RU2559785C1 - Method to monitor insulation resource of power transformer - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: signal θ_"п" from temperature sensor from the most heated point of transformer 2 comes to input of controller 5, which performs functions of analogue-to-digital conversion of the signal from temperature sensor 2, temperature data recording and storing; processing of recorded data, determining minimum and maximum temperature values and counting quantity of n heating-cooling cycles with temperature drop per more than Δθ=αθ_r. Calculation of remaining insulation resource for transformer windings as per formula

where t is time of on state; µ=0.116 is proportionality factor characterising temperature wear; θ_r is rated temperature, k₁ and k₂ are weight coefficients equal to design coefficient of resource wear for transformer insulation, α is coefficient depending on material of windings and insulation for the period t. Data of full operation time t and remaining resource T are transferred through bus bar 3 to computer 5 for recording and storing and displayed by means of monitor 6.

EFFECT: higher accuracy of resource control.

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Description

The present invention relates to electrical engineering and is intended to control the life of dry power transformers.

, где t - время включенного состояния; µ=0,116 - коэффициент пропорциональности, характеризующий температурный износ; θ_Н - номинальная температура, и рассчитывают остаточный ресурс (Ермаков В.Ф., Балыкин Е.С., Горобец А.В., Коваленко А.Н. Опытный образец микропроцессорного счетчика ресурса силовых трансформаторов / Известия вузов. Электромеханика, 2013, №1. - С. 68-70; А.с. СССР 2041496, МПК G06F 7/18, 1991).Known methods for controlling the insulation resource of a power transformer, in which the temperature θ _{p of the} most heated point of the transformer is measured, wear is calculated by the formula $${\displaystyle \underset{0}{\overset{t}{\int }}{e}^{\mu ({\theta }_P-\theta n)}dt}$$

where t is the on time; µ = 0,116 - proportionality coefficient characterizing temperature wear; θ _N is the nominal temperature, and the residual life is calculated (Ermakov V.F., Balykin E.S., Gorobets A.V., Kovalenko A.N. A prototype microprocessor counter for the resource of power transformers / News of Universities. Electromechanics, 2013, no. 1.- S. 68-70; A.S. USSR 2041496, IPC G06F 7/18, 1991).

Known methods provide control of the insulation resource of the transformer based on the consideration of thermal wear. This does not take into account the important component of wear due to thermomechanical destruction of the insulation.

Therefore, a disadvantage of the known methods is the low accuracy of monitoring the insulation resource.

, где t - время включенного состояния; µ=0,116 - коэффициент пропорциональности, характеризующий температурный износ;Of the known technical solutions, the closest to the proposed achieved result is a method of controlling the insulation resource of a power transformer, in which the temperature θ _{P of the} most heated point of the transformer is measured, wear is calculated by the formula $${\displaystyle \underset{0}{\overset{t}{\int }}{e}^{\mu ({\theta }_P-\theta n)}dt}$$

where t is the on time; µ = 0,116 - proportionality coefficient characterizing temperature wear;

θ _n is the nominal temperature, and the residual life is calculated (RF Patent No. 2384879, IPC G06F 17/18, 2010).

When implementing the known method during operation of the transformer, the value of the residual life is continuously calculated and compared with the limit value, upon reaching which a control signal is generated. The known method provides control of the resource of the transformer based on taking into account the thermal wear of the insulation. This does not take into account the important component of wear due to thermomechanical destruction of the insulation. Since the linear expansion coefficients of the conductors and the insulation do not coincide, when the heating – cooling cycle is repeated many times, cracks, delamination, and other mechanical damage are formed in the insulation, accompanied by a sharp decrease in electrical parameters.

Thus, the disadvantage of this method is the low accuracy of control of the insulation resource.

The purpose of the invention is to improve the accuracy of monitoring the resource of isolation of the transformer.

, где t - время включенного состояния; µ=0,116 - коэффициент пропорциональности, характеризующий температурный износ; θ_н - номинальная температура, и рассчитывают остаточный ресурс, согласно изобретению дополнительно определяют количество n циклов «нагревание - охлаждение» с перепадом температуры более Δθ=αθ_н, где α - коэффициент, зависящий от материалов обмоток и изоляции, за время t, и определяют остаточный ресурс по формуле: $$T=T_0-k_1{\displaystyle \underset{0}{\overset{t}{\int }}{e}^{\mu ({\theta }_{п}-\theta н)}dt-k_{2}n(\tau )}$$

, где Т₀ - номинальный ресурс изоляции трансформатора, k₁ и k₂ - весовые коэффициенты, равные расчетным коэффициентам ресурсного износа изоляции трансформатора.This goal is achieved by the fact that in the method of controlling the insulation resource of the power transformer, at which the temperature θ _{P of the} most heated point of the transformer is measured, wear is calculated by the formula $${\displaystyle \underset{0}{\overset{t}{\int }}{e}^{\mu ({\theta }_P-\theta n)}dt}$$

where t is the on time; µ = 0,116 - proportionality coefficient characterizing temperature wear; θ _n is the nominal temperature, and the residual life is calculated, according to the invention, the number of n heating-cooling cycles with a temperature difference of more than Δθ = αθ _n , where α is the coefficient depending on the materials of the windings and insulation, over time t, is determined and determined residual life according to the formula: $$T=T_0-k_{\mathrm{one}}{\displaystyle \underset{0}{\overset{t}{\int }}{e}^{\mu ({\theta }_P-\theta n)}dt-k_{2}n(\tau )}$$

where T ₀ is the nominal insulation resource of the transformer, k ₁ and k ₂ are weight coefficients equal to the calculated life wear factors of the transformer insulation.

Compared with the closest similar technical solution, the proposed method has the following new features:

- determine the number of n cycles "heating - cooling" with a temperature difference of more than Δθ = αθ _n , where α is a coefficient depending on the materials of the windings and insulation, for a time t;

- determine the residual life of the insulation of the transformer according to the formula:

where T ₀ - nominal insulation resource of the transformer, k ₁ and k ₂ - weighting factors equal to the estimated coefficients of the resource wear of the insulation of the transformer.

Therefore, the claimed technical solution meets the requirement of "novelty."

For each of the distinguishing features, a search is made for known technical solutions in the field of electrical engineering, automation, control and diagnostics.

The operation of determining the number of n cycles "heating - cooling" with a temperature difference of more than Δθ = αθ _n , where α is a coefficient depending on the materials of the windings and insulation, over time t, is not found in the known methods for a similar purpose.

The operation of determining the residual life of the insulation of the transformer windings by the formula

, $$T=T_0-k_{\mathrm{one}}{\displaystyle \underset{0}{\overset{t}{\int }}{e}^{\mu ({\theta }_P-\theta n)}dt-k_{2}n(t)}$$

,

where T ₀ is the nominal resource of the transformer, k ₁ and k ₂ are weight coefficients equal to the calculated coefficients of the resource wear of the insulation of the transformer, in the known methods for a similar purpose was not found.

Thus, these features provide the claimed technical solution according to the requirement of "significant differences".

When implementing the proposed technical solution, it is possible to increase the accuracy of monitoring the transformer resource by taking into account not only the thermal aging of the insulation, but also its thermomechanical wear. Evaluation of thermomechanical wear is carried out by counting the number of heating-cooling cycles with a temperature drop of more than Δθ = αθ _n that occur when the transformer is turned on or the loads are connected. When heated, thermal deformation of the conductive elements and insulation occurs. Since the materials of insulation and conductors have different temperature coefficients of linear expansion, deformation causes a mechanical load on the insulation. Especially adverse effect on insulation is exerted by multiple cycles of “heating - cooling”, for example, with frequent switching on. Accounting for thermomechanical wear of insulation can improve the accuracy of monitoring the insulation resource.

Therefore, the claimed technical solution meets the requirement of "positive effect".

The essence of the proposed method for monitoring the insulation resource of a power transformer is illustrated by drawings. In FIG. 1 is a functional diagram of a power transformer insulation resource monitoring system. The drawing indicates: 1 - power transformer, 2 - temperature sensor of the most heated point of the transformer, 3 - data bus, 4 - controller, 5 - industrial computer, 6 - monitor.

The operation of the control circuit of the insulation resource of the power transformer is as follows. The signal from the temperature sensor of the most heated point of the transformer 2 is fed to the input of the controller 5. Controller 5 performs the following functions:

- analog-to-digital conversion of the signal from the temperature sensor 2;

- registration and storage of temperature data;

- processing of recorded data, determination of minimum and maximum temperature values;

- counting the number of n cycles "heating - cooling" with a temperature difference of more than Δθ = αθ _n ;

- calculation of the total operating time (on state) of the transformer;

- calculation of the residual life of the insulation of the transformer windings according to the formula

Data on the total operating time t and the value of the residual life T on the bus 3 are transmitted to the computer 5 for registration and storage and displayed using the monitor 6.

In FIG. Figure 2 shows diagrams of the temperature change θ _{p of the} most heated point of the transformer and the counting of the heating – cooling cycles at which the temperature difference exceeds Δθ = αθ _n .

, где t - время включенного состояния; µ=0,116 - коэффициент пропорциональности, характеризующий температурный износ; θ_н - номинальная температура, рассчитывают остаточный ресурс, дополнительно определяют количество n циклов «нагревание - охлаждение» с перепадом температуры более Δθ=αθ_н, где α - коэффициент, зависящий от материалов обмоток и изоляции, за время t, и определяют остаточный ресурс по формулеThus, the use in a known method of controlling the insulation resource of a power transformer, at which the temperature θ _{p of the} most heated point of the transformer is measured, wear is calculated by the formula $${\displaystyle \underset{0}{\overset{t}{\int }}{e}^{\mu ({\theta }_P-\theta n)}dt}$$

where t is the on time; µ = 0,116 - proportionality coefficient characterizing temperature wear; θ _n - nominal temperature, calculate the residual life, additionally determine the number of n cycles “heating - cooling” with a temperature drop of more than Δθ = αθ _n , where α is the coefficient depending on the materials of the windings and insulation over time t, and determine the residual life by the formula

where T ₀ is the nominal insulation resource of the transformer, k ₁ and k ₂ are weight coefficients equal to the calculated coefficients of the resource wear of the insulation of the transformer, which allows to increase the accuracy of monitoring the resource of insulation of the transformer.

Using the proposed method with automated monitoring and diagnostics of transformers will help to improve the reliability and quality of electrical equipment.

Claims (1)

The method of controlling the insulation resource of the power transformer, in which the temperature θ _{p of the} most heated point of the transformer is measured, wear is calculated by the formula
$${\displaystyle \underset{0}{\overset{t}{\int }}{e}^{\mu ({\theta }_P-{\theta }_n)}dt}$$

,
where t is the on time; µ = 0,116 - proportionality coefficient characterizing temperature wear; θ _n is the nominal temperature, and the residual life is calculated, characterized in that it additionally determines the number of n cycles of “heating - cooling” with a temperature difference of more than Δθ = αθ _n , where α is a coefficient depending on the materials of the windings and insulation, for time t, and determine the residual resource by the formula:

where T ₀ is the nominal resource of insulation of the transformer, k ₁ and k ₂ are weight coefficients equal to the calculated coefficients of the resource wear of the insulation of the transformer.

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