WO2015139654A1 - 直流剩余电流检测装置 - Google Patents

直流剩余电流检测装置 Download PDF

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Publication number
WO2015139654A1
WO2015139654A1 PCT/CN2015/074668 CN2015074668W WO2015139654A1 WO 2015139654 A1 WO2015139654 A1 WO 2015139654A1 CN 2015074668 W CN2015074668 W CN 2015074668W WO 2015139654 A1 WO2015139654 A1 WO 2015139654A1
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Prior art keywords
residual current
current transformer
voltage
comparator
residual
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PCT/CN2015/074668
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English (en)
French (fr)
Inventor
徐磊
陈永亮
杨世江
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上海电科电器科技有限公司
浙江正泰电器股份有限公司
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Application filed by 上海电科电器科技有限公司, 浙江正泰电器股份有限公司 filed Critical 上海电科电器科技有限公司
Priority to EP15765183.7A priority Critical patent/EP3121609B1/en
Publication of WO2015139654A1 publication Critical patent/WO2015139654A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
    • G01R15/185—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core with compensation or feedback windings or interacting coils, e.g. 0-flux sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/10—Measuring sum, difference or ratio
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
    • H02H3/33—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers

Definitions

  • This invention relates to residual current sensing techniques and, more particularly, to a DC residual current sensing device powered by a unipolar power supply.
  • the conventional residual current detecting method includes an AC type residual current detecting method for detecting only a power frequency sinusoidal residual current, and a type A residual current detecting method for detecting a power frequency sine and a pulsating DC residual current, and for detecting a smooth DC residual.
  • Current type B residual current detection method usually uses the alternating residual current existing in the primary winding of the residual current transformer to generate an alternating magnetic field, thereby inducing a corresponding alternating inductance in the secondary winding of the residual current transformer. Current to achieve detection of residual current.
  • the pulsating DC residual current has no large variation range of the power frequency sinusoidal residual current, there is also a variation of the current, thereby generating an effective magnetic flux change, and then an induced current can be obtained in the secondary winding of the residual current transformer.
  • the residual current generated is no longer just a power frequency sinusoidal waveform, pulsating DC, but also a smooth DC waveform.
  • the magnetic core magnetic field used for sinusoidal AC residual current or pulsating DC residual current protection is biased, even close to saturation, resulting in a decrease in the magnetic field strength and induced potential of the magnetic core, thereby making the residual current transformer The detection sensitivity of the secondary winding is lowered.
  • U.S. Patent No. 4,276,510 issued to U.
  • the principle is that the secondary coil of the current transformer is connected to the high frequency AC source, and an inductive sensor alternately senses the inductance of the secondary winding. Any change in inductance is due to the influence of the low frequency primary current, which is used to induce the third coil. The current, the third coil current, therefore becomes the exact value of the primary current.
  • the key principle of US4,276,510 is to change the inductance (permeability), that is, it cannot be saturated first, nor can it not reach saturation when it fails (unless the fault current is too small), before full saturation
  • the commutation time depends on the values of R1, R2, R3 and the transistor turn-on voltage.
  • US 4,276,510 requires a third coil and a complex analog circuit, which greatly increases the difficulty and cost of implementation and affects the detection accuracy.
  • the other existing DC residual current detecting methods mostly use the high-frequency AC source to pass the secondary coil of the residual current transformer, and the DC residual current is generated by the core saturation generating the alternating excitation current with equal positive and negative peak values.
  • the prior art excitation circuit often requires a bipolar power supply, which leads to an increase in power consumption, and requires component construction such as a transformer to cause a complicated structure, which greatly increases the cost of the circuit.
  • the more complex excitation circuit also brings great challenges to the size design and electromagnetic compatibility of small protection devices.
  • the present invention is directed to a DC residual current detecting device having a full current detecting capability, a simple structure, and being driven by a unipolar power source.
  • a DC residual current detecting device which is driven by a unipolar power supply, comprising: a power conversion self-balancing circuit, a square wave pulse voltage driving circuit, a residual current transformer and a comparator.
  • the input end of the power conversion self-balancing circuit is connected to the unipolar power supply, and the power conversion self-balancing circuit converts the unipolar power supply into a bipolar power supply and outputs the power conversion self-balancing circuit for the square wave pulse voltage driving circuit and the residual current mutual inductance. Powered by the comparator and comparator.
  • the residual current transformer is formed with an RL multivibrator, and the square wave pulse voltage driving circuit cyclically applies a positive and negative direction voltage to the secondary winding of the residual current transformer, and the residual current transformer outputs a corresponding sampling voltage.
  • the comparator obtains the sampling voltage of the residual current transformer output, and generates the square wave signal of the positive and negative alternating with the comparator threshold voltage, and the square wave signal is fed back to the square wave pulse voltage driving circuit as the output of the comparator. Drive signal.
  • the output of the comparator also serves as an output of the DC residual current sensing device to characterize the polarity and magnitude of the DC residual current.
  • the residual current transformer includes a magnetic core, a multi-turn inductor, and a sampling resistor.
  • the magnetic core is an amorphous alloy material, and the distribution line to be subjected to DC residual current detection passes through the magnetic core, and the distribution line and the magnetic core constitute the primary winding of the residual current transformer.
  • a multi-turn inductor is wound around the core to form the secondary winding of the residual current transformer.
  • the multi-turn inductor and the sampling resistor form an RL multivibrator. The sampling voltage is obtained from both ends of the sampling resistor.
  • the comparator is a hysteresis comparator comprising a first operational amplifier, the inverting input of the first operational amplifier is coupled to the sampling resistor via a current limiting resistor to obtain a sampled voltage, the non-inverting input of the first operational amplifier The terminal is connected to the threshold voltage generating circuit to obtain the threshold voltage, the output of the first operational amplifier is connected to the current limiting resistor and the filter capacitor, and the current limiting resistor and the filter capacitor limit current, suppress interference and filter the output of the first operational amplifier.
  • the square wave pulse voltage driving circuit is a half bridge voltage driving circuit composed of an NPN transistor and a PNP transistor.
  • the bases of the two transistors are connected to each other, and the positive and negative alternating square wave signals output by the comparator are connected.
  • Different triodes are respectively connected, the emitters of the two triodes are connected to each other and the square wave pulse driving voltage is output to the secondary winding of the residual current transformer, the collector of the NPN transistor is connected to the forward power source, and the collector connection of the PNP transistor is negative. power supply.
  • the maximum collector current of the NPN transistor and the PNP transistor is related to the number of winding turns of the multi-turn inductor of the residual current transformer, the characteristics of the core, and the resistance of the sampling resistor.
  • the power conversion self-balancing circuit includes a second operational amplifier, and the non-inverting input of the second operational amplifier is connected to the resistor series voltage divider, and the two ends of the resistor series voltage divider are respectively connected to the positive polarity of the unipolar power supply.
  • the inverting input of the second operational amplifier is grounded through a low-resistance resistor, and the output of the second operational amplifier is connected to the inverting input to form a voltage follower to form two sets of symmetric positive and negative power supplies: Positive and ground of the polar power supply, negative pole of the unipolar power supply and ground.
  • the first operational amplifier and the second operational amplifier are of the same type, with a slew rate of ⁇ 13 V/us, a gain bandwidth of ⁇ 4 MHz, and a maximum current output of ⁇ 35 mA.
  • the RL multivibrator of the residual current transformer forms an RL multi-resonance based on the non-linear magnetization curve characteristics of the ferromagnetic material.
  • the secondary winding of the residual current transformer, the square wave pulse voltage driving circuit and the comparator form a cyclic self-oscillation, and the residual current mutual inductance
  • a square wave voltage is applied across the secondary winding of the device to cyclically change the direction of current flowing through the secondary winding of the residual current transformer such that the core of the residual current transformer switches between positive and negative saturation.
  • the positive and negative saturation excitation currents of the core of the residual current transformer are symmetrical when there is no DC residual current in the primary winding of the residual current transformer.
  • the positive and negative saturation excitation currents of the core of the residual current transformer are asymmetric.
  • the average value of the output of the comparator characterizes the polarity and magnitude of the DC residual current in the secondary winding of the residual current transformer; this voltage average is related to the duty cycle of the square wave signal.
  • the DC residual current detecting device of the present invention is capable of detecting a residual current in a full current range including a smooth DC residual current, a power frequency sinusoidal residual current, a pulsating DC residual current, or a residual current superimposed thereon.
  • the DC residual current detecting device is constructed by using a few low-cost components, driven by a unipolar power supply, and converts the unipolar power supply into a bipolar power supply through a power conversion self-balancing circuit, so that the device works more reliably, has a simple structure, and is easy to operate. achieve.
  • FIG. 1 discloses a circuit configuration diagram of a DC residual current detecting device according to an embodiment of the present invention.
  • FIG. 2 is a circuit diagram showing the structure of a residual current transformer in a DC residual current detecting device according to an embodiment of the present invention.
  • FIG. 3 is a block diagram showing the circuit structure of a comparator in a DC residual current detecting device according to an embodiment of the present invention.
  • FIG. 4 is a block diagram showing the circuit structure of a square wave pulse voltage driving circuit in a DC residual current detecting device according to an embodiment of the present invention.
  • FIG. 5 illustrates a power conversion in a DC residual current detecting device according to an embodiment of the present invention.
  • FIG. 6 discloses a magnetization curve of a magnetic core of a residual current transformer in a DC residual current detecting device according to an embodiment of the present invention.
  • Figure 7 is a waveform diagram showing the excitation voltage across the secondary coil of the residual current transformer, the excitation current in the secondary coil, and the voltage across the sampling resistor in the absence of residual current.
  • Figure 8 is a waveform diagram showing the excitation voltage across the secondary coil of the residual current transformer, the excitation current in the secondary coil, and the voltage across the sampling resistor in the presence of residual current.
  • the DC residual current detecting device of the invention is a DC residual current detecting device based on RL multi-resonance oscillating power supplied by a unipolar power source, based on the characteristics of the non-linear magnetization curve of the ferromagnetic material, using the RL multi-resonant sway to the residual current transformer
  • the core is magnetically modulated to characterize the DC residual current that cannot be detected by conventional residual current transformers through the output of a particular electronic circuit.
  • FIG. 1 discloses a circuit configuration diagram of a DC residual current detecting device according to an embodiment of the present invention.
  • the DC residual current detecting device is driven by a unipolar power source, and includes: a power conversion self-balancing circuit 102, a square wave pulse voltage driving circuit 104, a residual current transformer 106, and a comparator 108.
  • the input end of the power conversion self-balancing circuit 102 is connected to the unipolar power supply, and the power conversion self-balancing circuit 102 converts the unipolar power supply into a bipolar power supply and outputs the power conversion self-balancing circuit to the 102 square wave pulse voltage driving circuit 104.
  • the residual current transformer 106 and the comparator 108 are powered.
  • the residual current transformer 106 is formed with an RL multivibrator, the square wave pulse voltage driving circuit 104 cyclically applies a positive and negative direction voltage to the secondary winding of the residual current transformer 106, and the residual current transformer 106 outputs a corresponding sampling voltage.
  • the comparator 108 obtains the sampling voltage output by the residual current transformer 106, and generates the square wave signal of the positive and negative alternating with the threshold voltage of the comparator 108, and the square wave signal is fed back to the square wave pulse as the output of the comparator 108.
  • the voltage driving circuit 104 serves as a driving signal.
  • comparator 108 also acts as an output of the DC residual current sensing device to characterize the DC residual The polarity and magnitude of the residual current.
  • FIG. 2 discloses a circuit configuration diagram of a residual current transformer in a DC residual current detecting device according to an embodiment of the present invention.
  • the residual current transformer includes a magnetic core 201, a multi-turn inductor 202, and a sampling resistor Rs.
  • the magnetic core 201 is an amorphous alloy material, and the distribution lines A, B, C, and N to be subjected to DC residual current detection pass through the magnetic core 201, and the distribution lines A, B, C, N and the magnetic core 201 constitute residual current mutual inductance.
  • the primary winding of the device is amorphous alloy material
  • the magnetic core 201 is made of an amorphous alloy material having good high-frequency characteristics, and the amorphous alloy magnetic core 201 can be magnetically saturated by requiring only a small exciting current Ie at a relatively high frequency in a normal operating state.
  • amorphous alloys have higher saturation magnetic induction and initial permeability, lower residual magnetic induction and coercivity, and better squareness. Therefore, only a small excitation current is required to operate the magnetic core 201 of the amorphous alloy at a higher frequency, which is very advantageous for reducing power consumption and simplifying circuit design.
  • the multi-turn inductor 202 is wound around the magnetic core 201 to form a secondary winding of the residual current transformer.
  • the multi-turn inductor 202 and the sampling resistor Rs constitute an RL multivibrator.
  • the sampling voltage is obtained from both ends of the sampling resistor Rs.
  • the excitation voltage of the residual current transformer is supplied by the square wave pulse voltage drive circuit 104.
  • FIG. 3 discloses a circuit configuration diagram of a comparator in a DC residual current detecting device according to an embodiment of the present invention.
  • the comparator 106 is a hysteresis comparator, and includes a first operational amplifier U1A.
  • the inverting input terminal of the first operational amplifier U1A is connected to the sampling resistor via a current limiting resistor to obtain a sampling voltage, and the non-inverting input terminal of the first operational amplifier U1A is connected.
  • the output of the first operational amplifier U1A is connected to the current limiting resistor and the filter capacitor, and the current limiting resistor and the filter capacitor limit current, suppress interference and filter the output of the first operational amplifier.
  • the first operational amplifier U1A is also connected to the forward power supply Vcc and the negative power supply Vss. Referring to FIG. 3, the first operational amplifier U1A can select a high-performance operational amplifier TL082 with high gain, low noise, and large output current.
  • the basic parameters are as follows: slew rate ⁇ 13V/us, gain bandwidth ⁇ 4MHz, maximum current output ⁇ 35mA.
  • the resistor R4 and the resistor R5 constitute a threshold voltage generating circuit, provide a threshold voltage Ur, and are connected to the in-phase input of the first operational amplifier U1A. The input terminal uses this potential point as the non-inverting input voltage of the first operational amplifier U1A.
  • Resistor R3 and resistor R6 are current resistors.
  • resistor R3 One end of the resistor R3 is connected to the inverting input terminal of the operational amplifier U1A, and the other end is connected to the sampling resistor Rs.
  • the resistor R3 limits the input current of the first operational amplifier U1A.
  • Resistor R6 is coupled to the output of first operational amplifier U1A, and resistor R6 limits the output current of first operational amplifier U1A.
  • Capacitor C2 acts to suppress interference and filtering.
  • FIG. 4 discloses a circuit configuration diagram of a square wave pulse voltage driving circuit in a DC residual current detecting device according to an embodiment of the present invention.
  • the square wave pulse voltage driving circuit 104 is a half bridge voltage driving circuit composed of an NPN transistor and a PNP transistor.
  • the bases of the two transistors are connected to each other, and the positive and negative alternating square wave signals output by the comparator are respectively turned on differently.
  • the triode, the emitters of the two triodes are connected to each other and output a square wave pulse driving voltage to the secondary winding of the residual current transformer.
  • the collector of the NPN transistor is connected to the forward power source, and the collector of the PNP transistor is connected to the negative power source.
  • the maximum collector current of the NPN transistor and the PNP transistor is related to the number of winding turns of the multi-turn inductor of the residual current transformer, the characteristics of the core, and the resistance of the sampling resistor.
  • a half-bridge voltage driving circuit composed of an NPN transistor Q1 and a PNP transistor Q2.
  • the bases of the two transistors Q1 and Q2 are connected to each other and are turned on according to the positive and negative of the output voltage of the comparator 106 to turn on the different transistors.
  • the emitters of the transistors Q1 and Q2 are connected to each other and output a square wave pulse driving voltage to the secondary winding of the residual current transformer.
  • the collector of the NPN transistor Q1 is connected to the forward power source Vcc, and the collector of the PNP transistor Q2 is connected to the negative power source Vss.
  • the maximum collector current that the two transistors can pass is determined by the number of turns of the secondary winding of the residual current transformer (the number of turns of the multi-turn inductor), the characteristics of the core, and the resistance of the sampling resistor.
  • the square wave pulse voltage drive circuit is a half bridge voltage drive circuit whose TTL drive signal is provided by the comparator output.
  • the collectors of the NPN transistor and the PNP transistor are respectively connected to the positive and negative power supply voltages, so that the half bridge voltage driving circuit can turn on the different transistors according to the positive and negative voltages of the comparator output voltage, thereby circulating to the residual current transformer.
  • the secondary winding provides a positive and negative voltage while providing sufficient energizing excitation current to magnetically saturate the core without the output current capability of the op amp itself of the comparator.
  • FIG. 5 discloses a circuit configuration diagram of a power conversion self-balancing circuit in a DC residual current detecting device according to an embodiment of the present invention.
  • Power conversion self-balancing circuit 102 includes a second operational amplifier U2B, the non-inverting input of the second operational amplifier U2B is connected to the resistor series divider, and the two ends of the resistor series divider are respectively connected to the positive and negative ends of the unipolar power supply, and the second operational amplifier
  • the inverting input of U2B is grounded through a low-resistance resistor, and the output of the second operational amplifier U2B is connected to the inverting input to form a voltage follower to form two sets of symmetric positive and negative power supplies: the positive pole of the unipolar power supply ( Vcc) and ground (GND), the negative (Vss) and ground (GND) of the unipolar power supply.
  • Vcc and Vss are the positive and negative ends of the externally input unipolar power supply
  • the non-inverting input of the second operational amplifier U2B is connected to the resistor series divider
  • the resistor series divider is composed of the equivalent resistor R8 and The R9 was constructed.
  • the two ends of the resistor series divider are respectively connected to Vcc and Vss.
  • the resistor R9 is connected to the forward power source Vcc
  • the resistor R8 is connected to the negative power source Vss.
  • the second operational amplifier U2B itself is constructed to be a voltage follower state with the output connected to the inverting input.
  • One end of the low resistance resistor R7 is connected to the inverting input terminal of the second operational amplifier U2B, and the other end is used as a reference ground node (GND) of the entire residual current detecting circuit for eliminating the influence of the discreteness of the internal parameters of the operational amplifier.
  • Vcc and GND two sets of symmetric positive and negative power supplies have been formed: Vcc and GND, Vss and GND. These two sets of power supplies provide the required bipolar power supply for the operation of the comparator 106 and the square wave pulse voltage driving circuit 104.
  • Capacitors C3 and C5 are decoupling capacitors. Capacitors C3 and C5 are connected to forward power supply Vcc and negative power supply Vss.
  • Capacitor C3 is connected to negative power supply Vss, and capacitor C5 is connected to forward power supply Vcc. Capacitor C4 is connected in parallel with resistor R8 to suppress interference and filtering.
  • the second operational amplifier U2B can select the same type as the first operational amplifier U1A in the comparator 106, such as a high-gain, low-noise, high-output high-performance operational amplifier TL082, and the basic parameters are as follows: slew rate ⁇ 13V/us, gain Bandwidth ⁇ 4MHz, maximum current output ⁇ ⁇ 35mA. Alternatively, you can use a dual op amp to combine the two directly.
  • the power conversion self-balancing circuit is composed of a resistor series voltage divider and an operational amplifier connected to a voltage follower.
  • the operational amplifier has a symmetrical resistor series voltage divider connected to the non-inverting input terminal. Connect the positive and negative terminals of the unipolar power supply separately, and the operational amplifier is also powered by the unipolar power supply. With the linear operating characteristics of the op amp, the potential between the output of the op amp and the voltage divider is exactly equal.
  • the inverting input of the operational amplifier is connected in series with a low-value resistor as the reference ground node of the entire residual current detecting circuit for eliminating the discreteness of the internal parameters of the operational amplifier. Impact.
  • the unipolar power supply that supplies the power required for the operation of the operational amplifier is thus divided into two sets of symmetric positive and negative power supplies.
  • the output current capability of this circuit depends on the output current capability of the op amp. If a large output power is required, a power integrated circuit with a high open-loop gain (such as TDA2030) can be used to replace the resistor series divider. Compared with a simple resistor series voltage divider circuit, the power integrated circuit does not generate a large deviation between the positive and negative voltages of the bipolar power supply due to the asymmetry of the back end load. Therefore, the accuracy of the operational amplifier is not affected, and the accuracy of the residual current detection is ensured.
  • the basic working principle of the DC residual current detecting device is as follows:
  • the RL multivibrator of the residual current transformer forms an RL multi-resonance based on the nonlinear magnetization curve characteristic of the ferromagnetic material.
  • the secondary winding of the residual current transformer, the square wave pulse voltage driving circuit and the comparator form a cyclic self-oscillation, and a square wave voltage is applied across the secondary winding of the residual current transformer, and the cyclic change flows through the residual current transformer.
  • the current direction of the secondary winding causes the core of the residual current transformer to switch between positive and negative saturation.
  • the positive and negative saturation excitation currents of the core of the residual current transformer are symmetrical.
  • the positive and negative saturation excitation currents of the core of the residual current transformer are asymmetric.
  • the average value of the output of the comparator characterizes the polarity and magnitude of the DC residual current in the secondary winding of the residual current transformer, which voltage average is related to the duty cycle of the square wave signal.
  • the residual current transformer, the comparator, and the square wave pulse voltage driving circuit are cyclically self-excited, and a square wave voltage of a certain frequency is generated at both ends of the secondary winding coil of the residual current transformer, and the flow is changed cyclically.
  • the current direction of the secondary winding of the residual current transformer is such that the core continuously switches between forward saturation and negative saturation.
  • Figures 6-8 illustrate the working principle and working process of the present invention.
  • 6 shows a magnetization curve of a magnetic core of a residual current transformer in a DC residual current detecting device according to an embodiment of the present invention.
  • Br represents residual magnetic induction
  • Hc is coercive force
  • Bs is saturation magnetic induction.
  • Figure 7 is a waveform diagram showing the excitation voltage across the secondary coil of the residual current transformer, the excitation current in the secondary coil, and the voltage across the sampling resistor in the absence of residual current.
  • Figure 8 is a waveform diagram showing the excitation voltage across the secondary coil of the residual current transformer, the excitation current in the secondary coil, and the voltage across the sampling resistor in the presence of residual current.
  • the same reference numerals denoted by t, t1, t2, and t3 in Fig. 6, Fig. 7, and Fig. 8 are points in time at which the core working state is turned to explain the conversion of the working process of the present invention.
  • T1 and T2 indicated by the same reference symbols in Figs. 7 and 8 are the positive and negative conduction times of the square wave pulse voltage driving circuit 104, respectively.
  • the residual current is a negative (reference direction) DC current (when there is residual current)
  • the excitation current required for the positive half cycle is larger, and the minimum current required for the negative half cycle is higher. Small, the average is no longer zero.
  • FIG. 6, FIG. 7 and FIG. 8 are only examples for explaining the working principle of the present invention, and the specific pattern may be different due to the number of secondary winding turns of the residual current transformer, the characteristics of the magnetic core, the resistance of the sampling resistor, and the like. And there are differences.
  • the DC residual current detecting device of the present invention is capable of detecting a residual current in a full current range including a smooth DC residual current, a power frequency sinusoidal residual current, a pulsating DC residual current, or a residual current superimposed thereon.
  • the DC residual current detecting device is constructed by using a few low-cost components, driven by a unipolar power supply, and converts the unipolar power supply into a bipolar power supply through a power conversion self-balancing circuit, so that the device works more reliably, has a simple structure, and is easy to operate. achieve.

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  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
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Abstract

一种直流剩余电流检测装置，由单极性电源驱动，包括：电源转换自平衡电路（102），输入端连接到单极性电源，电源转换自平衡电路（102）将单极性电源转换为双极性电源并输出，电源转换自平衡电路（102）为其它部件供电；剩余电流互感器（106），形成有RL多谐振荡器，方波脉冲电压驱动电路（104）循环为剩余电流互感器（106）的次级绕组施加正负方向电压，剩余电流互感器（106）输出相应的采样电压；比较器（108），获取剩余电流互感器（106）输出的采样电压，将该采样电压与比较器阈值电压比较并产生正负交替的方波信号，该方波信号作为比较器（108）的输出反馈给方波脉冲电压驱动电路（104）作为驱动信号，比较器（108）的输出还作为直流剩余电流检测装置的输出以表征直流剩余电流的极性和大小。

Description

直流剩余电流检测装置 技术领域
本发明涉及剩余电流检测技术，更具体地说，涉及一种由单极性电源供电的直流剩余电流检测装置。
背景技术
传统的剩余电流检测方法技术包括用于仅检测工频正弦剩余电流的AC型剩余电流检测方法，以及检测工频正弦、脉动直流剩余电流的A型剩余电流检测方法，和用于检测平滑直流剩余电流的B型剩余电流检测方法。其中AC型剩余电流检测方法通常是利用剩余电流互感器初级绕组中存在的交变的剩余电流，产生交变的磁场，从而在剩余电流互感器次级绕组中也感应出相应的交变的感应电流，从而实现剩余电流的检测。另外脉动直流剩余电流虽然没有工频正弦剩余电流变化范围大，但同样存在着电流的变化量，从而产生有效磁通量变化，继而可以在剩余电流互感器次级绕组中得到感应电流。
随着电力电子技术的发展，变频器、医疗设备和UPS等设备的应用日益广泛，这些设备发生故障时，产生的剩余电流不再只是工频正弦波形、脉动直流，也会呈现平滑直流波形。在这种复杂波形条件下，用于正弦交流剩余电流或脉动直流剩余电流保护的磁芯磁场会发生偏置，甚至接近饱和，导致磁芯的磁场强度和感应电势降低，从而使剩余电流互感器次级绕组的检测灵敏度降低。
公开号为US4,276,510的美国专利提出了一种为电流互感器测量原边电流的设备。其原理为电流互感器的次级线圈通以高频交流源，一个电感传感器交替感应次级绕组电感，任何电感的变化都是因为低频原边电流的影响，它被用来感应出第三线圈电流，第三线圈电流因此成为测量原边电流的精确值。US4,276,510的关键原理是让电感(磁导率)变化，即不能先饱和，也不能故障时达不到饱和(除非故障电流太小)，完全饱和前换 向，换向时间取决于R1、R2、R3的值和晶体管导通电压。US4,276,510需要第三线圈和复杂的模拟电路，大大增加了实现的难度和成本，影响检测精度。
现有的其它直流剩余电流检测方法虽然多数也是将剩余电流互感器的次级线圈通以高频交流源，通过磁芯饱和产生交变、正负峰值相等的激磁电流的方法来检测直流剩余电流。但是为了得到正负交变的激磁电流，对于现有技术的激磁电路往往需要双极性电源，从而导致功耗增加，而且需要变压器等元件构建导致结构复杂，大大增加了电路的成本。另外，比较复杂的激磁电路也对小型保护装置的尺寸设计和电磁兼容带来极大考验。
发明内容
本发明旨在提出一种具备全电流检测能力、结构简单并且由单极性电源驱动的直流剩余电流检测装置。
根据本发明的一实施例，提出一种直流剩余电流检测装置，由单极性电源驱动，包括：电源转换自平衡电路、方波脉冲电压驱动电路、剩余电流互感器和比较器。
电源转换自平衡电路的输入端连接到单极性电源，电源转换自平衡电路将单极性电源转换为双极性电源并输出，电源转换自平衡电路为方波脉冲电压驱动电路、剩余电流互感器和比较器供电。
剩余电流互感器形成有RL多谐振荡器，方波脉冲电压驱动电路循环为剩余电流互感器的次级绕组施加正负方向电压，剩余电流互感器输出相应的采样电压。
比较器获取剩余电流互感器输出的采样电压，将该采样电压与比较器阀值电压并产生正负交替的方波信号，该方波信号作为比较器的输出反馈给方波脉冲电压驱动电路作为驱动信号。
比较器的输出还作为所述直流剩余电流检测装置的输出以表征直流剩余电流的极性和大小。
在一个实施例中，剩余电流互感器包括磁芯、多匝电感和采样电阻。 磁芯为非晶合金材料，待进行直流剩余电流检测的配电线路穿过磁芯，配电线路和磁芯构成剩余电流互感器的初级绕组。多匝电感缠绕于磁芯上，构成剩余电流互感器的次级绕组。多匝电感和采样电阻构成RL多谐振荡器。采样电压从采样电阻的两端获得。
在一个实施例中，比较器是滞回比较器，包括第一运算放大器，第一运算放大器的反相输入端经由限流电阻后连接到采样电阻以获取采样电压，第一运算放大器的同相输入端连接到阈值电压产生电路以获取阈值电压，第一运算放大器的输出端连接到限流电阻和滤波电容，限流电阻和滤波电容对第一运算放大器的输出进行限流、抑制干扰和滤波。
在一个实施例中，方波脉冲电压驱动电路是由一个NPN三极管和一个PNP三极管组成的半桥电压驱动电路，两个三极管的基极相互连接，由比较器输出的正负交替的方波信号分别导通不同的三极管，两个三极管的发射极相互连接并向剩余电流互感器的次级绕组输出方波脉冲驱动电压，NPN三极管的集电极连接正向电源，PNP三极管的集电极连接负向电源。
在一个实施例中，NPN三极管和PNP三极管的最大集电极电流与剩余电流互感器的多匝电感的绕组匝数、磁芯的特性以及采样电阻的阻值相关。
在一个实施例中，电源转换自平衡电路包括第二运算放大器，第二运算放大器的同相输入端连接到电阻串联分压器，电阻串联分压器的两端分别连接到单极性电源的正负两端，第二运算放大器的反相输入端通过低阻值电阻接地，第二运算放大器的输出端与反相输入端连接，构建成电压跟随器，形成两组对称的正负电源：单极性电源的正极与地、单极性电源的负极与地。
在一个实施例中，第一运算放大器和第二运算放大器为相同型号，压摆率≥13V/us、增益带宽≥4MHz，最大电流输出≥±35mA。
在一个实施例中，剩余电流互感器的RL多谐振荡器基于铁磁材料的非线形磁化曲线特性而形成RL多谐振荡。剩余电流互感器的次级绕组、方波脉冲电压驱动电路和比较器三者形成循环自激振荡，在剩余电流互感 器的次级绕组两端施加方波电压，循环改变流过剩余电流互感器的次级绕组的电流方向，使剩余电流互感器的磁芯在正向饱和与负向饱和之间转换。
在一个实施例中，剩余电流互感器的初级绕组不存在直流剩余电流时，剩余电流互感器的磁芯的正、负向饱和激磁电流对称。剩余电流互感器的初级绕组存在直流剩余电流时，剩余电流互感器的磁芯的正、负向饱和激磁电流不对称。
在一个实施例中，比较器的输出的电压平均值表征剩余电流互感器的次级绕组中的直流剩余电流的极性和大小；该电压平均值与方波信号的占空比相关。
本发明的直流剩余电流检测装置能够检测包括平滑直流剩余电流、工频正弦剩余电流、脉动直流剩余电流或者与之叠加的剩余电流在内的全电流范围内的剩余电流。该直流剩余电流检测装置利用少数低成本元件搭建，由单极性电源驱动，通过电源转换自平衡电路将单极性电源转换成双极性电源，使得该装置工作更可靠，结构简单，且容易实现。
附图说明
本发明上述的以及其他的特征、性质和优势将通过下面结合附图和实施例的描述而变的更加明显，在附图中相同的附图标记始终表示相同的特征，其中：
图1揭示了根据本发明的一实施例的直流剩余电流检测装置的电路结构示意图。
图2揭示了根据本发明的一实施例的直流剩余电流检测装置中剩余电流互感器的电路结构示意图。
图3揭示了根据本发明的一实施例的直流剩余电流检测装置中比较器的电路结构示意图。
图4揭示了根据本发明的一实施例的直流剩余电流检测装置中方波脉冲电压驱动电路的电路结构示意图。
图5揭示了根据本发明的一实施例的直流剩余电流检测装置中电源转 换自平衡电路的电路结构示意图。
图6揭示了根据本发明的一实施例的直流剩余电流检测装置中剩余电流互感器的磁芯的磁化曲线。
图7揭示了在不存在剩余电流时，剩余电流互感器的次级线圈两端的激磁电压、次级线圈中的激磁电流以及采样电阻两端的电压的波形图。
图8揭示了在存在剩余电流时，剩余电流互感器的次级线圈两端的激磁电压、次级线圈中的激磁电流以及采样电阻两端的电压的波形图。
具体实施方式
本发明的直流剩余电流检测装置是一种由单极性电源供电的基于RL多谐振荡的直流剩余电流检测装置，基于铁磁材料非线形磁化曲线特性，利用RL多谐振荡对剩余电流互感器铁芯进行磁调制，将传统剩余电流互感器无法检测的直流剩余电流，通过特定电子电路的输出量表征出来。
参考图1所示，图1揭示了根据本发明的一实施例的直流剩余电流检测装置的电路结构示意图。该直流剩余电流检测装置由单极性电源驱动，包括：电源转换自平衡电路102、方波脉冲电压驱动电路104、剩余电流互感器106和比较器108。
电源转换自平衡电路102的输入端连接到单极性电源，电源转换自平衡电路102将单极性电源转换为双极性电源并输出，电源转换自平衡电路为102方波脉冲电压驱动电路104、剩余电流互感器106和比较器108供电。
剩余电流互感器106形成有RL多谐振荡器，方波脉冲电压驱动电路104循环为剩余电流互感器106的次级绕组施加正负方向电压，剩余电流互感器106输出相应的采样电压。
比较器108获取剩余电流互感器106输出的采样电压，将该采样电压与比较器108阀值电压并产生正负交替的方波信号，该方波信号作为比较器108的输出反馈给方波脉冲电压驱动电路104作为驱动信号。
比较器108的输出还作为直流剩余电流检测装置的输出以表征直流剩 余电流的极性和大小。
参考图2所示，图2揭示了根据本发明的一实施例的直流剩余电流检测装置中剩余电流互感器的电路结构示意图。剩余电流互感器包括磁芯201、多匝电感202和采样电阻Rs。磁芯201为非晶合金材料，待进行直流剩余电流检测的配电线路A、B、C、N穿过磁芯201，配电线路A、B、C、N和磁芯201构成剩余电流互感器的初级绕组。磁芯201由具有较好的高频特性的非晶合金材料制作，正常工作状态下在较高频率时仅需很小的激磁电流Ie就能使非晶合金磁芯201达到磁饱和状态。与坡莫合金相比，非晶合金具有更高的饱和磁感应强度和初始磁导率，同时具有更低的剩余磁感应强度和矫顽力，并且其矩形度也较好。因此，工作在较高频率时仅需很小的激磁电流就能使非晶合金的磁芯201达到磁饱和状态，这对降低电源功耗、简化电路设计是非常有利的。图2中A、B、C、N四线导电体为可能存在剩余电流的配电线路，同时穿过剩余电流互感器的磁芯201，作为剩余电流互感器的初级绕组。多匝电感202缠绕于磁芯201上，构成剩余电流互感器的次级绕组。多匝电感202和采样电阻Rs构成RL多谐振荡器。采样电压从采样电阻Rs的两端获得。剩余电流互感器的激磁电压由方波脉冲电压驱动电路104提供。
参考图3所示，图3揭示了根据本发明的一实施例的直流剩余电流检测装置中比较器的电路结构示意图。比较器106是滞回比较器，包括第一运算放大器U1A，第一运算放大器U1A的反相输入端经由限流电阻后连接到采样电阻以获取采样电压，第一运算放大器U1A的同相输入端连接到阈值电压产生电路以获取阈值电压，第一运算放大器U1A的输出端连接到限流电阻和滤波电容，限流电阻和滤波电容对第一运算放大器的输出进行限流、抑制干扰和滤波。第一运算放大器U1A还连接到正向电源Vcc和负向电源Vss。参考图3所示，第一运算放大器U1A可以选用高增益、低噪声、大输出电流的高性能运算放大器TL082，基本参数如下压摆率≥13V/us、增益带宽≥4MHz，最大电流输出≥±35mA。电阻R4与电阻R5构成阈值电压产生电路，提供阈值电压Ur，并连接到第一运算放大器U1A的同相输 入端将此电位点作为第一运算放大器U1A的同相输入端输入电压。电阻R3与电阻R6是电流电阻。电阻R3的一端连接运算放大器U1A的反相输入端，另一端连接采样电阻Rs，电阻R3限制第一运算放大器U1A的输入电流。电阻R6连接到第一运算放大器U1A的输出端，电阻R6限制第一运算放大器U1A的输出电流。电容C2起到抑制干扰与滤波作用。
参考图4所示，图4揭示了根据本发明的一实施例的直流剩余电流检测装置中方波脉冲电压驱动电路的电路结构示意图。方波脉冲电压驱动电路104是由一个NPN三极管和一个PNP三极管组成的半桥电压驱动电路，两个三极管的基极相互连接，由比较器输出的正负交替的方波信号分别导通不同的三极管，两个三极管的发射极相互连接并向剩余电流互感器的次级绕组输出方波脉冲驱动电压，NPN三极管的集电极连接正向电源，PNP三极管的集电极连接负向电源。NPN三极管和PNP三极管的最大集电极电流与剩余电流互感器的多匝电感的绕组匝数、磁芯的特性以及采样电阻的阻值相关。如图4所示，NPN三极管Q1和PNP三极管Q2组成的半桥电压驱动电路。两个三极管Q1和Q2的基极相互连接，并根据比较器106的输出电压的正负以导通不同的三极管。三极管Q1、Q2的发射极相互连接并向剩余电流互感器的次级绕组输出方波脉冲驱动电压，NPN三极管Q1的集电极连接正向电源Vcc，PNP三极管Q2的集电极连接负向电源Vss。两个三极管能够通过的最大集电极电流根据剩余电流互感器的次级绕组的匝数(多匝电感的匝数)、磁芯的特性以及采样电阻的阻值确定。方波脉冲电压驱动电路是一个半桥电压驱动电路，其TTL驱动信号由比较器输出提供。NPN三极管和PNP三极管的集电极分别连接至正向和负向电源电压，这样半桥电压驱动电路就可以根据比较器输出电压的正负以导通不同的三极管，从而循环向剩余电流互感器的次级绕组提供正负方向的电压，同时能够提供足够能量的激磁电流使磁芯达到磁饱和状态，而无需受限制于比较器的运算放大器本身的输出电流能力。
参考图5所示，图5揭示了根据本发明的一实施例的直流剩余电流检测装置中电源转换自平衡电路的电路结构示意图。电源转换自平衡电路 102包括第二运算放大器U2B，第二运算放大器U2B的同相输入端连接到电阻串联分压器，电阻串联分压器的两端分别连接到单极性电源的正负两端，第二运算放大器U2B的反相输入端通过低阻值电阻接地，第二运算放大器U2B的输出端与反相输入端连接，构建成电压跟随器，形成两组对称的正负电源：单极性电源的正极(Vcc)与地(GND)、单极性电源的负极(Vss)与地(GND)。如图5所示，Vcc和Vss为外部输入的单极性电源的正负两端，第二运算放大器U2B同相输入端连接到电阻串联分压器，电阻串联分压器由等值电阻R8和R9构建形成。电阻串联分压器的两端分别与Vcc与Vss相连，具体而言，电阻R9连接到正向电源Vcc，电阻R8连接到负向电源Vss。第二运算放大器U2B本身构建成为一个电压跟随器状态，输出端连接到反相输入端。低阻值电阻R7的一端与第二运算放大器U2B反相输入端相连，另一端作为整个剩余电流检测电路的参考地节点接地(GND)，用于消除由于运算放大器内部参数的离散性的影响。至此就形成了两组对称的正负电源：Vcc与GND、Vss与GND，这两组电源为比较器106、方波脉冲电压驱动电路104工作提供所需要的双极性电源。电容C3、C5同为退耦电容，电容C3和C5连接到正向电源Vcc和负向电源Vss，其中电容C3连接到负向电源Vss，电容C5连接到正向电源Vcc。电容C4与电阻R8并联，起到抑制干扰和滤波的作用。第二运算放大器U2B可与比较器106中的第一运算放大器U1A选择相同型号，如高增益、低噪声、大输出电流的高性能运算放大器TL082，基本参数如下压摆率≥13V/us、增益带宽≥4MHz，最大电流输出≥±35mA。或者，也可以将使用双运算放大器，直接将两者组合在一起。总体而言，电源转换自平衡电路由电阻串联分压器和连接成电压跟随器的运算放大器组成，运算放大器同相输入端接有对称的电阻串联分压器，该电阻串联分压器的两端分别连接单极性电源的正负两端，同时运算放大器也由该单极性电源供电。利用运算放大器的线性工作特性，运算放大器输出端与分压点间的电位严格相等。同时运算放大器的反相输入端串联一个低值电阻后作为整个剩余电流检测电路的参考地节点，用于消除由于运算放大器内部参数的离散性 的影响。至此供给运算放大器工作所需电能的单极性电源，被分隔成两组对称的正负电源。该电路的输出电流能力取决于运算放大器的输出电流能力。若需要较大的输出功率，还可以采用开环增益高的功率集成电路(如TDA2030等)来替换电阻串联分压器。功率集成电路与简单的电阻串联分压电路相比，所产生的双极性电源不会因为后端负载存在不对称性，而导致该双极性电源正、负电压之间出现较大的偏差，从而不会影响到运算放大器的精度，保证了剩余电流检测的准确性。
该直流剩余电流检测装置的基本工作原理如下：剩余电流互感器的RL多谐振荡器基于铁磁材料的非线形磁化曲线特性而形成RL多谐振荡。剩余电流互感器的次级绕组、方波脉冲电压驱动电路和比较器三者形成循环自激振荡，在剩余电流互感器的次级绕组两端施加方波电压，循环改变流过剩余电流互感器的次级绕组的电流方向，使剩余电流互感器的磁芯在正向饱和与负向饱和之间转换。
在剩余电流互感器的初级绕组不存在直流剩余电流时，剩余电流互感器的磁芯的正、负向饱和激磁电流对称。在剩余电流互感器的初级绕组存在直流剩余电流时，剩余电流互感器的磁芯的正、负向饱和激磁电流不对称。比较器的输出的电压平均值表征剩余电流互感器的次级绕组中的直流剩余电流的极性和大小，该电压平均值与方波信号的占空比相关。
更具体而言，利用剩余电流互感器、比较器、方波脉冲电压驱动电路三者循环自激磁现象，在剩余电流互感器的次级绕组线圈两端产生一定频率的方波电压，循环改变流过剩余电流互感器次级绕组的电流方向，从而使磁芯不停的在正向饱和与负向饱和之间转换。当剩余电流互感器的初级绕组(一般为1匝)不存在直流剩余电流时，根据铁磁材料磁化曲线的对称性，磁芯正、负向饱和激磁电流存在对称关系，所以采样电阻Rs两端的电压保持对称，此时比较器输出量的电压平均值为零。当剩余电流互感器的初级绕组(一般为1匝)存在直流剩余电流时，在直流偏置磁场的作用下，磁芯正、负向饱和激磁电流不再对称，导致采样电阻Rs两端的电压不再对称，此时比较器输出量的电压平均值不为零，而且该值与剩余电 流互感器次级绕组中的直流剩余电流的极性和大小存在一定关系。比较器输出量的电压平均值的改变是由于方波脉冲电压驱动电路正、负电压导通时间改变而导致的，实质上为激磁方波电压的占空比发生变化。
图6～图8进一步描述了本发明的工作原理和工作过程。其中图6揭示了根据本发明的一实施例的直流剩余电流检测装置中剩余电流互感器的磁芯的磁化曲线。在图6中，Br表示剩余磁感应强度，Hc为矫顽力，Bs为饱和磁感应强度。
图7揭示了在不存在剩余电流时，剩余电流互感器的次级线圈两端的激磁电压、次级线圈中的激磁电流以及采样电阻两端的电压的波形图。图8揭示了在存在剩余电流时，剩余电流互感器的次级线圈两端的激磁电压、次级线圈中的激磁电流以及采样电阻两端的电压的波形图。在图6、图7和图8中相同参考符号表示的t、t1、t2、t3为磁芯工作状态发生转折的时间点，以便说明本发明工作过程的转化。在图7和图8中相同参考符号表示的T1、T2分别为方波脉冲电压驱动电路104的正负导通时间。
在当剩余电流为零时(即不存在剩余电流时)，剩余电流互感器的次级线圈两端的激磁电压、次级线圈中的激磁电流以及采样电阻Rs两端电压的波形图由图7所示，此时T1＝T2，此阶段工作过程如下：
(1)假设当t＝0时刻，激磁电压恰好为正半波，当0<t<t1时，磁芯处于磁化曲线负向磁饱和区，此阶段磁感应强度B变化比较小，剩余电流互感器次级线圈阻抗也比较小，激磁电流Ie从零迅速上升。
(2)当t1<t<t2时，磁环曲线进入线性阶段，此时磁感应强度B变化比较大，激磁阻抗变大，激磁电流上升缓慢。
(3)当t2<t<t3时，磁芯进入正向磁饱和区，磁感应强度B开始变小，激磁电流从零迅速上升；
(4)当t＝t3时刻，激磁电流达到峰值Ir，采样电阻电压达到滞回比较器阈值电压Ur，激磁电压反转，进入负半周期，此阶段的激磁电流与正周期的变化过程相似，整个过程正负半周期对称。
在当剩余电流为正向(参考方向)直流时(存在剩余电流时)，剩余 电流互感器的次级线圈两端激磁电压、次级线圈中的激磁电流以及采样电阻Rs两端电压的波形图由图8示意，此时T1<T2，此阶段工作过程大致与剩余电流为零时类似，但正向(参考方向)直流剩余电流存在时，在正向(参考方向)直流偏置磁场的作用下，正半周期所需激磁电流比较小，负半周期要克服正向(参考方向)直流电流偏置，所需激磁电流Ie比较大，正负饱和区激磁电流不再对称。
类似的，当剩余电流为负向(参考方向)直流电流时(存在剩余电流时)，与前述的正向直流相反，正半周期所需激磁电流较大，负半周期所需激次电流较小，平均值也不再为零。
需要说明的是，图6、图7和图8只是示例说明本发明的工作原理，其具体图形可能因为剩余电流互感器的次级绕组匝数、磁芯的特性、采样电阻的阻值等不同而有所差别。
本发明的直流剩余电流检测装置能够检测包括平滑直流剩余电流、工频正弦剩余电流、脉动直流剩余电流或者与之叠加的剩余电流在内的全电流范围内的剩余电流。该直流剩余电流检测装置利用少数低成本元件搭建，由单极性电源驱动，通过电源转换自平衡电路将单极性电源转换成双极性电源，使得该装置工作更可靠，结构简单，且容易实现。
上述实施例是提供给熟悉本领域内的人员来实现或使用本发明的，熟悉本领域的人员可对上述实施例做出种种修改或变化而不脱离本发明的发明思想，因而本发明的保护范围并不被上述实施例所限，而应该是符合权利要求书提到的创新性特征的最大范围。

Claims (10)

  1. 一种直流剩余电流检测装置，其特征在于，由单极性电源驱动，包括：电源转换自平衡电路、方波脉冲电压驱动电路、剩余电流互感器和比较器；
    电源转换自平衡电路的输入端连接到单极性电源，电源转换自平衡电路将单极性电源转换为双极性电源并输出，电源转换自平衡电路为方波脉冲电压驱动电路、剩余电流互感器和比较器供电；
    剩余电流互感器形成有RL多谐振荡器，方波脉冲电压驱动电路循环为剩余电流互感器的次级绕组施加正负方向电压，剩余电流互感器输出相应的采样电压；
    比较器获取剩余电流互感器输出的采样电压，将该采样电压与比较器阀值电压并产生正负交替的方波信号，该方波信号作为比较器的输出反馈给方波脉冲电压驱动电路作为驱动信号；
    比较器的输出还作为所述直流剩余电流检测装置的输出以表征直流剩余电流的极性和大小。
  2. 如权利要求1所述的直流剩余电流检测装置，其特征在于，所述剩余电流互感器包括磁芯、多匝电感和采样电阻；
    所述磁芯为非晶合金材料，待进行直流剩余电流检测的配电线路穿过磁芯，配电线路和磁芯构成剩余电流互感器的初级绕组；
    多匝电感缠绕于磁芯上，构成剩余电流互感器的次级绕组；
    多匝电感和采样电阻构成RL多谐振荡器；
    采样电压从采样电阻的两端获得。
  3. 如权利要求2所述的直流剩余电流检测装置，其特征在于，所述比较器是滞回比较器，包括第一运算放大器，第一运算放大器的反相输入端经由限流电阻后连接到采样电阻以获取采样电压，第一运算放大器的同相 输入端连接到阈值电压产生电路以获取阈值电压，第一运算放大器的输出端连接到限流电阻和滤波电容，限流电阻和滤波电容对第一运算放大器的输出进行限流、抑制干扰和滤波。
  4. 如权利要求3所述的直流剩余电流检测装置，其特征在于，所述方波脉冲电压驱动电路是由一个NPN三极管和一个PNP三极管组成的半桥电压驱动电路，两个三极管的基极相互连接，由比较器输出的正负交替的方波信号分别导通不同的三极管，两个三极管的发射极相互连接并向剩余电流互感器的次级绕组输出方波脉冲驱动电压，NPN三极管的集电极连接正向电源，PNP三极管的集电极连接负向电源。
  5. 如权利要求4所述的直流剩余电流检测装置，其特征在于，所述NPN三极管和PNP三极管的最大集电极电流与剩余电流互感器的多匝电感的绕组匝数、磁芯的特性以及采样电阻的阻值相关。
  6. 如权利要求4所述的直流剩余电流检测装置，其特征在于，所述电源转换自平衡电路包括第二运算放大器，第二运算放大器的同相输入端连接到电阻串联分压器，电阻串联分压器的两端分别连接到单极性电源的正负两端，第二运算放大器的反相输入端通过低阻值电阻接地，第二运算放大器的输出端与反相输入端连接，构建成电压跟随器，形成两组对称的正负电源：单极性电源的正极与地、单极性电源的负极与地。
  7. 如权利要求6所述的直流剩余电流检测装置，其特征在于，所述第一运算放大器和第二运算放大器为相同型号，压摆率≥13V/us、增益带宽≥4MHz，最大电流输出≥±35mA。
  8. 如权利要求6所述的直流剩余电流检测装置，其特征在于，所述剩余电流互感器的RL多谐振荡器基于铁磁材料的非线形磁化曲线特性而形 成RL多谐振荡；
    剩余电流互感器的次级绕组、方波脉冲电压驱动电路和比较器三者形成循环自激振荡，在剩余电流互感器的次级绕组两端施加方波电压，循环改变流过剩余电流互感器的次级绕组的电流方向，使剩余电流互感器的磁芯在正向饱和与负向饱和之间转换。
  9. 如权利要求8所述的直流剩余电流检测装置，其特征在于，
    剩余电流互感器的初级绕组不存在直流剩余电流时，剩余电流互感器的磁芯的正、负向饱和激磁电流对称；
    剩余电流互感器的初级绕组存在直流剩余电流时，剩余电流互感器的磁芯的正、负向饱和激磁电流不对称。
  10. 如权利要求9所述的直流剩余电流检测装置，其特征在于，
    所述比较器的输出的电压平均值表征剩余电流互感器的次级绕组中的直流剩余电流的极性和大小；该电压平均值与所述方波信号的占空比相关。
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