KR100919293B1 - Detecting device series arcs in electrical systems ane methode for detecting the same - Google Patents

Abstract

PURPOSE: A detecting device series arcs in electrical systems and a method for detecting the same are provided to increase the reliability of detecting arc by attenuating a periodic component with a phase inversed signal by 180 degree and detecting only the arch signal. CONSTITUTION: A detecting device series arcs in electrical systems is composed of a high pass filter(110), a phase shift unit(120). The high pass filter detects a high frequency component of the arc by receiving power supply voltage, and the phase shift unit outputs the signal which is shifted by a ± 180 degrees. The adder detects serial arc by adding the high frequency component with the series arch having 180 degrees phase shift. The phase shift unit shifts a phase to improve the detection reliability of the series arc among the high frequency component detected from the high pass filter.

Description

DECATING DEVICE SERIES ARCS IN ELECTRICAL SYSTEMS ANE METHODE FOR DETECTING THE SAME

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrical systems, and more particularly, to an apparatus and method for serial arc detection of an electrical system to improve detection reliability and reduce malfunctions.

Recently, according to the statistical analysis of electrical accidents, the proportion of electric fires among the total fires in the past 10 years decreased from 34.9% in 1996 to 30.9% in 2005.

However, the number of electrical fires has been maintained at about 10,000 each year, and short circuits and short-circuit accidents account for 68.8% of the causes of electrical fires.

On the other hand, the series arc of the electric fire occurs at incomplete connection of a single conductor, such as when the connection of the outlet is loose or when the wire of the electric wire is partially cut when the electric heater or the electric equipment is used.

Since the current of series arc is always limited by the impedance of load, the energy level is lower than that of parallel arc, but it continuously releases heat to oxidize, thermally decompose surrounding insulation, and eventually short circuit, short circuit and Causes a fire.

On the other hand, low voltage networks of 600 volts or less are generally used for switchboards in certain areas, such as urban, industrial or commercial areas. In particular, the cables of the network are buried underground and are generally designed to be introduced at more than one point.

Such a cable may cause defects due to various causes such as thermal degradation, aging, moisture, or damage by animals such as mice or squirrels. A circuit breaker is provided to protect the network from the above-mentioned causes. A disconnect device that can disconnect the cable such as a fuse to insulate the faulty cable and minimize the failure of the network is provided at both ends of the cable. Required. The cable disconnection device is a device capable of safely acting on phase-to-phase defects such as high voltage and low impedance defects.

Wiring and earth leakage breakers are used at home to prevent fire or electric shock. The circuit breaker is used for the purpose of protecting the electric wire. Firstly, when the current exceeds the rated value while the load is in use, the current flowing inside the breaker flows higher than the normal current. This occurs, and the heat causes the internal bimetal to bend to block the operation of the electric appliance.

The second case is a short circuit between phases caused by a power tool or other metal object on the load side. In this case, since high current is generated instantaneously, the bimetal is heated to operate the magnet inside before the electric appliance is operated. , To block the operation of the electric appliance.

Such a high current generates a lot of magnetic fields, and the magnet inside the electric appliance is operated accordingly. In the case of the circuit breaker, the circuit breaker has a function of protecting the user by detecting a circuit and shutting off the power when the user is shocked while using the electric device.

In the United States, a Miniature Circuit Breaker is used for the switchboard and a Ground Fault Circuit Interrupter (GFCI) is used for the outlet where the user's hand directly contacts. The ground fault protection circuit breaker (GFCI) is a kind of ground fault breaker, has a high sensitivity ground fault detection function, and is mandatory to be used in places such as a kitchen, a bathroom, a parking lot, or a basement with a lot of moisture or moisture.

Despite the installation of circuit breakers and earth leakage breakers as described above, many fires occur worldwide every year, which causes arcing type faults to ground more frequently than the above phase faults. Because.

These arc faults are low current and high impedance and cause the cable disconnect device to not respond to the fault because it generates a current with a root mean square (RMS) below the thermal threshold of the breaker, As a result, fires often occur.

Nevertheless, the arc fault is very dangerous because it occurs at high temperatures, and can only be detected by the ground fault protection circuit breaker (GFCI) if the arc fault generates a sufficient leakage current through the ground.

In addition, since the breaker is operated when the current caused by the arc exceeds the thermal / magnetic structure parameter of the breaker, an arc fault protection circuit breaker (AFCI) capable of blocking the arc fault is required.

In particular, the Consumer Product Safety Commission (CPSC) determined that 40% of fires in 1997 were due to arc failure. thereafter,

The National Electric Code (NEC) has mandated the use of Arc Fault Circuit Interrupter (AFCI) in homes since January 2002.

The causes of arc defects vary greatly, for example, mechanical and electrical stress caused by aging, insulation and wiring breakdown, overuse or overcurrent, connection defects and excessive mechanical damage to insulation and wiring.

1 is a diagram illustrating a case where a series arc (contact arc) occurs between a general load and a conductive line connected in series.

As shown in FIG. 1, the conductive wires 14 and 16 constituting the cable 10 are separated and surrounded by an insulator 12 and insulated. The upper conductive line 14 of the conductive lines ruptured by a predetermined portion to generate a series gap 18.

In this state, if a series arc occurs, a large amount of heat is locally generated in the cable 10, and if a heat continues to occur so that the insulator 19 adjacent to the series arc generation point is ruptured or carbonized, a fire occurs. .

In the series arc generated as described above, the amount of current flowing through the arc is controlled by the load.

Therefore, studies on the prevention of electric fire through the detection of series arcs generated as above are being actively conducted, but the detection reliability is low in the case of minute discharge or intermittent arcs, and it is normal for nonlinear loads having similar electrical characteristics to some arcs. Since there is no distinction between state and arc generation, a reliable detection algorithm is required.

An object of the present invention is to provide an apparatus and method for detecting a series arc of an electrical system to improve the reliability of the series arc detection and to reduce the malfunction occurring in a nonlinear load.

In order to achieve the above object, a series arc detection apparatus of an electric system according to the present invention includes a high pass filter that detects a high frequency component of an arc included in the power supply voltage by receiving an input power supply voltage, and has a phase of ± 180 °. And a phase shifter for outputting a shifting signal, and an adder for detecting only a series arc by adding a high frequency component detected by the high pass filter and a phase shifted by ± 180 ° from the phase shifting means. The means is characterized in that the phase shift in order to improve the detection reliability of the series arc among the high frequency components detected by the high pass filter.

In addition, the series arc detection method of the electrical system for achieving the above object comprises the steps of detecting a high frequency component of the arc included in the power supply voltage by receiving a power supply voltage input using a high pass filter, phase shifting means; Outputting a signal having a phase shift of ± 180 ° by using a signal, and adding a high frequency component detected through the high pass filter and a phase shifted by ± 180 ° through the phase shifting means through an adder to detect only a series arc And the phase shifting means shifts the phase to improve detection reliability of the series arc among the high frequency components detected by the high pass filter.

The apparatus and method for detecting serial arc of an electric system according to the present invention have the following effects.

In other words, by canceling out the periodic components of the signal detected through the high pass filter with the 180 ° phase inversion signal, detecting only the arc signal appearing randomly when the serial arc occurs, improving the reliability of the serial arc detection and preventing the malfunction occurring in the nonlinear load. Can be reduced.

1 is a diagram illustrating a case where a series arc (contact arc) occurs between a general load and a conductive line connected in series.

2 is a graph showing typical series arc voltage and current waveforms of a heater (resistive load) load simulated using an arc generator.

3 is a block diagram schematically showing an apparatus for detecting a series arc in an electric system according to the present invention.

Figure 4a is a circuit diagram showing a high pass filter of the series arc detection apparatus according to the present invention

4B is a graph showing the frequency characteristics of FIG. 4A

FIG. 5 is a waveform diagram illustrating a series arc detection method using a series arc detection apparatus of the electrical system of FIG. 3.

6 is a diagram showing voltage waveforms measured at both ends of an incandescent lamp and an output voltage of a high pass filter during phase control by a dimmer;

FIG. 7A illustrates an example in which the phase shift method is applied to the filter output voltage measured in FIG. 6.

7B is a diagram showing a case where a series arc is arbitrarily generated using an arc generator.

* Description of the symbols for the main parts of the drawings *

110: high pass filter 120: phase shift means

130: an adder

First, the present invention provides a detection method capable of distinguishing a pseudo arc signal generated by a series arc discharge signal and a nonlinear load. To this end, the series arc is simulated for incandescent lamps controlled by a dimmer, a representative nonlinear load, and the electrical signals are measured and analyzed when a steady state and an arc occur.

In addition, by applying a high-pass filter that can minimize the influence of power frequency components and detect inherent high frequency components due to arc generation, and applying the proposed algorithm, the frequency of occurrence of high frequency pulses due to steady state and series arc generation Analyze the size.

In general, a series arc occurs when a part of a conductor to which power is applied is incompletely connected, and a voltage drop of several hundreds of mA to several tens of V occurs across the contact surface.

2 is a graph showing typical series arc voltage and current waveforms of a heater (resistive load) load simulated using an arc generator.

As shown in FIG. 2, the arc voltage shows a square wave shape rapidly rising and decreasing near the zero point, and the arc current has a zero-delay of about 200 to 300 μs near the zero point due to the onset and disappearance of the discharge. It can be seen.

On the other hand, the generation of arc causes the load impedance to change nonlinearly. In this case, unlike the normal load, high frequency components inherent in the arc are generated.

Therefore, the serial arc detection apparatus of most electric systems applies a high pass filter circuit having a specific frequency band to detect the high frequency component of the arc and distinguish between the steady state and the occurrence of the arc.

However, when detecting a series arc using the high pass filter circuit as described above, it includes not only the high frequency component of the series arc but also the high frequency component generated by the nonlinear load.

Accordingly, an embodiment of the present invention provides an apparatus and method for serial arc detection of an electrical system capable of detecting only serial arc by adding a high frequency component detected by applying a high pass filter circuit and a signal having a phase shift of ± 180 ° in phase shifting means. In other words, the present invention outputs a signal shifted by ± 180 ° through a phase shifting means to remove the periodic components of the signal detected through the high pass filter, and the signal detected through the high pass filter from the adder. And adding a phase shifted signal from the phase shifting means, the periodic signal component of the high frequency components cancels out and only the arc signal generated randomly remains, thereby providing a serial arc detection apparatus and method for an electrical system capable of detecting only a series arc. It is.

Hereinafter, an apparatus and method for detecting a series arc of an electric system according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram schematically illustrating a series arc detection apparatus of an electric system according to the present invention.

The apparatus for detecting a series arc of the electric system according to the present invention includes a high pass filter 110, a phase shifting unit 120, and an adder 130, as shown in FIG.

The high pass filter 110 is a filter that receives the input power voltage and detects a high frequency component of the arc included in the power voltage.

The phase shifting unit 120 outputs a signal shifting the phase by ± 180 °, and the phase shifting unit 120 improves the detection reliability of the series arc among the high frequency components detected by the high pass filter 110. Phase shift.

The adder 130 detects only a series arc by adding a high frequency component detected by the high pass filter 110 and a phase shifted by ± 180 ° from the phase shifting means 120. That is, the adder 130 When the signal detected by the high pass filter 110 and the phase shifted signal from the phase shifting means 120 are added, the periodic signal component among the high frequency components cancels out and only the randomly generated arc signal remains. Only arcs are detected.

Meanwhile, although the high pass filter 110 is described as an embodiment in an embodiment of the present invention, the present invention is not limited thereto, and a low pass filter, a band pass filter, a signal processing algorithm, and any combination thereof may be used.

In the present invention, a high pass filter as shown in FIG. 4A is used to remove power frequency components and detect only a high frequency arc signal.

That is, FIG. 4A is a circuit diagram showing a high pass filter of the serial arc detection apparatus according to the present invention, and FIG. 4B is a graph showing the frequency characteristics of FIG. 4A.

As shown in Figs. 4A and 4B, the high pass filter 110 is composed of a two stage coupling capacitor and a detection impedance, and the low pass cutoff frequency is 3 kHz. By using the high pass filter 110, the 60Hz power supply component can attenuate 80dB or more, and the high frequency component, that is, the series arc component, can be detected without attenuation.

The method for detecting the high frequency component of the arc included in the power supply voltage using the high pass filter 110 has the advantage of simplifying the circuit configuration, but if the actual normal load characteristics include the high frequency component similar to the arc, It is difficult to distinguish between electrical and arc discharge signals.

Therefore, in the present invention, the phase shifting means (120 in FIG. 3) is added to improve the detection reliability of the serial arc.

That is, FIG. 5 is a waveform diagram for explaining a series arc detection method using the series arc detection apparatus of the electrical system of FIG.

As shown in FIG. 5, the high frequency component generated by the nonlinear load among the signals detected through the high pass filter 110 has a constant period and repeatability unlike the disordered discharge signal caused by arc generation.

Subsequently, a signal obtained by shifting the phase 180 degrees from the phase shifting means 120 is output.

When the signal detected through the high pass filter 110 from the adder 130 and the phase shifted signal from the phase shifting unit 120 are added, the periodic signal component among the high frequency components cancels out and only the arc signal generated randomly. In other words, to remove the periodic components of the signal detected through the high pass filter 110, the signal is shifted ± 180 ° through the phase shifting means 120, and the high pass from the adder 130 When the signal detected through the pass filter 110 and the phase shifted signal from the phase shifting unit 120 are added, periodic signal components of the high frequency components are canceled and only the arc signal generated randomly remains to detect only the serial arc. Can be.

In the method of detecting a series arc of the electrical system according to the present invention as described above, a signal of up to twice as long as the arc signals do not overlap with each other.

In the present invention, in order to confirm the applicability of the phase shift method, the signal measured by the oscilloscope is transmitted to a PC, calculated using Equation 1, and only the arc signal is detected.

Arc Signal = (V _{- ph} -V ₀ )-(V ₀ -V _{+ ph} )

Here, V ₀ is a detected signal, and V _{− ph} and V _{+ ph} are signals shifted in phase by -180 ° and + 180 °, respectively. That is, V ₀ is a signal detected through the high pass filter, and V _{− ph} and V _{+ ph} are signals that are phase shifted by ± 180 ° through the phase shifting means.

Therefore, in the serial arc, as shown in Equation 1, the signal detected through the high pass filter and the signal phase shifted by ± 180 ° through the phase shifting means are added to finally detect the arc signal.

Generally, incandescent lamps are in phase voltage and current, and are typical resistive loads, exhibiting linear electrical characteristics. However, when the brightness of the light is adjusted by using a dimmer, a discontinuous section occurs in the current even in a steady state due to the phase control of a switching element such as an SCR. As a result, a high frequency component is generated in voltage or current.

In addition, since the high frequency component is very similar to the electrical characteristics of the arc signal, the arc detection circuit using a filter may malfunction due to the occurrence of an arc even in a steady state.

FIG. 6 is a diagram illustrating voltage waveforms measured at both ends of an incandescent lamp and an output voltage of a high pass filter during phase control by a dimmer. FIG.

As shown in Fig. 6, when the voltage across the incandescent lamp is cut off by phase control, a high frequency pulse which is the filter output voltage is detected at the same firing angle. This indicates that although the incandescent lamp is in a normal lighting state, the output of the high pass filter indicates that an arc has occurred.

Therefore, the reliability of detection can be further improved in the method of detecting the occurrence of arc by using a simple filter circuit for a nonlinear load, such as when using a dimmer.

6, the upper side is a ramp voltage [100 V / div, 10 ms], and the lower side is a filter output voltage [5 V / div, 10 ms].

In the present invention, the serial arc detection method using the phase shifting means detects only an arc signal that appears disordered when the serial arc is generated by removing the periodic component of the signal detected through the high pass filter.

In the incandescent lamp load by the dimmer, the output voltage of the high pass filter varied with the firing angle, and the largest output voltage was detected at 60 °. Therefore, the experiments were carried out for the firing angle, which is most influenced by the dimmer in arc detection.

FIG. 7A illustrates an example in which the phase shift method is applied to the filter output voltage measured in FIG. 6.

As shown in FIG. 7A, a high frequency pulse voltage is generated through a high pass filter every time the voltage is cut off by phase control, but a series arc does not occur, and its magnitude and frequency are generated every half cycle of voltage. A certain pattern is formed. Therefore, when the phase shift method is applied, the voltage components periodically generated are canceled with each other, and thus the output voltage of the filter is reduced.

7B shows a case where a series arc is arbitrarily generated using an arc generator.

As shown in FIG. 7B, by the phase control, the output of the filter is detected not only a constant periodic component but also a sporadic arc signal due to series arc generation. Applying the phase shift method, the output of the filter decreases the periodic components and increases the random high frequency components by the series arc.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention It will be apparent to those skilled in the art.

Claims (5)

A high pass filter which receives an input power supply voltage and detects a high frequency component of the arc included in the power supply voltage; Phase shifting means for outputting a signal shifting the phase by ± 180 °, And an adder for detecting only a series arc by adding a high frequency component detected by the high pass filter and a phase shifted by ± 180 ° in the phase shifting means. And said phase shifting means shifts a phase in order to improve the detection reliability of the series arc among the high frequency components detected by said high pass filter. delete 2. The apparatus of claim 1, wherein the high pass filter comprises a two stage coupling capacitor and a detection impedance. Detecting a high frequency component of an arc included in the power supply voltage by receiving a power supply voltage input using a high pass filter; Outputting a signal having a phase shift of ± 180 ° using a phase shifting means; And adding only a high frequency component detected by the high pass filter and a phase shifted by ± 180 ° through the phase shifting means through an adder to detect only the serial arc, And said phase shifting means shifts a phase in order to improve the detection reliability of the series arc among the high frequency components detected by said high pass filter. The method of claim 4, wherein the arc signal is arc signal = (V _−ph −V ₀ ) − (V ₀ −V _{+ ph} ), wherein V ₀ is a detected signal, V _−ph and V _{+. ph} is the phase shifted signal by -180 ° and + 180 °, ie, V ₀ is the signal detected through the high pass filter, and V _{- ph} and V _{+ ph} are ± 180 ° through the phase shifting means. And a phase shifted signal).