## 1 Introduction
### Glowing Condition and Arc Fault
The low-voltage arc-fault mechanism is similar to its high-voltage counterpart, but the discharge is not energetic enough to produce large arcs that can cause burns to objects in the surrounding environment. However, even though the low-voltage discharge is not intense enough to melt and break open the electrical contact, it can still be hazardous. The low-power electrical discharge can continuously accumulate heat at the affected area, resulting in the build-up of oxide layers. The oxides created by an arc fault can then induce glowing conditions, which eventually lead to an ignition when the temperature becomes higher than the flashpoint of the material surrounding the contact point. This includes the plastic housing and insulation that surrounds old electrical wires. The first type of arc fault is called short-circuit arc, which is categorized as a type of parallel arc fault. This phenomenon occurs when the live electrical wire is exposed due to mechanical failure or the degradation of the insulating and protective layers surrounding it. The live wire is then loosely connected to either a hot-to-neutral or a hot-to-ground cable. If two wires are tightly connected, then the connection can generate a substantial amount of heat proportional to the amount of current at the load center, which is enough to cause an extreme fire hazard. On the other hand, if two wires are loosely connected, then it is possible to obtain what is known as a \"sputtering arc\". This type of parallel arc is a low-current arcing between two wires that can generate enough heat to damage the insulation around the affected area. Once the majority of the insulation is damaged, it opens a path through which a high amount of current can flow. Modern electrical breakers can reliably detect this type of arc, greatly reducing the fire hazard risk associated with this phenomenon. The second type of arc fault is called a series arc fault. It is a relatively new phenomenon and the least understood of the arc-fault types. Series arcing occurs when a broken wire arcs to itself in a colinear fashion. The electrical spark caused from the broken contact of the wire is perceived as an arc. This kind of arcing is relatively low-current compared to a parallel arc fault. However, the heat generated by it is sufficient to damage or destroy the surrounding insulation and to ignite any flammable substances near the arcing area. In a controlled experiment testing series arcing at sea level and at atmospheric pressure, according to the Paschen curve, the lowest breakdown voltage is 327 V, which is higher than the electrical sources used by household devices. Having a lower breakdown voltage is possible, but the distance between the two gaps must be extremely small and the wires must be passing the original AC signal. Since the voltage in an alternating current is not constant, neither is the arcing. DC series arcing is often not a concern as a potential fire hazard since high-voltage DC systems are not widely used in residential areas. In factories, high-voltage DC systems are usually well monitored, and they tend to have protections built into them to prevent damage to machines. It is difficult to detect a fire hazard from a low AC voltage, such as the 100 V power sources that are widely employed in Japanese consumer products, and to predict when and where it will happen. Electrical devices that change their current draw based on temperature can falsely identify a hazard as a glowing connection. Placing a temperature sensor near the electrical contact point is not a reliable solution since a glowing connection can happen at any point where there is a loose connection. This includes places within the machine or within the construction wall where a wire has broken. Series arc faults are also difficult to detect since a device has to be able to distinguish differences in the RF (Radio Frequency) component of the waveform between normal operation and operation after an arc fault has developed.