is selected from the ratio N≥70.

The invention is illustrated by drawings, where in Fig.1. a graph of the spectrum of polarization currents (spectrum of dielectric absorption) is presented; figure 2. shows a graph of the dependence of the lifetime on the value of tpi for the average equipment (transformer).

The method consists in controlling the value of the generalized polarization index tpi (total polarization index), which reflects the intensity of the structural polarization developing at the interface: oil is a solid dielectric and is a function of the state of contacting materials. To assess the state of the control object, the tpi value is compared with the calculated value of tpi _calculation. characterizing the state of the average unit of similar equipment. Comparison of the measured value of tpi with its maximum permissible value of tpi _before. , which determines the maximum permissible state of the monitored period, allows us to estimate the value of the remaining resource. The aging process (calibration characteristic) in this case is presented in the form of a mathematical model formed on the basis of the analysis of the results of monitoring a large number (N> 50) of similar equipment and reflecting the experience of operating the products for a long time.

The value of tpi is nothing more than the maximum value of the dependence t * i (t) = f (t), where i (t) is the magnitude of the polarization current normalized to the leakage current I _ut .

$$i\left(t\right)=\left(I\left(t\right)-I_{\mathrm{at}t}\right)/I_{\mathrm{at}t}.\begin{array}{cccc}& & & \end{array}\left(\mathrm{one}\right)$$

I (t) is the value of the measured current at time. The dependence t * i (f) = f (f) is a curve passing through a maximum.

The dependence t * i (t) = f (t) for the real insulation gap of the transformer with a maximum operating voltage of 110 kV (Fig. 1) reflects the dielectric absorption spectrum in the time interval (0 ÷ 600) sec. In this time interval, the dielectric absorption spectrum is represented by two main absorption bands. (1 - absorption band with a maximum in the interval (50 ÷ 250) sec; 2 - absorption band with a maximum in the interval (300 ÷ 500) sec.). The magnitude of the first maximum is determined by the processes of structural polarization developing at the interface between liquid and solid dielectrics, and depends on the properties and state of the materials in contact. The magnitude of the second maximum is determined by the processes of structural polarization taking place in the bulk of the liquid dielectric, and reflects the level of its aging. Thus, by controlling the magnitude of both maxima and their position on the time axis, information is obtained on the state of the dielectric materials forming the controlled gap. Established empirically the t _w = f (tpi) reflects the existing laws of the aging fleet of equipment in operation, and its approximation in the form of a mathematical equation

$$t_{\mathrm{well}}=A*tp{i}^{-n}\begin{array}{cccc}& & & \end{array}\left(2\right)$$

is a mathematical model of its aging process. In addition, it is possible to quantify the value of the remaining time resource of the operated equipment. For this, the measured tpi value is compared with its maximum permissible tpi value _before. determining the maximum permissible state of the controlled period Δt _life .

$$\Delta t_{\mathrm{well}\mathrm{and}s.}=t_{\mathrm{well}\mathrm{and}s.}\left[{\left(\frac{tpi}{tp{i}_{PRed}}\right)}^n-\mathrm{one}\right].\begin{array}{cccc}& & & \end{array}\left(3\right)$$

, когда эксплуатация изделия становится технически невозможна или экономически нецелесообразна. Точность оценки ресурса определяется достоверностью зависимости t_ж=f(tpi) для среднестатистического изделия, которая в данном способе принимается в качестве базы сравнения и которая была получена с помощью регрессионного анализа результатов контроля более 70 реально существующих трансформаторов напряжением 110 кВ, время эксплуатации которых укладывается в диапазоне от 24 до 55 лет. Точность оценок с каждым прошедшим годом увеличивается, так как число исследованных трансформаторов одного и того же типа возрастает. Установленные физические закономерности позволяют предложить новый способ определения состояния и ресурса работающей изоляционной конструкции. Суть его заключается в том, что из полученного опытным путем спектра диэлектрической абсорбции выделяют две его основные полосы поглощения, интенсивность и положение на временной оси которых позволяют судить о состоянии диэлектрических материалов, формирующих изоляционный промежуток. При этом величину ресурса оценивают путем сопоставления величины первого максимума (tpi) с расчетным значением tрi_пред, характеризующим состояние близкое к отказу среднестатистического промежутка, процесс старения которого представлен в виде математической модели, отражающей результаты контроля состояния большого числа (N≥70) однотипного оборудования, где N целое число. Математическая модель, в итоге формирует базу сравнения, в которой отражен накопленный опыт эксплуатации интересующего оборудования, что, в конечном счете, и позволяет повысить достоверность оценок состояния и точность определения ресурса.In these ratios, t _life. - time worked by controlled electrical equipment (product) in years; A and n are constants determined by the least squares method in the processing of experimental data .. The value of tpi _before. using approximating this dependence, find relationship (2) in magnitude $$t_{\mathrm{well}\mathrm{and}s.}^{PRed.}$$

when the operation of the product becomes technically impossible or economically impractical. The accuracy of the resource estimate is determined by the reliability of the dependence t _W = f (tpi) for the average product, which in this method is taken as a comparison base and which was obtained by regression analysis of the results of control of more than 70 really existing transformers with a voltage of 110 kV, the operating time of which fits into range from 24 to 55 years. The accuracy of estimates increases with each passing year, as the number of investigated transformers of the same type increases. The established physical laws make it possible to propose a new method for determining the state and life of a working insulating structure. Its essence lies in the fact that two main absorption bands are distinguished from the experimentally obtained dielectric absorption spectrum, the intensity and position on the time axis of which allow us to judge the state of the dielectric materials forming the insulating gap. In this case, the resource value is estimated by comparing the value of the first maximum (tpi) with the calculated value tpi _before characterizing the state close to the failure of the average statistical interval, the aging process of which is presented in the form of a mathematical model that reflects the results of monitoring the state of a large number (N≥70) of the same type of equipment, where N is an integer. The mathematical model, as a result, forms the comparison base, which reflects the accumulated experience of operating the equipment of interest, which, ultimately, allows to increase the reliability of state assessments and the accuracy of determining the resource.

The method of determining the state and resource of the insulation gap, as a sequence of technological operations, is implemented as follows.

1. The insulation gap to be monitored is previously discharged for the required time interval.

2. The dependence I (t) is measured in the selected time interval (0 ÷ 600 sec), controlling for this the current value in the interval every 5 sec, and the leakage current I _{ut is} estimated _. .

3. A dielectric absorption spectrum is formed for the controlled insulating gap, which is the dependence t * I (t) = f (t).

4. From the obtained spectrum, which is a curve passing through a maximum, using the method proposed by Hideharu Matsuura and Takashi Hose "Graphical peak analysis method for determining densities and emission rates of traps in dielectric film from transient discharge current". // Journal Applied Physics, 2002, vol. 91, No. 4, p.p.2085-2092, distinguish two main absorption bands, the parameters of which carry basic information about the state and life of the isolation gap.

5. Comparing the measured value of tpi with the calculated tpi _calculation. calculated using the relation (2) for t _W equal to the number of worked calendar years of the product at the time of its control, evaluate how much the degree of aging of the controlled insulation gap differs from the degree of aging of the average, for which not only the value of tpi, but also the value of the resource is known (Fig. .2).

The information obtained in this way allows you to quantify the desired parameters. A distinctive feature of the proposed method is the formation of a mathematical model as the basis of the comparison base according to the results of the control of actually operated equipment. (As a rule, specially created physical or mathematical models only with a large approximation reflect the physical processes occurring in insulating structures. In such cases, the comparison base is represented in the form of master curves, calibration characteristics, reference points, etc.: Y. Takezava at all. Thermal Deterioration Diagnostics by Optical Fiber Sensors for Mica-epoxy Insulation of HV Induction Motors. - IEEE Transaction on Dielectrics and Electrical Insulation. - V.4. - No. 1, February 2001).

To identify the controlled equipment, the curve t * i (t) = f (t) is laid out on two main absorption bands (Fig. 1), with which the tpi value and the condition of the equipment as a whole are determined. Estimated value of tpi _calc. determined by the curve shown in figure 2, or by the calculated ratio (2) describing the aging process of the average unit of controlled equipment. As a result, Δt _life. , determined by the formula (3), allows you to quantify how true the age of the controlled product differs from its average counterpart. When implementing the control method, the identified distinctive signs in combination with other signs provide a technical result, which consists in increasing the reliability of assessing the state and value of the isolation resource. Improving the reliability of assessing the state and life of the insulation gap is achieved by experimentally controlling the value of tpi determined by the intensity of the polarization processes developing at the interface: oil - solid dielectric, and directly dependent on the characteristics and condition of the contacting materials. The value of tpi is compared with its calculated value of tpi _calculation. characterizing the aging process of an average unit of equipment over time, since the comparison base is formed on the basis of the results of monitoring a large number of actually operated equipment.

The use of the invention provides an increase in the reliability of assessing the condition and resource of the isolation gap

Claims (1)

A method for determining the state and life of an insulating system of electrical equipment, which consists in forming a dielectric absorption spectrum for a controlled insulating gap and using the calibration characteristic to determine the worked out and residual insulation resource, characterized in that the insulating gap is pre-discharged for the required time interval, the current is measured in the selected time interval from 0 to 600 s, controlling for this the magnitude of the current I (t) at regular intervals and the leakage current Iout is estimated, from the spectrum obtained in this way, which is a curve dependence t · I (t) = f (t) passing through a maximum, two main absorption bands are distinguished, while the maximums of the first and second absorption bands are monitored and their position on the time axis, they obtain information about the state of dielectric materials, the controlled insulation gap, and the resource value is estimated by the value of the generalized polarization index, which is the maximum value of the function t I (t), by comparing with the calculated value characterizing the state of the average statistical interval, the aging process of which is presented in the form of a mathematical model formed on the basis of the results of monitoring the state of N equipment that has been in operation for a long time, where N is an integer and is selected from the ratio N≥70 .

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