JP5469052B2 - Winding insulation characteristics evaluation method - Google Patents

Description

  The present invention relates to a winding insulation characteristic evaluation method for evaluating the insulation state of a winding of a rotating electrical machine such as an electric motor or a generator.

  In general, it is important to measure an insulation characteristic due to secular change in an electric device such as an electric motor in order to evaluate the deterioration degree and remaining life of the electric device. Therefore, the insulation resistance measuring instrument is used to measure the insulation resistance in the initial state and the insulation resistance after aging, and the measured values are compared to estimate the presence or absence of deterioration and the remaining life. However, since the insulation resistance value varies depending on the situation at the time of measurement, that is, the ambient temperature and humidity, and the moisture absorption of the device under measurement, it is difficult to accurately evaluate the degree of deterioration of the device.

  Therefore, the conventional insulation diagnosis method makes it possible to estimate insulation deterioration by paying attention to the difference in the environmental condition where the winding is placed, that is, the difference in insulation characteristics between the dry state and the moisture absorption state. Since the insulation resistance of the advanced insulator is extremely lowered in the moisture absorption state, the degree of insulation deterioration is diagnosed by measuring the difference in resistance value between the dry state and the moisture absorption state. (For example, refer to Patent Document 1). Specifically, the insulation resistance in the moisture absorption state where the winding was exposed to steam and forcedly absorbed and the insulation resistance in the dried state after drying were measured to obtain the ratio of these insulation resistances. When compared with the result of measuring the dielectric breakdown voltage due to voltage application, there is a correlation between the insulation resistance ratio and the insulation resistance breakdown voltage, so that it is possible to estimate the insulation degradation state and the dielectric breakdown strength.

JP-A-58-55768

  However, in the conventional insulation diagnosis method, the insulation resistance in the moisture absorption state after the aging and the insulation resistance in the dry state are measured, and the insulation resistance state and the dielectric breakdown strength are estimated by comparing the insulation resistance. Actually, the insulation resistance, capacitance, and tan δ (dielectric loss tangent) values vary depending on the dry / moisture absorption state of the winding and the temperature of the winding. It is difficult to accurately evaluate the degree of insulation deterioration only by the insulation characteristics of the alternating current test and the tan δ test. Conventional methods for evaluating insulation characteristics do not take into account changes in insulation resistance, capacitance, and tan δ (dielectric loss tangent) due to the drying / moisture absorption state of the winding and the temperature of the winding. There has been a problem that the insulation characteristics of the winding cannot be said to have been evaluated.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a method for evaluating the insulation characteristics of a winding that can accurately evaluate the insulation characteristics of a winding after a lapse of time. Yes.

In order to solve the above problems, the insulating characteristic evaluation method of the winding of the present invention, the insulating characteristic evaluation method of winding evaluating insulating properties of the winding after aging, the electrostatic capacitance C, the dielectric loss tangent (tan [delta ₀ ), Winding drying / humidity evaluation index I _X (= R · C ₀ / Kc /) defined by the insulation resistance R and the capacitance ratio K _C (= C / C ₀ , C ₀ : initial capacitance). tan δ ₀ ), the insulation characteristics of the winding in the dry / moisture absorption evaluation index after the aging are converted into the insulation characteristics of the winding in the dry / moisture absorption evaluation index in the initial state, and the converted winding The insulation characteristics of the winding after the lapse of time are evaluated by comparing the insulation characteristics with the insulation characteristics of the winding in the initial state.

According to the method for evaluating the insulation characteristics of a winding according to the present invention, the insulation resistance, capacitance, and dielectric loss tangent (tan δ ₀ ) are used for the evaluation, and the condition of the drying / moisture absorption state of the winding and the temperature of the winding after aging Even if the insulation characteristics are different from those at the initial state, the insulation resistance, capacitance, and tan δ (dielectric loss tangent) are converted into the same conditions as the dry / moisture-absorbed state at the time of initial state insulation characteristics evaluation. As a result, it is possible to accurately evaluate the insulation characteristics after aging regardless of the drying / moisture absorption state of the winding and the temperature of the winding.

It is a flowchart which shows the evaluation procedure in embodiment of this invention. It is a figure which shows the dielectric loss tangent-voltage characteristic after the initial state in the embodiment of this invention, and aged. It is a figure which shows the current-time characteristic for measuring the insulation resistance in embodiment of this invention. It is a figure which shows the electric current-voltage characteristic after the initial state in embodiment of this invention, and aged. It is a figure which shows the insulation characteristic by the electric current rapid increase voltage after the initial state in the embodiment of this invention, and aged. It is a figure which shows the insulation characteristic by the current gradient increase rate after the initial state in the embodiment of this invention, and aged. It is a figure which shows the insulation characteristic by the insulation resistance after the initial state in the embodiment of this invention, and aged. It is a figure which shows the insulation characteristic by the electrostatic capacitance after the initial state in the embodiment of this invention, and aged. It is a figure which shows the insulation characteristic by the dielectric loss tangent after the initial state in the embodiment of this invention, and aged. It is a figure which shows the insulation characteristic by the dielectric loss tangent variation | change_quantity after the initial state in the embodiment of this invention, and aged.

Hereinafter, a method for evaluating an insulation characteristic of a winding according to an embodiment of the present invention will be described with reference to FIGS. In the insulation characteristic evaluation of the present invention, a drying / moisture absorption evaluation index Ix defined by the formula (1) is newly introduced.
Ix = R · C ₀ / Kc / tan δ ₀ (1)
Here, R is the insulation resistance of the winding, C ₀ is the initial capacitance of the winding, tan δ ₀ is the dielectric loss tangent of the winding at low voltage, and K _C is the capacitance ratio of the winding (C / C ₀ ).
In the moisture absorption state, the insulation resistance R decreases, and the dielectric loss tangent tan δ ₀ and the capacitance C increase. Conversely, in the dry state, the insulation resistance R increases, and the dielectric loss tangent tan δ ₀ and the capacitance C decrease.

  FIG. 1 is a flowchart showing an evaluation procedure in the winding insulation characteristic evaluation method according to the embodiment. FIG. 2 is a diagram showing an initial state and a dielectric loss tangent (tan δ) -voltage characteristic (tan δ-V characteristic) of a stator winding of a rotating electrical machine such as a generator after a lapse of time. FIG. 3 is a diagram showing current-time characteristics (It characteristics) for measuring the insulation resistance. FIG. 4 is a diagram showing current-voltage characteristics (IV characteristics) after the initial state and aging.

In the winding insulation characteristic evaluation method according to the embodiment, as shown in the flow chart showing the evaluation procedure of FIG. 1, the AC test, the insulation resistance measurement, and the AC current test of the winding in the initial state and after the aging are performed. The dry / moisture absorption evaluation index Ix is obtained from the measured capacitance C, dielectric loss tangent tan δ, and insulation resistance R, respectively, and the insulation characteristics (current) after the lapse of time from the measurement results of the current sudden increase voltage Pi and the current gradient a. Rapid increase voltage ratio Es / Pi, current gradient increase rate (a−a ₀ ) / a ₀ , insulation resistance R, capacitance C, dielectric loss tangent tan δ and dielectric loss tangent change amount Δtan δ) in the initial state of dry / moisture evaluation index Ix Insulation characteristics serving as a judgment material for judging the insulation deterioration and remaining life of the winding by converting to the initial condition and comparing with the insulation characteristics in the initial state.

  Next, the procedure for evaluating the insulation characteristics of the winding will be described with reference to FIGS. First, the insulation characteristics of the winding in the initial state and the insulation characteristics of the winding after aging are obtained (S1 to S4, S5 to S8). As a measurement item, an AC test, an insulation resistance measurement, and an AC current test are performed (S1, S5).

  In the AC test, an AC voltage is applied between the conductor part of the winding and the iron core (earth), and capacitances C and C ′ and dielectric loss tangent (tan δ, tan δ ′) are measured (FIG. 2). Here, the winding temperature is measured at the same temperature. In the figure, the dielectric loss tangent (tan δ) in the initial state is represented by a solid line, and the dielectric loss tangent (tan δ) after the passage of time is represented by a broken line. The symbol “′” indicates a value after aging.

In the insulation resistance measurement, a DC voltage is applied between the conductor portion of the winding and the iron core (earth) to measure the insulation resistances R and R ′ of the winding (FIG. 3). When the DC voltage Ed is applied to the winding, the current I changes with the measurement time t. The insulation resistance R is obtained by dividing the DC voltage Ed by the current I. In the insulation evaluation of the present invention, any current value at the time of charging or discharging may be used. The charging current is the actual measured total charging current Ip and the charging current Ia obtained by subtracting the saturation charging current (indicated by the broken line on the left in FIG. 3) from the total charging current Ip, and the discharging current is the actual measured total discharging current Id. The discharge current Ir obtained by subtracting the saturation discharge current (indicated by the broken line on the right in FIG. 3) from the total discharge current Id, and the measurement time t also differ depending on 30 seconds, 1 minute, and 10 minutes. It is assumed that the insulation resistance R uses the charging current Ia _{1 min} in minutes. The same applies to the insulation resistance R ′ after a lapse of time. The insulation resistance R depends on the winding temperature. The insulation resistance R decreases when the winding temperature is high, and increases when the winding temperature is low. For this reason, the initial state and the measurement after aging are carried out at the same temperature.

In the alternating current test, an alternating voltage is applied between the conductor portion of the winding and the iron core (earth), and current-voltage characteristics (IV characteristics) are measured (FIG. 4). In FIG. 4, the current in the initial state is represented by a solid line, and the current after aging is represented by a broken line. The current gradient a ₀ , a at the current before and after the current sudden increase voltage Pi and the current sudden increase voltage Pi in the initial state, and the current gradient at the current before and after the current sudden increase voltage Pi ′ and the current sudden increase voltage Pi ′. Find a ₀ ', a'.

In the measurement of the dielectric loss tangent, as shown in FIG. 2, the initial dielectric tangent at low voltage is tan δ ₀ , the dielectric tangent after aging is tan δ ₀ ′, and the initial value between the dielectric tangent at high voltage and the dielectric loss tangent at low voltage. The amount of change in dielectric loss tangent in the state is Δtan δ, and the amount of change in dielectric loss tangent after aging is Δtan δ ′.

  In the insulation resistance measurement, AC current test, and dielectric loss tangent measurement of the winding after the aging, in addition to the measurement in the dry / moisture absorption state where the winding is placed, the winding is heated to the dry / moisture absorption state. Measurements under different conditions are also performed.

Subsequently, a capacitance ratio Kc (= C / C ₀ , C ₀ is an initial capacitance) is calculated (S2, S6). In the winding in the initial state, Kc = 1.

The dry / moisture absorption evaluation index Ix in the initial state is obtained by using the insulation resistance R, the initial capacitance C ₀ , the capacitance ratio Kc, and the dielectric loss tangent tan δ ₀ at low voltage. Similarly, the dry / moisture absorption evaluation index Ix ′ after the aging is obtained using the insulation resistance R ′, the initial capacitance C ₀ , the capacitance ratio Kc ′, and the dielectric loss tangent tan δ ₀ ′ at low voltage (S3, S7). ).

Subsequently, the insulation characteristics of the winding in the initial state and after aging are calculated (S4, S8). The items of the insulation characteristics used for the determination of the deterioration of the insulation and the remaining life are the ratio (Es / Pi) of the current sudden increase voltage Pi to the AC rated voltage Es of the winding, the current gradient at the voltage before and after the current sudden increase voltage Pi. The increase rate ((a−a ₀ ) / a ₀ ), insulation resistance R, capacitance C, dielectric loss tangent tan δ, and dielectric loss tangent change amount are Δtan δ.

  The insulation characteristic of the winding with respect to the dry / moisture absorption evaluation index Ix ′ after the aging is converted into an insulation characteristic in accordance with the condition of the dry / moisture absorption evaluation index Ix in the initial state (S9).

  FIG. 5 shows a case where the current sudden increase voltage Pi ratio (Es / Pi) is used as the insulation characteristic. Es / Pi '(A) after the lapse of time is converted into a value Es / Pis under the condition of the dry / moisture absorption evaluation index Ix. For this reason, in order to change the drying / moisture absorption state of the winding after the lapse of time, Es / Pi ″ (×) is set on the drying / moisture absorption evaluation index Ix ″ by heating the winding and increasing the dryness. Ask. The Es / Pis (Δ) in the initial state is defined as the converted Es / Pis (Δ) where the point intersecting the drying / moisture absorption evaluation index Ix on the extended line of the straight line connecting Es / Pi ′ (▲) and Es / Pi ″ (×) is obtained. Compare with / Pi (●). This converted insulation characteristic shows the secular change of the original insulation characteristic by comparing B with the dry / moisture absorption condition in the same condition as the initial condition compared with A compared without considering the dry / moisture absorption condition. Can be evaluated with high accuracy.

FIG. 6 shows a case where the current gradient increase rate ((a−a ₀ ) / a ₀ ) at the voltages before and after the current sudden increase voltage Pi is used as the insulation characteristic. The aged (a′−a ₀ ′) / a ₀ ′ (▲) is converted into a value (a _S −a _0S ) / a _{0S under} the condition of the dry / moisture absorption evaluation index Ix. For this reason, in order to change the drying / moisture absorption state of the winding after the lapse of time, the winding is heated to increase the dryness on the drying / moisture absorption evaluation index Ix ″ (a ″ −a ₀ ″). ) / A ₀ ″ (×). Crosses the dry / moisture absorption index Ix on the extension of the straight line connecting (a′−a ₀ ′) / a ₀ ′ (▲) and (a ″ −a ₀ ″) / a ₀ ″ (×) The point to be converted is converted into (a _S −a _0S ) / a _0S (Δ) and compared with (a−a ₀ ) / a ₀ (●) in the initial state. This converted insulation characteristic shows the secular change of the original insulation characteristic by comparing B with the dry / moisture absorption condition in the same condition as the initial condition compared with A compared without considering the dry / moisture absorption condition. Can be evaluated with high accuracy.

  FIG. 7 shows a case where the insulation resistance R (MΩ) is used as an insulation characteristic. R '(▲) after the lapse of time is converted into a value Rs under the condition of the dry / moisture absorption evaluation index Ix. For this reason, in order to change the drying / moisture absorption state of the winding after the lapse of time, the winding is heated, and R ″ (x) is obtained on the drying / moisture absorption evaluation index Ix ″ with increased dryness. A point where the dry / moisture absorption evaluation index Ix intersects on the extended line of the straight line connecting R ′ (▲) and R ″ (×) is compared with R (●) in the initial state as converted Rs (Δ). . This converted insulation characteristic shows the secular change of the original insulation characteristic by comparing B with the dry / moisture absorption condition in the same condition as the initial condition compared with A compared without considering the dry / moisture absorption condition. Can be evaluated with high accuracy.

  FIG. 8 shows a case where the capacitance C (μF) is used as an insulation characteristic. The C ′ (）) after the lapse of time is converted into a value Cs under the condition of the dry / moisture absorption evaluation index Ix. For this reason, in order to change the drying / moisture absorption state of the winding after a lapse of time, the winding is heated, and C ″ (x) is obtained on the drying / moisture absorption evaluation index Ix ″ with increased dryness. A point where the dry / moisture absorption evaluation index Ix intersects on the extended line of the straight line connecting C ′ (▲) and C ″ (x) is compared with C (●) in the initial state as converted Cs (Δ). . This converted insulation characteristic shows the secular change of the original insulation characteristic by comparing B with the dry / moisture absorption condition in the same condition as the initial condition compared with A compared without considering the dry / moisture absorption condition. Can be evaluated with high accuracy.

FIG. 9 shows a case where the dielectric loss tangent tan δ ₀ (%) at low voltage is used as the insulation characteristic. The tan δ ₀ ′ (▲) after the lapse of time is converted into a value tan δ ₀ s under the condition of the dry / moisture absorption evaluation index Ix. Therefore, in order to change the drying / moisture absorption state of the winding after aging, the winding is heated to obtain tan δ ₀ ″ (×) on the drying / moisture absorption evaluation index Ix ″ with increased dryness. . On the extended line of the straight line connecting tan δ ₀ ′ (▲) and tan δ ₀ ″ (×), a point intersecting with the dry / moisture absorption evaluation index Ix is converted into tan δ ₀ s (Δ), and the initial state tan δ ₀ ( ● Compare with. This converted insulation characteristic shows the secular change of the original insulation characteristic by comparing B with the dry / moisture absorption condition in the same condition as the initial condition compared with A compared without considering the dry / moisture absorption condition. Can be evaluated with high accuracy.

  FIG. 10 shows a case where the dielectric loss tangent variation Δtan δ (%) is used as the insulation characteristic. Δtanδ ′ (▲) after the lapse of time is converted to a value Δtanδs under the condition of the dry / moisture absorption evaluation index Ix. For this reason, in order to change the drying / moisture absorption state of the winding after the lapse of time, Δtanδ ″ (×) is obtained on the drying / moisture absorption evaluation index Ix ″ with increased dryness by heating the winding. On the extended line of the line connecting Δtanδ ′ (▲) and Δtanδ ″ (×), a point intersecting with the dry / moisture absorption evaluation index Ix is compared with Δtanδs (Δ) converted to the initial state Δtanδ (●). . This converted insulation characteristic shows the secular change of the original insulation characteristic by comparing B with the dry / moisture absorption condition in the same condition as the initial condition compared with A compared without considering the dry / moisture absorption condition. Can be evaluated with high accuracy.

  Finally, if necessary, the insulation characteristics of the winding in the initial state are compared with the converted insulation characteristics of the winding, and the insulation deterioration of the winding and the remaining life are evaluated (S10).

  Thus, in the winding insulation characteristic evaluation method according to the embodiment, the insulation of the winding is introduced by introducing the dry / moisture absorption evaluation index defined by the capacitance, dielectric loss tangent, insulation resistance, and capacitance ratio. It is possible to evaluate the characteristics without being influenced by the dry / moisture absorption state, and there is a remarkable effect that the insulating characteristics of the winding after the lapse of time can be accurately evaluated.

In the present embodiment, the case of evaluating the insulation characteristics of the stator winding of a rotating electrical machine such as a generator has been described. However, even if the insulation characteristics of the winding of other electrical equipment are evaluated. The same effect can be obtained.

Claims (7)

In the method of evaluating the insulation characteristics of the winding to evaluate the insulation characteristics of the winding after the aging,
Winding dry / moisture evaluation index I _X defined by capacitance C, dielectric loss tangent tan δ ₀ , insulation resistance R and capacitance ratio K _C (= C / C ₀ , C ₀ : initial capacitance) = R · C ₀ / Kc / tan δ ₀ ), and the insulation characteristics of the winding in the dry / moisture absorption evaluation index after the aging are converted into the insulation characteristics of the winding in the dry / moisture absorption evaluation index in the initial state. A method for evaluating an insulation characteristic of a winding, wherein the insulation characteristic of the coil after the aging is evaluated by comparing the converted insulation characteristic of the winding with the insulation characteristic of the winding in an initial state.   2. The method for evaluating insulation characteristics of a winding according to claim 1, wherein a current rapid increase voltage ratio Es / Pi obtained by dividing the rated voltage Es by the current rapid increase voltage Pi is used as the insulation characteristic of the winding. As the insulation characteristic of the winding, the current gradient increase rate (a−a ₀ ) / a ₀ (a: high voltage side current gradient, a ₀ : low voltage side current gradient) at the voltage before and after the current sudden increase voltage Pi is used. The method for evaluating an insulation characteristic of a winding according to claim 1.   The insulation characteristic evaluation method for a winding according to claim 1, wherein an insulation resistance R is used as the insulation characteristic of the winding.   The method for evaluating insulation characteristics of a winding according to claim 1, wherein a capacitance C is used as the insulation characteristics of the winding. 2. The method for evaluating an insulation characteristic of a winding according to claim 1, wherein a dielectric loss tangent tan δ ₀ at a low voltage is used as the insulation characteristic of the winding. The dielectric loss tangent variation Δtanδ, which is the difference between the dielectric loss tangent tan δ ₀ at a low voltage and the dielectric loss tangent tan δ at a high voltage, is used as the insulation characteristic of the winding. Insulation property evaluation method.

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