The Application of Nanocrystalline and Amorphous Alloys in Smart Meters

Current transformer sensors, loaded by a precision resistor, are widely spread in electric energy metering devices. The core of such appliance is made from iron-based materials. So it comes in the magnetic saturation when a constant component of current is present or when current overloads occur, which affects the accuracy of energy accounting. Additionally, there is a possibility of electric energy meter readings distortion due to the impact of external magnetic field on transformer sensors. Nanocrystalline and amorphous alloys could help to neutralize these negative influences.

Iron-based amorphous alloys are characterized by high magnetic induction of saturation (Bs 1,5-1,6 T) and low losses on alternating magnetization in conventional and high frequencies.

Measurement errors of transformer-based current sensors are determined by the limited magnetic perme-ability of a magnetic core and non-zero value of the load resistance.The error of the current transformer decreases with the magnetic resistance of the magnetic circuit reduction.  I.e. the more the magnetic permeability of the material, the more the cross section of the core and the less its length and also the less its secondary load (ideal case –a short circuit  mode), the smaller the error. Magnetic permeability depends on the magnetic field intensity and  is almost constant only in the weak fields region. Since transformers operate in weak fields, it is necessary to use materials with high initial magnetic permeability. Such properties are peculiar  for modern nanocrystalline and amorphous alloys. Their advantage is the narrow hysteresis loop, which reduces the magnet-ic saturation of the core CT. Physico-chemical properties of modern  nanocrystalline and amorphous materials help to improve the accuracy of electric energy meters and minimize the possibility of their readings corruption through external magnetic fields using.