AC Current Sensor for Measuring Electric AC Current in a Conductor and an Indicator System Comprising Such a Sensor
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Abstract
The invention concerns a current sensor (22; 24; 26) for substantially in real time measuring electric current in a conductor. It is suitable for application in an indicator system (1) such as a short circuit indicator system for measuring instantaneous i.e. live current value, power, reactive power, phase angle, polarity, short circuits, in single or averaged values. It comprises current responsive means comprising a current transformer (2210), adapted for mounting adjacent to said electric conductor; and sensor circuitry (2220) comprising means for emitting a non-electrical wave signal as an output; said sensor circuitry (2220) comprises current level converter circuitry (2222) comprising a current-to-frequency converter adapted to provide said non-electrical wave signal as a current level indication pulse signal (CS1) having a pulse frequency (Pfcs) which is proportional to said real time electric conductor current, when the latter is within a predetermined current interval (I1-I2). Thus, a low cost sensor is provided. The invention further relates to an indicator system (1) for an electric conductor. It comprises at least one of the above mentioned current sensors (22; 24; 26); a communication link (32; 34; 36) for relaying at least said non-electrical wave signal from said current sensor; voltage measurement means (40; 2240) for performing a voltage measurement over said electric conductor; a detection unit (5) operable for sensing at least the frequency of at least a current pulse signal and translating it to a current corresponding to the frequency of said current pulse signal; current threshold means operable for determining whether the current corresponding to the frequency of said current pulse signal (CS) is above a predetermined current threshold (Imax); and voltage threshold means operable for determining whether the voltage measured by said voltage measurement means (40; 2240) is below a predetermined voltage threshold (Vmin) after a predetermined time period (ti) after said current threshold means has made a positive determination; and current state display means (532; 534; 536) operable for indicating currents states that has occurred on said electric conductor, e.g. when said voltage threshold means has made a positive determination. Thus, a rapid and reliable current state indicator system is provided, which may be adapted for use for electric conductors in both LV, MV and HV power lines.
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Citations
62 Claims
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1-47. -47. (canceled)
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48. An AC current sensor (22;
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24;
26) for performing a substantially real time measurement of electric AC current magnitude in a conductor and for generating a non-electrical wave signal as an output, said non-electrical wave signal comprising a series of pulses having a frequency, which is proportional to the magnitude of current measured, said current sensor comprising;a current responsive means comprising an inductive wire-wound current transformer (2210), adapted for mounting adjacent to said electric conductor, said current responsive means providing electrical power as a driving current for said current sensor; a sensor circuitry (2220) comprising current level indication circuitry (2222) comprising a current-to-frequency converter adapted to provide said non-electrical wave signal as a substantially real time current level indication pulse signal (CS1) having a pulse frequency (PfCS) which is proportional to the magnitude of said conductor current when it is within a predetermined current interval (I1-I2); and said sensor circuitry (2220) further comprising a means (2230) for emitting said non-electrical wave signal as an output, said circuitry (2220) further being adapted for providing at least one further non-electrical wave indication signal, e.g. a sensor availability indication signal (AS) and/or a voltage lost signal (VLS) and/or a current phase angle indication signal (PAS) and current polarity indication signal (POS) and/or power flow direction signal (BS). - View Dependent Claims (49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62)
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24;
Specification