Which type of disconnect is specifically hazardous to open when it carries load current?

• A. Grounding Switch
• B. Load-break Disconnect
• C. Non-load Break Disconnect
• D. Bus Duct

Answer: (C)

Opening a switch that isn’t designed to interrupt current while there is load is dangerous because the electrical arc can form and persist as the contacts separate. A non-load-break disconnect is built only to provide isolation when the circuit is de-energized; it has no proper arc-quenching capability for breaking load current. If you try to open it with current flowing, the arc can damage the device, cause a flash, and endanger nearby personnel. In contrast, a load-break disconnect is designed to interrupt current, so it can be opened under load when properly rated. Grounding switches and bus ducts serve different purposes and aren’t the devices intended to interrupt live circuits in normal switching.