WEAK POINTS OF CURRENT SENSORS IN STATIC ENERGY METERS

Pavel Mlejnek -Petr Kašpar

   Currently the measurement of consumed energy is one of the most important measurements in residences, factories and other facilities connected to public power network. Due to growing costs of electrical energy some consumers try to tamper the energy meters in order to measure less energy. Well-known trick (which works even with electromechanical energy meter to slow down the rotating disc) is to put strong permanent magnet on energy meter close to current transformers and saturate their cores. This article deals with the problem of dc magnetic flux in the core of current transformers and shows that this attack upon energy meter can cause the opposite effect – the energy meter can measure greater consumption than in reality.

Keywords: current transformer, energy meter, dc tolerance, dc magnetic field

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