Current transformers are special transformers for the proportional transformation of high currents into direct measurable values. Their construction and physical operating principle enable an electrolytic separation of the primary circuit from the measured circuit, thereby providing a safety mechanism when switching on the measuring appliance in the event of a fault.
The products complied with VDE 0414, BS 7262 and IEC 185 standard.
Measuring current transformer is an encapsulated type which intended to supply to indicative devices, integrated meter and similar apparatus.
They are characterized by their accuracy and for saturating at moderate over current. This effect protects the measuring instruments from possible over current.
Burden is the impedance of the secondary circuit in ohms and power factor. For the measurement or protection relay operating via a current transformer, in order to operate them, the primary current has to induce the power required in the secondary current of the instrument or relay. This induced power must be equal or higher than the losses in the power line + consumption of the measurement instrument or protection relays.
The burden imposed on a current transformer consist mainly of:
• The impedance of wiring cable between current transformer and instruments/relay
• The impedance of the instrument/relay
• The sum of the above constitute the external burden required