WO2007004698A1 - Leakage current detection apparatus and leakage current detection method - Google Patents

Abstract

A leakage current detection apparatus for detecting a leakage current occurring at an electric line under test and caused by the capacitance relative to the ground. A leakage current I is detected from an electric line (A) under test, and the detected leakage current I is amplified by a first amplifier circuit (11). The signal amplified by the first amplifier circuit (11) is further amplified by a second amplifier circuit (13). On the basis of the signal amplified by the first amplifier circuit (11) and the signal amplified by the first and second amplifier circuits (11, 13), a multiplexer (20) selects a signal most suitable to be input to an A/D converter (21). A voltage applied to the electric line (A) under test is detected and the detected voltage is divided, after which the multiplexer (20) selects a signal most suitable to be input to the A/D converter (21). On the basis of the digital signal converted by the A/D converter (21), an arithmetic circuit (22) performs a predetermined calculation, thereby detecting a leakage current Igc caused by the capacitance relative to the ground.

Description

 Leakage current detection device and leakage current detection method

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to a leakage current detection apparatus and method for determining an insulation state of an electrical device by measuring a leakage current and a voltage fundamental wave flowing in an electric line, and in particular, flowing in a measured electric line. The present invention relates to a leakage current detection apparatus and method for detecting leakage currents of a ground insulation resistance component and a ground capacitance component.

 This application claims priority on the basis of Japanese Patent Application No. 2005-197949 filed in Japan on July 6, 2005, which is incorporated herein by reference. .

 Background art

 [0002] In everyday life, it is rare to be aware of the existence of electricity, but as is well known, it is used as a source of energy and in various fields including information and communication. It has become an indispensable existence for society.

 On the other hand, the use of electricity is convenient, but it also has a very dangerous side if it is not properly managed and used, and there are many possibilities of causing serious accidents such as electric fires and electric shocks.

 For example, one of the causes of serious accidents is leakage current, which is closely related to poor insulation of electrical circuits and equipment. However, investigating this leakage current requires a lot of time, and it is necessary to measure the value of insulation failure with an insulation resistance meter after a power failure. However, in today's social situation, computers are used in various areas of society, and a system that operates continuously for 24 hours has been constructed by expanding the use of intelligent buildings and factory automation (FA). In order to measure the leakage current, it is temporarily impossible to make a power outage.

 Therefore, at present, due to the demand for uninterruptible power supply due to such advanced information technology, leakage current measurement that can be measured without turning off electricity from the method of insulation resistance meter with electric power failure management of electric circuits and equipment. Has been moved to the earth leakage circuit breaker and earth leakage fire alarm

Claims

The scope of the claims

 [1] 1. Leakage current detection means for detecting the leakage current flowing in the measured electrical line;

 Voltage detection means for detecting the voltage applied to the measured electric line, and the analog Z digital for converting the leakage current detected by the leakage current detection means and the voltage detected by the voltage detection means into digital signals, respectively. Conversion means; and harmonic component removal means for removing harmonic components of the digital signal converted by the analog Z digital conversion means;

 Phase angle detection means for detecting a phase angle between the leakage current and the voltage based on the digital signal from which the harmonic component has been removed by the harmonic component removal means;

 A leakage current detection apparatus comprising: calculation means for calculating a leakage current caused by ground capacitance based on the phase angle detected by the phase angle detection means and the leakage current.

 [2] 2. Further, the first noise component removing means for removing the noise component of the leakage current detected by the leakage current detecting means and the noise component of the voltage detected by the voltage detecting means are removed. Second noise component removing means for

 The analog Z digital means converts the leakage current from which the noise component has been removed by the first noise component removal means and the voltage from which the noise component has been removed by the second noise component removal means, into a digital signal, respectively. The leakage current detection device according to claim 1, wherein

[3] 3. The leakage current detecting device according to claim 1, further comprising a switching switch for selecting an electric system of the measured electric line to be measured.

[4] 4. When the measured electrical line is a single-phase type, the leakage current (Igc) due to the earth ground capacitance is

 Igc = sin 0 X IO

 The leakage current detection device according to claim 1, wherein the leakage current detection device is calculated by: Where 10 is the leakage current detected by the leakage current detecting means, and Θ is the phase angle between the leakage current and the voltage.

[5] 5. When the electrical system of the electrical line to be measured is a three-phase multi-wire electrical system, the earth ground capacitance The leakage current (Igc) due to the quantity is

 Igc = (10 X sin θ Ζ 3) — 10 X cos θ

 The leakage current detection device according to claim 1, wherein the leakage current detection device is calculated by: Where 10 is the leakage current detected by the leakage current detecting means, and Θ is the phase angle between the leakage current and the voltage.

 [6] 6. The display device according to claim 1, further comprising display means for displaying a measurement result obtained by measuring a leakage current component caused by a capacitance to ground measured from the measured electric line. Leakage current detector.

[7] 7. Leakage current detection process for detecting the leakage current flowing in the measured electrical line;

 A voltage detection step for detecting a voltage applied to the measured electrical line, an analog for converting the leakage current detected in the leakage current detection step and the voltage detected in the voltage detection step into a digital signal, respectively. Digital conversion process,

 A harmonic component removing step of removing harmonic components of the digital signal converted in the analog-digital conversion step;

 A phase angle detection step of detecting a phase angle of the leakage current and the voltage based on the digital signal from which the harmonic component has been removed in the harmonic component removal step;

 A leakage current detection method comprising: a calculation step of calculating a leakage current caused by a ground capacitance based on the detected phase angle and the leakage current in the phase angle detection step.

 [8] 8. A first noise component removal step for removing the noise component of the leakage current detected in the leakage current detection step, and a first noise component removal step for removing the noise component of the voltage detected in the voltage detection step. And 2 noise component removal step,

 In the analog-to-digital conversion step, the noise component is removed in the leakage current obtained by removing the noise component in the first noise component removal step and in the second noise component removal step. 8. The leakage current detection method according to claim 7, wherein each of the voltages is converted into a digital signal.

[9] 9. Prior to detection of the above leakage current, select the electrical system of the measured electrical line to be measured. The leakage current detection method according to claim 7, wherein:

[10] 10. When the measured electrical line is a single-phase electrical system, the leakage current (Igc) due to the earth ground capacitance is

 Igc = sin 0 X IO

 The leakage current detection method according to claim 7, wherein the leakage current detection method is calculated by: Where 10 is the leakage current detected by the leakage current detecting means, and Θ is the phase angle between the leakage current and the voltage.

[11] 11. When the electrical system of the measured electrical line is a three-phase multi-wire system, the leakage current (Igc) due to the earth ground capacitance is

 Igc = (10 X sin θ Ζ 3) — 10 X cos θ

 The leakage current detection method according to claim 7, wherein the leakage current detection method is calculated by: Where 10 is the leakage current detected by the leakage current detecting means, and Θ is the phase angle between the leakage current and the voltage.