Non-contact voltage sensor device

Abstract

This non-contact voltage sensor device comprises: a probe electrode (10) that observes an AC voltage on a power line (2) having a conductor (2a) to which power is supplied from an AC power supply (1) and an insulator 2b covering the conductor (2a), the probe electrode (10) being in a state of electrical non-contact with the conductor (2a) in the power line (2); a dielectric relaxation compensation circuit (31) which has an input end electrically connected to the probe electrode (10) and which simulates the complex impedance from the conductor (2a) in the power line (2) to said input end; and a frequency compensation circuit (32) which has an input terminal (32a) electrically connected to an output end of the dielectric relaxation compensation circuit (31) and which compensates for the frequency characteristics of the amplitude and phase of a waveform in the AC voltage from the dielectric relaxation compensation circuit (31).

Description

Non-contact voltage sensor device

[0001] This disclosure relates to a non-contact voltage sensor device.

[0002] When measuring the voltage of power lines, non-contact voltage sensor devices are needed to avoid and prevent serious accidents such as short circuits and electric shocks. As a non-contact voltage sensor device, a technique is known in which the AC voltage applied to the core wire of a power line is observed through a coupling capacitance of a small capacitance of a few pF generated between the core wire of the power line and the probe electrode, without the probe electrode coming into contact with the core wire of the power line. Patent Document 1 proposes a non-contact voltage sensor device that suppresses the phase shift of the AC voltage applied to the core wire of the power line being observed, and accurately observes the AC voltage and phase applied to the core wire of the power line.

[0003] The non-contact voltage sensor device described in Patent Document 1 includes a probe electrode placed on a coating covering the core wire of a power line, an impedance circuit whose input terminal is connected to the probe electrode and which simulates the complex impedance from the core wire to the input terminal, and an operational amplifier whose positive input terminal is connected to ground, negative input terminal is connected to the input terminal of the impedance circuit, and output terminal is connected to the output terminal of the impedance circuit, and outputs an AC voltage to the output terminal that is in opposite phase to the AC voltage applied to the core wire.

[0004] WO2021 / 090478 publication

[0005] There are power distribution (power supply) systems that supply power by applying a voltage with a frequency of 0.5 kHz or higher to the core wire of a power line. In such power supply systems, polymer materials such as polyvinyl chloride (PVC), which are dielectric materials with generally high electrical insulating properties, are widely used as coatings for power lines.

[0006] Dielectric materials made of polymers exhibit dielectric polarization, where electric dipoles are induced in response to an externally applied electric field, causing polar molecules to orient in accordance with the applied electric field. However, if the externally applied electric field is, for example, an applied voltage with a frequency of 0.5 kHz or higher, a delay occurs in the orientation response to changes in the applied electric field, and heat generation at the molecular level becomes a factor in dielectric loss.

[0007] In response to this delay in orientation response, dielectric relaxation occurs, which is a phenomenon in which the dielectric constant exhibits frequency characteristics. Dielectric relaxation is a phenomenon in which the dielectric constant decreases, electrical conductivity increases, and dielectric loss increases as the frequency of the applied AC increases.

[0008] The inventors have found that in a non-contact voltage sensor device, in a power supply system where a voltage with a frequency of 0.5 kHz or higher is applied to the core wire of a power line, dielectric relaxation occurs in the coating of the power line, causing errors due to the frequency characteristics of the coupling capacitance between the core wire of the power line and the probe electrode. This results in a deterioration of the observation accuracy with respect to the amplitude and phase of the observed AC voltage.

[0009] This disclosure has been made in view of the above-mentioned points, and aims to provide a non-contact voltage sensor device that can suppress errors included in the waveform of the AC voltage observed in a non-contact state via a probe electrode, even if dielectric relaxation occurs in the coating on the power line.

[0010] The non-contact voltage sensor device according to this disclosure comprises: a probe electrode that observes an AC voltage in a power line having a conductor supplied with power from an AC power source and an insulator covering the conductor in an electrically non-contact state with respect to the conductor in the power line; a dielectric relaxation compensation circuit whose input terminal is electrically connected to the probe electrode and which simulates the complex impedance from the conductor in the power line to the input terminal; and a frequency compensation circuit whose input terminal is electrically connected to the output terminal of the dielectric relaxation compensation circuit and which compensates for the frequency characteristics of the amplitude and phase of the waveform of the AC voltage from the dielectric relaxation compensation circuit.

[0011] According to this disclosure, a dielectric relaxation compensation circuit is provided that is electrically connected between the probe electrode and the frequency compensation circuit, with its input terminal electrically connected to the probe electrode, and which simulates the complex impedance of the observation system. Therefore, even if dielectric relaxation occurs in the coating of the power line, the deterioration of observation accuracy can be reduced.

[0012] This is a block diagram of a non-contact voltage sensor device according to Embodiment 1. This is a circuit diagram showing the dielectric relaxation compensation circuit in the non-contact voltage sensor device according to Embodiment 1. This is a diagram showing the frequency characteristics of the non-contact voltage sensor device. This is a block diagram of a non-contact voltage sensor device as a comparative example. This is a block diagram of a non-contact voltage sensor device according to Embodiment 2. This is a flowchart showing the gain setting process of the dielectric relaxation compensation circuit in the non-contact voltage sensor device according to Embodiment 2.

[0013] Embodiment 1. A non-contact voltage sensor device 100 according to Embodiment 1 will be described with reference to Figures 1 and 2. The non-contact voltage sensor device 100 according to Embodiment 1 is a non-contact voltage sensor device that measures (observes) the AC voltage Vin supplied (applied) to the conductor 2a of the power line 2 without making contact with the conductor 2a of the power line 2, with respect to a pair of two-wire cables consisting of a power line 2, which is a cable supplied with power from an AC power source 1, and a reference line 3, which is a cable with a reference potential, for example, ground potential. Vin represents the AC voltage value, that is, the amplitude of the AC voltage.

[0014] One terminal of the AC power supply 1 is connected to the conductor 2a of the power line 2, and the AC power supply 1 supplies power of AC voltage Vin to the conductor 2a of the power line 2. The other terminal of the AC power supply 1 is connected to a reference potential point (reference potential node), for example, the ground potential point, and is connected to the conductor 3a of the reference line 3. The AC voltage Vin is the voltage generated in the conductor 2a of the power line 2 when power is supplied from the AC power supply 1 to the conductor 2a of the power line 2, and is, for example, an AC voltage of 100V or 200V with a frequency of 0.5kHz or higher.

[0015] The power line 2 has a conductor (cable core wire) 2a to which power is supplied from one terminal of the AC power source 1, and an insulator 2b covering the conductor 2a. The reference line 3 is connected to the other terminal of the AC power source 1 and has a conductor (cable core wire) 3a to which the reference potential is set, and an insulator 3b covering the conductor 3a. The power line 2 and the reference line 3 constitute a pair of two-wire cables.

[0016] Insulators 2b and 3b are dielectric materials, such as polyvinyl chloride (PVC). Because this type of dielectric has a broad bandcap, a delay occurs in the orientation response to electric field changes at high frequencies, for example, frequencies above 0.5 kHz. This delay in the orientation response leads to dielectric relaxation, a phenomenon in which frequency characteristics appear in the dielectric constant. This dielectric relaxation in the dielectric depends on conditions such as the manufacturing process of the dielectric (degree of polymerization of the polymer), the components of the additives, or the amount of additives, and is affected by the relaxation time, applied frequency, and amount of degradation.

[0017] The non-contact voltage sensor device 100 receives power from an AC power source 1 and applies it to a conductor 2a of a power line 2. The non-contact voltage sensor device 100 observes (measures) the waveform of the voltage value Vin (voltage amplitude) in the conductor 2a. The non-contact voltage sensor device 100 includes a probe electrode 10, a probe cable 20, and a sensor circuit 30.

[0018] The non-contact voltage sensor device 100 measures the voltage value (voltage amplitude) in the conductor 2a by utilizing the minute coupling capacitance C0 generated between the probe electrode 11 and the conductor 2a of the power line 2. The probe electrode 11 is positioned in contact with or close to the surface of the insulator 2b of the power line 2 so as to surround the insulator 2b of the power line 2, and is a probe that observes the AC voltage Vin without directly connecting the electrode to the conductor 2a of the power line 2, that is, in an electrically non-contact state with the conductor 2a of the power line 2.

[0019] When the probe electrode 10 is positioned close to the conductor 2a of the power line 2, a coupling capacitance C0 is generated between the probe electrode 10 and the conductor 2a of the power line 2. The probe electrode 10 is, for example, a rectangular plane with a length and width of 1 cm each, and has a curved surface that conforms to the surface of the insulator 2b of the power line 2. When a probe electrode 10 with a length and width of 1 cm is used, the coupling capacitance C0 generated between the probe electrode 10 and the conductor 2a of the power line 2 is a minute capacitance of about a few pF.

[0020] Furthermore, an insulating resistance, which is the DC resistance of the insulator 2b, exists between the probe electrode 10 and the conductor 2a of the power line 2. The coupling capacitance C0 and the insulating resistance are connected in parallel between the probe electrode 10 and the conductor 2a of the power line 2.

[0021] The probe cable 20 electrically connects the probe electrode 10 and the input terminal 30a of the sensor circuit 30. The probe cable 20 has a conductor (cable core wire) at one end electrically connected to the probe electrode 10 and the other end connected to the input terminal of the sensor circuit 30, and an insulator covering the conductor.

[0022] The complex impedance Zobs from the conductor 2a of the power line 2 to the input terminal 30a of the sensor circuit 30 is hereinafter referred to as the complex impedance Zobs of the observation system. The complex impedance Zobs of the observation system is the combined complex impedance of the complex impedance generated between the probe electrode 10 and the conductor 2a of the power line 2 and the complex impedance present in the conductor of the probe cable 20.

[0023] The complex impedance generated between the probe electrode 10 and the conductor 2a of the power line 2 is the complex impedance resulting from the parallel combination of the coupling capacitance C0 and insulation resistance present between the probe electrode 10 and the conductor 2a of the power line 2. The complex impedance present in the conductor of the probe cable 20 is the complex impedance resulting from the parallel combination of the capacitance and insulation resistance present in the conductor of the probe cable 20.

[0024] The sensor circuit 30 converts the voltage waveform detected by the probe electrode 10 into digitized voltage data. The input terminal 30a of the sensor circuit 30 is electrically connected to the probe electrode 10 via the conductor of the probe cable 20. The digitized voltage data of the voltage waveform detected by the probe electrode 10 is output to the output terminal 30b of the sensor circuit 30.

[0025] The sensor circuit 30 includes a dielectric relaxation compensation circuit 31, a frequency compensation circuit 32, and an analog-to-digital (AD) converter 33. The input terminal of the dielectric relaxation compensation circuit 31 is connected to the input terminal 30a of the sensor circuit 30 and is electrically connected to the probe electrode 10 via the conductor of the probe cable 20. The output terminal of the dielectric relaxation compensation circuit 31 is electrically connected to the input terminal 32a of the frequency compensation circuit 32.

[0026] The dielectric relaxation compensation circuit 31 is a circuit that simulates the complex impedance Zobs of the observation system. The dielectric relaxation compensation circuit 31 is a circuit composed of circuit elements that model the complex impedance Zobs of the observation system. The dielectric relaxation compensation circuit 31 is proportional to the complex impedance Z of the observation system. Ｇ This is a circuit with a value of .

[0027] The dielectric relaxation compensation circuit 31 is composed of circuit elements that do not include the dielectric relaxation effect, that is, the dielectric relaxation effect is not included with respect to the complex impedance Zobs of the observation system where dielectric relaxation occurs, and compensates for the dielectric relaxation in the complex impedance Zobs of the observation system. By forming a composite impedance with the complex impedance Zobs of the observation system, the dielectric relaxation compensation circuit 31 reduces the deterioration of observation accuracy due to dielectric relaxation occurring in the insulator 2b of the power line 2.

[0028] The overall gain of the sensor circuit 30 is calculated by the complex impedance Zobs of the observation system and the complex impedance Z of the dielectric relaxation compensation circuit 31. Ｇ The gain Ga of the AC voltage observed by the sensor circuit 30 is set by the voltage division, and the dielectric relaxation compensation circuit 31 also functions as a gain control circuit that sets (controls) the gain Ga of the entire sensor circuit 30. That is, the gain Ga (real value) of the AC voltage observed by the sensor circuit 30 is expressed by the following equation (2).

[0029] Vout = -Ga × Vin ···(1) Ga = Zint / (Zobs + Z Ｇ ) ···(2) In the above formula (1), Vout is the amplitude of the AC voltage observed by the sensor circuit 30 (AC voltage value: output voltage value), and Vin is the amplitude of the AC voltage applied to the conductor 2a of the power line 2 (AC voltage value). In the above formula (2), Zobs is the value of the complex impedance of the observation system, Z Ｇ is the value of the complex impedance of the dielectric relaxation compensation circuit 31, and Zint is the value of the complex impedance of the impedance circuit 322 in the frequency compensation circuit 32 described later.

[0030] The complex impedance Z Ｇ of the dielectric relaxation compensation circuit 31 and the complex impedance Zint of the impedance circuit 322 are in a proportional relationship with respect to the complex impedance Zobs of the observation system. Then, the AC voltage Vout observed by the sensor circuit 30 has a phase difference of 0 (zero) in waveform with respect to the AC voltage Vin applied to the conductor 2a of the power line 2.

[0031] As understood from the above formula (2), the gain Ga is inversely proportional to the combined complex impedance (Zobs + Z Ｇ ) of the complex impedance Zobs of the observation system and the complex impedance Z Ｇ of the dielectric relaxation compensation circuit 31. Therefore, by making the complex impedance Z Ｇ exist, the contribution degree of the complex impedance Zobs of the observation system including the effect of dielectric relaxation to the gain Ga can be reduced. By setting the complex impedance Z Ｇ of the dielectric relaxation compensation circuit 31 to a large value with respect to the complex impedance Zobs of the observation system, the influence of the complex impedance Zobs of the observation system can be reduced, and as a result, the deterioration of the observation accuracy due to dielectric relaxation can be reduced.

[0032] The complex impedance Z ＧIncreasing it to a large value means reducing the gain Ga. By providing the dielectric relaxation compensation circuit 31 so as to reduce the gain Ga, the observation (measurement) accuracy with respect to the AC voltage Vin in the AC power applied to the conductor 2a of the power line 2 is improved.

[0033] The dielectric relaxation compensation circuit 31 is a circuit that simulates the complex impedance Zobs of the observation system. As shown in FIG. 2, in particular, it is composed of a parallel circuit of a capacitive element (capacitor) 31a (first) and a resistive element 31b (first) that simulate the parallel combination of the coupling capacitance C0 and the insulation resistance. The capacitive element (capacitor) 31a has excellent dielectric properties and does not include the effect of dielectric relaxation.

[0034] One node of the capacitive element 31a is connected to the input terminal 30a of the sensor circuit 30 and is electrically connected to the probe electrode 10 through the conductor of the probe cable 20. The other node of the capacitive element 31a is electrically connected to the input terminal 32a of the frequency compensation circuit 32.

[0035] In the frequency band to be observed in the AC voltage Vin, if the resistance value of the insulation resistance in the insulator 2b of the power line 2 is sufficiently high compared to the reactance of the capacitive element 31a of the dielectric relaxation compensation circuit 31, the resistive element 31b of the dielectric relaxation compensation circuit 31 may be omitted. Also, the capacitive element 31a may be a variable capacitor, and the resistive element 31b may be a variable resistor.

[0036] The input terminal 32a of the frequency compensation circuit 32 is electrically connected to the output terminal of the dielectric relaxation compensation circuit 31. The output terminal 32b of the frequency compensation circuit 32 is electrically connected to the input terminal of the AD converter 33. The frequency compensation circuit 32 compensates for the frequency characteristics of the amplitude and phase of the waveform in the AC voltage from the dielectric relaxation compensation circuit 31.

[0037] The frequency compensation circuit 32 includes an operational amplifier (amplifier) ​​321 and an impedance circuit (negative feedback circuit) 322. The inverting input terminal - of the operational amplifier 321 is electrically connected to input terminal 32a and electrically connected to the output terminal of the dielectric relaxation compensation circuit 31. The non-inverting input terminal + of the operational amplifier 321 is connected to a reference potential point (reference potential node). The output terminal of the operational amplifier 321 is electrically connected to output terminal 32b.

[0038] The input terminal of the impedance circuit 322 is electrically connected to the inverting input terminal of the operational amplifier 321. The input terminal of the impedance circuit 322 is electrically connected to input terminal 32a and electrically connected to the probe electrode 10 via the dielectric relaxation compensation circuit 31 and the conductor of the probe cable 20. The output terminal of the impedance circuit 322 is electrically connected to the output terminal of the operational amplifier 321.

[0039] The impedance circuit 322 is composed of a parallel circuit of a (second) capacitive element (capacitor) 322a and a (second) resistive element 322b, which simulate the complex impedance Zobs of the observation system. The impedance circuit 322 is composed of the complex impedance Zint of the capacitance value C1 of the capacitive element (capacitor) 322a and the resistance value R1 of the resistive element 322b. In other words, the complex impedance Zint simulates the complex impedance Zobs of the observation system.

[0040] The capacitive element 322a simulates the coupling capacitance C0, and the capacitance value C1 of the capacitive element 322a is equivalent to the capacitance value C0 of the coupling capacitance C0. As the capacitive element 322a, for example, a capacitor having a capacitance value C1 that is equivalent to the capacitance value C0 of the coupling capacitance measured in advance is selected.

[0041] The resistive element 322b simulates the insulation resistance of the insulator 2b of the power line 2, and the resistance value R1 of the resistive element 322b is equivalent to the resistance value of the insulation resistance of the insulator 2b of the power line 2. As the resistive element 322b, for example, a resistor is selected that has a resistance value R1 equivalent to the resistance value of the insulation resistance estimated in advance based on the insulating material of the insulator 2b of the power line 2 and the size of the probe electrode 10.

[0042] The input terminal 32a of the frequency compensation circuit 32 is virtually short-circuited by the operational amplifier 321. The operational amplifier 321 outputs an AC voltage to the output terminal that cancels out the AC voltage detected by the probe electrode 10, so that the non-inverting input terminal + and the inverting input terminal - have the same voltage.

[0043] In other words, the operational amplifier 321 operates so that the waveform of the AC voltage Vout appearing at its output terminal follows the waveform of the AC voltage Vin being observed in a phase-inverted (out-of-phase) state. As a result, the output terminal 32b of the frequency compensation circuit 32 outputs the waveform of the AC voltage Vout that follows the waveform of the AC voltage Vin being observed in a phase-inverted (out-of-phase) state.

[0044] The input terminal of the AD converter 33 is electrically connected to the output terminal 32b of the frequency compensation circuit 32. The AD converter 33 converts the AC voltage Vout, which is an analog signal output from the output terminal of the operational amplifier 321, into a digital AC voltage Vout. The AC voltage Vout, which is a digital signal output from the output terminal 30b of the sensor circuit 30 connected to the output terminal of the AD converter 33, is in opposite phase to the AC voltage Vin applied to the conductor 2a of the power line 2. Therefore, a display device (not shown) that receives the AC voltage Vout output from the output terminal 30b of the sensor circuit 30 inverts the sign of the AC voltage Vout and displays the observed waveform for the AC voltage Vin applied to the conductor 2a of the power line 2.

[0045] Next, we will explain how the non-contact voltage sensor device 100 according to Embodiment 1 can suppress errors in the waveform of the AC voltage Vin observed in a non-contact state via the probe electrode 10, even if dielectric relaxation occurs in the dielectric 2b in the power line 2. Figure 3 shows the frequency characteristics E (numerical) of the amplitude value of the AC voltage Vout in an ideal simulation result where the effect of dielectric relaxation in the dielectric 2b in the power line 2 is eliminated, and the frequency characteristics S (measurement) of the amplitude value of the AC voltage Vout in an actual measurement result in a comparative example.

[0046] In Figure 3, the horizontal axis represents the frequency [MHz] of the AC voltage Vin applied to the conductor 2a of the power line 2, and the vertical axis represents the amplitude [dB] of the AC voltage Vout output from the output terminal 30b of the sensor circuit 30.

[0047] A comparative example is a non-contact voltage sensor device 101, as shown in Figure 4, which lacks the dielectric relaxation compensation circuit 31 found in the non-contact voltage sensor device 100 according to Embodiment 1. Specifically, compared to the non-contact voltage sensor device 100 according to Embodiment 1 shown in Figure 1, the input terminal 32a of the frequency compensation circuit 32 is directly connected to the input terminal 30a of the sensor circuit 30, and the input terminal 32a of the frequency compensation circuit 32 is connected to the other end of the conductor of the probe cable 20. All other aspects are the same.

[0048] On the other hand, the simulation results show the frequency characteristics E of the amplitude value of an ideal AC voltage Vout in the non-contact voltage sensor device 100 according to Embodiment 1, where the dielectric relaxation compensation circuit 31 eliminates the dielectric relaxation effect in the dielectric 2b of the power line 2.

[0049] As can be seen from Figure 3, the frequency characteristics E of the simulation result and the frequency characteristics S of the measured result in the comparative example show a discrepancy in the amplitude value of the AC voltage Vout at frequencies of approximately 0.5 kHz or higher for the frequency of the AC voltage Vin applied to the conductor 2a of the power line 2. The frequency characteristics E of the simulation result show a flat frequency characteristic for the amplitude value of the AC voltage Vout in the range of AC voltage Vin frequency from 0.5 kHz to 30 MHz.

[0050] In contrast, the comparative example shows a frequency characteristic in which the amplitude of the AC voltage Vout decreases as the frequency increases, at frequencies of 0.5 kHz or higher for the AC voltage Vin. The decrease in the amplitude of the AC voltage Vout at frequencies of 0.5 kHz or higher for the AC voltage Vin in the comparative example is an error that cannot be ignored in non-contact voltage observation of the AC voltage Vin.

[0051] The non-contact voltage sensor device 100 according to Embodiment 1, by providing a dielectric relaxation compensation circuit 31, can reduce the contribution of the complex impedance Zobs of the observation system, including the effect of dielectric relaxation, to the gain Ga of the sensor circuit 30, and can bring the frequency characteristic E of the simulation result closer to the frequency characteristic S of the actual measurement result in the comparative example. That is, in the non-contact voltage sensor device 100 according to Embodiment 1, the complex impedance Z in the dielectric relaxation compensation circuit 31 Ｇ By making it larger with respect to the complex impedance Zobs of the observation system, the frequency characteristics of the non-contact voltage sensor device 100 according to Embodiment 1 approach the frequency characteristics E obtained from the simulation.

[0052] The non-contact voltage sensor device 100 according to Embodiment 1 is a non-contact voltage sensor device that observes the AC voltage Vin applied to the conductor 2a of the power line 2 through a coupling capacitance, which is a minute capacitance of several pF, generated between the conductor 2a of the power line 2 and the probe electrode 10, without the probe electrode 10 coming into contact with the conductor 2a of the power line 2. The input terminal is electrically connected to the probe electrode 10, and the output terminal is electrically connected to the input terminal of 32. A dielectric relaxation compensation circuit is provided that simulates the complex impedance from the conductor 2a of the power line 2 to the input terminal. Therefore, even for frequencies of AC voltage Vin of 0.5 kHz or higher, a decrease in the amplitude value of AC voltage Vout can be prevented, and a flat frequency characteristic can be achieved. Errors included in the observed waveform for AC voltage Vin can be suppressed, thereby reducing the deterioration of observation accuracy due to dielectric relaxation in the dielectric 2b of the power line 2.

[0053] Embodiment 2. A non-contact voltage sensor device 100A according to Embodiment 2 will be described with reference to Figures 5 and 6. The non-contact voltage sensor device 100 according to Embodiment 1 is configured as a dielectric relaxation compensation circuit 31 that simulates the complex impedance Zobs of the observation system, using a parallel circuit of a capacitive element 31a and a resistive element 31b.

[0054] In contrast, the non-contact voltage sensor device 100A according to Embodiment 2 uses a dielectric relaxation compensation circuit 31A, and a complex impedance Z ＧThe difference lies in the circuit configuration, which allows the value of to be switched between multiple values; otherwise, it is the same. In Figures 5 and 6, the same reference numerals as in Figures 1 and 2 indicate the same or equivalent parts.

[0055] As shown in Figure 5, the non-contact voltage sensor device 100A according to Embodiment 2 includes a probe electrode 10, a probe cable 20, a sensor circuit 30A, and a switching control unit 40. The sensor circuit 30A includes a dielectric relaxation compensation circuit 31A, a frequency compensation circuit 32, and an AD converter 33.

[0056] The input terminal of the dielectric relaxation compensation circuit 31A is connected to the input terminal 30Aa of the sensor circuit 30A, and is electrically connected to the probe electrode 10 via the conductor of the probe cable 20. The output terminal of the dielectric relaxation compensation circuit 31A is electrically connected to the input terminal 32a of the frequency compensation circuit 32.

[0057] The dielectric relaxation compensation circuit 31A is a circuit that simulates the complex impedance Zobs of the observation system, and the complex impedance Z is changed by a switching signal from the switching control unit 40. Ｇ This is a circuit that can switch the value of multiple complex impedances Z to multiple different values. Ｇ Each of these values ​​is proportional to the value of the complex impedance Zobs of the observation system.

[0058] The dielectric relaxation compensation circuit 31A has a plurality of unit circuits electrically connected in parallel between its input terminal, which is electrically connected to the probe electrode 10 via the conductor of the probe cable 20, and the input terminal 32a of the frequency compensation circuit 32. Each of the plurality of unit circuits has parallel circuits 311, 312, and 313 of (first) capacitive elements 311a, 312a, and 313a and (first) resistive elements 311b, 312b, and 313b, and switch elements 311S, 312S, and 313S connected in series to the parallel circuits 311, 312, and 313.

[0059] Each of the parallel circuits 311, 312, and 313 is a circuit that simulates the complex impedance Zobs of the observation system, and the complex impedance Z Ｇ The values ​​of are different from each other. The complex impedance of each parallel circuit 311, 312, and 313 is proportional to the complex impedance Zobs of the observation system.

[0060] Each capacitive element 311a, 312a, and 313a is a capacitor that simulates the coupling capacitance C0 in a parallel configuration of coupling capacitance C0 and insulation resistance, and the capacitance values ​​of each capacitive element 311a, 312a, and 313a are different from each other. Each resistive element 311b, 312b, and 313b is a resistor that simulates the insulation resistance in a parallel configuration of coupling capacitance C0 and insulation resistance, and the resistance values ​​of each resistive element 311b, 312b, and 313b are different from each other.

[0061] Each capacitive element 311a, 312a, and 313a may be a variable capacitor for fine adjustment of capacitance values, and each resistive element 311b, 312b, and 313b may be a variable resistor for fine adjustment of resistance values. Each switch element 311S, 312S, and 313S is controlled on or off by a switching signal from the switching control unit 40, and is, for example, a transistor element.

[0062] The switching control unit 40 receives the AC voltage Vout, which is a digital signal from the AD converter 33, and determines whether the value of the AC voltage Vout (voltage amplitude value) is above a threshold. If it is below the threshold, it changes the switching signal it outputs; if it is above the threshold, it maintains the switching signal. The threshold is a value used to determine whether the AC voltage Vout from the AD converter 33 is at a level sufficient for observation. If the value of the AC voltage Vout is above the threshold, it is considered to be within the actual range of the dynamic range of the AD converter 33.

[0063] The switching signal has seven possible states: turning on all three switch elements 311S, 312S, and 313S; turning on two of the three switch elements 311S, 312S, and 313S and turning off one; and turning on one of the three switch elements 311S, 312S, and 313S and turning off two.

[0064] The switching signal from the switching control unit 40 is transmitted to the complex impedance Z in the dielectric relaxation compensation circuit 31A. ＧThis is a signal that changes the value of sequentially from the largest value to the smallest value. In other words, the dielectric relaxation compensation circuit 31A first selects the complex impedance Z of the largest value among the three switching elements 311S, 312S, and 313S based on the switching signal. Ｇ Select one value, and then select smaller values ​​in order. Next, select an even smaller value using a switching signal that turns on two switch elements, and finally, use a switching signal that turns on all three switch elements 311S, 312S, and 313S to select the complex impedance Z. Ｇ The value is reduced to the smallest possible value.

[0065] Complex impedance Z in dielectric relaxation compensation circuit 31A Ｇ As is clear from equation (2) above, the sequential change in the value of means that the gain Ga in the sensor circuit 30A is sequentially changed from a small value to a large value. That is, the dielectric relaxation compensation circuit 31A is set to a state where the gain Ga of the sensor circuit 30A is set to the minimum necessary circuit gain with respect to the AC voltage Vin applied to the conductor 2a of the power line 2, by the selection of parallel circuits 311, 312, and 313 by the switching signal from the switching control unit 40, and the observation (measurement) of the AC voltage Vout with respect to the AC voltage Vin is performed in the sensor circuit 30A.

[0066] The dielectric relaxation compensation circuit 31A allows the gain Ga of the sensor circuit 30A to be set to the minimum necessary value, thereby maximizing the effect of the dielectric relaxation compensation circuit 31A and suppressing the effects of dielectric relaxation occurring in the insulator 2b of the power line 2. In other words, the complex impedance Z in the dielectric relaxation compensation circuit 31A corresponds to the minimum necessary gain Ga of the sensor circuit 30A. Ｇ By increasing the value of , the influence of the complex impedance Zobs of the observation system can be reduced, and as a result, the degradation of observation accuracy due to dielectric relaxation occurring in the insulator 2b of the power line 2 can be reduced, and a frequency characteristic with a flat amplitude and phase can be obtained for the observed AC voltage Vout with respect to the AC voltage Vin applied to the conductor 2a of the power line 2.

[0067] Although the dielectric relaxation compensation circuit 31A was described as having three unit circuits, each consisting of parallel circuits 311, 312, and 313 and a series configuration of switch elements 311S, 312S, and 313S, it may have two, or even four or more. In short, the dielectric relaxation compensation circuit 31A can have multiple unit circuits.

[0068] The switching control unit 40 consists of a CPU (Central Processing Unit), a large-capacity semiconductor memory (RAM: Random Access Memory), and a storage device (ROM: Read-only memory) such as a hard disk drive or SSD. The output of the switching signal is a program stored in the ROM, which the CPU reads into the RAM, and then executes under the control and management of the CPU.

[0069] Next, the operation of the non-contact voltage sensor device 100A according to Embodiment 2, mainly focusing on the switching operation in the dielectric relaxation compensation circuit 31A by the switching control unit 40, will be explained using Figure 6. First, the probe electrode 10 is attached to the power line 2, which is the object to be observed. That is, the probe electrode 10 is placed in contact with or close to the surface of the insulator 2b of the power line 2 so as to surround the insulator 2b (preparation step ST01). After the probe electrode 10 is attached to the power line 2, the operation of the non-contact voltage sensor device 100A is started.

[0070] In step ST1, the switching control unit 40 provides the switching signals that minimize the gain Ga of the sensor circuit 30A as an initial setting to the switching elements 311S, 312S, and 313S, and proceeds to step ST2. That is, the switching control unit 40 turns on the switching element with the largest complex impedance ZG among the switching elements 311S, 312S, and 313S. The complex impedance ZG in the dielectric relaxation compensation circuit 31A at this time Ｇ The value of takes its maximum value, and the influence (contribution) of the complex impedance Zobs of the observation system to the gain Ga of the sensor circuit 30A is minimized.

[0071] In step ST2, the switching control unit 40 receives the AC voltage Vout observed by the sensor circuit 30, that is, the value (voltage amplitude value) of the AC voltage Vout output from the output terminal 30Ab of the sensor circuit 30, as the result of measurement by the sensor circuit 30A, and proceeds to step ST3. In step ST3, the switching control unit 40 compares the value of the AC voltage Vout with a threshold.

[0072] If the switching control unit 40 finds that the value of the AC voltage Vout is below the threshold as a result of the comparison, it determines "NO" that the amplitude of the AC voltage Vout, which is the input voltage of the AD converter 33, that is, the analog signal output from the frequency compensation circuit 32, is not at a level sufficient for observation, that is, it is outside the actual range of the dynamic range of the AD converter 33, and proceeds to step ST4.

[0073] If the switching control unit 40 finds that the value of the AC voltage Vout is above the threshold as a result of the comparison, it determines that the amplitude of the AC voltage Vout, which is the input voltage of the AD converter 33, is at a level sufficient for observation, and determines "YES". It maintains the switching signal that holds the switch state of the switch elements 311S, 312S, and 313S, and proceeds to step ST5.

[0074] In step ST3, if it is determined that the amplitude of the analog signal, the AC voltage Vout, is not at a level sufficient for observation, in step ST4, the switching control unit 40 outputs a switching signal to the switching elements 311S, 312S, and 313S to indicate the switching state of the switching elements 311S, 312S, and 313S in order to increase the gain Ga of the sensor circuit 30A by one step.

[0075] In other words, in step ST4, the switching control unit 40 outputs a switching signal that turns on only the switching element with the second largest complex impedance among the parallel circuits 311, 312, and 313, and the process returns to step ST2. In step ST2, the switching control unit 40 receives the value of the AC voltage Vout observed by the sensor circuit 30A, whose gain Ga has been increased by one step, and in step ST3, the switching control unit 40 compares the value of the AC voltage Vout with a threshold value.

[0076] In step ST3, the gain Ga of the sensor circuit 30A is increased one step at a time by repeating steps ST3 → ST4 → ST2 → ST3 until the switching control unit 40 determines that the value of the AC voltage Vout is equal to or greater than a threshold. Note that the complex impedance Z in the dielectric relaxation compensation circuit 31A Ｇ The value decreases by one step each time you proceed to step ST4.

[0077] In step ST3, if the switching control unit 40 determines that the value of the AC voltage Vout is equal to or greater than a threshold, in step ST5, the sensor circuit 30A outputs the observed AC voltage Vout, corresponding to the AC voltage Vin applied to the conductor 2a of the power line 2, from the output terminal 30Ab to a display device (not shown).

[0078] Step ST1 is the complex impedance Z in the dielectric relaxation compensation circuit 31A. Ｇ Steps ST2 to ST4 involve setting the initial value of the complex impedance Z in the dielectric relaxation compensation circuit 31A by the switching control unit 40. Ｇ Step ST5 is the step of determining the value. Step ST5 is the actual operational step in which the non-contact voltage sensor device 100A actually measures the AC voltage Vin applied to the conductor 2a of the power line 2. Steps ST2 to ST4 are stored as a program in the ROM of the computer.

[0079] The non-contact voltage sensor device 100A according to Embodiment 2 is provided with a dielectric relaxation compensation circuit 31A that electrically connects in parallel between the input terminal electrically connected to the probe electrode 10 and the input terminal 32a of the frequency compensation circuit 32. This circuit comprises multiple unit circuits, each having parallel circuits 311, 312, 313 of capacitive elements 311a, 312a, 313a and resistive elements 311b, 312b, 313b, and switch elements 311S, 312S, 313S connected in series to the parallel circuits 311, 312, 313. The switching control unit 40 controls the on / off state of the switch elements 311S, 312S, 313S. This allows the sensor circuit 30A to be set to the minimum necessary gain, in other words, the complex impedance Z in the dielectric relaxation compensation circuit 31A. Ｇ By setting the value of to a large value, the measurement process of the AC voltage Vin can be performed, and the deterioration of observation accuracy due to dielectric relaxation in the dielectric 2b of the power line 2 can be reduced.

[0080] Furthermore, it is possible to freely combine the embodiments, modify any component of each embodiment, or omit any component of each embodiment.

[0081] The non-contact voltage sensor device according to this disclosure is suitable, for example, for measuring the AC voltage of a power line in a power distribution (power supply) system that applies a voltage with a frequency of 0.5 kHz or higher and supplies power via a power line, in a non-contact manner with respect to the conductor of the power line.

[0082] 1 AC power supply, 2 power line, 2a conductor, 2b insulator, 3 reference line, 3a conductor, 3b insulator, 100 non-contact voltage sensor device, 10 probe electrode, 20 probe cable, 30 sensor circuit, 31, 31A dielectric relaxation compensation circuit, 31a, 311a, 312a, 313a (first) capacitive element, 31b, 311b, 312b, 313b (first) resistive element, 311, 312, 313 unit circuit, 32 frequency compensation circuit, 321 operational amplifier, 311S, 312S, 313S switching element, 322 impedance circuit, 33 AD converter, 40 switching control unit.

Claims

1. A non-contact voltage sensor device comprising: a probe electrode for observing an AC voltage in a power line having a conductor supplied with power from an AC power source and an insulator covering the conductor, in an electrically non-contact state with respect to the conductor in the power line; a dielectric relaxation compensation circuit whose input terminal is electrically connected to the probe electrode and which simulates the complex impedance from the conductor in the power line to the input terminal; and a frequency compensation circuit whose input terminal is electrically connected to the output terminal of the dielectric relaxation compensation circuit and which compensates for the frequency characteristics of the amplitude and phase of the waveform of the AC voltage from the dielectric relaxation compensation circuit.

2. The non-contact voltage sensor device according to claim 1, wherein the value of the complex impedance in the dielectric relaxation compensation circuit is proportional to the value of the complex impedance from the conductor in the power line to the input terminal of the dielectric relaxation compensation circuit.

3. The non-contact voltage sensor device according to claim 1 or claim 2, wherein the value of the complex impedance in the dielectric relaxation compensation circuit is greater than the value of the complex impedance from the conductor in the power line to the input terminal of the dielectric relaxation compensation circuit.

4. The non-contact voltage sensor device according to any one of claims 1 to 3, wherein the dielectric relaxation compensation circuit has a first capacitive element electrically connected between an input terminal electrically connected to the probe electrode and an input terminal of the frequency compensation circuit.

5. The non-contact voltage sensor device according to any one of claims 1 to 3, wherein the dielectric relaxation compensation circuit has a first capacitive element and a first resistive element electrically connected between an input terminal electrically connected to the probe electrode and an input terminal of the frequency compensation circuit.

6. The non-contact voltage sensor device according to claim 1, wherein the circuit is capable of switching the value of the complex impedance of the dielectric relaxation compensation circuit to a plurality of values.

7. The non-contact voltage sensor device according to claim 6, wherein the dielectric relaxation compensation circuit has a plurality of unit circuits electrically connected in parallel between an input terminal electrically connected to the probe electrode and the input terminal of the frequency compensation circuit, and each of the plurality of unit circuits has a parallel circuit of a first capacitive element and a first resistive element and a switch element connected in series with the parallel circuit.

8. The non-contact voltage sensor device according to any one of claims 1 to 7, wherein the frequency compensation circuit comprises an operational amplifier whose inverting input terminal is electrically connected to the output terminal of the dielectric relaxation compensation circuit, whose non-inverting input terminal is connected to a reference potential node, and whose output terminal is electrically connected to an output terminal, and an impedance circuit having a second capacitive element and a second resistive element electrically connected in parallel between the output terminal and the inverting input terminal of the operational amplifier.

9. The non-contact voltage sensor device according to claim 8, wherein the capacitance value of the second capacitive element of the impedance circuit in the frequency compensation circuit is equivalent to the capacitance value of the coupling capacitance generated between the conductor in the power line and the probe electrode, and the resistance value of the second resistive element of the impedance circuit in the frequency compensation circuit is equivalent to the resistance value of the insulation resistance of the insulator in the power line.

10. A non-contact voltage sensor device comprising: a probe electrode for observing the voltage in a power line having a conductor supplied with power from an AC power source and an insulator covering the conductor, in an electrically non-contact state with respect to the conductor in the power line; a first capacitive element with one node electrically connected to the probe electrode; an operational amplifier with its inverting input terminal electrically connected to the other node of the first capacitive element and its non-inverting input terminal connected to a reference potential node; and a second capacitive element connected between the output terminal and the non-inverting input terminal of the operational amplifier.

Images