RESIDUAL CURRENT DEVICE WITH HIGH IMMUNITY TO NUISANCE TRIPPING

Residual current devices, though offering a high degree of protection from fire and electric shock hazards, are notoriously prone to nuisanc e tripping. Efforts have been made to counter the problem primarily by the use of simple time delays, with a moderate degree of success. Thi s paper presents two techniques that greatly reduce the vulnerability to nuisance tripping: phase detection to eliminate sensitivity to capa citive leakage and a more elaborate two-stage time delay to reduce vul nerability to transients. Results obtained with a prototype design are presented to confirm the improvement in performance.