I am a High Voltage Journeyman Lineman with over 30 years in the industry. I have held a multitude of titles, including High Voltage Power Lineman Instructor, and have worked for various contractors. A high voltage power line should have circuit reclosures. When objects such a tree limbs etc make contact with the line, the circuit will fault. A reclosure allows the circuit to shut off and on three times in 3-5 seconds in an attempt to clear the fault. When the fault cannot be cleared, the circuit is shut down. The reclosure should have been taken out of service prior to trimming the tree. Normally when qualified line workers are on the line, safety measures demand these reclosures be taken out of service to prevent the circuit from turning back on or reenergizing in the event a phase-to-phase or phase-to-ground contact is made. More often than not, tree companies work around energized lines. Some utility companies will have an additional standby lineman on site to watch the workmen as a secondary safety measure. There is also the option to de-energize and ground the circuit. However, depending on the work location and number of customers, de-energizing is not always the utilities first choice.