CASE STUDY: GROUND LEAD FAILURE Situation: Worker approaches the enclosure and the disconnect switch for the 480V power source is in the OFF position. The disconnect switch has failed with one phase (L1) in the closed position (L2, L3 are open). The ground leads of the devices are NOT connected to ground because of an improper installation or termination failure. The worker applies a lock. Following safety procedures, the worker performs an absence of voltage test with the electrical enclosure closed using a permanently mounted device. Permanently Mounted Device Failure Mode Potential Cause System State Ground lead(s) are NOT connected to ground Voltage Test Station (VTS) C A N A D I A N A U TO M AT I O N Improper installation or termination failure Disconnect is in the OPEN/OFF position with L1 energized Red wired are energized at 480V L1 L2 L3 Test Portal Front of Door VeriSafeTM Absence of Voltage Tester Detection YES - the AVT will detect open ground (or phase) lead(s) and communicate the installation of sensor leads is not verified Absence of Voltage Tester ester (AVT) ( VT) Test Portal Ground leads are not connected Failure Effect AVT will detect open ground lead(s) and communicate installation is the reason the absence of voltage test cannot be confirmed NO - voltage measurement results in zero voltage when voltage is present NO - the L1 LED for the voltage indicator will not be illuminated and measurement results in zero voltage when voltage is present Worker erroneously considers electrical enclosure as deenergized Incident Consequence None - Incident Avoided Worker opens equipment while energized * Probable shock or * Equipment damage is likely VOLUME 3, ISSUE 2 40