Broadband electromagnetic sensor and manufacturing method thereof

Abstract

A broadband electromagnetic sensor comprises: an amplifier circuit having a gain of at least 26 dB through its bandwidth; and a sensing section electrically connected to the amplifier circuit and including a coil array structure of a plurality of coils, in which each of the plurality of coils has a different length from the other coils and detects a signal having a frequency within its own frequency bandwidth, the plurality of coils together can detect a signal having a frequency within the frequency bandwidth of the sensor, and wherein the frequency bandwidth of the sensor ranges from about 1 MHz to 100 MHz, such that the sensor can detect partial discharges from the high voltage device without physical contact with the high voltage device.

Description

Technical Field

[0001] The present disclosure relates to a broadband electromagnetic sensor and a manufacturing method thereof. Background Art

[0002] High-voltage power transmission and transformation equipment is an important part of the power system, and the stability of its operation is directly related to the smooth operation of the power grid. Any fault in the power grid will have a significant impact on industry and society. Insulation aging or defects in high-voltage power equipment can manifest as partial discharge, which, if allowed to develop, may have continuous physical effects and chemical reactions. Long-term partial discharge will accelerate insulation damage and potentially damage high-voltage power equipment. Therefore, in order to ensure the safe and reliable operation of high-voltage power equipment, it is necessary to perform continuous early monitoring of partial discharge so as to detect faults as early as possible and perform preventive replacement or repair of the equipment. Partial discharge is a local electrical discharge that only partially bridges the insulation between conductors and is usually the result of local electrical stress concentration in or on the surface of the insulator. Generally, partial discharge appears as pulses with a duration far less than 1 microsecond. Due to the very short pulse time, the frequency range of the discharge signal can span from direct current (DC) to several gigahertz (GHz). The harm of partial discharge to electrical insulation has a cumulative effect. It is considered to be one of the most decisive indicators of electrical insulation deterioration. In particular, partial discharge monitoring is an important part of the insulation maintenance of the covered conductors of medium-voltage overhead power lines. The insulation of the covered conductors prevents phase-to-phase short circuits when a fault occurs on them. Since the value of the abnormal leakage current is very small, standard digital relay protection cannot respond to such low currents.

[0003] Currently available methods and systems for detecting partial discharge include ultrasonic methods. However, ultrasonic methods have low sensitivity and are vulnerable to environmental noise. Chemical methods are not suitable for continuous monitoring and cannot detect the severity of partial discharge. Optical technology methods are only applicable to transparent insulators. Existing current sensors are vulnerable to electromagnetic interference. For example, Rogowski coils are commonly used to measure high-frequency currents and large currents due to their air-core skeletons. Due to many advantages such as non-magnetic saturation, light weight, simple structure, wide dynamic bandwidth, non-invasive isolation, linearity, etc., the air-core skeleton makes Rogowski coils very popular current sensors. Sensitivity and accuracy are key indicators for evaluating the performance of Rogowski coils. However, the accuracy of Rogowski coils is vulnerable to the structure of the coil and the frequency of the measured current. In addition, Rogowski coils are vulnerable to the position and shape of the primary conductor.

[0004] There is a method for detecting high-frequency current transformer (HFCT) sensors, which is widely used for partial discharge detection. In use, the HFCT sensor is clamped around the cable core rather than around the earth sheath because this can achieve a better signal-to-noise ratio. The HFCT sensor has a split core structure, which consists of an induction coil with a ferromagnetic core. The applied HFCT sensor has a bandwidth with a -3dB lower cut-off frequency at approximately 5 MHz and a -3dB upper cut-off frequency at approximately 100 MHz. This is to avoid capturing in-situ noise below 1 MHz. The HFCT sensor has the advantage of allowing installation during operation, and the directionality of the partial discharge current pulse can contribute to partial discharge localization purposes. However, the HFCT sensor needs to be clamped on the cable, is large in size, has a bulky core, and is vulnerable to large current saturation. This makes it difficult to apply in many cases where space is limited or the cable is inaccessible.

[0005] Therefore, it is desirable to provide an efficient and effective solution for partial discharge detection as a valuable tool for detecting abnormal events and abnormalities in medium-voltage overhead lines to establish a preventive maintenance plan before electrical components fail. Summary of the Invention

[0006] This application discloses a broadband electromagnetic sensor using electromagnetic coupling technology based on multimode resonator theory. In an exemplary embodiment, the sensor is capable of detecting signals having frequencies, for example, in the range from approximately 1 MHz to 100 MHz. In an exemplary embodiment of use, the sensor is configured to detect partial discharges from high-voltage power transmission and transformation equipment without the need for physical contact between the sensor and the high-voltage power transmission and transformation equipment. The low-cost, lightweight sensor is not affected by large current saturation, does not require the use of any magnets, and is capable of detecting partial discharges at a distance of at least one meter from the partial discharge source without the need to be fixed around the cable of the equipment.

[0007] According to a first aspect, there is provided a method for manufacturing a broadband electromagnetic sensor, the broadband electromagnetic sensor including an amplifier circuit connected to a sensing portion, the sensing portion including a coil array structure of a plurality of coils, wherein each coil is capable of detecting a signal having a frequency within its own frequency bandwidth, and wherein the coil array structure is capable of detecting a signal having a frequency within the frequency bandwidth of the broadband electromagnetic sensor, the method including the following steps:

[0008] (a) Represent the sensing portion as a theoretical circuit, wherein each of the plurality of coils is represented by a theoretical inductor having a theoretical inductance, and perform circuit simulation on the theoretical circuit to obtain the circuit simulation results of the theoretical circuit and obtain the theoretical inductance of each coil;

[0009] (b) Calculate the length of each coil according to the theoretical inductance of each coil using a predetermined method, and draw the integrated layout of multiple coils according to the calculated length of each coil;

[0010] (c) Create a coil model of each coil in the integrated layout using electromagnetic simulation software, and perform electromagnetic simulation on the coil model to obtain the electromagnetic simulation results of the coil model;

[0011] (d) Create a coil equivalent circuit model of each coil model, where each coil model is represented as an inductor connected in parallel with a capacitor and in series with a resistor, and perform circuit simulation on the coil equivalent circuit model to obtain the circuit simulation results of the coil equivalent circuit model, and determine the inductance, resistance, and capacitance of each coil model when the circuit simulation results of the coil equivalent circuit model best match the electromagnetic simulation results of the coil model;

[0012] (e) Use the two coil models created in step (c) to create a dual-coil model of two coils in the integrated layout, and perform electromagnetic simulation on the dual-coil model to obtain the electromagnetic simulation results of the dual-coil model;

[0013] (f) Use the two coil equivalent circuit models created in step (d) to create a dual-coil equivalent circuit model of the dual-coil model, where the dual-coil equivalent circuit model includes the mutual inductance in the dual-coil model, and perform circuit simulation on the dual-coil equivalent circuit model to obtain the circuit simulation results of the dual-coil equivalent circuit model, and determine the mutual inductance in the dual-coil model when the circuit simulation results of the dual-coil equivalent circuit model best match the electromagnetic simulation results of the dual-coil model;

[0014] (g) Repeat steps (e) and (f) for each different pair of coils in the integrated layout to determine the mutual inductance between each different pair of coils in the integrated layout;

[0015] (h) Use all the coil equivalent circuit models created in step (d) to create an integrated layout equivalent circuit model, where the integrated layout equivalent circuit model includes the mutual inductance between each different pair of coils in the integrated layout, and perform circuit simulation on the integrated layout equivalent circuit model to obtain the circuit simulation results of the integrated layout equivalent circuit model, and determine the optimized inductance of each coil model when the circuit simulation results of the integrated layout equivalent circuit model best match the circuit simulation results of the theoretical circuit;

[0016] (i) Recalculate the length of each coil according to the optimized inductance of each coil using a predetermined method, and redraw the integrated layout of multiple coils according to the recalculated length of each coil; and

[0017] (j)Manufacture a coil array structure on a printed circuit board according to the redrawn integrated layout.

[0018] The theoretical circuit in step (a) may include a ladder structure similar to a band-pass filter, where each element of the ladder structure includes one of the theoretical inductors electrically connected to a theoretical capacitor, and where each element is configured according to a preselected response type.

[0019] The preselected response type may be one of the following: Butterworth response, Chebyshev response, and elliptical response.

[0020] The method further includes: creating a circuit verification model of two coils including the confirmed mutual inductance between the two coils after step (h), and performing circuit simulation on the circuit verification model to obtain the circuit simulation results of the circuit verification model, wherein the matching of the circuit simulation results of the circuit verification model and the circuit simulation results of the two-coil equivalent circuit model confirms the mutual inductance between the two coils.

[0021] The circuit verification model of the integrated layout may include a T-type circuit.

[0022] The electromagnetic simulation results and the circuit simulation results may include the variation of input impedance and scattering parameters with frequency.

[0023] The method may further include: manufacturing an amplifier circuit on the printed circuit board and connecting the amplifier circuit to the coil array structure.

[0024] The method may further include: after step (i), creating a redrawn integrated layout model of the redrawn integrated layout using electromagnetic simulation software, performing electromagnetic simulation on the redrawn integrated layout physical model to obtain the electromagnetic simulation results of the redrawn integrated layout physical model, and comparing the electromagnetic simulation results of the redrawn integrated layout physical model with the circuit simulation results of the theoretical circuit to confirm the length of each coil recalculated.

[0025] According to a second aspect, there is provided a broadband electromagnetic sensor, the broadband electromagnetic sensor including: an amplifier circuit having a gain of at least 26 dB over its bandwidth; and a sensing portion including a coil array structure of a plurality of coils, wherein each of the plurality of coils has a different length from other coils, and each coil detects a signal having a frequency within its own frequency bandwidth, such that the plurality of coils together can detect a signal having a frequency within the frequency bandwidth of the sensor, and wherein the frequency bandwidth of the sensor ranges from about 1 MHz to 100 MHz, such that the sensor can detect partial discharge from a high-voltage device without physical contact with the high-voltage device.

[0026] The coil array structure can be arranged as an integrated layout on a printed circuit board, where the integrated layout is optimized to minimize the area required for supporting the coils on the printed circuit board.

[0027] Each coil can be represented by an equivalent circuit model that includes a capacitor connected in parallel with an inductor and an inductor connected in series with a resistor.

[0028] The sensing part can be represented by an equivalent circuit model that incorporates the mutual inductance between each different pair of coils in the coil array.

[0029] The coil array structure includes one of the following: a rectangular shape, a circular shape, a three-dimensional structure.

[0030] A broadband electromagnetic sensor can be produced by the method of the first aspect. Description of the Drawings

[0031] In order to fully understand the present invention and easily put the present invention into practice, exemplary embodiments of the present invention will now be described only by way of non-limiting examples, and this description refers to the accompanying illustrative drawings.

[0032] Figure 1 is a schematic diagram of a single coil and a corresponding impedance parameter curve graph when the single coil detects an electromagnetic wave signal.

[0033] Figure 2 is when by Figure 1 The single coil detects the input electromagnetic wave signal, and the graph of the input and output magnitudes in the frequency domain and the time domain.

[0034] Figure 3 is a schematic diagram of a dual coil system and a corresponding impedance parameter curve graph when the dual coil system detects an electromagnetic wave signal.

[0035] Figure 4 is when Figure 3 The dual coil system detects the input electromagnetic wave signal, and the graph of the input and output magnitudes in the frequency domain and the time domain.

[0036] Figure 5 is an exemplary integrated layout equivalent circuit model of an exemplary broadband electromagnetic sensor.

[0037] Figure 6 is an exemplary band-pass filter ladder structure circuit representing the radiator or broadband sensing part of a broadband electromagnetic sensor.

[0038] Figure 7 is a schematic diagram of a printed circuit board assembly of an exemplary broadband electromagnetic sensor including a sensing part connected to an amplifier circuit.

[0039] Figure 8 is a photograph of a printed circuit board assembly fabricated according to Figure 7 the schematic diagram shown.

[0040] Figure 9 is an integrated layout schematic of an exemplary four - coil system for the sensing portion of a broadband electromagnetic sensor for Figure 7 and Figure 8 .

[0041] Figure 10 is Figure 5 a graph of the input impedance of the integrated layout equivalent circuit model.

[0042] Figure 11 is an exemplary embodiment of the amplifier circuit of a broadband electromagnetic sensor.

[0043] Figure 12(a) is Figure 9 an exemplary coil model of the exemplary first coil of the four - coil system.

[0044] Figure 12(b) is the first exemplary coil equivalent circuit model of the coil model of Figure 12(a).

[0045] Figure 12(c) is a graph of the input impedance of the coil model of Figure 12(a).

[0046] Figure 12(d) is the second exemplary coil equivalent circuit model of the coil model of Figure 12(a).

[0047] Figure 12(e) is a graph of the input impedance of the coil equivalent circuit model of Figure 12(c).

[0048] Figure 13(a) is Figure 9 an exemplary coil model of the exemplary second coil of the four - coil system.

[0049] Figure 13(b) is a graph of the input impedance of the coil model of Figure 13(a).

[0050] Figure 13(c) is the exemplary coil equivalent circuit model of the coil model of Figure 13(a).

[0051] Figure 13(d) is a graph of the input impedance of the coil equivalent circuit model of Figure 13(c).

[0052] Figure 14(a) is an exemplary dual - coil model of an exemplary dual - coil system including the coil model of Figure 13(a) and the coil model of Figure 14(a).

[0053] Figure 14(b) is a graph of the input impedance of the dual - coil model of Figure 14(a).

[0054] Figure 14(c) is an exemplary dual - coil equivalent circuit model of the dual - coil model of Figure 14(a).

[0055] Figure 14(d) is a graph of the input impedance of the dual - coil equivalent circuit model of Figure 14(c).

[0056] Figure 14(e) is an exemplary T - type circuit verification model of the exemplary dual - coil system of Figure 14(a).

[0057] Figure 14(f) is a MATLAB calculation of the input impedance of the T - type circuit verification model of Figure 14(e).

[0058] Figure 15 is a photograph of a broadband electromagnetic sensor of a printed circuit board assembly including Figure 8

[0059] Figure 16 is a schematic diagram of the assembly steps of the broadband electromagnetic sensor.

[0060] Figure 17 is a schematic diagram of a set - up for testing the manufactured Figure 16 broadband electromagnetic sensor.

[0061] Figure 18 is a graph of an exemplary measurement waveform obtained using an HFCT sensor and the manufactured Figure 16 broadband electromagnetic sensor when partial discharge is detected.

[0062] Figure 19 is a photograph of an actual high - voltage device having units of Figure 16 sensors attached to a plurality of cables of the actual high - voltage device.

[0063] Figure 20 is from Figure 19 the set - up of a phase - resolved partial discharge pattern.

[0064] Figure 21 is a flowchart of an exemplary method for producing a broadband electromagnetic sensor. Detailed Description

[0065] Exemplary embodiments of a method 90 for producing a broadband electromagnetic sensor 10 and exemplary embodiments of the broadband electromagnetic sensor 10 will be described with reference to Figures 1 to 21 wherein like reference numerals are used to denote like or similar components in the drawings.

[0066] Generally, a single coil as Figure 1 shown has a narrow frequency bandwidth and a high quality factor. When a planar electromagnetic (EM) wave is in asFigure 1 When radiating at the single coil shown, in the frequency domain, if the input spectrum is broadband, the output spectrum is narrowband, and in the time domain, if the input signal is a chirp signal, the output signal is a sinusoidal signal with reduced magnitude, as Figure 2 can be seen. The simulation results verify that the single coil resonates at a narrow frequency bandwidth, as Figure 1 can be seen. When a plane EM wave radiates at the dual coil system shown in Figure 3 , in the frequency domain, if the input spectrum remains broadband, the output spectrum has two narrowbands, and in the time domain, if the input signal is also a chirp signal, the output signal has more frequency components, as Figure 4 shown. The simulation results verify that the dual coil system resonates at two narrowbands, as Figure 3 shown.

[0067] By increasing the number of coils cascaded or paralleled in the system, the system can generate multiple resonant frequencies, enabling it to receive / radiate time domain signals of multiple frequencies. Due to the frequency response non-flatness, the system can effectively receive / radiate signals with discontinuous frequencies. Thus, as Figure 5 shown in the exemplary integrated layout equivalent circuit model of Figure 7 and Figure 8 , the broadband electromagnetic sensor 10 of the present disclosure is made of several coils and several added capacitors. In an exemplary embodiment, the broadband electromagnetic sensor 10 includes an amplifier circuit 20( Figure 6 ) electrically connected to a sensing portion 30 shown in the printed circuit board assembly of Figure 9 . The amplifier circuit 20 may include associated improved circuits added to amplify the input analog signal, and the improved circuits have a gain of at least 26 dB over its bandwidth. The sensing portion 30 includes a coil array structure 37 of multiple planar or three-dimensional coils or inductors (31, 31, 33, 34, Figure 9 ), accompanied by one or more capacitors to tune its resonant frequency. Each coil 31, 32, 33, 34 is capable of detecting a signal having a frequency within its own frequency bandwidth, and the coil array structure 37 is capable of detecting a signal having a frequency within the frequency bandwidth of the broadband electromagnetic sensor 10. The required center frequency and its bandwidth of each coil 31, 31, 33, 34 are related to the order of the bandpass filter. The scattering parameters of the sensing portion 30 are shown in Figure 10 , indicating that broadband sensing characteristics are obtained.

[0068] In an exemplary method 90( Figure 21 ) for manufacturing the broadband electromagnetic sensor 10, the sensing portion 30 can be represented as a theoretical circuit 39, as Figure 11As shown. In the theoretical circuit 39, each of the multiple coils 31, 32, 33, 34 can be represented by a theoretical inductor having a self-inductance (or theoretical inductance) L'. The theoretical circuit 39 may include a ladder structure similar to a band-pass filter, where each element of the ladder structure (indicated by the dashed line) includes one of the theoretical inductors electrically connected to a theoretical capacitor having a theoretical capacitance C'. Each element is configured according to a preselected response type. For example, the response type can be Butterworth response, Chebyshev response, or elliptic response. The theoretical inductor and theoretical capacitor of each element can be in series or parallel relationship with each other according to the preselected response type, and the elements in the ladder structure can have different response types from each other.

[0069] Based on the selected frequency response type, center frequency, and bandwidth of the sensor 10, by performing a circuit simulation on the theoretical circuit 39 to obtain the circuit simulation results of the theoretical circuit 39 and obtain the theoretical inductance L' of each coil (901, Figure 21 ), the order and theoretical element values L' and C' of each element in the ladder structure theoretical circuit 39 can be determined. The circuit simulation results can include the input impedance of the theoretical circuit 39.

[0070] Based on the obtained theoretical inductance L' of each of the coils 31, 32, 33, 34, a known method (such as the method described in the publication "H. Greenhouse, 'Design of Planar Rectangular Microelectronic Inductors,' in IEEE Transactions on Parts, Hybrids, and Packaging, vol. 10, no. 2, pp. 101 - 109, June 1974") can be applied to estimate the length of each of the coils 31, 32, 33, 34 based on the self - inductance. In other words, a predetermined method can be used to calculate the length of each of the coils 31, 32, 33, 34. Other exemplary methods for calculating the coil length based on the theoretical inductance L' of the coils 31, 32, 33, 34 can be found in the following publications: "S.D. Barman, A.W. Reza, N. Kumar, Md.E. Karim, A.B. Munir, 'Wireless powering by magnetic resonant coupling: Recent trends in wireless power transfer system and its applications,' Renewable and Sustainable Energy Reviews, 2015" and "T. Imura and Y. Hori, 'Maximizing air gap and efficiency of magnetic resonant coupling for wireless power transfer using equivalent circuit and Neumann formula,' IEEE Transactions on Industrial Electronics, vol. 58, no. 10, Oct. 2011". After calculating the length of each coil, an integrated layout 38 of the plurality of coils 31, 32, 33, 34 is drawn based on the calculated length of each coil ( Figure 9 )(902, Figure 21 ). Preferably, the integrated layout 38 minimizes the area of the printed circuit board 50 of the actual coils on which the coil array structure 27 will be fabricated.

[0071] Generally, after printing coils 31, 32, 33, 34 on a printed circuit board and before connecting coils 31, 32, 33, 34 together through vias and traces, the coils 31, 32, 33, 34 represented by theoretical inductors 100, 200, 300, 400 are simulated (electromagnetic simulation and circuit simulation) to obtain the actual self - inductance of the coils and the mutual inductance between them. Then, coils 31, 32, 33, 34 together with the added capacitors are connected together as a ladder structure similar to a band - pass filter and are simulated again (electromagnetic simulation) to obtain electromagnetic simulation results, which may include the variation of input impedance and scattering parameters with frequency. At the same time, by using the obtained self - inductance and mutual inductance, an equivalent circuit model 45 of the sensing part 30 of the broadband electromagnetic sensor 10 is constructed to obtain circuit simulation results ( Figure 10 ), which may include the variation of input impedance and scattering parameters. According to the basic definitions of conductor resistance and capacitance between conductors, the resistance and self - capacitance of coils 31, 32, 33, 34 are calculated and considered in the equivalent circuit model 45 of the sensing part 30. Due to mutual inductance effects and modeling problems, the input impedance diagram of the equivalent circuit model 45 may have some differences compared with the theoretical input impedance of the theoretical circuit 39. After optimizing the equivalent circuit model 45 for the theoretical values, the lengths of coils 31, 32, 33, 34 are recalculated, and the design process is repeated to obtain a more accurate electromagnetic sensor 10. The above steps are described in more detail below.

[0072] In an exemplary method 90, coil models 40 (FIG. 12(a), FIG. 13(a)) of each of the coils 31, 32, 33, 34 in the integrated layout 38 are created using electromagnetic simulation software, and subsequently electromagnetic simulation is performed on the coil models 40 to obtain electromagnetic simulation results of the coil models 40 (FIG. 12(c)) (903, Figure 21 ). Coil equivalent circuit models 41 (FIG. 12(b), FIG. 12(d)) of each coil model 40 are also created, where each coil model 40 is represented as an inductor connected in parallel with a capacitor and in series with a resistor. Then, circuit simulation is performed on the coil equivalent circuit models 41 to obtain circuit simulation results of the coil equivalent circuit models 41 (FIG. 12(e), FIG. 13(d)). For each coil model 40, given resonance, its inductance, resistance, and capacitance are tuned until the circuit simulation results of the coil equivalent circuit models 41 (FIG. 12(e), FIG. 13(d)) best match (coincide) with the electromagnetic simulation results of the coil models 40 (FIG. 12(c), FIG. 13(b)) (904, Figure 21 ), thereby determining the inductance, resistance, and capacitance at the resonance of each coil model 40 for each of the coils 31, 32, 33, 34.

[0073] It can be understood that as long as two coils are arranged closely adjacent to each other, mutual inductance will be generated. To determine the mutual inductance between each different pair of coil models among all the coil models 40 that have been previously created, first, two coil models 40 that have been previously created are used to create a dual-coil model 42 of two coils in the integrated layout 38. In an exemplary embodiment of the dual-coil model 42 including coil 1 and coil of two coil models 40 as shown in FIG. 14(a), the specifications of the dual-coil model 42 can be as follows. All trace widths are 1 mm. All gaps between the traces are 0.4 mm. The copper trace thickness is 0.018 mm. Printed circuit board substrate: FR4 substrate, with a dielectric constant Er of 4.2 and a thickness of 0.2 mm. Coil 1 has three turns, and coil 2 has two turns. External capacitors are connected in parallel to each coil, and then they are resonated at 10 MHz. The frequency range is 0.1 MHz to 10 MHz. Electromagnetic simulation is performed on the dual-coil model 42 to obtain the electromagnetic simulation results (905, Figure 21 ).

[0074] Then, two related coil equivalent circuit models 41 that have been previously created are used to create a dual-coil equivalent circuit model 43 of the dual-coil model 42. It should be noted that the dual-coil equivalent circuit model 43 includes the mutual inductance M in the dual-coil model 42 as visible in FIG. 14(c) ab , which can be achieved by adding coupling by a circuit simulation tool. By performing circuit simulation on the dual-coil equivalent circuit model 43 to obtain the circuit simulation results of the dual-coil equivalent circuit model 43 as shown in FIG. 14(d), the mutual inductance M ab can be tuned to best match the circuit simulation results (FIG. 14(d)) of the dual-coil equivalent circuit model 43 with the electromagnetic simulation results (FIG. 14(b)) of the dual-coil model 42, thereby determining the mutual inductance M ab (906, Figure 21 ). These steps 905, 906 are repeated for every distinct pair of coils in the integrated layout 98 to determine the mutual inductance between each different pair of coils in the integrated layout 38 (907, Figure 21 ). Therefore, when the circuit simulation results (FIG. 14(d)) of the dual-coil equivalent circuit model 43 with coupling or mutual inductance are consistent with the electromagnetic simulation results (FIG. 14(b)), the mutual inductance M ab between the two coils is confirmed and solved.

[0075] Optionally, a circuit verification model 44 of the two coil models 40 can be created, which includes the confirmed mutual inductance M in the dual-coil model 42 that can be created as shown in FIG. 14(e) abThen, for example, circuit simulation can be performed on the circuit verification model 44 using MATLAB to obtain circuit simulation results of the circuit verification model 44 that may include Z e (the input impedance of the circuit verification model 44). The circuit verification model 44 can be optimized using MATLAB by tuning the mutual inductance M ab , capacitance, and resistance in the circuit verification model 44 such that the circuit simulation results (Figure 14(f)) best match the circuit simulation results of the dual-coil equivalent circuit model 43 (Figure 14(d). Then, the dual-coil equivalent circuit model 43 can be completed using the confirmed values of the mutual inductance M ab , capacitance, and resistance.

[0076] In an exemplary method 90, after the mutual inductance M ab between each different pair of coils in the integrated layout 38 has been obtained, an integrated layout equivalent circuit model 45 can be created that includes the mutual inductance M ab between all different pairs of coil models in the integrated layout 38, as Figure 5 shown. Circuit simulation is performed on the integrated layout equivalent circuit model 45 to obtain circuit simulation results of the integrated layout equivalent circuit model 45 ( Figure 10 ). By tuning one or more of the inductance, resistance, and capacitance of one or more of the coil models 40 in the integrated layout equivalent circuit model 45 such that the circuit simulation results of the integrated layout equivalent circuit model 45 ( Figure 10 ) best match the circuit simulation results (e.g., input impedance) of the theoretical circuit 39, an optimized inductance (908, Figure 21 ) can be determined for each coil model 40 of each of the coils 31, 32, 33, 34 in the integrated layout 38.

[0077] Based on its optimized inductance, the length of each of the coils 31, 32, 33, 34 is recalculated using the above-described predetermined method, and then the integrated layout 38 of the plurality of coils is redrawn according to the recalculated lengths of each of the coils 31, 32, 33, 34 (99, Figure 21 ). Optionally, method 90 may include creating a redrawn integrated layout model of the redrawn integrated layout using electromagnetic simulation software and performing electromagnetic simulation on the redrawn integrated layout physical model to obtain electromagnetic simulation results of the redrawn integrated layout physical model. Then, the electromagnetic simulation results of the redrawn integrated layout physical model can be compared with the circuit simulation results of the theoretical circuit 39 to confirm the recalculated lengths of each of the coils 31, 32, 33, 34.

[0078] To fabricate the broadband electromagnetic sensor 10, a coil array structure 38 (910, Figure 21)。The amplifier circuit 20 is also fabricated on the printed circuit board 50 and connected to the coil array structure 38 to form a printed circuit board assembly 51. Notably, in the coil array structure 38 including multiple coils 31, 32, 33, 34, each of the multiple coils 31, 32, 33, 34 has a different length from the other coils. In this way, each coil detects a signal having a frequency within its own frequency bandwidth, such that the multiple coils 31, 32, 33, 34 together can detect a signal having a frequency within the frequency bandwidth of the sensor 10.

[0079] To verify the operation of the broadband electromagnetic sensor 10 for partial discharge detection, a prototype as Figure 15 shown was fabricated, where the sensing part 20 has dimensions of 39.6 mm × 52.6 mm and is connected to the amplifier circuit 20 using a SubMiniature version A (SMA) connector. The amplifier circuit 20 was added to increase the detection distance of the antenna array and increase the distance from the power equipment. The prototype thus includes a broadband sensing part 30 and an amplifier circuit 20 part. Its structure is simple and the cost is low. The conceptual equivalent circuit model of the prototype includes a 4th-order inductor-capacitor resonant circuit, and each resonant circuit consists of inductors and capacitors connected in series or in parallel.

[0080] To protect Figure 8 the printed circuit board assembly shown, the printed circuit board assembly can be encapsulated in a plastic housing. In the fabricated experimental prototype, the encapsulation has dimensions of 12.5 mm × 48 mm × 100 mm, as Figure 16 shown, and has an opening to allow the prototype to be placed and fixed on the cable of the power equipment where partial discharge is to be detected using a releasable tie.

[0081] Using an experimental platform as Figure 17 shown, the fabricated prototype of the broadband electromagnetic sensor 10 was used to detect partial discharge. The sensor 10 was connected to an FPGA (Field Programmable Gate Array) and placed near a high-voltage switchgear. The partial discharge of the high-voltage switchgear was detected by the sensor 10, and the collected data was transmitted via the Internet to a backend system for processing and display. The computer terminal of the backend system displayed the phase-resolved partial discharge (PRPD) of the high-voltage switchgear.

[0082] The sensitivity of the prototype sensor 10 was verified by changing its position relative to the partial discharge source. In tests conducted using a calibrator as a partial discharge source with 5 pC, the prototype sensor 10 was placed near the cable of the calibrator, and the detected partial discharges were obtained and displayed on the screen of an oscilloscope. A commercial HFCT sensor was similarly placed around the cable and used to detect partial discharges from the calibrator. Compared with the commercial HFCT sensor, the oscilloscope results obtained by the prototype sensor had a similar pattern but with a larger magnitude, as Figure 18 shown. When the prototype sensor 10 was placed 1 meter away from the power equipment being detected, the prototype sensor 10 was still able to detect partial discharges, while the commercial HFCT sensor performed poorly. Table 1 below shows the results of tests conducted using the prototype sensor 10 and the commercial HFCT sensor when placed 1 meter away from voltage sources with different applied voltages.

[0083] Table 1

[0084]

[0085] As Figure 19 shown, the prototype sensor 10 was also tested on an actual high-voltage device by attaching the units of the sensor 10 to multiple cables of the device. Figure 20 The PRPD results obtained by the sensor 10 are shown in. It can be seen from the experimental tests conducted that the developed broadband electromagnetic sensor 10, which includes four planar coils and an additional capacitor produced using the above method 90, has broadband characteristics and is capable of detecting partial discharges even at a certain distance from the high-voltage device.

[0086] Although exemplary embodiments of the present invention have been described in the foregoing description, those skilled in the art should understand that many changes can be made to the details of the design, construction, and / or operation without departing from the present invention. However, it will be understood that many further changes, modifications, and substitutions can be made to various aspects of the embodiments within the spirit and scope of the appended claims. For example, although the coil array structure shown in the figures has a generally rectangular shape, the coil array structure can have other configurations, such as circular, three-dimensional, or any other arbitrary shape.

[0087] Throughout this specification and the accompanying claims, unless the context requires otherwise, the word "comprise" and variations such as "comprising" or "includes" will be understood to imply the inclusion of the stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. The citation of any prior publication (or information derived therefrom) or any known matter in this specification is not and should not be taken as an admission or acknowledgement or any form of implication that the prior publication (or information derived therefrom) or known matter forms part of the common general knowledge in the field to which this specification pertains.

Claims

1. A method for manufacturing a broadband electromagnetic sensor, the broadband electromagnetic sensor including an amplifier circuit connected to a sensing part, the sensing part including a coil array structure of a plurality of coils, where each coil can detect a signal having a frequency within its own frequency bandwidth, and where the coil array structure can detect a signal having a frequency within the frequency bandwidth of the broadband electromagnetic sensor, the method comprises the following steps: (a) Represent the sensing part as a theoretical circuit, where each of the plurality of coils is represented by a theoretical inductor having a theoretical inductance, and perform circuit simulation on the theoretical circuit to obtain the circuit simulation result of the theoretical circuit and obtain the theoretical inductance of each coil; (b) Calculate the length of each coil according to the theoretical inductance of each coil using a predetermined method, and draw the integrated layout of the plurality of coils according to the calculated length of each coil; (c) Create a coil model of each coil in the integrated layout using electromagnetic simulation software, and perform electromagnetic simulation on the coil model to obtain the electromagnetic simulation result of the coil model; (d) Create a coil equivalent circuit model of each coil model, where each coil model is represented as an inductor connected in parallel with a capacitor and connected in series with a resistor, and perform circuit simulation on the coil equivalent circuit model to obtain the circuit simulation result of the coil equivalent circuit model, and determine its inductance, resistance and capacitance for each coil model when the circuit simulation result of the coil equivalent circuit model best matches the electromagnetic simulation result of the coil model; (e) Use two coil models created in step (c) to create a two-coil model of two coils in the integrated layout, and perform electromagnetic simulation on the two-coil model to obtain the electromagnetic simulation result of the two-coil model; (f) Use two coil equivalent circuit models created in step (d) to create a two-coil equivalent circuit model of the two-coil model, where the two-coil equivalent circuit model includes the mutual inductance in the two-coil model, and perform circuit simulation on the two-coil equivalent circuit model to obtain the circuit simulation result of the two-coil equivalent circuit model, and determine the mutual inductance in the two-coil model when the circuit simulation result of the two-coil equivalent circuit model best matches the electromagnetic simulation result of the two-coil model; (g) Repeat steps (e) and (f) for each different pair of coils in the integrated layout to determine the mutual inductance between each different pair of coils in the integrated layout; (h) Create an integrated layout equivalent circuit model using all the coil equivalent circuit models created in step (d), where the integrated layout equivalent circuit model includes the mutual inductance between each different pair of coils in the integrated layout, and perform circuit simulation on the integrated layout equivalent circuit model to obtain the circuit simulation results of the integrated layout equivalent circuit model, and when the circuit simulation results of the integrated layout equivalent circuit model best match the circuit simulation results of the theoretical circuit, determine the optimized inductance for each coil model; (i) Recalculate the length of each coil according to the optimized inductance of each coil using the predetermined method, and redraw the integrated layout of the multiple coils according to the recalculated length of each coil; And (j) Manufacture the coil array structure on a printed circuit board according to the redrawn integrated layout.

2. The method according to claim 1, wherein, the theoretical circuit in step (a) includes a ladder structure of a band-pass filter, where each element of the ladder structure includes one of the theoretical inductors electrically connected to a theoretical capacitor, and where each element is configured according to a preselected response type.

3. The method according to claim 2, wherein, the preselected response type is one of the following: Butterworth response, Chebyshev response, and elliptical response.

4. The method according to any one of claims 1 to 3, further comprising: Immediately after step (h), create a circuit verification model of the two coils including the confirmed mutual inductance between the two coils, and perform circuit simulation on the circuit verification model to obtain the circuit simulation results of the circuit verification model, where the matching of the circuit simulation results of the circuit verification model with the circuit simulation results of the two-coil equivalent circuit model confirms the mutual inductance between the two coils.

5. The method according to claim 4, wherein, the circuit verification model of the integrated layout includes a T-type circuit.

6. The method according to any one of claims 1 to 5, wherein, the electromagnetic simulation results and the circuit simulation results include the variation of input impedance and scattering parameters with frequency.

7. The method according to any one of claims 1 to 6, further comprising: Manufacture the amplifier circuit on the printed circuit board and connect the amplifier circuit to the coil array structure.

8. The method according to any one of claims 1 to 7, further comprising: After step (i), use the electromagnetic simulation software to create a redrawn integrated layout model of the redrawn integrated layout, perform electromagnetic simulation on the redrawn integrated layout physical model to obtain the electromagnetic simulation results of the redrawn integrated layout physical model, and compare the electromagnetic simulation results of the redrawn integrated layout physical model with the circuit simulation results of the theoretical circuit to confirm the recalculated length of each coil.

9. A broadband electromagnetic sensor, comprising: An amplifier circuit having a gain of at least 26 dB over its bandwidth; And A sensing part, which includes a coil array structure of a plurality of coils, wherein each of the plurality of coils has a different length from other coils, and each coil detects a signal having a frequency within its own frequency bandwidth, such that the plurality of coils together can detect a signal having a frequency within the frequency bandwidth of the sensor, and wherein the frequency bandwidth of the sensor ranges from about 1 MHz to 100 MHz, such that the sensor can detect partial discharge from the high-voltage device without physically contacting the high-voltage device.

10. The broadband electromagnetic sensor according to claim 9, wherein, the coil array structure is arranged as an integrated layout on a printed circuit board, and wherein the integrated layout is optimized to minimize the area of the printed circuit board required to support the coils.

11. The broadband electromagnetic sensor according to claim 9 or claim 10, wherein, each coil can be represented by an equivalent circuit model, the equivalent circuit model including a capacitor connected in parallel with an inductor and the inductor connected in series with a resistor.

12. The broadband electromagnetic sensor according to any one of claims 9 to 11, wherein, the sensing part can be represented by an equivalent circuit model incorporating the mutual inductance between each different pair of coils incorporated in the coil array.

13. The broadband electromagnetic sensor according to any one of claims 9 to 12, wherein, the coil array structure includes one of the following: a rectangular shape, a circular shape, a three-dimensional structure.

14. The broadband electromagnetic sensor according to any one of claims 9 to 13, the broadband electromagnetic sensor being produced by the method according to any one of claims 1 to 8.

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