JP2584251B2 - Insulation deterioration diagnosis device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an insulation deterioration diagnosis apparatus capable of diagnosing an insulation deterioration state of a power device such as a power cable, a capacitor, and a transformer without stopping power supply without changing a live state.

[Prior art]

Insulating materials, especially polymer materials, may gradually decrease their insulating performance during use due to various causes. This phenomenon is deterioration. The deterioration phenomenon of the insulating material includes high pressure deterioration, ultraviolet light deterioration, discharge deterioration, chemical deterioration and the like. Such deterioration of the insulating material varies depending on the type of the insulating material used and the place where the insulating material is used. However, knowing the state of deterioration of this insulating material is extremely important for preventing a major accident by replacing the insulating material before the dielectric breakdown occurs, or by replacing the used portion of the insulating material. It is important. Further, development of a method of diagnosing the state of insulation deterioration under a live line is desired from the viewpoint of stable power supply. Conventionally, a method as shown in FIGS. 3 and 4 has been adopted. Each of these states has been developed with the power cable as the measurement target. FIG. 3 shows a high-voltage bus 10
A parallel circuit of switches S1, S2, S3, S4 and a capacitor C1 is connected to the midpoint G1 of 0, and the other end of this parallel circuit is grounded. DC power supplies 110 and 120 are inserted and connected to the switches S2 and S3 in opposite directions. In addition, a low-impedance ground is connected to one end of the cable 130 connected to the high-voltage bus 100 with the resistor R1, and a capacitor is connected in parallel with the switch S5.
C2 is connected. FIG. 4 shows a live line diagnosis of the cable 300 for extracting electric power from the high voltage distribution line 200. The switches S10 and S20 are provided on the ground line of the cable 300, and the live line diagnosis device is connected in parallel to one of the ground lines. 400 is connected. These two conventional devices both detect the current flowing through the insulator of the power cable, and attempt to determine the degree of deterioration of the insulating material based on the magnitude of the current.

[Problems to be solved by the invention]

However, according to these conventional methods, it is difficult to accurately detect the degree of deterioration of the insulating material. The current generated when a voltage is applied to the insulating material is divided into those that flow inside the insulating material (the insulation resistance is volume resistance) and those that flow along the surface (the insulation resistance is the surface resistance). In particular, the leakage current flowing along the surface of the insulating material may increase due to other factors without deterioration of the insulating material.
In addition, since the current flowing through the insulating material is very small, a change in the current cannot be easily determined, and the detection accuracy is low. Therefore, the insulation deterioration diagnosis of the insulating material does not always match the actual insulation deterioration state according to the conventional method, and it is necessary to perform measurement in accordance with a method based on another determination principle and perform a highly accurate insulation diagnosis. . SUMMARY OF THE INVENTION An object of the present invention is to easily, safely, and accurately determine the insulation deterioration state of a power device using an insulating material such as a power cable, a capacitor, and a transformer without stopping a power supply, while maintaining a live state. To diagnose.

[Means for solving the problems]

In order to achieve the above object, an insulation deterioration diagnosis device of the present invention is an insulation deterioration diagnosis device for detecting an insulation state of a power device including a high-voltage line and connected to the high-voltage line. A current transformer of a clamp type for detecting a current waveform flowing through the ground line, a current amplifying means for amplifying a current waveform output from the current transformer to a predetermined size, A voltage divider connected to the high voltage line and detecting a voltage waveform supplied to the high voltage line;
A dielectric loss tangent calculating means for calculating a dielectric loss tangent (tan δ) from a phase difference obtained by comparing a current waveform amplified by the current amplifying means with a voltage waveform detected by the voltage divider;
And a correcting means for correcting a phase shift generated at the time of detecting the current waveform by the instrument current transformer. Further, the insulation deterioration diagnosing device of the present invention is provided with display means for displaying the insulation deterioration state in stages from the dielectric loss tangent calculated by the dielectric loss tangent calculation means.

[Action]

When detecting the insulation state of the power equipment connected to the high-voltage line including the high-voltage line, a clamp-type instrument current transformer is attached to the ground line of the power equipment, and the current of the current flowing through this earth line is detected. The waveform is detected, and the current waveform output from the current transformer for instrument is amplified to a predetermined magnitude by current amplification means. On the other hand, simultaneously with the detection of the current waveform, the voltage waveform supplied to the high-voltage line is detected by the voltage divider connected to the high-voltage line. The dielectric loss tangent (tanδ) is determined by the dielectric loss tangent calculating means from the phase difference obtained by comparing the voltage waveform detected by the voltage divider with the current waveform amplified by the current amplifying means. Diagnosing the insulation state of the power equipment connected to the high-voltage line including the line. When the dielectric loss tangent (tan δ) is obtained, the phase shift from the current waveform flowing through the earth line caused by the clamp-type instrument current transformer is corrected by the correction means.

【Example】

Hereinafter, examples of the present invention will be described. Dielectric tangent (tan
δ), and the present invention is to diagnose the insulation state of the insulator by measuring the dielectric loss tangent. The dielectric loss tangent is the tangent tan δ of the dielectric loss angle δ. When an AC voltage is applied to a dielectric (poor conductor of electricity)
Ideally, the flowing current should be 90 ° ahead of the voltage phase. However, in practice, there is some delay in the phase advance angle 90 ° with respect to the voltage phase with respect to the current phase. The delay angle at this time represented by δ is the dielectric loss angle δ
It is. In other words, the current generated by applying an AC voltage to the dielectric leads the phase of the voltage by an advanced phase angle θ slightly less than 90 °, and this advanced phase angle θ is called a dielectric phase angle. The dielectric phase angle θ and the dielectric loss angle δ have a relationship of θ = 90 ° −δ. FIG. 1 shows an embodiment of the present invention. In the figure, a high-voltage line 1 is connected to a power device 2. This power device 2 includes a power cable, a transformer,
Ground insulation equipment such as capacitors. This power equipment 2
Are grounded from a predetermined location using the ground wire 3.
A clamp-type instrument current transformer 4 is attached to the ground wire 3. A current amplifier 5 is connected to the current transformer 4, and a dielectric loss tangent measuring device 6 is connected to the current amplifier 5. On the other hand, the voltage waveform of the voltage supplied to the high voltage line 1 is:
It is detected by the voltage divider 7 and input to the dielectric loss tangent measuring device 6. The dielectric loss tangent measuring device 6 measures from the maximum peak value of the voltage waveform input from the voltage divider 7 to the zero crossing of the current waveform output from the current amplifier 5 (the output from the current amplifier is output as a voltage value). Is calculated to obtain a dielectric loss angle δ value, and a dielectric loss tangent (tan) is calculated from the dielectric loss angle δ value.
δ) is calculated. That is, the time Δt from the peak value of the output voltage from the voltage divider 7 to the zero cross point of the output voltage from the current amplifier 5
And the dielectric loss angle δ is easily calculated by the following equation. (However, the frequency is 50 Hz.) In the case of a clamp-type current transformer for an instrument, the current waveform of the current output from the current amplifier 5 depends on the type of winding wound around the core, the number of turns of the winding, the current of the instrument current transformer. The ground wire 3 of the power equipment 2 depends on various causes such as the shape and the ambient temperature at the time of measurement.
Is out of phase with respect to the current waveform of the current flowing through. This phase shift can be corrected by the correction means. In the present embodiment, the voltage divider 7 is used for detecting the voltage waveform.
However, any device that can detect the waveform of the power supply voltage, such as a voltmeter using light or a detector using electrostatic induction, may be used instead of the voltage divider. Therefore, according to this embodiment, since the clamp-type instrument current transformer is used for current phase detection, the current waveform can be measured without cutting the ground wire and inserting another element. . Therefore, live line diagnosis can be performed in a short time on site, and there is no ground wire cutting work, so that there is a great advantage in terms of work safety. FIG. 2 shows another embodiment of the present invention. The difference between this embodiment and the embodiment shown in FIG. 1 is that the dielectric tangent measuring device 6 of the embodiment shown in FIG. 1 displays the deterioration state of the insulator in a stepwise manner corresponding to the value of the dielectric tangent. The point is that the device 10 is provided. Others are the same as the embodiment shown in FIG. The display device 10 includes, for example, a plurality of comparators, and compares the value of the dielectric loss tangent with the comparison value, and outputs the result based on the magnitude. That is,
This comparison value indicates the stepwise degree of insulation deterioration of the insulator. Therefore, according to the present embodiment, since the display can be performed stepwise in accordance with the degree of insulation deterioration of the insulator, anyone can easily determine the state of insulation deterioration of the insulator.

【The invention's effect】

As described above, according to the present invention, since the current transformer of the clamp type is used, the measurement of the current phase is simple, the work of removing the ground wire is not required, and the measurement of the dielectric loss tangent is performed. Can be implemented promptly. Further, according to the present invention, the state of insulation deterioration of the insulator can be detected accurately and easily by anyone at an early stage in a live state.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the present invention, and FIGS. 3 and 4 are circuit diagrams of a conventional insulation deterioration diagnosis apparatus. DESCRIPTION OF SYMBOLS 1 ... High voltage line 2 ... Electrical equipment 3 ... Earth wire 4 ... Current transformer for instrument 5 ... Current amplifier 6 ... Dielectric loss tangent measuring device 7 ... Voltage divider 10 ... Display device

Claims (2)

(57) [Claims] 1. An insulation deterioration diagnostic device for detecting an insulation state of a power device including a high-voltage line and connected to the high-voltage line. Clamp type current transformer for detection, current amplifying means for amplifying a current waveform output from the current transformer to a predetermined size, connected to the high voltage line and supplied to the high voltage line A voltage divider for detecting a voltage waveform detected by the current amplifier; and a dielectric tangent (tan δ) for calculating a dielectric loss tangent (tan δ) from a phase difference obtained by comparing the current waveform amplified by the current amplifier with the voltage waveform detected by the voltage divider. An insulation deterioration diagnosis device, comprising: a tangent calculation unit; and a correction unit that corrects a phase shift generated when a current waveform is detected by the instrument current transformer. 2. The insulation deterioration diagnosis apparatus according to claim 1, further comprising display means for displaying an insulation deterioration state in a stepwise manner based on the dielectric loss tangent calculated by said dielectric loss tangent calculation means.