JPS6367672B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for detecting dielectric breakdown in high voltage electrical equipment such as rotating electrical machines and stationary equipment. Recent high-voltage electrical equipment is trending toward larger capacity, higher voltage, and more compact size. In addition, by operating these high-voltage electrical devices to the end of their service life, we aim to make effective use of the equipment.
Preventive maintenance is becoming increasingly important in high-voltage electrical equipment. Among the parts and materials that make up high-voltage electrical equipment, insulating materials or systems are the weakest parts, so it is no exaggeration to say that the insulating materials or systems determine the lifespan of high-voltage electrical equipment. From this perspective, evaluation of insulation performance and lifespan of insulation through insulation diagnosis of high-voltage electrical equipment has become important. The insulation diagnostic tests include nondestructive insulation tests such as a dielectric loss tangent test, partial discharge test, and insulation resistance test, and a withstand voltage test based on electrical equipment technical standards. The test voltage in these insulation diagnostic tests is generally the rated voltage of high-voltage electrical equipment or a voltage higher than the rated voltage. Therefore, when the test voltage becomes high, an insulation breakdown accident may occur during the insulation diagnostic test. In particular, in electrical equipment that has been operated for a long period of time, the insulation has significantly deteriorated, making it easy for such insulation breakdown accidents to occur. If an insulation breakdown accident occurs during an insulation diagnostic test on electrical equipment, not only will there be a loss of the electrical equipment, but production equipment will be shut down and the impact on society will be significant. It is necessary to prevent this from happening. This invention was made in view of the above-mentioned points.During an insulation diagnostic test, when large partial discharge pulses that occur at intervals of several Hz to several tens of Hz suddenly begin to grow, the above-mentioned partial discharge By detecting the elongation of the partial discharge pulse per unit time of the maximum pulse among the pulses and detecting the dielectric breakdown of the insulating layer of the electrical equipment mentioned above, it is possible to prevent a major accident from occurring. The purpose is to provide a method for detecting destruction. Hereinafter, a case will be described in which a method for detecting dielectric breakdown according to an embodiment of the present invention is applied to an insulation diagnostic test of a model coil of a stator coil of high-voltage rotating electricity. FIG. 1 is a block diagram of a test circuit when the insulation diagnostic apparatus according to the present invention is applied to a partial discharge test of a model coil of a stator coil of high voltage rotating electricity. This circuit is generally used as a broadband method circuit for applying voltage to a model coil and detecting partial discharge (corona discharge) pulses generated in the insulating layer of the model coil. As is well known, if a void exists in the insulating layer of the test sample, the voltage applied to the test sample increases, and if the voltage applied to the void exceeds a certain value, the void will disappear. Causes dielectric breakdown. The formation time of the steep discharge pulse that occurs when the dielectric breakdown occurs in the sky is very short, less than a few microseconds, so a partial discharge measuring device 3 as shown in Fig. 1 is used to detect this discharge pulse. Commonly used. Now, the voltage from the high voltage power supply 1 is applied to the model coil 2, which is the test sample, and the voltage is increased using the step-up method of holding it for 1 minute in 5KV steps until the insulation layer of the model coil 2 undergoes dielectric breakdown (BD). As a result of measuring the partial discharge pulse generated in the insulating layer of the model coil 2 at this time with the partial discharge measuring device 3,
The relationship between the maximum amount of discharged charge and the applied voltage was as shown in FIG. The insulation configuration of the insulation system of the model coil tested in this case and the conditions for forced deterioration of the model coil are shown in Table 1.

[Table] In Table 1, the sample numbers are those subjected to thermal deterioration at 200℃ for 150 hours, and the sample numbers are those subjected to mechanical deterioration by applying a mechanical bending load of 500 kg using the four-point support method. . In addition, the sample number is a model coil that is not impregnated with epoxy resin. As shown in Figure 2, the maximum discharge charge gradually increases as the voltage increases for each sample.
It increases rapidly just before dielectric breakdown (BD). In particular, just before dielectric breakdown (BD), several Hz
Large partial discharge pulses that occur intermittently at intervals of several tens of Hz rapidly extend and lead to dielectric breakdown (BD). In the relationship between the maximum discharge charge and applied voltage in Figure 2, the relationship between the voltage at which large partial discharge pulses that occur intermittently at intervals of several Hz to several tens of Hz begin to grow rapidly and the voltage at which dielectric breakdown (BD) occurs. Figure 3 shows this. As shown in Figure 3, there is a nearly proportional relationship between the voltage at which large partial discharge pulses that occur intermittently at intervals of several Hz to several tens of Hz begin to grow rapidly and the voltage at which dielectric breakdown (BD) occurs. Therefore, it is possible to detect dielectric breakdown (BD) in advance by detecting the voltage at which intermittent large partial discharge pulses begin to grow rapidly. From the above viewpoint, an apparatus for actually carrying out the dielectric breakdown detection method of the present invention will be described. In FIG. 1, a partial discharge pulse detected by a partial discharge measuring device 3 is input into a dielectric breakdown detection device 4, and a negative polarity pulse among the partial discharge pulses is converted into a positive polarity pulse by a phase inversion circuit. Since this converted pulse is a pulse that attenuates over several microseconds, a peak hold circuit extends the peak of the pulse with the maximum value among the partial discharge pulses to about several seconds, and this signal is further amplified using an amplifier. be. As a peak hold circuit, Optical
Electronics Incorporated's Peak sense and
Hold analog memory (Model 5030A) was used. In the relationship between the maximum discharge charge and the applied voltage in Figure 2, the partial discharge pulse per unit time when a large partial discharge pulse that occurs intermittently at intervals of several hertz to several tens of hertz begins to grow rapidly. The elongation is detected by the controller circuit of the dielectric breakdown detection device 4 shown in FIG. The power source 1 is configured to be cut off immediately. Further, even if the maximum discharge charge amount of the partial discharge pulse that occurs intermittently begins to increase rapidly and reaches 10 ^-7 C or more, the high voltage power supply 1 can be shut off. The dielectric breakdown detection device 4 includes a display circuit that displays the maximum discharge charge amount of the pulse having the maximum value among the partial discharge pulses, and a display circuit that displays the maximum discharge charge amount of the pulse having the maximum value among the partial discharge pulses, and a display circuit that displays the maximum discharge charge amount of the pulse having the maximum value among the partial discharge pulses. An alarm circuit is installed to notify you when the weather has deteriorated. In the explanation of the above embodiment, an example was shown in which a partial discharge measuring device using a broadband method was used as a method for detecting partial discharge pulses, but the method is not limited to this method. A similar effect can be achieved using a measuring device. Further, the use is not limited to a partial discharge measuring device, and a commonly used discharge pulse detector may be used. Further, although an example in which the present invention is applied to a partial discharge test of a test sample has been described, the same effect can be obtained even if the present invention is applied during a withstand voltage test. As described above, according to the present invention, when performing an insulation diagnostic test, a discharge pulse in which a large partial discharge pulse that occurs intermittently at intervals of several Hz to several tens of Hz begins to grow rapidly is detected, and this By detecting the elongation of the partial discharge pulse per unit time when the discharge pulse begins to rapidly elongate, it is possible to detect dielectric breakdown of the insulating layer of the above-mentioned electrical equipment, thereby preventing the occurrence of major accidents caused by dielectric breakdown. The present invention provides a method for detecting dielectric breakdown that can be detected quickly, and has great practical effects. In addition, since the test voltage in the insulation diagnostic test of electrical equipment is usually the rated voltage of the electrical equipment or a voltage higher than the rated voltage, the insulation breakdown detection device according to the present invention did not predict insulation breakdown. The electrical equipment can be operated thereafter. Furthermore, for electrical equipment for which dielectric breakdown has been predicted, equipment renewal plans can be considered in advance as part of preventive maintenance, which further enhances this effect.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a test circuit for a partial discharge test of a stator coil of a high-voltage rotating electrical machine to which an embodiment of the present invention is applied, and Fig. 2 is a characteristic showing the relationship between the maximum amount of discharged charge and the applied voltage. 3 are characteristic diagrams showing the relationship between the voltage at which intermittent large partial discharge pulses begin to rapidly extend and the voltage at which dielectric breakdown occurs. In the figure, 1 is a high voltage power supply, 2 is a model coil, 3 is a partial discharge measuring device, 4 is a dielectric breakdown detection device, and 5 is a control cable.

Claims (1)

[Claims] 1. In an insulation diagnostic test in which voltage is applied to an electrical device and partial discharge pulses in the insulating layer of the electrical device are measured, large partial discharge pulses occur at intervals of several Hz to several tens of Hz. The dielectric breakdown of the insulating layer of the electrical equipment is detected by detecting the elongation of the partial discharge pulse per unit time of the maximum value pulse among the partial discharge pulses when the partial discharge pulse begins to increase rapidly. A method for detecting dielectric breakdown characterized by the following. 2. The dielectric breakdown detection method according to claim 1, wherein the signal of the pulse having the maximum value among the partial discharge pulses is delayed from several milliseconds to several seconds.