Current measuring device based on a Rogowski coil with an additional winding

Abstract

This utility model relates to electrical measuring equipment and is designed to measure electric current. The meter comprises a split Rogowski coil with a measuring winding connected to a signal processing device with an integrator. The coil is equipped with an additional winding connected via a switching device to a controlled current source. In self-monitoring mode, a test magnetic flux is generated, and the measurement channel's conversion factor is determined based on the response of the measuring winding, and functional diagnostics are performed. In the main mode, the additional winding is set to a high-impedance state. The use of an additional winding allows the use of a low-power current source, since the required test magnetic flux is generated by the number of winding turns without the need to pass a large current through the primary circuit. The technical result is a reduction in measurement error.

Description

[0001] This utility model relates to electrical measuring equipment and is intended for measuring electric current in AC circuits, primarily in relay protection and automation systems, as well as for monitoring and diagnosing electrical equipment. The utility model can be used at power facilities, including digital substations, where increased reliability of the measuring channel and the ability to monitor its operational status are required.

[0002] A technical solution is known that involves calibrating a Rogowski-type current transducer and its measuring circuit by applying a test signal and analyzing the response [US Patent No. 9507006]. A disadvantage of this approach is that the calibration signal is applied through the coil's measuring circuit, which complicates the separate organization of measurement and test modes and reduces versatility when replacing the coil, since the accuracy of sensitivity calculations depends on the specific coil design and its connection method.

[0003] A solution is also known that allows for real-time calibration by injecting a calibration current into a conductor geometrically corresponding to the primary conductor and located parallel to it, wherein the calibration current induces a calibration component of the voltage in the Rogowski coil, and signal processing performs comparison and correction [US Patent No. 9684017]. The disadvantage of this solution is the need to implement an additional calibration current conductor near the primary conductor (geometric reference, installation, layout restrictions), which complicates implementation on existing equipment and makes the system less versatile when replacing sensors, and may also require an additional high-power current source to ensure a sufficient level of the verification signal.

[0004] The closest in technical essence is the standard DC meter [RU patent No. 2155966, published 10.09.2000], containing a Rogowski coil and an integrating operational amplifier and equipped with a compensating winding connected through a recording device to a source of adjustable current, while an increase in accuracy is achieved by a compensation measurement method.

[0005] A drawback of the measuring device is that the additional (compensating) winding is used to compensate for the measured signal and does not provide the generation of a controlled test magnetic flux, which would allow the measurement channel's conversion coefficient to be determined from the measurement winding's response without interrupting or switching the primary circuit. Furthermore, the prototype does not provide for disconnecting the additional winding and switching it to a high-impedance state in the primary measurement mode. Consequently, the additional circuit may introduce parasitic interference into the measurement channel, leading to increased measurement error and reduced measurement reliability.

[0006] The technical problem of the utility model is the creation of a current meter based on a Rogowski coil, which ensures a reduction in measurement error by eliminating the influence of an additional winding in the main mode.

[0007] The technical result is achieved in that the current meter comprises a Rogowski coil with a measuring winding and a signal processing device including an integrator, wherein the Rogowski coil is provided with an additional winding coaxially located relative to the measuring winding. The additional winding is connected to a controlled current source via a switching device and is configured to generate a test magnetic flux. The signal processing device is connected to the measuring winding, the controlled current source, and the switching device and is configured to determine the conversion factor based on the response of the measuring winding when the test magnetic flux is generated by the additional winding, and is also configured to control the switching device and the controlled current source. The switching device is configured to transfer the additional winding to a high-resistance state in the main measurement mode.The signal processing device is configured to control the mode of determining the conversion coefficient of the measuring device.

[0008] The figure shows a current measuring device.

[0009] The device comprises a Rogowski coil 1 mounted on a conductor 2 with a measured current I(t). A measuring winding 3 is placed on the coil 1, the terminals 4 of which are connected to a signal processing device 5, implemented with an integrator and generating an output signal at the output 6. An additional winding 7 is placed on the same coil 1, connected by terminals 8 through a switching device 9 to a controlled current source 10. The coil connector assembly is designated 11. The signal processing device 5 is configured to control the switching device 9 and the current source 10 in the self-monitoring mode.

[0010] The device operates as follows. In the basic mode, when current flows through conductor 2, a voltage U(t) is generated in measuring winding 3, proportional to the derivative of the measured current. Signal processing unit 5 performs integration and generates a current signal at output 6. In this mode, switching device 9 disconnects auxiliary winding 7 and switches it to a high-impedance state, eliminating the influence of the auxiliary circuit on the measurement.

[0011] In the self-test mode, the signal processing device 5 connects the additional winding 7 via the switching device 9 and sets the test current I to the source 10 теcт, which generates a test magnetic flux. Based on the response of measuring winding 3, signal processing device 5 determines the measurement channel conversion factor and, if necessary, adjusts the measurement scaling. Based on the comparison of the test response with the expected value, a signal indicating the proper functioning of the measuring channel or a warning signal indicating a decrease in reliability is generated. After the test is completed, additional winding 7 is disconnected and placed in a high-impedance state.

[0012] This mode enables interchangeability of coil 1 and signal processing device 5 by automatically determining the conversion factor when replacing the coil, as well as functional monitoring of the measuring channel based on the test response. In the main mode, the influence of the additional circuit is eliminated by setting the additional winding 7 to a high-impedance state. Furthermore, the use of an additional winding allows the use of a low-power current source, since the required test magnetic flux is generated by the number of winding turns and does not require a large current to flow through the primary circuit.

Claims

1. A current meter comprising a Rogowski coil with a measuring winding and a signal processing device including an integrator, characterized in that the Rogowski coil is provided with an additional winding coaxially located relative to the measuring winding, wherein the additional winding is connected to a controlled current source through a switching device and is configured to form a test magnetic flux, and the signal processing device is connected to the measuring winding, the controlled current source and the switching device and is configured to determine the conversion factor of the meter based on the response of the measuring winding when forming the said test magnetic flux.

2. A current meter according to paragraph 1, characterized in that the switching device is designed with the possibility of switching the additional winding to a high-resistance state in the main measurement mode.

3. A current meter according to paragraph 1, characterized in that the signal processing device is designed with the ability to control the mode for determining the conversion coefficient of the meter.

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