JPH0638097B2 - Insulation deterioration diagnosis method for electric equipment winding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for diagnosing insulation deterioration of electric equipment windings.

[Prior Art] As is well known, insulation of electric device windings causes insulation deterioration over time, and periodic diagnosis of these and accurate grasp of deterioration status are important for stable operation of the apparatus.

It is known that the insulation characteristics of the winding change greatly under the influence of humidity, but there is no technology for quantitatively diagnosing the deterioration tendency and the degree of deterioration. Although the estimation of the life in the experimental theoretical mode is also shown, it is difficult to set various constants to apply it to the field.

In the generally used megger method, the influence of humidity is not taken into consideration only by grasping the insulation resistance value, and the change appears largely depending on the measurement timing, and the actual condition of the equipment cannot be accurately determined. For this reason, as a proposal,
There are JP-A-60-47990 and JP-A-55-10884. The former measures a thermogravimetric ratio by minutely sampling a part of the insulation structure of the winding and judges the insulation deterioration of the winding from the weight reduction ratio.The latter applies a large current to the coil and gives electromagnetic force vibration. It detects looseness.

[Problems to be Solved by the Invention] However, the method disclosed in JP-A-60-47990 can be applied when the insulation is considerably damaged and the coil is withered. In the case of Japanese Patent No. 10884, it is a technique that can be applied when there is looseness in the winding wire, and neither is suitable for determining insulation deterioration due to environmental conditions such as pollution and moisture absorption.

Therefore, it is an object of the present invention to provide a diagnostic method that can reliably determine insulation deterioration even if the insulation of the electric device winding changes significantly due to the influence of humidity.

[Means for Solving the Problem] The present invention provides a method for diagnosing insulation deterioration of electric device windings.
Insulation resistance Rx ₁ (MΩ) measured for the electric equipment winding when the humidity is Hx ₁ (%) and insulation resistance Rx ₂ (Measured for the electric equipment winding when the humidity is Hx ₂ (%) MΩ) to the following
Find m in equation (1) When Hx ₁ and Rx ₁ satisfy the following equation (2), or Hx ₂
And Rx ₂ satisfy the following equation (3), it is diagnosed that there is no deterioration that hinders the insulation resistance of the electric device.

log (JEC-54 standard) <logRx ₁ + m (log90-logHx ₁ ) ……… (2) log (JEC-54 standard) <logRx ₂ + m (log90−logHx ₂ ) ……… (3) However JEC-54 Standard = (Rated voltage) / (Electrical equipment capacity + 1000) [Operation] Insulation deterioration of electric equipment windings is due to thermal and mechanical deterioration over time, and environmental deterioration due to contamination of bare conductors, which is a structural feature. It can be roughly divided into In both cases, when the deterioration phenomenon progresses, the insulator is placed in a state of easily absorbing moisture. Therefore, the present inventors have made a detailed investigation on the humidity and the insulation resistance of the windings of many electric devices, and have found that there is a strong correlation between the two.

First, the relationship between humidity and insulation resistance will be described.

Fig. 4 shows a characteristic diagram of humidity and insulation resistance. According to a new finding of the present inventors, the humidity H is 30% to 90% between the common logarithm logH of the humidity H (%) and the common logarithm logR of the insulation resistance R (MΩ) of the electric device winding. There is a strong negative linear correlation in the range. The inclination angle m of this correlation can be obtained by the following equation (1).

Here, Rx ₁ is the insulation resistance of the electric equipment winding measured at a humidity of Hx ₁ , and Rx ₂ is the insulation resistance of the electric equipment winding measured at a humidity of Hx ₂ . Note that Hx ₁ and Hx ₂ are humidity values at the time of measurement, which are arbitrarily measured.

The deterioration pattern can be represented by straight lines a, b, and c. A straight line a shows a pattern of a good electric device in which insulation deterioration hardly progresses due to humidity. The straight line c indicates the insulation moisture absorption deterioration pattern peculiar to electric equipment in which the insulation resistance changes greatly with a small change in humidity. The straight line b is between the straight lines a and c, and shows a pattern in which the insulation resistance gradually deteriorates as the humidity rises. This is because the insulating material of the winding absorbs moisture due to withering, stains, etc., and leakage current easily flows in the insulating layer or on the surface, which increases. Normally, it is the insulation control limit that the insulation resistance value of an electric device changes 100 times between fine weather and cloudy weather. For example, m = -15 is preferable as an obstacle.

The equation (1) can be rewritten as the following equation (1 ').

As already mentioned, the relation of the equation (1) holds for the same electric equipment winding even when the humidity is 90%. Therefore, in equation (1 '), instead of Hx ₂ and Rx ₂ , the humidity is 90% (H = 90) and the humidity is
The insulation resistance R90 at 90% can be used, and the following (4)
The formula is obtained.

By rearranging equation (4), the following equation (5) is obtained.

logR90 = logRx ₁ + m (log90−logHx ₁ ) ... (5) Similarly, in the formula (1 ′), Hx ₁ and Rx ₁ are replaced by humidity 9
Using insulation resistance R90 when 0% (H = 90) and humidity is 90%,
By rearranging the equations as in the case of the equation (5), the following equation (6) is obtained.

_{logR90 = logRx 2 + m (log90} -logRx 2) ... (6) As mentioned above, the insulation resistance Rx ₁ humidity in Hx _1, humidity of an insulating resistance Rx ₂ in Hx ₂ (1) electrical equipment up by formula If the m of the wire is calculated, the insulation resistance R90 of the electric equipment winding when the humidity is 90% can be easily calculated by using the equation (5) or the equation (6) without actually measuring the humidity at 90%. It can be calculated.

Next, the insulation resistance that electric equipment windings should have will be described. The JEC-54 standard of the following formula (7) is shown as the minimum insulation resistance required for the operation of electric equipment such as a DC machine.

In the equation (7), the rated voltage (V) means the maximum operating voltage, and the electric equipment capacity (KW) means the maximum capacity. The JEC-54 standard does not specify the insulation resistance at a specific humidity. However, since the insulation resistance drops significantly when the humidity rises, for example, even for electric equipment windings that meet the JEC-54 standard when the humidity is 70%, the insulation resistance will increase when the humidity is 90%. It may be insufficient.

In the present invention, the insulation deterioration of the winding is diagnosed so that the JEC-54 standard can be achieved even when the humidity is 90%. That is, the humidity
Diagnosis is made so that the insulation resistance R90 at 90% satisfies the following expression (8).

JEC-54 standard <R90 ......... (8) This equation (8) can be achieved by satisfying the following equation (9).

log (JEC-54 standard) <logR90 ... (9) Substituting logR90 in Eq. (5) or Eq. (6) into Eq. (9) gives Eq. (2) or (3) below.

log (JEC-54 standard) <logRx ₁ + m (log90-logHx ₁ ) ... (2) log (JEC-54 standard) <logRx ₂ + m (log90-logHx ₂ ) ... (3) Many electric device windings It is extremely difficult to concentrate the insulation resistance measurement when the humidity is 90%. On the other hand, the insulation resistance measured by ignoring humidity is not a guideline for stable operation of the electric equipment winding when the humidity is 90%.

In the present invention, the insulation resistance of the electric equipment winding is measured regularly or whenever necessary, and the humidity and insulation resistance (for example, Hx ₁ , Rx ₁ ) at the time of measurement are recorded as daily management. When diagnosing the insulation resistance of the electric device at a later date, the humidity at the time of diagnosis and the insulation resistance of the electric device at the time of diagnosis (for example, Hx ₂ , Rx ₂ )
By using equation (1) and equation (2) or equation (3), the insulation resistance of the electrical equipment winding can be measured according to JEC-54 even when the humidity is 90%.
Can be diagnosed to meet the criteria. Needless to say, Hx ₂ and Rx ₂ at the time of the diagnosis can be used as Hx ₁ and Rx _{1 at} the time of the next diagnosis.

The inventors of the present invention investigated the insulation resistance measured on the electric equipment winding in use by the% Mg of the following formula (10) in comparison with the JEC-54 standard, and the results are shown in FIG.

As shown in FIG. 3, since% Mg decreases with the lapse of time, it is important to diagnose the insulation deterioration of electric equipment windings.

Combining the above m-value method and% Mg method, the vertical axis shows the correlation coefficient m value with humidity, and the horizontal axis shows% Mg based on the insulation resistance measured at 70% humidity. Below% M
The gm value control chart) is shown in FIG. In Fig. 1, H ₁ is the line with% Mg 1 and H ₂ is the electrical equipment winding because the insulation resistance is above the JEC-54 standard even in the case of humidity (90% humidity) during rainfall. The% Mg line is shown. For example, m = -15 and% Mg
The electric equipment winding of 42.7 has an insulation resistance of 42.7 times that of JEC-54 standard when the humidity is 70%, but the humidity during rain is 90%.
In the case of,% Mg becomes 1.0. Therefore, in the method of the present invention, the range where% Mg of this electric device winding is 42.7 or more is evaluated as good insulation resistance.

The% Mg-m value control chart is obtained by dividing the average humidity and the humidity during rainfall into stepwise level judgments in order to maintain the adaptability of the% Mg> 1.0, which is the operation limit index, to the climate. It is a control chart which can judge insulation deterioration at a glance by combination. Furthermore, it has the feature that the deterioration pattern of the insulator can be easily identified from the plot area. For example, a region with low m-value insulation value around% Mg <1.0 shows insulation deterioration pattern due to conductive dust, and a region with high m-value insulation value near% Mg = 1.0 shows insulation deterioration due to dust adhesion that tends to absorb moisture. It can be discriminated as a pattern, and will be the basis for determining insulation measures and timing in terms of electrical equipment management.

The% Mg value varies greatly depending on the humidity timing during measurement, but as the dielectric strength required for the operation of electrical equipment,% Mg> 1.
0 is the operation limit index and the minimum required level.

The diagnostic method of the present invention is applicable to the insulation deterioration diagnosis of the windings of all electric devices, but the insulation measuring method etc. is determined according to each device, especially in the case of a DC machine, the armature must be removed from the brush at the time of measurement. It is necessary to collect the data in a floating state and at the same time measure the humidity inside the machine while paying attention to the cooling air.

Insulation measurement must be performed continuously, not for a short time, until the PI value stabilizes, to prevent the insulation resistance from changing under the influence of humidity.

[Embodiment] 20 after operation in which insulation deterioration is predicted to progress considerably 20
This diagnostic method was applied to a DC machine that was about a year old. The results are shown in Table 1 below.

As a comparative example, the insulation deterioration was determined at each humidity by the Megger method.

When Table 1 is plotted on the% Mg-m value control chart, it becomes as shown in Figure 2.

From the figure, in the case of DCM 400 kW, it is shown from the figure that there is a region requiring countermeasures and that measures for improving the insulation of the electric device winding should be rapidly implemented. In the case of DCM 950 kW,% Mg is 1.0 or more, but the m value is large and% Mg is high when it rains.
Is in the area of caution below 1.0, indicating that continuous monitoring is required.

In addition, * 1 DCM2250KW, insulation level before countermeasure is m value = 18,% Mg = 0.85, and it is judged from the deterioration pattern that the insulation is deteriorated by dust that easily absorbs moisture, and insulation improvement measures (cleaning varnish treatment with organic solvent) It is the insulation level for several years after carrying out.

As is clear from the figure, it is possible to sufficiently cope with changes in humidity, which is a characteristic of DC machine insulation, and at the same time, to confirm the absolute value level of insulation resistance. Also, as is clear from Table 1 above, it can be seen that with the megger method, which has been generally used as a standard in the past, the judgment greatly changes depending on the humidity condition at the time of measurement, and proper judgment cannot be made.

[Effects of the Invention] According to the diagnostic method of the present invention, it is not necessary to dismantle the actual machine,
As the deterioration over time progresses, it becomes possible to prevent the occurrence of insulation accidents in electrical equipment that is always used by numerically quantifying and quantitatively grasping the insulation characteristics that facilitate moisture absorption.

In addition, if the cleaning method is selected from organic solvent or steam cleaning and measures are taken to improve the insulation against deterioration that is found from the% Mg-m value control chart, the insulation of electrical equipment will be improved and the service life will be greatly extended. Is possible.

In this way, the present diagnostic method has a great effect on maintenance by clarifying the timing of preventive maintenance, including appropriate management of electrical equipment.

[Brief description of drawings]

FIG. 1 is an explanatory view of the% Mg-m value control chart, FIG. 2 is a% Mg-m value control chart of the data in Table 1 of the embodiment, and FIG. 3 is a view showing the relationship between% Mg and age. FIG. 4 is a graph showing the characteristics of humidity and insulation resistance (m-value characteristics).

Claims (1)

[Claims] 1. When diagnosing insulation deterioration of an electric equipment winding, the insulation resistance Rx ₁ (MΩ) measured for the electric equipment winding when the humidity is Hx ₁ (%%) and the humidity Hx ₂ ( %), The m of the following equation (1) is obtained from the insulation resistance Rx ₂ (MΩ) measured for the electric device winding when When Hx ₁ and Rx ₁ satisfy the following equation (2), or Hx ₂
And Rx ₂ satisfy the following expression (3), it is diagnosed that there is no deterioration that hinders the insulation resistance of the electric equipment winding. log (JEC-54 standard) <logRx ₁ + m (log90−logHx ₁ ) ... (2) log (JEC-54 standard) <logRx ₂ + m (log90−logHx ₂ )… (3) However, JEC-54 standard = (Rated voltage) / (Electrical equipment capacity +1000)