JPH0728512B2 - Method for obtaining residual rate of dielectric breakdown voltage of rotating electric machine winding, and method for estimating remaining life of rotating electric machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a method for obtaining a residual ratio of a winding breakdown voltage used in diagnosing a remaining life of a rotating electric machine winding, and the method thereof. The present invention relates to a remaining life estimation method that uses the residual rate of winding insulation breakdown withstand voltage.
It is a new proposal for a method of estimating the remaining insulation life of the rotating electric machine winding that causes fluctuations in reactive power (hereinafter referred to as VAR fluctuations).

[Conventional technology]

Generally, not only for rotating electrical machines, but for electrical equipment, deterioration of electrical insulators eventually appears as a decrease in dielectric breakdown withstand voltage,
In order for these electric devices to operate without problems, it is necessary to have a dielectric breakdown withstand voltage that meets the operating conditions required for each device.

Conventionally, as a method for estimating the remaining rate of the above-mentioned dielectric breakdown withstand voltage (hereinafter referred to as BDV (BREAK DOWN VOLTAGE) remaining rate) of the insulation applied to the windings of rotating electric machines, the document "Life diagnosing technology for large rotating machine coils" (Hitachi Review, VOL67, No.2, 1985-2).

In this document, the following four points are cited as the causes of deterioration of the winding insulation to which a high voltage exceeding 6.6 KV is applied.

(1) Electrical deterioration (voltage degradation) Generally, void discharge in the winding insulating layer represented by the Vt characteristic, and deterioration due to training in a region where the electric field strength is high.

(2) Deterioration due to heat cycle Since the linear expansion coefficient of the conductor and the insulating layer is different due to the start / stop of the generator or load fluctuation, shear force is generated at the boundary between them and the conductor and the insulating layer are separated. Or, it affects the expansion of voids in the insulating layer. In addition, the winding itself heat-extends, which causes a bending moment at the winding end, which causes a decrease in the insulating layer at the slot outlet and winding bend (the bent portion of the winding end immediately at the slot outlet). Causes bending fatigue in the cycle region.

(3) Mechanical deterioration Electromagnetic force during steady operation and abnormal operation such as sudden short circuit,
Deterioration due to high cycle fatigue due to core vibration.

(4) Thermal deterioration Degradation due to insulation range shrinkage, voiding due to thermal decomposition, and peeling.

From the factors described in (1) to (4) above, the BDV residual rate (V
_R / V _O ) is expressed by the following equation (1).

_{V R / V O = (V} E / V O × V H / V O × V T / V O) ... (1) V R; residual breakdown voltage resistance, _{V O;} initial breakdown withstand voltage _{V E} / V O; BDV residual rate due to voltage deterioration V _H / V _O ; BDV residual rate due to heat cycle deterioration V _T / V _O ; BDV residual rate due to thermal deterioration Therefore, according to equation (1), the operating time Y of the rotating electric machine and the number of start / stop Once N is determined, the BDV residual rate of winding insulation is based on a large number of experimental data, and the relationship between N and Y with BDV residual rate as a parameter. From a master curve, a certain number of start / stop times N ₁ and years of operation Y ₁ Therefore, the BDV residual rate V _R / V _O can be easily estimated. Hereinafter, this method is referred to as an NY map method.

[Problems to be Solved by the Invention]

It has been confirmed that the above-mentioned conventional technology can estimate the BDV residual rate of a rotating electric machine used in a steady state with various fluctuations with extremely high accuracy, but frequent load fluctuations and VAR fluctuations ( It is often seen in steel mill loads, etc.)
However, there is a drawback in that the accuracy is lowered in the rotating electric machine in which many factors that give great stress to the electric machine winding occur.

The present invention was considered as a method of compensating for the drawback of lowering the accuracy, and the purpose thereof is to consider a factor that gives a large stress to the rotating electric machine winding, specifically, load fluctuation, V
Using the AR variation, we improve the calculation accuracy of the BDV residual rate of the rotating electrical machine used under the operating condition where the variation factor frequently occurs, and by using it, we can estimate the residual insulation life of the rotating electrical machine by using the method. To provide.

[Means for Solving the Problems]

The purpose of the above is to convert each factor that applies a large stress to the winding insulation to the equivalent number of start / stop times, correct the actual number of start / stop times to this equivalent number of start / stop times, and use the equivalent start / stop times. Achieve by doing. That is, in the N-Y map method, which is a conventional technique, the number of times of starting and stopping is merely the number of times of starting and stopping the device. Therefore, in this case, the coefficient of linear expansion differs between the starting and stopping of the device. A shearing force is generated at the boundary between the winding conductor and the insulating layer, and a factor that influences separation of the conductor and the insulating layer or expansion of voids in the insulating layer is lacking.

However, the phenomenon that affects the insulating layer also appears due to a change in temperature rise due to, for example, load fluctuations and VAR fluctuations that also appear during operation after startup.

Therefore, the mere number of start-stops used in the past is corrected by adding a number obtained by converting factors such as load fluctuation and VAR fluctuation into an equivalent number of start-stops, and this is treated as the number of equivalent start-stops of the rotating machine. Therefore, the accuracy of the NY map is remarkably improved.

[Action]

In order to equivalently convert the number of electrical fluctuations of load fluctuations and VAR fluctuations into the number of start and stop times, it is necessary to compare the difference in the strain level of the winding insulation caused by each fluctuation. To know the distortion level, first,
The number of load fluctuations (including magnitude) and the number of VAR fluctuations (including magnitude) are converted into temperature rise values. (Here, start-stop means the change from no load to the rated load, and is an electrical event.) Each temperature rise value obtained is related to the type of insulation and the length of the winding. Then, the strain value obtained experimentally is used to convert into strain. Then, if this strain is obtained, the strain can be quantified by the bending fatigue curve of the insulator by applying it to the bending fatigue curve of the insulator. The bending fatigue curve of an insulator is
Similar to the strain, it can be determined by experimentally applying bending fatigue depending on the type of the insulator and measuring the number of times the fracture (or the occurrence of crack) is reached.

Using the linear cumulative fatigue damage rule (hereinafter simply referred to as the minor rule), the bending fatigue count obtained by such a conversion method is added to the actual start / stop count to account for load fluctuations and VAR fluctuations. It is possible to calculate the number of stops.

As described above, the equivalent number of start and stop is not limited to the actual number of start and stop, and includes the number of times when load fluctuation and VAR fluctuation are converted into temperature rise values and converted into equivalent number of start and stop. , It is possible to estimate the BDV residual rate with higher accuracy by supplementing the conventional NY map method for calculating the BDV residual rate.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

The BDV residual ratio of the present invention is, in addition to the actual number of times of starting and stopping, load fluctuation as a factor that gives stress to the winding insulation, VA
Using R fluctuation, each factor is converted into the value of temperature rise as follows. FIG. 1 shows a flow for obtaining the BDV residual rate according to the method of the present invention. The temperature increase of the winding due to start / stop is the temperature increase from the start to the rated load state. You can ask for this, T ₁
And

Next, the temperature rise due to load fluctuation and VAR fluctuation is calculated from the change in current and the electrical resistance of the winding in which the current flows. Let these be T ₂ and T ₃ , respectively.

The temperature rise conversion value calculated in this way is the temperature rise due to start / stop due to the relationship between the temperature rise and strain that can be experimentally determined by the type of insulation material applied to the winding shown in FIG. The strain generated by T ₁ is ε ₁ , the temperature rise due to load change is T ₂ , the strain caused by T ₂ is ε ₂ , and the strain ε ₃ caused by temperature rise due to VAR change can be calculated. Second
The relationship between the temperature rise of the winding insulation shown in the figure and the strain caused by it varies depending on the winding size.Therefore, when setting the master curve, the type of insulating material applied and the winding length
Since it changes depending on Lc, experiment each one in consideration of the actual application situation, create several types, and familiarize yourself in advance with the specifications of the rotating electrical machine to which this method is applied, and use the optimum one. is necessary.

Using the strains ε ₁ , ε ₂ and ε ₃ generated by the respective temperature rises obtained by the above method, the relation graph between the strain of the insulator and the bending vibration fatigue number shown in FIG. (Referred to as a curve), the bending vibration fatigue counts N ₁₀ , N ₂₀ , N ₃₀ corresponding to ε ₁ , ε ₂ , ε ₃ are obtained. This N ₁₀ , N ₂₀ , N ₃₀ is ε ₁ , ε ₂ ,
When each strain of ε ₃ is applied to an insulator, the number of life bending vibration fatigue until the insulator is broken or cracked is calculated by using an SN curve obtained experimentally. It is possible to do.

The data obtained as described above is the data obtained by replacing the stress applied to the winding insulation by the temperature rise due to load fluctuation and VAR fluctuation with bending vibration fatigue frequency.

Therefore, these bending vibration fatigue counts N ₁₀ , N ₂₀ and N ₃₀ are calculated using the Miner's law from the known data of actual start / stop count N ₁ , load change count N ₂ and VAR change count N _{3 to} date. Then, the equivalent start / stop frequency N _E is calculated by the following equation.

Since the equivalent start / stop frequency N _E obtained by the above equation has a form in which load fluctuation and VAR fluctuation are taken into consideration, it is necessary to apply it to the conventionally known NY map. Thus, the BDV residual rate can be estimated. Furthermore, it is also possible to determine the lightness of the usage status of the rotating machine by obtaining the difference between the actual number of times of starting and stopping and the equivalent number of times of starting and stopping by this method. Fig. 4 shows the number of equivalent start-ups and stoppages obtained by this method and the number of years of operation on the NY map.
It is a graph showing the BDV residual rate.

According to the present invention, in addition to the actual number of times of starting and stopping, factors that give stress to the winding insulation (in this embodiment, load fluctuation and VA
(R fluctuation) is also equivalently converted to the number of times of starting and stopping, and the equivalent number of times of starting and stopping is calculated, so it is possible to estimate the BDV residual rate with high accuracy and determine the usage status of the rotating machine. It can be used as an index.

Then, by applying the above BDV residual rate, it is possible to create a graph for estimating the remaining life of the rotating machine shown in FIG. This is to predict the future driving mode from the driving modes from the past to the present and to see the change over time in the BDV residual rate.

The method will be described below.

From the operation history of the target rotating machine up to the present, for example, the number of start-stops per year, the magnitude and number of load fluctuations,
It is also possible to calculate the magnitude and number of VAR fluctuations.
Further, the deviation between the actual number of times of starting and stopping and the number of times of equivalent starting and stopping can be obtained.

From the future, these data will be grasped on a yearly basis, and the BDV residual rate for each operating years will be graphed as shown in FIG. Future BDVs required in this way
The remaining rate naturally shows a limit value, and the number of years of operation at that point can be known as the period during which the winding of the rotary machine must be updated.

In addition, FIG. 5 shows a graph for estimating the useful life as an average value. In practice, the average value for management is not used, but it will be corrected to the lower limit considering the value called standard deviation σ. Fig. 6 shows standard deviation σ
In the graph of (%), this value is obtained from the time ratio of the rate at which the BDV residual rate changes.

〔The invention's effect〕

According to the present invention, not only the actual number of starting and stopping of the rotating machine, but also load variation and VAR variation, which are other factors that give a large stress to the winding insulator, are equivalently converted into the number of starting and stopping and added. Therefore, the BDV residual rate, which is different from the simple determination of the actual start / stop frequency, has the effect of being able to obtain a highly accurate BDV residual rate from the relationship between the equivalent start / stop frequency and the number of years of operation.

Furthermore, it was calculated from the number of equivalent starts and stops by this method.
When performing remaining life diagnosis using the value of BDV residual rate,
The accuracy is significantly improved compared to that by the actual start / stop circuit, and it can contribute to the improvement of the reliability of the rotating machine under the operating conditions where particularly frequent start / stop, load fluctuation, and VAR fluctuation occur.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining a method for obtaining a residual ratio of the present invention, FIG. 2 is a diagram for converting a conversion value of temperature rise into strain of an insulator, and FIG. 3 is strain and bending of an insulator. FIG. 4 is a diagram in which the number of vibration fatigues is experimentally obtained, FIG. 4 is a diagram commonly used as a conventionally-known N-Y map, and FIGS. 5 and 6 are diagrams for explaining a residual life estimation method according to the present invention. FIG. T ₁ , T ₂ , T ₃ …… Temperature rise conversion value, ε ₁ , ε ₂ , ε ₃ …… Strain value of insulator, Lc ₁ , Lc ₂ , Lc ₃ …… Winding size.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroshi Miyao, 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture, Hitate Works, Ltd., Hitachi Research Laboratory (72) Ryozo Takeuchi, 4026, Kuji Town, Hitachi City, Ibaraki, Ltd. Inside Hitachi Research Laboratory (72) Inventor Masatoshi Taniguchi 3-1-1 Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Factory (72) Inventor Masami Sukeda 3-1-1 Sachimachi, Hitachi City, Ibaraki Hitachi, Ltd. Hitachi factory (72) Inventor Takashi Usui 3-1-1, Saiwaicho, Hitachi, Ibaraki Stock company Hitachi Ltd. Hitachi factory

Claims (6)

[Claims] 1. A method of obtaining a residual ratio of dielectric breakdown withstand voltage of a winding insulator of a rotating electric machine from the number of starting and stopping of the rotating electric machine and an operating time, wherein the starting and stopping times are stressed to the winding insulator. Select the actual number of starts and stops and other factors as factors that give
Each factor is converted to a temperature rise value, and the temperature rise value is converted into an equivalent number of start-stops using the strain and bending vibration fatigue number experimentally obtained from the insulator, and the equivalent value obtained from each factor is converted. A method of obtaining the residual rate of dielectric breakdown withstand voltage of the rotating electric machine winding from the operating time of the rotating electric machine, which is obtained as the sum of the number of times of starting and stopping. 2. A method for obtaining a residual ratio of dielectric breakdown withstand voltage of a rotating electric machine winding, wherein load fluctuation is selected as another factor that gives stress to the winding insulator according to claim 1. 3. A method for obtaining a residual rate of dielectric breakdown withstanding voltage of a rotating electric machine winding, wherein reactive power fluctuation is selected as another factor that gives stress to the winding insulator according to claim 1. 4. A residual ratio of dielectric breakdown withstand voltage of a rotary electric machine winding, wherein load fluctuation and reactive power fluctuation are selected as other factors that give stress to the winding insulation according to claim 1. How to ask. 5. A factor which gives a stress to a winding of a rotating electric machine is selected, the factor is converted into a temperature rise value, and the temperature rise value is converted into a strain generated in an insulator obtained experimentally, and the strain is generated. Is converted to an experimentally obtained bending vibration fatigue number of the insulator, and the bending vibration fatigue number is converted to a start / stop number, and the equivalent start / stop number obtained by converting the winding number from the operating time of the rotating electric machine. A method of obtaining the remaining rate of breakdown withstand voltage of an insulator. 6. A factor that applies stress to a winding of a rotating electric machine is selected, the factor is converted to a temperature rise value, and the temperature rise value is converted to a strain generated in an experimentally obtained insulator, and the strain is generated. Is converted into an experimentally obtained bending vibration fatigue number of the insulator, and the equivalent starting / stopping number obtained by converting the bending vibration fatigue number into the starting / stopping number is calculated from the past to the present,
The residual rate of the breakdown withstand voltage of the winding insulation obtained from the number of equivalent start-stops and the operating time of the rotating electrical machine is used to predict the residual rate of the breakdown withstand voltage of the winding insulation in the future. Remaining life estimation method.