Apparatus and methods thereof for error correction in split core current transformers
First Claim
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1. An apparatus comprising:
- at least one analog section comprising a current transformer having a transformer core configured to mount around an alternating current (AC) power line alternating at a fixed frequency making the AC power line a primary winding of the current transformer and further comprising a resonance capacitor connected in parallel to a secondary winding of the current transformer to resonate with the secondary winding inductance at the primary fixed frequency, the resonance capacitor'"'"'s value being selected so that maximum resonance is achieved at low currents of the primary winding and at a low non-linear range of a magnetization curve of the transformer core, the analog section for harvesting energy from the secondary winding on the transformer core, and storing it for use by components of the apparatus and periodically switching to allow sampling of a current flowing through the current transformer by a sense resistor;
a memory containing therein at least a calibration coefficient for correction of a vector generated respective of the sampling of a current flowing through the current transformer, the vector including a plurality of cycles over a plurality of periods of the fixed frequency;
a microcontroller connected to the at least one analog section to receive harvested energy and to the memory, to determine;
the vector, at least a value respective of the vector the value corrected as the at least a calibration coefficient, a time stamp;
a transmitter connected to the microcontroller enabled to periodically transmit, under the control of the microcontroller the at least a value, the time stamp, and the at least a calibration coefficient;
such that a receiver of the at least a value may use the at least a value for determination of at least an electrical parameter.
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Abstract
Apparatus and methods are provided for electrical parameter measurements at points of interest, such as circuit breakers, machines, and the like. The devices which comprise of components that may require corrections, such as the errors induced by, but not limited to, the use of a split core mounted around a current carrier, and hence calibration coefficients are provided based on test, measurements and/or calculations respective of the devices. These coefficients may be stored in a database for retrieval when calibration of measurements received from a measuring device. In one embodiment at least one of the calibration coefficients is stored on the measuring device.
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Citations
29 Claims
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1. An apparatus comprising:
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at least one analog section comprising a current transformer having a transformer core configured to mount around an alternating current (AC) power line alternating at a fixed frequency making the AC power line a primary winding of the current transformer and further comprising a resonance capacitor connected in parallel to a secondary winding of the current transformer to resonate with the secondary winding inductance at the primary fixed frequency, the resonance capacitor'"'"'s value being selected so that maximum resonance is achieved at low currents of the primary winding and at a low non-linear range of a magnetization curve of the transformer core, the analog section for harvesting energy from the secondary winding on the transformer core, and storing it for use by components of the apparatus and periodically switching to allow sampling of a current flowing through the current transformer by a sense resistor; a memory containing therein at least a calibration coefficient for correction of a vector generated respective of the sampling of a current flowing through the current transformer, the vector including a plurality of cycles over a plurality of periods of the fixed frequency; a microcontroller connected to the at least one analog section to receive harvested energy and to the memory, to determine;
the vector, at least a value respective of the vector the value corrected as the at least a calibration coefficient, a time stamp;a transmitter connected to the microcontroller enabled to periodically transmit, under the control of the microcontroller the at least a value, the time stamp, and the at least a calibration coefficient; such that a receiver of the at least a value may use the at least a value for determination of at least an electrical parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A system comprising:
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an interface to a network; a processor communicatively coupled through the interface to the network; a database communicatively coupled to the processor, the data base containing at least a calibration coefficient of a plurality of self-powered power sensors (SPPSs), each SPPS comprising at least one analog section comprising a current transformer having a transformer core configured to mount around an alternating current (AC) power line alternating at a fixed frequency making the AC power line a primary winding of the current transformer and further comprising a resonance capacitor connected in parallel to a secondary winding of the current transformer to resonate with the secondary winding inductance at the primary fixed frequency, the resonance capacitor'"'"'s value being selected so that maximum resonance is achieved at low currents of the primary winding and at a low non-linear range of a magnetization curve of the transformer core, the analog section for harvesting energy from the secondary winding on the transformer core, and storing it for use by components of the apparatus and periodically switching to allow sampling of a current flowing through the current transformer by a sense resistor; and a memory communicatively coupled to the processor containing therein instructions that when executed by the processor configure the system to;
receive from at least an SPPS communicatively coupled to the system at least a vector generated respective of the sampling of a current flowing through the current transformer, the vector including a plurality of cycles over a plurality of periods of the fixed frequency and a unique identification (UID) of the SPPS;
extract from the database the at least a calibration coefficient respective of the SPPS and the at least a vector; and
, adjust the received at least a vector according with the at least a calibration coefficient. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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23. A method comprising:
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receiving at least a unique identification (UID) from a self-powered power sensor (SPPS), the SPPS comprising at least a resonance capacitor connected in parallel to a secondary winding of a current transformer of the SPPS, the resonance capacitor to resonate with the secondary winding inductance at a primary fixed frequency of the primary winding fed from a powerline, the resonance capacitor'"'"'s value being selected so that maximum resonance is achieved at low currents of the primary winding and at a low non-linear range of a magnetization curve of the transformer core; receiving a vector generated respective of the sampling of a current flowing through the primary winding of the current transformer, the vector including a plurality of cycles over a plurality of periods of the fixed frequency; retrieving at least a calibration coefficient respective of the SPPS; and adjusting the vector using the at least a calibration coefficient. - View Dependent Claims (24, 25, 26, 27, 28, 29)
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Specification