JPH0278974A - Electric apparatus - Google Patents

Abstract

PURPOSE:To surely detect a partial discharge by providing a 1st and a 2nd loop circuits in a location near the windings to output the 1st and the 2nd voltage signals which the signal components corresponding to the magnetic field components of an electromagnetic wave crossed each other are made to have mutually reverse phase. CONSTITUTION:When the partial discharge is generated from the windings 6, 7, 8, the electromagnetic wave is reached to detection probes 10, 11 and crossed over, then an induced voltage is generated in accordance with an intensity of the electromagnetic wave. Magnetic field induced voltages on the 1st and the 2nd voltage signals have the same levels but the reverse phases; on the other hand, electrostatic induced voltages have the same levels and the same phases. So, in a differential amplifier circuit 16, the electric field induced voltages are offset, and the magnetic field induced voltages are superimposed and amplified. The difference voltage amplified in the circuit 16 is supplied to a spectrum analyzer 17 to measure the frequency region, then by analyzing the result, whether the partial discharge is generated in the windings or not can be decided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electrical device having a function of detecting partial discharge generated in a winding.

(Prior art) For example, in a transformer as an electrical device filled with sulfur hexafluoride gas (SFO), an organic polymer material such as polyethylene terephthalate, which has poor reliability against electric discharge, is used as an insulating material for the winding. may be used. In such a case, if partial discharge occurs in the winding, there is a risk that the insulation performance will deteriorate, so sufficient consideration is taken in the design to prevent partial discharge from occurring in the winding as much as possible.

However, when partial discharge occurs in the windings due to long-term operation, it is desirable to promptly deal with the problem, and for this reason, various devices and methods for detecting discharge have been devised. That is, JP-A-57-80572
As shown in this publication, partial discharge can be detected from both signals of current pulse and discharge sound accompanying partial discharge, or as shown in Japanese Patent Application Laid-open No. 123916/1982, optical fiber detection can be used near the arc contact. There is a method of installing a device to detect the light generated during abnormal conditions. Also, JP-A-57-11
As shown in Japanese Patent No. 2232, there is a method of detecting the occurrence of corona discharge by using a loop antenna to detect electromagnetic waves emitted due to corona discharge.

(Problem to be solved by the invention) However, in the various detection methods described above, the detection signal is not only weak (noise resistance is low), so the detection signal must be amplified or the noise contained in the detection signal must be separated. However, this has the disadvantage that the overall configuration becomes complicated.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an electrical device with a simple configuration and a function capable of reliably detecting partial discharge occurring in a winding.

[Structure of the Invention] (Means for Solving the Problems) The electrical equipment of the present invention has first and second first and second electrical devices located near the windings, in which signal components corresponding to magnetic field components of interlinked electromagnetic waves have opposite phases to each other. This circuit is provided with first and second loop circuits that output two voltage signals, respectively.

(Function) When partial discharge occurs in the winding, electromagnetic waves accompanying the partial discharge are emitted from the winding and interlink with the first and second loop circuits. Then, a magnetic field induced voltage corresponding to the magnetic field component of the electromagnetic wave and an electric field induced voltage corresponding to the electric field component are generated in each loop circuit, and these combined voltages are respectively output from each loop circuit as the first and second voltage signals. Output. At this time,
In the first and second voltage signals, the magnetic field induced voltages are out of phase with each other, whereas the electric field induced voltages are in phase. Therefore, by determining the differential voltage between the first and second voltage signals output from each loop circuit, the signal component due to the electric field component of the electromagnetic wave is canceled out and nullified, whereas the signal component due to the magnetic field component The component is further strengthened, thereby making it possible to reliably detect partial discharges occurring in the windings while preventing the influence of electric field noise.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 3 shows an inner iron-shaped eating utensil main body 1.

That is, the transformer main body 1 is formed by winding wires 6, 7, 8 around the legs 3, 4.5 of the iron core 2. Further, the windings 6, 7.8 are insulated using, for example, polyethylene terephthalate. As shown in FIG. 2, the transformer main body 1 is housed in a case 9, and in the housed state, the case 9 is filled with sulfur hexafluoride gas (SF8).

Now, 10 is the detection probe which is the first loop circuit, 11
is the detection probe which is the second loop circuit, and these are arranged in a state of opposition between each winding, and the arrangement position is such that the insulation performance is abnormal between it and the high voltage part of each winding 6.7.8 during operation. It is set in a position that does not cause And each detection probe 10. , 11 are connected to a signal cable 12, and the signal cable 12 is led out from the case 9.

Here, the connection relationship between the detection probe 10.11 and the signal cable 12 will be explained with reference to FIG.

That is, one end side of each detection probe 10.11 is commonly connected to the ground line 13 of the signal cable 12, and the other end side is connected to the signal line 14.15 of the signal cable 12, respectively. 16 is a differential amplifier circuit connected to each detection probe 10.11 via a signal cable 12, which calculates the difference between each voltage applied from each signal line 14.15, and amplifies the difference voltage. Output. Reference numeral 17 denotes a spectrum analyzer connected to the differential amplifier circuit 16, which determines the frequency band of the differential voltage provided from the differential amplifier circuit 16.

Next, the operation of the above configuration will be explained.

When a partial discharge occurs in any part of the windings 6, 7.8 during operation of the transformer, electromagnetic waves are emitted from the windings into the case 9. Then, was it released from the winding? [The first wave reaches the detection probe 10.11 and interlinks with it, and an induced voltage corresponding to the intensity of the interlinked electromagnetic wave is generated in the detection probe 10.11. Here, since the electromagnetic wave consists of a magnetic field component and an electric field component, the induced voltage generated in each detection probe 10.11 is formed from the magnetic field induced voltage generated by the magnetic field component and the electrostatic induced voltage generated by the electric field component. A composite signal is output from each signal line 14, 15 as a first and second voltage signal. Therefore, due to the connection relationship shown in Figure 1, the magnetic field induced voltages in the first and second voltage signals are at the same level and have opposite phases, whereas the electrostatic induced voltages are at the same level and in phase. There is. Therefore, when the differential voltage between the first and second voltage signals is determined in the differential amplifier circuit 16, the electric field induced voltage is canceled out and nullified.
The magnetic field induced voltage is doubled by being superimposed. Then, the differential voltage amplified by the differential amplifier circuit 16 is sent to the spectrum analyzer 17, and its frequency band is determined by API. Therefore, by analyzing the frequency band of the differential voltage using the spectrum analyzer 17, it is possible to determine whether partial discharge has occurred in the winding.

Now, the applicant forcibly generates partial discharge in the winding,
The frequency band of the differential voltage at that time was determined 7111 times by the spectrum analyzer 17, and the experimental results are shown in FIG. From this experiment, it was possible to confirm the generation of electromagnetic waves (signal level -40 to -70 dB) associated with partial discharge, particularly in a frequency band of 10 MHz or less. Note that the amount of charge released due to the net discharge was 800 pc.

In short, according to the above configuration, partial discharge occurs due to the connection relationship between the pair of detection probes 10 and 11. Since it is possible to reliably detect only the magnetic field component in the electromagnetic waves emitted by the sensor, even if electric field noise is applied to the detection probe 10, 11, its influence can be eliminated and the magnetic field component associated with partial discharge can be reliably detected. can be detected. Moreover, while obtaining such excellent effects, the configuration can be implemented with a simple configuration that only involves devising the connection of the annular detection probe 10, 11, compared to the conventional method of detecting H4I electricity using an antenna. The overall configuration does not become complicated.

Furthermore, since the detection probe 10.11 is located within the case 9, external noise is shielded by the case 9 and is prevented from reaching the detection probe 10.11.
This further improves noise resistance.

In the above embodiment, the partial discharge that occurs in the winding of a gas insulated transformer is detected, but instead of this, it can be applied to detect the partial discharge that occurs in the winding of an oil-immersed transformer, a rotating machine, or an electric device such as an axle. It may also be applied to the detection of partial discharges.

[Effects of the Invention] As is clear from the above description, the electrical equipment of the present invention has first and second first and second wires located near the windings in which the signal components corresponding to the magnetic field components of interlinked electromagnetic waves are in reverse phase with each other. By providing first and second loop circuits that output voltage signals, respectively, and calculating the difference between the first and second voltage signals, the influence of electric field noise can be prevented. With this configuration, partial discharge generated in the winding can be reliably detected, which is an excellent practical effect.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a configuration diagram of the main parts, Fig. 2 is a cross-sectional view of the transformer, Fig. 3 is a front view of the transformer main body, and Fig. 4 is a frequency diagram. FIG. 3 is a characteristic diagram showing the relationship between signal level and signal level. In the figure, 1 is the transformer body, 6.7.8 is the winding, 9 is the case, 10 is the detection probe (first loop circuit), 11 is the detection probe (second loop circuit), and 16 is the differential The amplifier circuit 17 is a spectrum analyzer. Applicant Toshiba Corporation Figure 1 Figure 3 Frequency (MHz)

Claims (1)

[Claims] 1. In an electrical device having a winding, a voltage signal located near the winding and outputting first and second voltage signals in which signal components corresponding to magnetic field components of interlinked electromagnetic waves are in opposite phases to each other, respectively. An electrical device comprising a first loop circuit and a second loop circuit.