JPH0254183A - Discriminating method of corona discharge - Google Patents

Abstract

PURPOSE:To perform exact discrimination without using an expensive constant- voltage power source, by counting a pulse signal from a detecting means and by discriminating the occurrence of a corona discharge when the pulse signal is generated at the value more than prescribed for a unit time. CONSTITUTION:When a corona discharge occurs in a primary coil 1a of a pole transformer 1, a change in voltage appears in secondary coils 1b and 1c, a current pulse flows through a low-tension distribution line 1c and a change in magnetic flux occurs around the line. Thereby a current flows through an air-core coil 5, an electromotive power generated by an electromagnetic induc tion action thereof is given as a detection signal to a counter 8 through an amplifier 6 and a band-pass filter 7, and the number of discharges is thereby counted. Since the corona discharge occurs in large numbers in every time in proximity to positive and negative peak voltages of a line frequency on the occasion, the corona discharge is judged to occur when the detection signal is counted by a prescribed value, e.g. 500 to several K discharges/sec., in the counter 8. An indicating element 9 is driven by an output signal of the counter 8 on the occasion, and the occurrence of the corona discharge is indicated by a lamp/buzzer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a corona discharge discrimination method for discriminating corona discharge such as partial discharge generated inside a power transformer from mixed noise.

[Prior Art] When high-voltage power equipment such as pole transformers is used for a long period of time, partial discharge (hereinafter referred to as corona discharge) tends to occur particularly in the windings, and this corona discharge can cause insulation breakdown accidents. Sometimes. In order to prevent this dielectric breakdown accident, it is necessary to periodically detect corona discharge in high-voltage power equipment. Conventionally, as a method for detecting corona discharge in pole transformers, corona discharge such as impedance was applied to the transformer under test. There is a method in which a corona detector is directly connected through a detection sensor, and the detector detects pulse voltage changes caused by corona discharge occurring in the winding portion of the transformer to be tested.

However, when using this corona discharge detection method to detect corona discharge in a test sample during actual operation, a corona detection sensor or a corona detector must be installed on the transformer under test that is connected to the high-voltage distribution line, which is a high-voltage power supply. Since direct connection is required, such connection work is extremely difficult and dangerous, making it impractical. Moreover, it is easily affected by radio noise, various switch noises, etc. that enter from high-voltage distribution lines, and there is a risk that these noises may be mistaken for corona discharge.

Therefore, in order to avoid the effects of the above-mentioned radio noise and various switch noises, there is a corona discharge detection device shown in Figure 3 that is driven by a constant voltage power supply separate from the high-voltage distribution line and detects corona discharge in the test sample. .

In this detection device, a signal source 103 is connected via an amplifier 102 to a low voltage winding 101 of a pole transformer 101, which is a test sample, and a corona detector 105 is connected to the low voltage winding 101b via a capacitor 104. It is connected. 101C is a high voltage winding of the pole transformer 101.

When a partial discharge (hereinafter referred to as a corona discharge) occurs in the winding portion of the pole transformer 101, a voltage pulse caused by this discharge is detected by the corona detector 105 via the capacitor 104.

[Problem to be solved by the invention] In the former conventional technology, the voltage pulse from the transformer under test connected to the high-voltage distribution line is detected by a corona discharge sensor, so it is easily affected by noise from the high-voltage distribution line. , corona discharge could not be accurately determined.

Also, the latter conventional technology uses radio noise.

In order to avoid the effects of switch noise, etc., an expensive and high quality constant voltage power supply is required.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for determining corona discharge that can accurately determine corona discharge without using a high-quality and expensive constant voltage power source. .

[Means for Solving the Problems] The present invention uses a counter to count pulse signals from a detection means for detecting corona discharge, and determines that corona discharge is occurring when the pulse signals occur at a predetermined value or more per unit time. It is characterized by [Function] Every time a corona discharge from high-voltage power equipment, etc. occurs, many pulse signals are generated in clusters near the positive and negative peak voltages of the line frequency. On the other hand, in the case of thyristor noise that occurs in synchronization with the line frequency generated on the load side, a sporadic pulse signal is generated every cycle, and in the case of switch noise, a pulse signal is generated randomly and non-periodically. Occur. From the above conditions, if a pulse signal of a predetermined value or more is generated per unit time, it can be determined that corona discharge is occurring.

[Example] An example of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a pole transformer connected to high voltage distribution lines 2a and 2b of 6600 V 150 or 60 Hz.

This pole transformer 1 has a primary winding 1a and secondary windings lb, l.
c, high pressure 66. OOV voltage 10
It transforms into a low voltage of 0V. Secondary winding lb, lc
Loads 4a, 4b are connected to the low-voltage distribution lines 3a, 3b, 3c on the side, and 95 is an air-core coil for detecting changes in magnetic flux caused by corona discharge of the pole transformer 1. This air-core coil 5 is arranged so as to interlink with the magnetic field generated around the low-voltage distribution line 3c. An amplifier 6 is connected to the output terminal of this air core coil 5.
．． A counter 8 is connected via a bandpass filter 7. This counter 8 counts the detection signals detected by the air-core coil 5 within a unit time (for example, 1 second) set by a timer, and determines that corona discharge has occurred when the counted value reaches a predetermined value or more. Outputs a signal to A display section 9 such as a lamp or a buzzer is connected to the counter 8, and is driven by the output signal of the counter 8.

10 is a high frequency component current Ih generated by the load 4b.
This is a high frequency bypass capacitor that bypasses the air core coil 5 so that it does not flow through the air core coil 5, and is also used to bypass high frequency component current due to corona discharge.

Now, when corona discharge occurs in the primary coil 1a of the pole transformer 1 in actual operation, it appears as a voltage change in the secondary coils 1b and lc. This voltage change results in a current change supplied to the loads 4a and 4b, and the low voltage distribution line 3C has a frequency of several tens of KHz to
A current pulse of several MHz components flows. Low voltage distribution line 3C
Magnetic flux changes of high-frequency components occur around the current pulse due to the current pulse. This change in magnetic flux causes a current to flow through the air-core coil 5, and the electromotive force generated by this electromagnetic induction is sent to the amplifier 6 as a detection signal. After being processed through a bandpass filter 7, the signal is applied to a counter 8 to count the number of discharges. At this time, since many corona discharges occur in clusters near the positive and negative peak voltages of the line frequency, the counter 8 detects a detection signal caused by the corona discharge by a predetermined value, for example, 500 to several times, per unit time. /sec is counted, it is determined that corona discharge is occurring. At this time, the output signal from the counter 8 causes the display section 9 to
is activated, and a lamp or buzzer indicates that corona discharge is occurring.

On the other hand, when a current pulse caused by noise or switch noise generated on the load side flows through the low-voltage distribution line 3c, the change in magnetic flux is detected by the air-core coil 5. At this time, the thyristor noise that occurs in synchronization with the line frequency only occurs sporadically every cycle, and the switch noise occurs aperiodically and randomly, so the detection signal counted by the counter 8 is 500 to several times. It is determined that it is not a corona discharge.

In this way, by focusing on the corona discharge state that occurs in large numbers near the positive and negative peak voltages of the line frequency each time and establishing judgment criteria, it is possible to accurately detect corona discharge without using a high-quality and expensive constant-voltage power supply. It is possible to distinguish between

In addition, by detecting magnetic flux changes in high-frequency components caused by current pulses generated around the low-voltage distribution line 3c using the air-core coil 5, it is possible to detect changes in the magnetic flux during actual operation by simply placing the air-core coil 5 along the low-voltage distribution line 3c. Corona discharge can be easily detected without removing the washing transformer 1. Moreover, since corona discharge can be detected in an insulated state,
Such detection work can be performed safely.

In addition, for high frequencies, as shown in Figure 2,
The low-voltage distribution lines 3a, 3b, and 3c connected to the secondary windings lb and lc of the transformer 1 are considered to be L-type, and the L and bypass capacitor 10 constitute an LPF circuit. This LPF circuit can cut high frequency component noise generated in the loads 4a and 4b, and
Since the high-frequency component current Ih generated at t'' can be bus-passed by the bypass capacitor 10, the current Ic caused by corona discharge can be detected with high accuracy.

Furthermore, since current changes are captured by the air-core coil 5, this method has the advantage that it is less affected by noise such as radio noise than the direct method. Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without changing the gist.

For example, in the above embodiment, an air-core coil was used as a means for detecting a gradual discharge, but a coil with eight windings on a magnetic material was used.
A clip-on type current transformer that operates as a :N transformer may also be used.

[Effects of the Invention] According to the present invention, it is possible to provide a method for detecting corona discharge that can accurately determine corona discharge without using a high-quality and expensive constant voltage power source.

[Brief explanation of the drawing]

Figure 1 shows a corona discharge detection bag to which the present invention is applied! FIG. 2 is an equivalent circuit diagram for explaining the embodiment, and FIG. 3 is a schematic diagram showing a conventional corona discharge detection device. 1...washing transformer 1a...-next winding lb,
lc...Secondary windings 2a, 2b...High voltage distribution lines 3a, 3b, 3c...Low voltage distribution lines

Claims (1)

[Claims] A method for determining corona discharge, which comprises counting pulse signals from a detection means for detecting corona discharge with a counter, and determining corona discharge when the pulse signals are generated per unit time by a predetermined value or more.