Summary

Conventional current measurement, power and electrical energy is performed using a 1 or 5 amp secondary current (CT). The current is transferred to the measuring or control device, where it is converted by a secondary set of additional currents to levels of milli-amperes, in order to adjust to the voltage and current levels corresponding to electronic systems. ).

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Disadvantages of the method are:

• Dual conversion increases inaccuracy

• A large physical size is required, especially when the distance between the two currents and the device is large

• Danger of electric shock and the obligation to use mechanical short clamps

• Lack of linearity throughout the domain

• Possibility of resonance between the two transformers limits their response

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The article will present an engineering solution based on HACS (High Accuracy Current Sensors) type current sensors that include two currents with a nominal secondary current of 20 mA and an internal control and protection circuit. Using HACS with a measuring or control device adapted to this sensor saves the use of two internal currents (CTin), reduces the size of the controller and gives many advantages:

• Significantly higher accuracy (Class 0.1)

• Physically small size, especially when used over long distances

• Use of low cross-section conductors

• The secondary can be left without short and there is no danger of the secondary burning due to a disconnect in the circuit

• Extremely high linearity, ranging from 0.5% to several times the rated current

• One transducer prevents resonance and allows an excellent response to changes

• Compliance with Class 0.5S precision standards with split core allows comfort in use without compromising on performance

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The article will present the limitations of existing methods, the design principles of the engineering solution and comparative tests performed in an ISO 17025 certified laboratory