Defining Arc Faults and Various Types of Arc Faults

Definition of Arc-Fault

An arc fault is a phenomenon that arises from the breakdown of the dielectric of a surrounding gas, resulting in the flow of electric current through a non-conductive medium like air. This electrical discharge generates high temperatures, often resulting in the formation of a spark or an open flame.

Wikipedia definition of Arc-Fault

Wikipedia definition: “An arc fault is a high power discharge of electricity between two or more conductors. This discharge generates heat, which can break down the wire’s insulation and trigger an electrical fire. Arc faults can range in current from a few amps up to thousands of amps, and are highly variable in strength and duration.”

Arc hazards

An arc fault not only damages or destroys surrounding insulation materials, rendering them ineffective, but it also poses a significant risk of igniting nearby materials. Various factors can contribute to arc faults in a photovoltaic system, such as loose connections, inadequate breaker maintenance, broken cables, aging or damaged insulation materials, or the presence of damp and corrosive wires. Due to the numerous wires on the DC side of the PV system, arc faults are more likely to occur.

The figure illustrates the different types of arc faults that can occur within photovoltaic systems. Essentially, an arc can be seen as a series connection between a variable resistor and a voltage source, with the arc voltage increasing proportionally to the current.

In most cases, the accumulated arc energy prior to protection activation serves as the primary parameter, which is used to establish benchmarks for assessing the effectiveness of AFCI (Arc Fault Circuit Interrupter) technology. We will delve into further explanation of AFCI technology later in this article.

Types of electric arc faults

There are three types of DC arcs:

• Series arcs

• Parallel arcs

• Ground arcs

The occurrence of series arcs is the most frequent (approximately 80%) due to the specific characteristics of electrical installations and PV power generation. Parallel arcs and ground arcs are less likely to happen, but they pose greater risks when they do occur.

Arc Fault Circuit Interrupter (AFCI) Technology

The Arc Fault Circuit Interrupter (AFCI) is an advanced technology used for protecting electric circuits. This specialised interrupter is designed to not only disconnect the circuit when there is a rise in current, like a conventional breaker, but also to specifically detect and respond to the formation of an electric arc on the load. The AFCI is capable of distinguishing between harmless electric arcs, such as the spark that occurs when plugging in a device or operating a light switch, and potentially dangerous arcs that could potentially lead to a fire, such as wire scratching or cracking. When a harmful arc is detected, the AFCI promptly interrupts the circuit, effectively preventing any further fire hazards.

Working Mechanism of the Interrupter

The interrupter incorporates electronic components that monitor the frequency of the current flowing through it. When an electric arc occurs, a high-frequency signal is generated, typically exceeding 100 kHz above the standard current frequency. The interrupter’s objective is to detect and capture this signal, subsequently disconnecting the circuit. Traditional circuit breakers, however, only disconnect the circuit if the current value surpasses a certain threshold. This poses a problem because in cases where a low-level continuous electric arc is present, a fire can potentially occur without the circuit being disconnected.

In order to address the issue of electric arcs, various solutions have been introduced to the commercial market, including several options available in Arab markets. One notable solution is the Huawei AFCI (Arc Fault Circuit Interrupter) solution, which will be further explored in the next paragraph.