This document provides general guidelines for the preparation of a functional specification for solid state electronic devices used mainly for compensation of voltage fluctuation. The guide covers devices rated to medium voltage (1 kV-35 kV). This device contains in general :an inverter, rectifier or dc to dc converter, energy storage device, injection transformer connected in series with the load and normally open by-pass switch. In order to interface these devices with the load additional equipment should be provided including current and potential transformer bypass and isolation breakers and three -phase low voltage service for auxiliary power.