JPH02181671A - Automatic partial discharge monitor device - Google Patents

Abstract

PURPOSE:To improve the reliability by monitoring the time difference between an acoustic signal and an electric signal and judging partial discharge when a signal having the same time difference is detected plural times. CONSTITUTION:The earth line of a transformer 7 is provided with a high-frequency CT9 which detects the partial discharge electrically with current pulses. Further, an ultrasonic wave microphone 1 which detects the partial discharge acoustically is installed on the main body tank wall of the transformer 7. Here, the inside of the transformer 7 is formed of an iron core 10, winding 4, and an in-loading tap switch 5. Initial partial discharge is caused at the weakest position, the part is unchanged unless insulation deterioration is developed, and the CT9 and microphone 1 continue to output electric and acoustic pulses. The acoustic signal is propagated as a sound wave, so it has a time difference from the electric signal and malfunction is judged when the time difference is large. Further, when the time difference becomes small and the same time difference is detected plural times, a partial discharge signal is judged to monitor partial discharge automatically with high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an automatic partial discharge monitoring device that automatically monitors partial discharges occurring inside oil-filled electrical equipment.

Conventional technology As a method for automatically measuring partial discharges occurring inside oil-immersed electrical equipment, a Rogowski coil is installed on the main body grounding wire or neutral point grounding wire, and the internal discharge is converted into an electrical signal pulse. Methods of detection and methods of installing an ultrasonic microphone in the main body of the device and detecting it as an acoustic signal have been used.

``Problem to be solved by the invention'' However, electrical means such as Rogowski coils react to signals from the ground system when operating auxiliary equipment such as on-load tap changers, and also react to noise from broadcast waves etc. This caused a reaction and malfunction. Furthermore, acoustic means using ultrasonic sensors react to the operating noise of auxiliary equipment or to external environmental sounds such as rain, causing malfunctions. One possible solution to this problem is to temporarily disable the monitoring device when a noise signal occurs, but the problem is that there are a wide variety of noise signals that can cause malfunctions, and it is difficult to determine when they occur. was there.

"Means for solving the problem" In order to remove the noise signal that causes this malfunction and detect only partial discharge inside the device, an electrical means is used to detect partial discharge as a current pulse from the main body or neutral point grounding wire. If a signal with the same time difference between the electrical signal and the acoustic signal is detected multiple times using an acoustic means of detection by installing an ultrasonic microphone on the main unit, it is a partial discharge signal within the device. This is what we recognize.

``Effect'' This prevents electrical malfunctions caused by broadcast waves, noise from the ground system, etc., and prevents electrical malfunctions caused by external environmental noise such as rain and acoustic noise during auxiliary equipment operation. Therefore, a highly reliable automatic partial discharge monitoring device can be obtained.

Embodiment FIG. 1 shows an embodiment of the present invention. As shown in FIG. A high-frequency CT 9 for detecting electrically is installed, and an ultrasonic microphone 1 for acoustically detecting partial discharge is installed on the tank wall of the main body of the transformer 7. In addition, in order to process the signals of the high frequency CT 9 and the ultrasonic microphone 1, the monitoring device main body 3 is connected via a transmission cable 8.
The configuration is connected to

Here, the inside of the transformer 7 is composed of an iron core 10, a winding 4 wound around the iron core 10, and an on-load tap changer 5, but the partial discharge that occurs inside the transformer is initially isolated. Occurs in the most vulnerable area. Therefore, the partial discharge occurrence position remains the same unless insulation deterioration significantly progresses, and several electrical pulses and acoustic pulses continue to be emitted in one cycle of the power supply frequency.

Furthermore, although the electrical signal of partial discharge is detected instantaneously, the acoustic signal propagates as a sound wave through the insulating oil filled in the transformer 7, so for example, the fIfi sonic microphone 1 detects the partial discharge sound. To do this, the time difference Δ1+ is shown by the following formula.
occurs. Δt+ = J r /c where jl is the distance between the partial discharge position in the transformer and the tank wall where the ultrasonic microphone 1 is placed a, and C is the propagation speed of sound in oil. That is, as shown in FIG. 2, a time difference of Δtl occurs between the electrical signal from the high-frequency CT 9 and the acoustic signal from the ultrasonic microphone 1, and this time difference is the same time difference if the partial discharge position is the same. Become.

Therefore, the time difference Δt1 between the electrical signal and the acoustic signal when a partial discharge occurs is stored in a storage element, etc. in the monitoring device main body 3, and compared with the time difference Δ1+'' when the next partial discharge occurs, the time difference Δt1 is several 10% If they are the same within the same range, it can be determined that the partial discharge occurs at the same location.

On the contrary, at the initial stage of partial discharge, it is unlikely that the partial discharge position will be dislocated, so the time difference Δt1 and Δtl
If the difference from ' is large, it can be determined that the malfunction is caused by an external factor (operating noise of a tap changer under load, operating noise of an oil feed pump, etc.).

Note that a more reliable configuration can be achieved by increasing the number of ultrasonic microphones to a plurality and performing the above-described determination for each microphone. Further, by determining that it is a partial discharge signal when the same time difference is detected three or more times, malfunction prevention can be made even more effective.

"Effects of the Invention" As described above, the present invention can provide eleven effects.

(1) In contrast to the electrical method of detecting partial discharge using current pulses, it is possible to prevent malfunctions caused by erroneous signals and radio signals entering from the ground system.

(2) In contrast to the acoustic method of detecting partial discharge using an ultrasonic microphone, it is possible to prevent malfunctions caused by operating noise of on-load tap changers, oil pumps, etc.

Due to the above effects, a highly reliable automatic partial discharge monitoring device can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic structure of an automatic partial discharge monitoring device for a transformer, and FIG. 2 is a diagram showing an electrical signal by a high frequency C'r and an acoustic signal by an ultrasonic microphone.

Claims (1)

[Claims] In an automatic partial discharge monitoring device that uses acoustic means to detect partial discharges occurring inside oil-filled electrical equipment using an ultrasonic microphone and electrical means to detect them using current pulses, the time difference between the acoustic signal and the electrical signal is monitored. If a signal is detected multiple times with the same time difference, it is determined that it is a partial discharge inside the device, and if the signal is different, it is assumed that the signal is generated from an on-load tap changer, circulation pump, etc., and a partial discharge is mistakenly detected inside the device. An automatic partial discharge monitoring device that performs prevention.