This guide covers how to install a surge protector correctly for every common scenario: single-phase and three-phase Type 2 AC SPDs, Type 1 SPDs at the service entrance, and DC SPDs for solar Photovoltaic (PV) systems — with wiring diagrams, step-by-step procedures, and. This guide covers how to install a surge protector correctly for every common scenario: single-phase and three-phase Type 2 AC SPDs, Type 1 SPDs at the service entrance, and DC SPDs for solar Photovoltaic (PV) systems — with wiring diagrams, step-by-step procedures, and. Essentially, a single-phase surge protector, or SPD (Surge Protective Device), is an electrical device that protects equipment from damage caused by overvoltage conditions, commonly known as transients or surges. In contrast to the steady voltage typically supplied to devices, a transient voltage. A Single Phase Surge Protector acts as a critical line of defense within electrical distribution boards, designed to divert transient overvoltages away from sensitive loads. It involves a single alternating current (AC) voltage waveform delivered through two wires: a live (hot) wire and a neutral wire. The connecting wires do not carry supply current.