Effective protection distance from cascade coordinated Surge Protective Devices to equipment in low-voltage AC power circuits

Protection of the equipment in low voltage AC power circuits against surges is based on wide application of Surge Protective Devices (SPDs). Cascade application of SPDs located at the service entrance of a building and near sensitive equipment is intended to ensure optimal energy distribution among installed SPDs, as well as proper equipment protection against surges. In the paper, scenarios of surges that are impinging at the service entrance of the building of interest and application of two-stage cascade protection have been analyzed. The influence of different cables lengths: arrester - suppressor (A-S) and suppressor - load (S-L), as well as influence of type and parameters of load on SPDs protection characteristics have been analyzed and discussed. Simulation programs ATP/EMTP and MATLAB are being used for analysis of several load types, namely resistive, inductive, capacitive, resistive - inductive and resistive -capacitive load, with the parameters of real devices which can be found in low-voltage AC power circuits. Performed analysis should to point on characteristics of loads and connecting cables which provide regular protection.