Electrical enclosure voltage protection system

An electrical isolation apparatus to automatically interrupt main power in advance of its junction to the main electrical panel whenever the main disconnect switch is turned off. A method for retrofitting an existing electrical panel enclosure with an electrical isolation box (EIB) is also disclosed, along with a retrofit kit. The electrical isolation apparatus includes an auxiliary relay resident in the main electrical panel enclosure and actuated by said main disconnect switch. The electrical isolation apparatus also includes the EIB in a second ride-on enclosure attached to the main panel enclosure. The EIB encloses a power contactor with at least one power contactor switch (three for three-phase). The control input of the power contactor is connected through both enclosures to the auxiliary relay resident in the main enclosure for controlling the power contactor. Indicator lights, a voltage monitor, and a reset/test switch panel-mounted on the EIB enclosure are also disclosed for status display. The foregoing avoids any high voltage condition in the main power receptacle after the disconnect is actuated, creating a safer work environment.