JPS6020154A - Diagnostic device of insulation deterioration of electric apparatus - Google Patents

Abstract

PURPOSE:To compare mutually an insulation characteristic by a normalized index, irrespective of a capacity, the number of poles, shape and a size, etc. of a rotary machine, by measuring the insulation resistance of an insulating part and an electrostatic capacity, and diagnosing a deterioration. CONSTITUTION:A power source part 3 consisting of a protective relay 31 for operating in case of dielectric breakdown of the winding of a rotary machine to be tested, and a transformer 32 is connected to a commercial frequency power source terminal 2, and motion switching devices 41A, 41B switch a voltage applied to the winding of the rotary machine to be tested from AC to DC, vice versa. An electrostatic capacity transducer 42 measures the capacity C of winding of the rotary machine to be tested when an AC voltage is applied, and an insulation resistance transducer 43 measures the insulation resistance R of winding of the rotary machine to be tested when a DC voltage is applied. Also, a multiplier 61 multiplies the insulation resistance and a signal of the electrostatic capacity, a deciding device 62 decides an RC value, the magnitude of a residual breakdown voltage is displayed on an indicator 71, and also, when it is decided that the winding of the rotary machine does not hold a dielectric strength required for operation, an alarm is raised by an alarm device 72.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diagnostic device for ascertaining the state of deterioration of insulating parts of electrical equipment, and particularly to a device for diagnosing deterioration by measuring the insulation resistance and capacitance of insulating parts. be.

Higher voltage ratings and voltages for both rotating electrical machinery and stationary equipment,
Because the capacity of single machines is on the rise, the impact of accidents involving these electrical devices on society and economic losses are extremely large. For this reason, there is an urgent need to establish preventive maintenance technology for electric aiming equipment.

Among accidents that occur while operating electrical equipment.

Accidents are particularly common in insulation parts, where there is a phenomenon called insulation deterioration.

Therefore, there is a desire for a diagnostic device that can accurately determine whether or not there will be any problems with future operation by examining the degree of deterioration of the insulating parts of electrical equipment.

BACKGROUND OF THE INVENTION Many types of measuring devices have been commercially available for measuring the insulation properties of electrical equipment. Examples include a DC insulation resistance meter that measures insulation resistance, a bridge that measures dielectric loss tangent (-δ) and capacitance, and a partial discharge measuring device that measures partial discharge pulses. Indicators of insulation properties obtained using the above-mentioned measuring device include insulation resistance, tan δ, the magnitude of two capacitance partial discharge pulses, and the number of pulses generated. However, the conventionally used indicators of insulation properties are:

It has been difficult to estimate the residual dielectric strength of electrical equipment because no correlation has been obtained with the degree of deterioration of the insulation part. In particular, when the motor windings become contaminated and absorb moisture from the surrounding atmosphere in which the motor is installed, the insulation resistance on the surface of the motor windings decreases.

There was a drawback that it was not possible to measure the insulation properties of the ground insulation layer, which was the purpose of the test, such as an increase in the δ value or an improvement in the single partial discharge characteristics.

In view of the above-mentioned drawbacks of the conventional examples, the present invention aims to provide an accurate insulation deterioration diagnosis device using the product of insulation resistance and capacitance as an index, which has a good correlation with the value of the residual dielectric strength of electrical equipment. It is. below.

An embodiment of the present invention will be described in detail with reference to a stator winding of a high-voltage motor.

Figure 1 shows a model coil of the stator winding of an AkV-class high-voltage motor, which was forcibly subjected to thermal deterioration 2 mechanical repeated fatigue deterioration, and then immersed in water to simulate the staining and moisture absorption of the actual machine. , which shows an example of the results of an insulation test after being taken out of water and left at room temperature for 12 hours or more.

In other words, the non-destructive insulation properties of the model coil are the insulation resistance R at one DC voltage /kV and the commercial frequency voltage /kV.
The product of the capacitance C in kv, that is, the RC value (unit: ΩF) is taken as an index, and the relationship between this value and the value of the residual dielectric strength is shown. As shown in the figure, there is a good correlation between the RC value and the residual dielectric strength, and as the RC value decreases, the residual dielectric strength decreases.

As insulation deterioration progresses due to thermal or mechanical stress, peeling, cracks, and cracks occur within the insulation layer.

This causes defects such as minute voids. When the surface of an insulating layer having these defects is contaminated by dust adhesion and the contaminant absorbs moisture, the insulation resistance of the surface decreases. Further, moisture absorbed by the contaminant enters into defective parts inside the insulating layer, and the insulation resistance inside the insulating layer decreases. Furthermore, contaminants on the surface of the insulating layer whose insulation resistance has decreased become a ground electrode, increasing the apparent capacitance, and moisture with a high dielectric constant entering the inside of the insulating layer, increasing the capacitance. .

Generally, as the rated capacity and number of poles of rotating machine windings increases, the number of windings increases, so the capacitance of one winding increases, but the insulation resistance tends to decrease.

For this reason, if rotating machine windings with the same rated voltage have different rated capacities and numbers of poles, the insulation characteristics cannot be compared with each other based on the values of capacitance and insulation resistance described above.

The index RC value used in this invention is a normalized index that allows comparison of insulation characteristics with each other regardless of the capacity, number of poles, shape, dimensions, etc. of the single-rotation machine in order to eliminate the above-mentioned drawbacks. In Figure 1, the RC for a new product is
The value is 10" (ΩF) or more, and the residual dielectric strength at this time is io.

(to). The higher the deterioration temperature and the longer the deterioration time during thermal deterioration, the smaller the RC value and the lower the residual dielectric strength. Even in mechanical repeated fatigue deterioration, the greater the stress applied to the insulating layer and the greater the number of repetitions, the smaller the RC value and the lower the residual dielectric strength. That is, the more severe the thermal deterioration or mechanical repeated fatigue deterioration that simulates the deterioration stress applied to the insulating layer of the winding of a one-rotation machine becomes, the smaller the RC value becomes, and the lower the residual dielectric strength becomes. For this reason, by measuring the RC value, the degree of insulation deterioration of the rotating machine winding can be grasped, and the remaining dielectric strength can be estimated from the RC value.

The present invention aims to provide an insulation deterioration diagnostic device that measures an RC value, determines the degree of insulation deterioration from the measured RC value, and displays the result.

FIG. 2 shows a basic block diagram of an apparatus for diagnosing insulation deterioration of electrical equipment according to the present invention.

This insulation deterioration diagnosis device l is connected to the commercial frequency power terminal of lθo■ and the commercial frequency power terminal of lθo■ through the switch shown in the figure, and is used to detect dielectric breakdown in the windings (not shown) of the rotating machine under test. A power supply unit 3 consisting of a protective relay 31, three transformers connected to the protective relay 31 to boost the voltage, and an alternating current voltage that is connected to the power supply unit 3 and applied to the windings of the rotating machine Motion switching devices F/A and lI/B that switch between DC and DC, are connected between these switching devices F/A and F/B, and when an AC voltage is applied, the capacitance C of the winding of the rotating machine under test is Capacitance converter Guko Switcher 4IzA to measure
and 4t/H, and consists of an insulation resistance converter q3, etc., which measures the insulation resistance R of the winding of the rotating machine under test when a DC voltage is applied; , a multiplier &/or multiplier that multiplies the measured insulation resistance and capacitance signals, a judgment unit 62 that judges the product of the insulation resistance and capacitance, that is, the RC value from the multiplier 61, and the like; A display 7/ is connected to the judgment device 6 and displays the judgment result numerically as the magnitude of the RC value or the magnitude of the estimated residual breakdown voltage, and a display device 7/ is connected to the judgment device 62 and displays the insulation necessary for the rotating machine winding to operate. Output unit 7 consisting of an alarm device 72 etc. that issues an alarm when it is determined that the proof strength is not maintained.
and a high voltage terminal S which is connected to the switching device HIROIB and supplies AC voltage or DC voltage to the windings of the rotating machine under test.

FIG. 2 shows a basic embodiment of the present invention, and there is a modification in which a voltage stabilizing circuit is used in the power source section 3, and a capacitance converter using a bridge circuit is used in the measuring section. Further, although the applied voltage for measuring insulation resistance or capacitance is DC or commercial frequency voltage /kV, it is not limited to this voltage.

The insulation deterioration diagnosis device l according to the present invention measures the insulation resistance and capacitance of the rotating machine windings at an applied voltage that is considerably lower than the rated voltage of the rotating machine under test, and uses the product of the two as an index. This system determines the degree of insulation deterioration of the wire and displays the results.As can be easily understood from the results shown in Figure 1, it is possible to grasp the degree of P edge deterioration, which is the purpose of this invention. Alternatively, there is an effect that the residual dielectric strength can be accurately estimated.

Although the embodiment of the present invention has been described with reference to a high-voltage rotating machine winding, the present invention can also be used to diagnose insulation deterioration in electrical machinery having a back electrode structure.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the RC value, which is the product of insulation resistance R and capacitance C, and residual breakdown voltage, and FIG. 2 is a block diagram showing a basic embodiment of the present invention. 1 is an insulation deterioration diagnosis device, 1 is a measurement section, 6 is a calculation section, and 7 is an output section. Agent Masuo Oiwa

Claims (1)

[Claims] (1) A measurement unit that measures the insulation resistance value and capacitance value of the insulated part of the 1-voltage device, and a measurement unit that is connected to this measurement unit and calculates the product of the insulation resistance value and the capacitance value. An apparatus for diagnosing insulation deterioration of electrical equipment, characterized in that it comprises a calculation unit that determines a calculated value, and an output unit that displays the results determined by the calculation unit. (A) The relationship between the ohm-farad product of the ohm value of insulation resistance and the farad value of capacitance and the dielectric breakdown voltage is used as the basis for determining insulation deterioration. Insulation deterioration diagnostic device for electrical equipment.