ARC Monitor

When the insulation between electrical conductors is no longer sufficient to contain the voltage within them, an arc flash occurs, which is a strong electric current and often a large explosion that passes through air. This causes a short circuit, allowing electricity to flow from conductor to conductor. Arc flashes can produce heat up to 20,000° C, generate audible noises exceeding 160dB, and emit ionizing radiation in addition to molten material from the source.

Human error is the leading cause of arc flashes, with 65% occurring while an operator is working on the switchgear. Here are some examples:

• Overtightened unions, loose/dry joints, series arcing, and thermal runway
• Animal/insect intrusion - these little buggers are always looking for a nice small warm home.
• Foreign objects left behind during construction or maintenance - tools can be left behind.
• Inadequate or incorrect maintenance - condensation under MCC top tiers is a classic cause of rust, which will eventually scale off and fail.
• The life cycle of aged switchgear and cabling is generally exceeded, which is exacerbated by poor and misinformed maintenance, and breaking capacity degrades over time.
• Opened compartment doors on live switchboards, introducing moist/dusty/salty air, which can result in a lower impedance between two points.

The Work Health and Safety Act of 2011 states that it is the responsibility of anyone conducting a business or undertaking at a workplace to keep their employees safe and prevent a potentially catastrophic event from occurring. The employer may be liable under the act if an arc flash accident occurred and the employer had reasonably practicable means of preventing it.

Although there is no specific standard in Australia for arc flash calculations, IEEE 1584 is used to determine the incident energy and arc flash boundary for electrical equipment installed. Arc Flash studies for coal mines have become a requirement of AS3007.

Within 1 ms, the TVOC-2 detects the light from an arc flash and sends the signal to the breaker. The total arc fault clearing time is less than 50ms when combined with ABB's Emax 2 circuit breaker.

If the switchgear is likely to be exposed to bright light, which could cause the TVOC-2 to trip, current can be added as a second condition. The current sensing unit CSU-2 is a TVOC-2 accessory that detects the current increase caused by an arc flash.

• Personnel and equipment are now more secure
• Reduces downtime following an arc accident
• No calibration is required, ensuring dependable operation and a quick installation.
• It is scalable to add up to 30 sensors to increase cabinet coverage from a single TVOC-2
• Current sensors based on Rogowski technology for quick and dependable installation

• SIL-2 certification in accordance with IEC 61508 and IEC 62061 ensures extremely dependable operation.
• Communication protocol - Modbus RTU
• ABB ability TM EDCS is integrated.
• Light and current are used in conjunction with CSU-2 to trip in less than 2ms.
• The CSU-2 alerts the user when current sensors fail.