Patent ID: 8643995
Filing Date: 2014-02-04
Classification: H02M

Abstract:
1. A device for protecting an electric system against overvoltage occurrences, the electric system being adapted to be subjected to voltages, which device comprises a plurality of surge arresters and comprises a detector configured to detect overvoltage occurrences in the electric system, the surge arresters of said plurality of surge arresters being connected in series, and said plurality of surge arresters comprises a first surge arrester which is connectable to ground and a second surge arrester which is connectable to the electric system which is to be protected, the device comprises a switch connected in parallel with the first surge arrester, and the switch is adapted to be open when no overvoltage occurrence is detected and adapted to close upon overvoltage occurrence detection and short-circuit the first surge arrester, wherein the first surge arrester, has a lower knee-point voltage in relation to the other surge arresters of said plurality of surge arresters and a lower knee-point voltage in relation to the second surge arrester, where the knee-point value of the first surge arrester is a normalized voltage value of 0.8 p.u. and the knee-point value of the second surge arrester is a normalized voltage value of 1.0 p.u.