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An arc flash is an electrical explosion that can greatly endanger human life as well as damage or destroy expensive equipment. In fact, arc-flash temperatures can reach 35,000° F, according to the U.S. Department of Health and Human Services.
Minimizing the length of electrical arcing events is crucial. One important component is the time required for a protection system to operate.
Arc-flash protection approaches
- Traditional, fast overcurrent protection: Arcing time is affected primarily by a protection relay’s operation time and the time required for a device, such as a circuit breaker, to extinguish the arc.
- Light and overcurrent-based protection: This method greatly reduces the operation time of the relay such that the dominant component of arcing time is a circuit breaker’s operation time.
- Light and overcurrent-based protection with short-circuit device: Though not applied on a regular basis today, short-circuit devices can reduce arcing time to only a few milliseconds by eliminating voltage after receiving a trip command, while the circuit breaker breaks current some tens of milliseconds later.
- Pre-emptive protection: Currently under development, this approach monitors for symptoms of slowly developing faults.
Arc protection systems are mainly composed of sensors (light and/or current), I/O units, a central unit, and communication cables. Selective protection is normally provided by dividing installations into individual protection zones.
Regardless of the arc-flash protection approach used, communication among protection system components and with its control system is a requirement.
In traditional arc-protection systems, architecture is centralized and the central unit is always required. The central unit monitors the system and maintains communication. In addition, the central unit can communicate with SCADA systems.
In an IEC 61850/GOOSE-based arc-flash protection system, however, the central unit is optional. Such a system is distributed instead of centralized. Ethernet-based communications in general and IEC 61850-based technology in particular, are rarely applied in arc-flash protection systems. Currently, GOOSE messages are limited to relay-to-relay communications in light/overcurrent-based arc-flash protection systems. GOOSE messaging could also be applied for communication between other components of arc-flash protection systems, but the essential question is whether GOOSE can provide the necessary speed and reliability.
To answer that question, we conducted a series of experiments. Learn about our conclusions in our free white paper, “Evaluating the Arc-Flash Protection Benefits of IEC 61850 Communication.”