A Study on the Operation Characteristics of Arc Fault Detection Device under Arc Generation

Heejun Kwon; SungHwan Kim; Jihee Lee; Kiseok Kim; Haiyoung Jung

doi:10.7731/KIFSE.e87fb1d2

Int J Fire Sci Eng > Volume 38(2); 2024 > Article

Kwon, Kim, Lee, Kim, and Jung: A Study on the Operation Characteristics of Arc Fault Detection Device under Arc Generation

Research Paper

International Journal of Fire Science and Engineering 2024;38(2):27-40.

Published online: June 30, 2024

DOI: https://doi.org/10.7731/KIFSE.e87fb1d2

A Study on the Operation Characteristics of Arc Fault Detection Device under Arc Generation

Heejun Kwon¹, SungHwan Kim², Jihee Lee³, Kiseok Kim³, Haiyoung Jung^4,^†

¹Department of Fire and Disaster Prevention Engineering, Semyung University, Choongbuk 27136, Republic of Korea

²Department of Fire Safety Engineering, Jeonju University, Jeonbuk-do 55069, Republic of Korea

³Lighting for Vision System Co, Yeonsu-gu, Incheon 21990, Republic of Korea

⁴Department of Fire and Disaster Prevention, Semyung University, Choongbuk 27136, Republic of Korea

^†Corresponding Author, TEL: +82-43-649-1695, FAX: +82-43-649-1787, E-Mail: hyjung@semyung.ac.kr

Received April 17, 2024 Revised April 30, 2024 Accepted May 1, 2024

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

According to the National Fire Agency's statistics in South Korea, the number of fires caused by electrical factors is increasing every year. Residual current devices and molded case circuit breakers are used to prevent electrical fires, but it is difficult to prevent electrical fires caused by arc generation. To prevent electrical fires caused by arc generation, studies on arc fault detection devices (AFDDs) and product development for commercial purposes are being conducted. However, the performance of AFDDs under real-life conditions has not been sufficiently verified. In this study, we conducted experiments on three types of AFDDs to verify their performance when a series arc is generated. Moreover, we performed arc waveform measurement and analysis. For the series arc test, we used a series arc generator based on the KS C IEC 62606 standard. We conducted arc-breaking experiments of the AFDDs with resistive and inductive loads and performed waveform measurement and analysis of the arc voltage and current.

Keywords: Arc fault detection device; Arc generator; Tracking fire; Series arc; Parallel arc

1. Introduction

According to the statistics of the National Fire Data System of the National Fire Agency in South Korea, from 2019 to 2023, 48,632 out of 193,999 total fires were caused by electrical factors, accounting for approximately 25.07%. It was the second leading cause of fires after negligence at 48.48% [1,2]. The causes of electrical fires are as follows: unidentified short circuit (30.33%), short circuit due to insulation deterioration (20.52%), short circuit due to poor contact (12.72%), short circuit due to tracking (10.65%), overload/overcurrent (7.79%), and others (7.33%). According to the statistics, the number of fires caused by electrical factors is increasing every year [3]. In particular, out of 289 fires in traditional markets during the same period, 127 fires were caused by electrical factors, accounting for the highest proportion [4,5]. Figure 1(a) shows fire statistics from 2019 to 2023, and Figure 1(b) shows detailed factors of electric fires.

Currently, it is mandatory in South Korea to install residual current devices (RCDs) and molded case circuit breakers (MCCBs) in indoor distribution boards to prevent electrical fires caused by overcurrent and electrical leakage. When a current of more than 30 mA flows to the ground, the RCD determines it as a leakage current via a zero current transformer (ZCT) and automatically breaks the circuit. The MCCB automatically breaks the circuit when an overcurrent of more than 1.25 times or two times the rated current is detected via an electronic or bimetal unit [6]. While RCDs and MCCBs are effective in preventing electrical fires caused by leakage current and overcurrent, they have difficulty preventing electrical fires caused by arc generation [7]. Electrical fires due to arc generation are caused by unidentified short circuits (28.6%), short circuits due to insulation degradation (20.5%), short circuits due to tracking (12.7%), short circuits due to crushing damage (4.6%), interlayer short circuits (1.2%), poor contact (10.2%), and partial disconnection (2.1%), and they account for 81.8% of all electrical fires. For this reason, arc fault detection devices (AFDDs) have been actively researched to prevent electrical fires caused by arc generation, but the performance of AFDDs under real-world conditions has not been sufficiently verified. In this study, three types of AFDDs commercially available in South Korea were tested for their arc interruption performance.

2. Theoretical Background

2.1 Characteristics of RCDs and domestic/foreign country standards of AFDDs

In South Korea, Article 304 of the Rules for the Occupational Safety and Health Standards mandates the installation of RCDs to prevent fires and electric shock. An RCD detects abnormal current in an electrical circuit and automatically breaks the current to prevent electrical fires and electric shock. A typical RCD comprises a ground-fault detector, trip device, and switching device, and is highly reliable due to the high precision of the ZCT. However, in an actual industrial environment, leakage fires occur due to RCD failure. When an RCD fails, a short circuit may occur due to insulation damage on multiple wires. Especially, when the leakage current in the form of a short circuit flows below the rated current of the RCD, it is difficult for the RCD to perform the interrupting operation. This type of short circuit can cause sparks or arcs, causing electrical fires. Therefore, to prevent fires caused by sparks or arcs, an AFDD is required to disconnect the power when an arc fault occurs due to a short circuit. As a standard for AFDDs in South Korea, the Korea Electro-technical Code (KEC) specifies the recommendation for the installation of arc fault detection devices, but it is not mandatory. In addition, KS C IEC 60364-4-42 421.7 recommends that special protective measures against the effects of arc faults should be adopted for branch circuits at the following locations [8].

① Lodging facilities (hotels, motels, inns, etc.)

② Places where there is a fire risk due to the nature of processing or materials, such as barns and woodworking shops

③ Places with combustible building materials, such as wooden buildings

④ Fire spreading structures

⑤ Places with irreplaceable items in case of loss, such as cultural properties (for example, museums)

By contrast, the standards in other countries include the following. In the United States, the UL 1699 arc-fault circuit interrupters AFCI was adopted, and the use of AFCIs in homes has been recommended since 2002. In 2013, the international standard IEC 62606 AFDD was established, and since 2018, testing standards and installation standards have been implemented in European countries such as Germany, the United Kingdom, Austria, and France, thus expanding the distribution of AFDDs [9]. Table 1 shows the standards for AFCIs/AFDDs at domestic and international.

2.2 Characteristics of arc

An arc is a high-temperature, light discharge phenomenon that occurs when the insulation of the air or insulating sheath between electrodes with a potential difference is destroyed, and it is accompanied by a sudden high temperature and white light due to plasma. In addition, arcing is caused by insulation degradation, tracking, crushing damage, interlayer insulation breakdown, unidentified short circuits, etc., and arcs are classified into serial arcs and parallel arcs. Moreover, an instantaneous discharge that occurs when electrodes are brought into contact, allowing current to flow, and then separated, is called a spark. If this phenomenon persists, it is defined as an arc. Figure 2 shows the impedance and equivalent circuit, assuming that the impedance up to the point of arcing comprises only the net resistance. In section ①, the applied voltage increases and there is no arc current. In section ②, the arc voltage is constant at , and arc current is generated. Then, no arc current is generated in section ③. In the next half cycle, the arc voltage and current waveforms have the same shape with opposite signs. Eq. (1) defines the applied voltage and arc voltage, and Eq. (2) is the equation for the arc current.

For the first half cycle, Eq. (1) is the equation for the voltage when a series arc is generated depending on the resistive load.

(1)

Section ①v=Vmsinωt0<t<tαSection ②v=Vαtα<t<πω-Section ③v=Vαπω-tα<t<πωtα

Here, V_msinωt is the applied voltage, V_α is the arc voltage, and tα=1ωsin-1VαVm

The equation for the arc voltage is given by Eq. (2):

(2)

Section ①i=00<t<tαSection ②i=Vmsinωt-VαRtα<t<πω-Section ③i=0πω-tα<t<πωtα

The root mean square value of the arc current is given by Eq. (3):

(3)

I=2ωπ∫tαπ2ωVmsinωt-VαR2dt

After integrating the above equation and reorganizing the terms, the arc current is expressed as in Eq. (4):

(4)

I=VmR2π12+x2π2-sin-1s-32x1-x2,

where x=VaVm

Figure 2 shows the equivalent circuit of a series arc, and Figure 3 shows the voltage and current in a series arc.

Series arcs occur in a state of being connected in series with the load and include arcs caused by poor contact, partial disconnection, and conductor wear. The magnitude of the arc current in a series arc is determined by the load, and the arc current generally does not exceed the rated current of the RCD. Therefore, even if a series arc occurs at the junction of wires or terminals, it will not be detected by the RCD and will progress to a fire [10]. In particular, a series arc often occurs at the junction, which is difficult to see with the naked eye and may be interpreted as a normal condition.

Parallel arcs occur in a state of being connected in parallel with the load and include arcs caused by insulation degradation, U-shaped wire fixtures, excessive bending of wires, and disconnection or rupture of a wire due to the effect of the pressure from a door gap or heavy object. When the fault impedance is low in parallel arcing, a large current is generated, allowing the RCD or MCCB to interrupt the circuit. However, when the fault impedance is high, insuffucient current flows, rendering the protective device ineffective. Because of these characteristics, parallel arcing can occur in power lines and electrical equipment, causing fires or safety accidents, and the Joule heat generated by parallel arcing can carbonize insulators, creating additional risks. Figure 4 illustrates series and parallel arcing. Figure 5 shows the causes of arcing in wires, such as insulation degradation, folded damage, crushing damage, and cover damage caused by a fixture (for example, a metal pin).

2.3 Characteristics of conventional circuit breakers and operating principles of AFDDs

Currently, circuit breakers such as RCDs and MCCBs are used to ensure the safety of electrical installations. However, RCDs and MCCBs have difficulty detecting arc currents. Parallel arcs with relatively large fault currents and ground arcs that generate leakage currents can be blocked relatively easily with conventional circuit breakers. However, in the case of series arcs, the small fault current due to the large arc impedance limits detection and blocking within the operating range of conventional circuit breakers. Therefore, the introduction of AFDDs capable of detecting and interrupting arcs is required to reduce electrical fires caused by series arcs. However, the AFDDs sold in South Korea are approximately 20 to 30 times more expensive than RCDs. Furthermore, the target arc current for detection has a low energy level because it is limited by the impedances at the time of arc generation and at the load, making detection using conventional RCDs and MCCBs difficult. In particular, in a phase control load with nonlinear characteristics, high-frequency signals similar to arc signals are generated even in normal operation, and thus, it is difficult to detect arc signals accurately. Figure 6 shows the characteristics of conventional circuit breakers against arcing, and Figure 7 shows the mechanism of arcing in low-voltage circuits.

Figure 8 shows the configuration and operation of AFDDs. The thermal and magnetic sensors configured in the AFDD are the same as those in a conventional circuit breaker and operate independently. The load current is detected using a load current sensor, and the output of the load current sensor is sent to an arc waveform filter that passes only the frequency of the arc waveform. The output of the arc waveform filter is then amplified through an amplifier and sent to a logic circuit that determines if an unstable waveform is present. Finally, if the logic circuit determines that there is a risk, the circuit breaker contact is opened. Moreover, a test circuit is configured to test the adequacy of the arc detection circuit. The test button is used to generate a signal similar to the arc output waveform, and if the AFDD operates normally, the circuit is opened by the generated arc output. The AFDD also uses a ZCT to detect and protect against arcing in advance. The output of the ZCT is fed through an amplifier to the logic circuit, and if it is determined to be risky, the circuit is closed.

2.4 Conditions of series arc test

The series arc test is performed by configuring the stationary and moving electrodes of the series arc generator so that the two electrodes are in contact and in a completely closed circuit. After power is applied, the moving electrode is separated from the stationary electrode by adjusting the distance control device of the moving electrode to produce an arc and conduct the test. Table 2 shows the test conditions (KS C IEC 62606) for the series arc test, and Figure 9 shows a schematic of the series arc generator and series arc test device.

2.5 Conditions of parallel arc test

The parallel arc generator suggested in KS C IEC 6260 uses a blade, and when two wires are short-circuited through the blade, an arc is generated. The dimensions of the blade of the parallel arc generator at a condition of 230-V applied voltage is 32 mm × 140 mm × 3 mm. Since the blade is damaged after one use, it should be configured for easy replacement, and it should be significantly hard and sharp to easily cut the wire. Table 3 shows the test conditions for the parallel arc test, and Figure 10(a) shows a parallel arc generator according to the KS C IEC 62606 standard and Figure 10(b) shows a schematic of the parallel arc test device. However, the parallel arc test was not performed in this study, because if the test is performed with the parallel arc generator suggested in KS C IEC 62606, a large spark and fire may occur when the blade and wires are short-circuited.

3. Details of Experiments

In this study, the series arc test was conducted on three AFDDs currently sold in South Korea to check if they trip in the event of arcing. The loads used in the experiments are as follows: a 3-kW heater was used as a resistive load and an electric fan was used as an inductive load. To measure the waveforms of the arc voltage and arc current during arcing, we analyzed the current and voltage in real-time using a current probe, a high-voltage differential probe, and an oscilloscope; we also checked whether the AFDD was operating properly. Table 4 shows the detailed specifications of the AFDDs used in this study, and Table 5 shows the detailed specifications of the load and measurement equipment.

3.1 Series arc interruption test

Figure 11(a) shows the series arc generator and Figure 11(b) shows the actaul arc test environment. Figure 12(a) shows the series arc generator before the test and Figure 12(b) shows a series arc being generated.

4. Experimental Results

4.1 AFDD operation test results by load under series arcing

The series arc test was performed on the AFDDs from Companies A, B, and C, which are commercially available in South Korea, with a resistive load and an instance load. The test was conducted using a series arc generator built in accordance with the KS C IEC 62606 standard. Figures 13, 14, and 15 show the results of arcing in a state where the resistive and instance loads of Companies A, B, and C are connected, respectively; the AFDDs did not trip. Series arcing occurred continuously for more than 30 s, but the AFDDs did not trip regardless of the type of load. Using the oscilloscope, it was found that the waveforms of the voltage and current changed when an arc was generated, and (f) in Figures 13, 14, and 15, respectively, show that the AFDDs of Companies A, B, and C remain turned on without performing the interrupting function.

4.2 Analysis of AFDD operation test results by load under series arcing

By analyzing the AFDD operation test results by load under series arcing, it was found that for the series arc waveform of the resistive load in Figure 16(a), the voltage waveform was distorted due to abnormal voltage fluctuation caused by the series arcing, and a transient voltage with a peak voltage of 12V was generated. However, the energy was relatively low. The shoulder phenomenon was not found in the current waveforms. Therefore, the distortion of the voltage waveform and occurrence of the peak voltage indicate that sufficient arcing occurred in the resistive load. However, since there was no shoulder phenomenon in the current, it is concluded that the power, not simply the current or voltage, in the resistive load was relatively low and not sufficient to trip the AFDD.

For the series arc waveform of the inductive load in Figure 16(b), the voltage waveform showed higher distortion than that of the resistive load, and the voltage fluctuations caused by the arc were clearly visible. The irregular changes in the voltage waveform were caused by the arc, and the shoulder phenomenon of the current waveform shows that the current increased instantaneously as the arc occurred continuously and persistently. By contrast, the magnitude of the current was 0.25 A, which was relatively small compared to that in the resistive load case. In short, arcing occurred sufficiently in the inductive load, and in particular, arcing was more clearly visible at the point where the shoulder phenomenon was observed. However, the current magnitude of 0.25 A was relatively small in terms of the power compared to that in the arc interrupting operation, as in the resistive load case. As a result, the AFDD did not trip.

5. Conclusion

In this study, three types of AFDDs commercially available in South Korea were tested for their operation under series arcing using resistive and inductive loads. The series arc test was performed using a series arc generator built in accordance with the KS C IEC 62606 standard, and the test results showed that arc interruption under series arcing was not effective for all the AFDDs of Companies A, B, and C, regardless of the type of load. As shown in Figure 16(a), the shoulder phenomenon was not found in the waveform of the arc current for the resistive load during series arc generation. The voltage waveform exhibited distortion due to the arc, but the peak voltage due to the overvoltage was at the level of 12 V, which was not high. Moreover, as shown in Figure 16(b), the shoulder phenomenon was found in the waveform of the arc current for the inductance load, but the magnitude of the arc current was 0.25 A, which was smaller than that of the resistive load due to the characteristics of the load. As a result, the interrupting operation condition of Un = 230 V according to KS C IEC 62606 was not met in the series arc tests of the AFDDs, although the series arc occurred continuously and persistently. Therefore, the AFDDs did not trip. In other words, since the three types of AFDDs in South Korea are designed in accordance with the international KS C IEC 62606 standard, it is judged that normal arc interruption was not achieved for arcs that do not meet this standard.

Through this study, it was found that since existing AFDDs in South Korea are designed to meet the KS C IEC 62606 standard for arc interruption performance, their interruption capabilities are somewhat inadequate for a variety of arcs. This is because existing AFDDs face the problem of sensitive responses to small arcs, and conservatively give more weight to non-fire alarms. However, arcs that may occur practically may have different shapes and sizes due to different loads or wire deterioration conditions. To ensure active protection against such arcs, future research will review the current UL1699 and KS C IEC 62606 standards, analyze the effects of harmonic signals during arcing, and analyze arcing patterns under different load conditions to improve the overall system stability and reliability of AFDDs.

Notes

Author Contributions

For research articles with several authors, a short paragraph specifying their individual contributions must be provided. The following statements should be used "Conceptualization, H.K. and S.K.; methodology, H.K. and S.K.; software, H.K. and S.K.; validation, J.L. and K.K. and H.J.; formal analysis, H.K. and S.K. and H.J.; investigation, H.K.; resources, J.L. and K.K.; data curation, H.K. and S.K.; writing—original draft preparation, H.K.; writing— review and editing, H.K. and S.K. and H.J.; visualization, H.J.; supervision, H.J.; project administration, H.J.; funding acquisition, H.J. All authors have read and agreed to the published version of the manuscript."

Conflicts of Interest

Authors must identify and declare any personal circumstances or interest that may be perceived as inappropriately influencing the representation or interpretation of reported research results. Declare conflicts of interest or state "The authors declare no conflict of interest."

Acknowledgments

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF: 2021R1G1A1014385)

Figure 1.

Fire occurrence status from 2019 to 2023, causes of electrical fires.

Figure 2.

Equivalent circuit of a series arc.

Figure 3.

Voltage and current in a series arc.

Figure 4.

Types of arcs.

Figure 5.

Causes of arc formation.

Figure 6.

Characteristics of conventional circuit breakers.

Figure 7.

Arc fire occurrence mechanism in low voltage circuits.

Figure 8.

Operating principle of arc fault detection devices.

Figure 9.

Schematic of series arc generator and test system.

Figure 10.

Schematic of the parallel arc test system.

Figure 11.

Series arc test environment.

Figure 12.

Series arc test.

Figure 13.

AFDD a rc test results (Company A).

Figure 14.

AFDD a rc test results (Company B).

Figure 15.

AFDD a rc test results (Company C).

Figure 16.

Arc test results of waveforms.

Table 1.

Domestic and Foreign Country Regulations for AFCI/AFDDs

Country	Regulation	Key Contents
USA	NEC	• (1999) Section 210.12 mandates protection via AFCI. It requires the installation of arc-fault circuit interrupters on all circuits supplying power to single-phase 125 V, 15 A, and 20 A outlets in bedrooms of dwelling units.
USA	NEC	• (2011) The AFCI requirement was expanded to include kitchens, living rooms, studies, bedrooms, and bathrooms in both new constructions and existing homes.
Canada	CEC	• (2002) Section 26.722 mandates that protection via AFCI must be provided for branch circuits supplying power to outlets installed in bedrooms of dwelling units.
Europe	IEC	• (2010) IEC 60364-4-42 recommends installing AFDDs in main circuits connected to loads such as washing machines, dryers, and dishwashers, as well as in locations such as lodging facilities, fire-spread structures, and places with irreplaceable items in case of loss.
Germany	DIN	• (2016) VDE 0100-420:2016-02 mandates the installation of AFDDs in public buildings such as factories, train stations, subway stations, museums, data centers, daycare centers, and nursing homes.
UK	BS	• (2018) Established BS 7671, recommending the use of AFDDs.
UK	BS	• (2022) BS 7671:2018+A2:2022 mandates the installation of AFDDs in certain high-risk residential buildings, student accommodations, and care homes.
Australia	AS/NZS	• (2018) AS/NZS 3000:2018 Cl 2.9.1 recommends using AFDDs in lodging facilities, combustible material storage facilities, fire-spread structures, etc. Cl 2.9.7 mandates the installation of arc-fault detection devices in New Zealand for combustible material storage facilities, irreplaceable item storage facilities, historically significant sites with flammable materials, and school dormitories.
Korea	KEC	• (2021) Section 113.3 mandates that electrical installations must be arranged to prevent combustible materials from igniting or being damaged due to high temperatures or arcs. Section 214.2 specifies that in branch circuits with a high risk of fire (20 A or lower), devices conforming to KS C IEC 62606 should be installed to mitigate the risk of fire caused by electrical arcs.

Table 2.

Test Conditions for AFDDs at U_n = 230 V in Series Arc Tests

Test Arc Current (A)	2.5	5	10	16	32	63
Maximum Break Time (s)	1	0.5	0.25	0.15	0.12	0.12

Table 3.

Test Conditions for AFDDs at U_n = 230 V in Parallel Arc Tests

Test Arc Current^a (A)	75	100	150	200	300	500
N^𝑏	12	10	8	8	8	8

^𝑎 : This test current refers to the inherent current before the arc within the test circuit.

^𝑏 : Refers to the number of half cycles at the rated frequency.

Table 4.

Detailed Specifications of Arc Fault Detection Devices

Company A		Company B		Company C
Items	Specification	Items	Specification	Items	Specification
Rated voltage	220 V, 60 Hz	Rated voltage	220 V, 60 Hz	Rated voltage	220 V, 60 Hz
Rated current	20 A, 30 A	Rated current	20 A, 32 A	Rated current	16 A, 20 A, 32 A
Rated sensitivity current	30 mA	Rated sensitivity current	30 mA	Rated sensitivity current	30 mA
Rated breaking current	2.5 kA	Rated breaking current	2.5 kA	Rated breaking current	2.5 kA
Rated non-operating current	15 mA	Rated non-operating current	15 mA	Rated non-operating current	15 mA
Operating time	0.03 s, less than 1 s under arc	Operating time	0.03 s, less than 1 s under arc	Operating time	0.03 s, less than 1 s under arc

Table 5.

Detailed Specifications of Experimental Equipment

Items	Product	Detailed Specifications
Resistive load	Electric heater	3 kW
Inductive load	Fan	60 W
High-voltage differential probe	ADP300	20 MHz/1.4 kV
Current probe	CP015	DC 15 A, AC 50 A (≤ 10 us)
Current probe	CP015	Sensitivity (per Division), 20 mA~10 A
Oscilloscope	HDO4054	500 MHz, 2.5 GS/S (10 GS/S WITH)
DSLR camera	A7c	2400 pixel, 10 fps, UHD 4 K

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