Overload is usually easy to understand: when the current exceeds the permissible range, the protection device operates and the circuit and equipment are protected. Arc faults, however, are more hidden, because an arc does not always bring an obvious large current.
In many fire hazards, the danger of arc risk lies not in how large the current is, but in the fact that the local temperature is high, the energy is concentrated, the arcing recurs persistently, and it does not necessarily trigger conventional overload protection.
1. What Is an Arc Fault?
Arc faults generally include series arcs, parallel arcs, poor-contact arcs, and arcs caused by insulation damage. Series arcs may occur at loose terminals, broken conductor strands, and poor plug-socket contacts; parallel arcs may result from insulation breakdown and abnormal discharge between conductors.
All of these arcs can produce high temperatures, sparks, and localized carbonization, gradually expanding the risk. Their common feature is that in the early stage they are not necessarily stable, continuous, or obvious.
2. Why May Conventional Protection Fail to Detect It?
Conventional circuit breakers are better at handling short circuits and overloads. If the arc fault current does not exceed the operating threshold, the protection device may not operate. This is especially true of series arcs, whose current is limited by the load and may not be much larger than the normal operating current.
Therefore, it cannot be assumed that no trip means no arc risk. An arc hazard may persist for a long time as intermittent pulses or waveform anomalies before the protection device ever operates.
3. What Early Features Do Arcs Have?
The early features of an arc usually appear in the waveform details, such as current discontinuity, half-cycle anomalies, high-frequency pulses, harmonic changes, increased noise density, and abnormal repetition. A single anomaly is not necessarily dangerous, but if it keeps growing along the time axis, it deserves attention.
At the same time, normal loads also produce disturbances. Switch operations, motor starting, power adapters, and variable-frequency devices can all bring similar noise. Arc detection must therefore identify dangerous features while filtering out normal disturbances.
4. Why Does Arc Detection Need Multi-Dimensional Features?
Looking at only one high-frequency signal easily causes false alarms. Effective identification requires combining current, voltage, harmonics, frequency-band features, time density, load scenarios, and duration. For different scenarios, the normal disturbance model also differs.
This is exactly where the difficulty of arc fault early warning lies: the system must not only know that an anomaly exists, but also determine whether the anomaly is a dangerous arc, whether it is growing continuously, and whether it requires an alarm and response.
5. How Does FEXLINK Understand Arc Fault Early Warning?
FEXLINK believes that arc fault identification is not a single-threshold problem, but a dynamic diagnostic problem at the waveform level, across multiple frequency bands and multiple time scales. FEXLINK's algorithms should combine low-frequency features, high-frequency features, half-cycle-level waveforms, and scenario filtering.
In terms of device capability, the existing high-precision electrical parameters and harmonic data can serve as the foundation, and the capability can then be further upgraded toward waveform-level arc identification.
Conclusion: The Difficulty of Arc Hazards Lies in "the Current May Not Be Large, but the Risk May Be High"
Arc faults are harder to detect than ordinary overloads because they are often hidden in waveform details and intermittent anomalies. Truly effective arc fault early warning requires multi-dimensional data, time-axis judgment, and filtering of normal disturbances.
