JP3163928B2 - Partial discharge measuring instrument - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a partial discharge measuring device for measuring a partial discharge which is one of the precursory phenomena of a failure for insulation diagnosis.

[0002]

2. Description of the Related Art In recent years, various insulating materials have been used for high-voltage electrical devices such as transformers in order to enhance their insulation (see, for example, Japanese Utility Model Application Laid-Open No. 56-134708). In addition, the life of an electric device depends on the insulation deterioration of the used insulating material. Therefore, in order to prevent a sudden failure of an electric device and use it safely, it is necessary to detect an initial stage of insulation deterioration such as partial discharge occurring in the insulation state. For this reason, a partial discharge measuring device is used for the purpose of grasping the insulation state of the electric device during operation, in addition to the periodic inspection performed by stopping the electric device.

Conventionally, a partial discharge measuring device of a large oil-immersed transformer has a configuration based on an electric method using a plurality of ultrasonic sensors, a current converter using a ferrite core disposed on a ground line, and the like, There was a configuration using a chemical method such as analyzing and quantifying gas components in oil of an oil-immersed transformer.

[0004] However, the above-described structure is not only complicated and expensive in structure, but also difficult to apply a chemical method to a mold transformer or the like other than an oil-immersed transformer. The method using the ultrasonic sensor of
The installation method is not simple, the sensor sensitivity decreases when air is used as the conductive medium, and the sensitivity decreases due to the influence of noise noise of surrounding equipment. In this method, it is difficult to detect a signal such as a weak partial discharge, and 1 MHZ from the response of the ferrite core.
There is a problem that it is difficult to detect a signal having a frequency of z or more.

In order to solve such a problem, the present inventors have considered the following partial discharge measuring device.

Hereinafter, a partial discharge measuring device which the present inventors have considered will be described with reference to the drawings.

FIG. 2 is a diagram showing a configuration of a conventional partial discharge measuring device. In FIG. 2, 1 is a transformer, 2 is a ground wire connected to the transformer 1, 4 is a sensor, and an inductance 6 which has low impedance at low frequency and has high impedance at high frequency, and two resistors connected in series. 5, the inductance 6 and the resistor 5 are connected in parallel. These resistors 5 are connected to the connection of the two resistors 5.
And a signal processing unit 8 for measuring a partial discharge generated in the transformer 1 based on a signal from the transformer 1.

In the above configuration, since the inductance 6 has a high impedance at a high frequency, the low frequency component of the current flowing through the sensor 4 mainly passes through the inductance 6 side, and the high frequency component mainly passes through the resistor 5 side. . Since the leakage current of the transformer 1 is at the commercial frequency,
Hz or 60 Hz, so that it mainly passes through the inductance 6 side. That is, as an example, the impedance of the resistor 5 using two resistors 5 each having a resistance value of 100Ω is 200Ω regardless of the frequency, and if the inductance 6 is 1 mH, the impedance is 0.1 when the frequency is 50 Hz. 314Ω, frequency 1M
Since it is 6280Ω when z and high frequency, low frequency flows on the inductance 6 side and high frequency flows on the resistor 5 side.

[0009]

However, in the above-described conventional configuration, when a large current flows through the ground wire 2 at the time of the ground fault of the transformer 1, a large voltage is generated by the inductance 6 due to the large current. If the resistor 5 has a low withstand voltage due to a voltage, the resistor 5 is destroyed. Furthermore, the signal processing unit 8 is made up of electronic components, and since these electronic components have a low withstand voltage, even the signal processing unit 8 is destroyed. If a person is touching the sensor 4, the large voltage may cause a dangerous amount of electricity to flow through the human body.

For the reasons described above, the conventional configuration has a problem that it is difficult to always safely monitor the partial discharge of the transformer 1 in a live state.

The present invention solves the above-mentioned conventional problems, and can constantly monitor electric equipment in a live state, and protects a signal processing unit for processing a partial discharge signal and a human body when an electric equipment is grounded. Therefore, an object of the present invention is to suppress the voltage generated by the sensor to a low voltage.

[0012]

According to a first aspect of the present invention, there is provided a partial discharge measuring instrument comprising: an inductance portion having a low impedance at a low frequency and having a high impedance at a high frequency; Detecting means for detecting discharge; protection means for suppressing a voltage generated in the inductance section to a predetermined value or less; and processing means for processing a detection signal of the detection means, wherein the inductance section, the detection means and the protection with connecting means in parallel, there is connected in series to a ground line of the electrical device, the coercive
The operating voltage of the protective means to the
Between the voltage value causing the air volume and the withstand voltage of the detection signal processing means.
The voltage is set to be lower than the lower voltage value .

[0013]

[0014]

In this configuration, when an electric device is grounded,
A large current flows through the ground line, and a large voltage is generated in the inductance unit and the detection unit. The voltage generated by the protection unit provided in parallel with the inductance unit and the detection unit is determined by the operating voltage of the protection unit. The maximum amount of electricity that does not pose a danger to the human body
Of the voltage value generated and the withstand voltage of the detection signal processing means,
Setting the operating voltage of the protection means below
Better protection of both human body and processing means
You.

[0015]

[0016]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a partial discharge measuring device according to one embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a transformer, which comprises a coil 12, an exterior part 13, and an insulator 14 for insulating them. 2 is a ground wire connected to the transformer 1, 3 is a sensor portion disposed on the ground wire 2, 4 is a sensor that forms the sensor portion 3, 5 is a resistor that forms the sensor 4, 6 is a sensor 4.
And an inductance connected in parallel with the resistor 5, which has a low impedance at a low frequency and a high impedance at a high frequency. Reference numeral 7 denotes a gas arrester which constitutes the sensor unit 3 and is provided in parallel with the sensor 4. Reference numeral 8 denotes a signal processing unit. Reference numeral 9 denotes a CT for detecting a current flowing through the ground wire 2 when a ground fault occurs. Reference numeral 10 denotes a ground fault. The relay 11 is a circuit breaker that cuts off power supply to the transformer 1. Sensor 4
Is lower than the input impedance of the signal processing unit 8.

The operation of the partial discharge measuring device configured as described above will be described. In this embodiment, the ground current means a large current that flows rapidly, such as when lightning strikes the transformer 1. The leakage current refers to a current flowing through the stray capacitance between the coil 12 of the transformer 1 and the exterior part 13 or a small amount of current constantly flowing due to contamination of the surface of the insulator 14. Further, the partial discharge current refers to a current at the time of discharging in a pulsed manner due to a gap inside the coil 12 or contamination on the surface of the coil 12.

When a partial discharge occurs in the transformer 1, the partial discharge current flows through the ground line 2 to the ground, and the partial discharge current is detected by the sensor 4 of the sensor unit 3 provided on the ground line 2. In order to detect partial discharge, it is desirable to detect only with the resistor 5, and if the resistance value of the resistor 5 is too small, the detection performance deteriorates.
When the real device is to be constantly monitored, the ground resistance value of the ground wire 2 is about 10 to 100Ω, but since the resistance 5 alone may exceed the ground resistance value, the inductance 6 is provided in parallel with the resistance 5. The impedance of the sensor 4 is lowered.

Another function of the inductance 6 is to prevent a ground fault current from flowing to the resistor 5, but the current flowing to the ground wire 2 when the transformer 1 is grounded is 50%.
Since the component is a Hz or 60 Hz component, the inductance 6 has a low impedance with respect to this component, and most of the ground fault current flows through the inductance 6 and hardly flows through the resistor 5, so that the resistor 5 for detecting partial discharge is a watt. An inexpensive and small one with a small number can be used. Note that the inductance 6 can be realized by winding the ground wire 2 several times.

Since the partial discharge current has a high frequency with respect to such a ground fault current, and the inductance 6 has a high impedance with respect to the high frequency, the partial discharge current flows through the resistor 5 and is detected as a partial discharge signal. The signal is input to the signal processing unit 8 and processed. The leakage current is 5 as described above.
The component is a 0 Hz or 60 Hz component, and the inductance 6 has a low impedance with respect to this component, so that the leakage current flows through the inductance 6.

Further, the sensor section 3 is provided directly on the ground wire 2 so that the partial discharge can be measured with high sensitivity. However, when the transformer 1 is grounded during the measurement of the partial discharge, a large current flows through the ground wire 2. This large current is dangerous because a voltage is generated at the output terminal of the sensor 4 due to the inductance 6 constituting the sensor 4, but the voltage at the output terminal of the sensor 4 is reduced by the gas arrester 7 provided in parallel with the sensor 4. The operating voltage of the arrester 7 is suppressed. The earth wire 2 is provided with an earth wire current detection CT 9, and the earth current when the transformer 1 is grounded is detected by the ground wire current detection CT 9, and a signal is sent to the ground fault relay 10. When the ground fault relay 10 operates, the supply of power to the transformer 1 is interrupted by the circuit breaker 11. By using the gas arrester 7 as a protection component, the sensor section 3 can be made small and inexpensive.

The safety standard value regarding the quantity of electricity at the time of electric shock is 30 mA · s so as not to give any danger to the human body (Guideline for protection of low-voltage ground faults JEAG 8101-71).
Electricity Standards Investigation Committee, Japan Electric Association, see)
Assuming that a normal earth fault relay 10 having an operation time of 0.1 ms or less is used and the resistance of the human body when wet is 500Ω, the operating voltage of the gas arrester 7 is desirably 150 V or less. In this case, even if a person touches the sensor unit 3, the amount of electricity flowing through the human body does not reach a dangerous amount of electricity.

The maximum operating voltage of the gas arrester 7 for preventing danger to the human body varies depending on the operation time of the ground fault relay 10. This is shown in comparison with (Table 1).

[0025]

[Table 1]

As described above, the maximum operating voltage of the gas arrester 7 must be determined based on the operation time of the ground fault relay 10.

In order to provide both protection of the human body and protection of the signal processing unit 8, the operating voltage of the gas arrester 7 must be set to the operating voltage for protecting the human body and the operating voltage for protecting the signal processing unit 8. It is necessary to decide on the lower voltage.
In this embodiment, the grounding relay 10 having an operation time of 0.1 ms is used. In this case, it is desirable to use the gas arrester 7 having an operation voltage of 150 V or less from the viewpoint of protection of the human body. Since a gas arrester having a withstand voltage of 400 V is used for 8, a gas arrester having an operating voltage of 150 V or less is used. In this embodiment, a gas arrester 7 having an operating voltage of 90 V was used. Thus, when the transformer 1 is grounded, both the human body and the signal processing unit 8 can be protected.

The same effect can be obtained by using a diode, a varistor, a surge absorber using a silicon PN junction, and a gap type surge absorber instead of the gas arrester 7 in antiparallel. Among these, it is desirable to use a gap-type surge absorber in consideration of safety such as repeated use and short-circuiting of the protective component in case of breakage.

Further, in the above embodiment, the description has been made using the transformer as the electric equipment, but it is needless to say that the present invention is not limited to this.

[0030]

As described above, the present invention suppresses the voltage generated by the partial discharge detecting means due to the ground fault of the electric equipment to a low voltage while constantly monitoring the partial discharge of the electric equipment in a live state, thereby reducing the signal processing. Danger to the human body by preventing damage to the parts, etc., and suppressing the generated voltage to a low voltage that does not allow the amount of electricity that would pose a danger to the human body even if the person touches the partial discharge detection means This makes it possible to realize an excellent partial discharge measuring instrument that can be protected from the above.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a partial discharge measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a conventional partial discharge measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transformer 2 Earth wire 3 Sensor part 4 Sensor 5 Resistance 6 Inductance 7 Gas arrester 8 Signal processing part 9 Earth wire current detection CT 10 Ground fault relay 11 Circuit breaker 12 Coil 13 Exterior part 14 Insulator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-175376 (JP, A) JP-A-5-67114 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 31/12 H02B 3/00

Claims (4)

(57) [Claims] 1. An inductance section which has a low impedance at a low frequency and has a high impedance at a high frequency, a detection means for detecting a partial discharge of an electric device, and a protection means for suppressing a voltage generated in the inductance section to a predetermined value or less. And a detection signal processing means of the detection means, wherein the inductance unit, the detection means and the protection means are connected in parallel, and a partial discharge measuring instrument connected in series to a ground wire of the electric device. Operation of the protection means
Generates a maximum amount of electricity that does not endanger the human body
The lower one of the voltage value and the withstand voltage of the detection signal processing means
Partial discharge measuring instrument set below the pressure value . 2. A current detecting means provided on a ground wire of an electric device.
And a ground fault relay connected to the current sensing means.
Supply of electric power to the electrical equipment
With a circuit breaker that shuts off the
The voltage value that generates the minimum amount of electricity is the operating time of the ground fault relay.
The partial discharge measuring device according to claim 1, which is determined by: 3. Low impedance at low frequency and high impedance at high frequency
Inductance part with high impedance and electrical equipment
Detecting means for detecting partial discharge of the
Protection means to keep the voltage generated in the unit below a certain value
And processing means for processing a detection signal of the detecting means,
The inductance part, the detection means, and the protection means are arranged side by side.
And connected in series with the grounding wire of the electrical equipment.
A connected partial discharge measuring device, wherein
Partial discharge measuring device using a gap type surge absorber . 4. The partial discharge measuring instrument according to claim 1 , wherein a gap type surge absorber is used as the protection means.