SPD protection distances to household appliances connected in parallel

The household appliances in buildings have increased rapidly in the recent years. However, the surge withstanding capability of these household appliances has not been increased. Therefore, it is necessary to install surge protection device (SPD) to prevent serious damage of household electrical appliances caused by the in-rushing surges. In order to avoid the oscillation phenomenon, the effective protection distance of SPDs should be addressed before installing SPDs in the buildings. This paper discussed the influence of a group of common household electrical appliances connected in parallel on the effective protection distance of an SPD to a household appliance. The surges impinging on the household appliances connected to a distribution system are analyzed using electromagnetic transient analysis software. It is found that the SPD's protection distance increases when multiple household appliances are connected in parallel. The SPD's effective protection distance for one specific household appliance, which is determined from the case in which only this household appliance is used, is a conservative value; even if other household appliances are connected with this appliance, the SPD still provides an effective protection to this specific appliance.