12Power

The short version: A show runs on venue power or generators, fed through heavy cables to a main distribution box and then to smaller ones at each stage. Audio gets its own clean circuit, separate from lights and video. Single-pole connectors are connected ground first and disconnected ground last, and hum is fixed on the signal side - never by defeating the safety ground.

Sources and sizing

Power comes from the grid (shore power) or from towable generators, often synchronized in pairs for redundancy at greenfield sites³¹⁷. Planning guidance is consistent: build 20-30% headroom above the expected peak, keep circuits at or below about 80% of their rating, allow for the inrush when amplifiers and moving lights switch on, and leave three-phase hookups to licensed electricians³¹⁷. Generators prefer to run at 50-75% of their rating; below about 30%, diesels suffer "wet stacking"³¹⁸.

Power flows from the source - a generator or, indoors, the venue's company switch (trade usage for the fused disconnect a venue provides for touring gear) - to a main distro (distribution box), then over feeder cable to sub-distros at each stage³¹⁸. The connectors on that feeder are typically cam-lok single-pole connectors, one per conductor. The US electrical code requires them to be listed and locking, color-coded (green for ground, white for neutral), and connected only by a qualified person or with interlocks: ground first, then neutral, then the hot legs, and the reverse to disconnect³¹⁹. A common entertainment color code for 120/208 V adds black, red and blue for the three phases (forum-sourced)³²⁰.

The codes, and what each one covers

In the US, temporary event power sits in several articles of the National Electrical Code (NFPA 70). Section numbers vary by edition, and jurisdictions adopt different editions, so check with the local authority:

• Article 520 covers theaters and permanent stage structures, including those at fairs and similar venues³²¹.
• Article 525 covers portable structures at carnivals, circuses, fairs and similar events - rides, tents, concessions - with rules such as 15 feet of clearance from overhead lines and extra-hard-usage cords³²²³²¹.
• Article 590 covers temporary installations generally; section 590.6(A) requires GFCI protection on 125 V 15, 20 and 30 A temporary receptacles³¹⁸.
• Section 406.13 covers single-pole separable connectors like cam-loks³¹⁹.

ANSI E1.19 is not a distribution or connector standard. It is ESTA's recommended practice for using Class A GFCIs - ground-fault protectors for personnel - in entertainment, covering circuits up to 100 A; Class A devices trip above 6 milliamps, and European RCDs do not meet the Class A definition³²³³²⁴.

Hum, ground loops and keeping audio clean

Run audio and lighting on separate circuits, and video too where possible: older dimmers and some LED fixtures inject noise, and separation also means a tripped lighting circuit will not kill the sound³¹⁷. A ground loop happens when equipment has a second path to ground through a signal cable's shield, and it shows up as hum³²⁵. The fixes are balanced lines, isolation transformers, a single reference ground point, lifting the ground on the signal side only, or digital and optical links³²⁵³¹⁷. The rule every guide repeats: "Never remove or defeat ground pins on plugs"³¹⁷.

A small battery backup on the booth's players, mixer and laptop is common practice to ride through a brief dropout or a tripped circuit. We found no authoritative source for it.

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