JPH01110267A - Insulation deterioration diagnostic apparatus - Google Patents

Abstract

PURPOSE:To diagnose the insulation deterioration state of a power machinery in a live wire state without stopping a power supply, by calculating dielectric loss tangent from the current phase detected by a clip-on type current probe and a voltage phase. CONSTITUTION:The power machinery 2 such as a power cable, a transformer or a condenser connected to a high voltage wire 1 is earthed using an earth wire 3. A clip-on type current probe 4 is fitted to the earth wire 3 to detect a current phase. The voltage phase of the voltage supplied to a voltage wire 1 is detected by a voltage divider 7 and inputted to a dielectric loss tangent measuring device 6 along with the output of a current amplifier 5. The dielectric loss tangent measuring device 6 calculates the positional difference up to the zero point cross of a current waveform from the max. peak value of a voltage waveform and calculates dielectric loss tangent from the calculated value. A display apparatus 10 stepwise displays the deterioration state of an insulator corresponding to the value of the dielectric loss tangent.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an insulation deterioration diagnosing device that can diagnose the insulation deterioration state of power equipment such as power cables, capacitors, transformers, etc. without stopping the power supply and in a live line state. [Conventional technology]

BACKGROUND OF THE INVENTION During use, insulating materials, particularly polymeric materials, may gradually degrade their insulating performance due to various causes. This phenomenon is called deterioration. This deterioration phenomenon of insulating materials includes high voltage deterioration, violet ray deterioration, discharge deterioration, chemical deterioration, and the like. The state of deterioration of such insulating materials differs depending on the type of insulating material used and the case in which it is used. However, knowing the state of deterioration of this insulating material is extremely important in preventing major accidents by replacing the insulating material or replacing the parts where the insulating material is used before dielectric breakdown occurs. It's important. Also,
From the viewpoint of stable power supply, it is desired to develop a method for diagnosing insulation deterioration under live wires. Conventionally, methods as shown in FIGS. 3 and 4 have been used. All of these states were developed with electric cables as the measurement object. Figure 3 shows the high voltage bus 10
Switch S11 S2j S31 s4 at midpoint G1 of 0
and a capacitor C1 are connected in parallel, and the other end of this parallel circuit is grounded. Also, switch S...
DC power sources 110 and 120 are inserted and connected to S and in opposite directions. In addition, one end of the cable 130 connected to the high voltage bus 100 is grounded at low impedance with a resistor R1, and
Switch S5 is connected. Further, a capacitor C2 is connected in parallel to this resistor R1 and switch S5. Further, FIG. 4 shows a diagram for performing a live line diagnosis of a cable 300 that extracts power from a high voltage distribution line 200.
Switches S10 and S20 are provided on the ground wire 00, and a live line diagnostic device 400 is connected in parallel to one of the ground wires. These two conventional devices both detect the current flowing through the insulator of the power cable, and try 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, using these conventional methods, it is difficult to accurately detect the degree of deterioration of the insulating material. When a voltage is applied to an insulating material, there are two types of current: one that flows inside the insulating material (this insulation resistance is the volume resistance), and the other that flows along the surface (this insulation resistance is the surface resistance). In particular, the leakage current flowing along the surface of the insulating material may become large due to other factors even if the insulating material does not deteriorate. Furthermore, since the current flowing through the insulating material is minute, changes in current cannot be easily determined, resulting in a problem of low detection accuracy. Therefore, the insulation deterioration diagnosis of insulating materials using conventional methods does not necessarily match the actual state of insulation deterioration, and it is necessary to carry out measurements in conjunction with methods based on other judgment principles to perform highly accurate insulation diagnosis. There is a problem with this.

[Means to solve the problem]

The present invention enables anyone to easily, safely, and accurately remove insulation materials from deteriorated insulation of power equipment such as power cables, capacitors, and transformers without stopping the power supply and without stopping the power supply. It is capable of diagnosing the insulation deterioration state of the power equipment used, and detects the insulation state of voltage equipment connected to the high voltage line, including high voltage lines. Current phase detection means detects the current phase by detecting the current waveform through a clip-on current probe; Voltage phase detection means connects a voltage divider or the like to the high voltage line to detect the voltage phase of the power supply. ,
The dielectric loss tangent detection means calculates a dielectric loss tangent from the current phase detected by the current phase detection means and the voltage phase detected by the voltage phase detection means. Further, the present invention is provided with display means for displaying insulation deterioration step by step from the dielectric loss tangent determined by the dielectric loss tangent detection means.

【Example】

Examples of the present invention will be described below. The present invention uses a dielectric loss tangent (t) that indicates the insulation state of an insulator.
an δ), and the insulation state of an insulator is diagnosed by measuring this dielectric loss tangent. This dielectric loss tangent refers to the tangent tan δ of the dielectric loss angle δ. Dielectric loss angle δ
This is because when an AC voltage is applied to a dielectric (a poor conductor of electricity), the current that flows ideally has a phase of 90° from the voltage.
However, the phase advance actually lags behind 90°, and this phase lag angle is expressed as δ. In other words, the current generated by applying an alternating voltage to a dielectric has a phase advance of θ, which is somewhat less than 90°.
This θ is called the dielectric phase angle. The relationship between the dielectric phase angle θ and the dielectric loss angle δ is θ=90″−δ. An embodiment of the present invention is shown in FIG. 1. In the figure, A power device 2 is connected to the high voltage line 1. This power device 2 is a ground insulating device such as a power cable, a transformer, or a capacitor. A clip-on type current probe 4 is attached to this ground wire 3.A current amplifier 5 is connected to this current probe 4. , a dielectric loss tangent measuring device 6 is connected.The current phase is detected by the current probe 4 and the current amplifying device.On the other hand, the voltage phase of the voltage supplied to the voltage line 1 is detected by the voltage divider 7. , is input to the dielectric loss tangent measuring device 6. In this dielectric loss tangent measuring device 6, the current waveform output from the current amplifier 5 (output from the current amplifier) is calculated from the maximum peak value of the voltage waveform input from the voltage divider 7. is output as a voltage value), calculates the δ value, and calculates the dielectric loss tangent (tan δ) from this δ value.In other words, the output voltage from the voltage divider 7 is The time Δt from the peak value to the zero cross point of the output voltage from the current amplifier 5 is detected, and the dielectric loss angle δ is easily calculated using the following formula: Δ t δ = 360 X □ 20 X 10 (However, the frequency Note that in this embodiment, a clip-on type current probe is used, and there may be a slight phase difference between the output voltage of the current amplifier 5 and the ground wire 3 of the power equipment 2. However, this phase difference can be corrected within the dielectric loss tangent measuring device 6.Also, in this embodiment, a voltage divider 7 is used to detect the voltage phase; Even if it is not, a voltmeter that uses light or
Any device that can detect the phase of the power supply voltage, such as a phase detector using electrostatic induction, may be used. Therefore, according to this embodiment, since a clip-on type current probe is used to detect the current phase, the current waveform can be measured without cutting the ground wire and inserting another element. Therefore, on-site live line diagnosis can be carried out in a short time, and since there is no need to cut the ground wire, there is a great advantage in terms of work safety. FIG. 2 shows another embodiment of the invention. This embodiment differs from the embodiment shown in FIG. 1 in that the dielectric loss tangent measuring device 6 of the embodiment shown in FIG. This is the point where the bag [10] was provided. The rest is the same as the embodiment shown in FIG. This display device 10 is composed of, for example, a plurality of comparators, and compares the value of the dielectric loss tangent with a comparison value, and outputs the result depending on the magnitude thereof. That is,
This comparison value indicates the gradual degree of insulation deterioration of the insulator. Therefore, according to this embodiment, since it is possible to display in advance in stages according to the degree of insulation deterioration of the insulator, anyone can easily determine the state of insulation deterioration of the insulator. [Effects of the Invention] As explained above, according to the present invention, since a clip-on type current probe is used, it is easy to measure the current phase, and the work of removing the ground wire is easy. The dielectric loss tangent can be measured quickly without the need for this method. Furthermore, according to this embodiment, the state of insulation deterioration of the insulator can be detected accurately and easily by anyone at an early stage in a live wire state.

[Brief explanation of the drawing]

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 diagnosing device of the present invention. It is.

Claims (2)

[Claims] (1) In a system that detects the insulation state of voltage equipment connected to high-voltage lines, including high-voltage lines, the current waveform is detected through a clip-on current probe to the ground wire of the power equipment, and the current current phase detection means for detecting the phase;
voltage phase detection means for detecting the voltage phase of the power supply by connecting a voltage divider or the like to the high voltage line; and a current phase detected by the current phase detection means and a voltage phase detected by the voltage phase detection means. An insulation deterioration diagnosing device comprising a dielectric loss tangent detection means for determining a dielectric loss tangent from a voltage phase. (2) An insulation deterioration diagnosing device according to claim 1, further comprising display means for displaying insulation deterioration in stages from the dielectric loss tangent determined by the dielectric loss tangent detection means.