On critical distance between an spd and protected appliance with respect to their voltage coordination

The paper deals with the assessment of the critical length between SPD and the equipment to be protected with the aim of proper coordination of the SPD protection level and the impulse withstand voltage of the equipment. Main concern has been paid to influence of different steepness of the front of lightning current and the SPD earthing conditions. In order to assess the relation between considered distance and voltage increase on the terminals of the device to be protected the P-Spice simulation has been applied.