Arc flash accidents in electrical installations have become a growing concern. While most types of electrical injuries have been significantly reduced as a result of improved technology and safety, arc flash incidents have emerged as one of the leading causes of serious injury or even death among electricity workers.
What is arc flash?
When the insulation between electrical conductors is no longer sufficient to contain the voltage within them, an arc flash occurs. This is a strong electric current and large explosion that passes through air.
Effects of arc flash
Arc flashes can produce heat up to 20,000°C, generate audible noises exceeding 160dB, and emit ionising radiation in addition to molten material from the source.
Therefore, an arc flash presents a very dangerous hazard for people. These hazards can include:
- Inhalation of toxic gases
- Burns of all degrees
- Injuries due to ejection of materials
- Permanent damages to hearing
- Death in extreme cases
Active protection against Arc flash
With active protection, this is meant to guarantee resistance to internal arcing by installing devices limiting the arc. There are two possible approaches for limiting the destructive effects of the arc:
- Use of overpressure detectors
These detectors are installed in the assembly arc. However, there are limitations with this method as it is difficult to predict the amount of overpressure generated by an arc fault inside a switchboard, which leaves switchboard safety unwarranted
- Light arc detectors (Arc Guard System™ TVOC-2)
Arc detectors, which sense the light flux (i.e. intense light radiation) associated with arc flash and are installed in the assembly. With a reaction time of about 1ms, the arcing control system detects the event and sends a tripping signal to the circuit breaker
ABB’s Arc flash solution: Integration of Arc Fault Detection technology
IPD presents ABB’s solution of an integrated system of Arc Fault Detection technology. Strategically integrating the Arc detectors (TVOC-2) with circuit breakers (SACE Emax 2), this can significantly reduce arc flash events.
These combined sensing systems accurately and consistently cut power to the fault within 35ms.
To provide even more protection, the detection system can be distributed through the sub-breakers at each sub-board and tiered back across each of those breakers to provide a coordinated shunting trip in order to avoid a cascading arc condition.
ABB Arc Guard System™ TVOC-2
ABB TVOC-2 Arc Guard System™ is SIL-2 certified according to IEC 61508 and IEC 62062 providing an unrivalled optical arc flash detection device with the fastest reaction time on the market. The TVOC-2 identifies the light from an occurring arc flash and transmits the signal to the breaker within one millisecond.
The Arc Guard System™ monitor can be mounted anywhere in the switchgear, such as in the breaker cubicle or a separate control cabinet. A separate tripping circuit handles tripping.
This method allows you to connect up to three breakers and, if necessary, trip different breakers depending on where the arc occurs.
If the supply voltage fails, energy is stored in the unit for up to 0.2 seconds of operation. Even if the voltage disappears at a short-circuit fault, this is enough to close the tripping circuit.
SACE Emax 2
SACE Emax 2 air circuit breakers are certified for Class 1 active energy measurement in compliance with the IEC61557-12 standard. The SACE Emax 2 protects against arc flash by:
- Limiting the arc when used in conjunction with TVOC-2
- The circuit is cut off when the current operates outside the voltage range of tolerance and insulation is no longer sufficient
- Mitigating the arc fault by utilising the Reduced Energy Let Through (RELT) with local maintenance switch with local status indicator
- The RELT (Reduced Energy Let Through) Ekip 2K-3 is an Emax 2 and Tmax XT dedicated module that is designed to receive the aforementioned input signal
- Via an external input (usually a simple selector switch with LED status indication), the circuit breaker’s thresholds and response times are decreased to considerably safer levels
- This is usually only enabled when personnel are near the live equipment
- When deactivated, the circuit breaker returns to its normal protection settings
ABB’s integration between TVOC-2 Arc and SACE Emax 2 device is saving lives. Its solid construction and reputation give those in the electrical industry peace of mind.
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