Electrical Safety - Grounding continuity

When you think that your lighting batten is inherently grounded, you may want to check that it really is grounded. Modern rigging systems use Nylatron (plastic) pulleys and the counterweight carraige arbor shoes may be Nylon, leaving the only electrical path back to the safety ground as the ground wire in the SO power cable or flexible conduit that feeds your plugstrip or plugbox. If the fixed conduit or flex conduit body is the only ground path you have, then the ground is broked (open circuit) if the conduit becomes separated.

The same is true if your ground lead on a lighting instrument becomes disconnected. This can happen several ways:

• A two wire connector (an old style two-pin 2P&G stage plug or a two-bladed Edison plug) is installed on a three-wire cable
• A ground-lift adapter is installed on the end of a normally grounded NEMA 5-15P connector
• The wire breaks internally
• The wire gets yanked-out of the connector body
• The wire gets yanked out of the lighting instrument body

In any case, you are in a situation that would let the fault current of an internal problem in a lighting instrument look for another path back to the source, and that path may be you!

Electrical Safety - Equipment Maintenance

Most stage equipment that uses electricity has a power cord with a (male) plug or (female) receptacle on one or both ends of it. Maintaining those connections is vital to both the operation of the device and the safety of those using it. Below is the back-end of a stage lighting instrument that has the cable strain relief missing, which in-turn allowed the inner wiring to become frayed and short-out to the casing. Here is a cable end plug that was hurredly assembled to get it working for a show, but the cable clamp (strain relief) was never tightened-down to take the stress off of the inner conductors.
Here is a 2P&G cable end that was not properly secured to the outher sheathing of the stage lighting instrument cable, and over time it frayed apart.

The same thing can happen to extension cords, twofers, and just about any other cable connection. When you find these types of equipment damage, the best thing to do is red-tag the equipment as non-usable, and submit it to your repair shop for correction

An ounce of prevention
In general, the root cause of these types of connector failures is due to people yanking on the cable instead of grasping the plug body when they remove them from their mating device. Take care of your equipment and it may not seek revenge by failing at five minutes to eight, or worse yet, shocking you to get your attention.