Service Entrance Equipment

Service entrance equipment is the electrical connection point of the utility (power company) to a facility.

Why do you care?

Because in order to use test equipment to perform measurements on service entrance equipment, it must have a Category IV rating. The assumption is that service entrance equipment is more subject to high voltage transients that could cause arc-flash hazards--like lightning, for instance. Test equipment must be designed to safely withstand such transients, without personnel injury. That means that a Category IV meter will not blow up in your face and injure you if lightning strikes the power grid.

That is, if you are wearing Personal Protective Equipment (PPE) per the NFPA 70E standard for Electrical Safety in the Workplace.

For a full explanation of the different category ratings of test equipment, see:

Electrical Measurement Safety Program.

The free safety CD available from that site is highly recommended for all entertainment electricians. Fluke does not even charge for shipping it to you, so get it!