WO2017108134A1 - Circuit pour détecter un risque de choc électrique - Google Patents

Circuit pour détecter un risque de choc électrique Download PDF

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Publication number
WO2017108134A1
WO2017108134A1 PCT/EP2015/081174 EP2015081174W WO2017108134A1 WO 2017108134 A1 WO2017108134 A1 WO 2017108134A1 EP 2015081174 W EP2015081174 W EP 2015081174W WO 2017108134 A1 WO2017108134 A1 WO 2017108134A1
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WO
WIPO (PCT)
Prior art keywords
voltage
sample
enclosure
line
neutral
Prior art date
Application number
PCT/EP2015/081174
Other languages
English (en)
Inventor
Guoqing Zhang
Haiding XING
Chen Zhang
Yingchun Shi
Original Assignee
Huawei Technologies Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Priority to CN201580083343.1A priority Critical patent/CN108027399B/zh
Priority to PCT/EP2015/081174 priority patent/WO2017108134A1/fr
Publication of WO2017108134A1 publication Critical patent/WO2017108134A1/fr

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Classifications

    • 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
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
    • 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
    • H02H3/14—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 occurrence of voltage on parts normally at earth potential

Definitions

  • the present invention relates to a detection circuit. More particularly, the present invention relates to a circuit for detecting electrical shock hazard on a metal enclosure of an alternating current (AC) equipment, an AC equipment and a communication system.
  • AC alternating current
  • AC Alternate Current
  • the metal enclosure may become electrical.
  • the metal enclosure is earthed well, there will be no electrical shock hazard, while a not well earthed metal enclosure represents, in case of a fault, an electrical shock hazard for people who touch it.
  • a conventional solution to detect electrical shock hazard on a metal enclosure of an alternating current (AC) equipment is to sample a voltage between a neutral conductor N and an earth pin of the socket or the device enclosure, to compare the sample voltage with a threshold voltage and to make a judgment.
  • a judging criterion is that, normally the voltage between the neutral conductor N and the device enclosure is low. Hence, if the sample voltage is lower than the threshold voltage, the device enclosure is considered to be no electrical shock hazard. If the sample voltage is higher than the threshold voltage, the device enclosure is considered to be electrical shock hazard.
  • the judge criterion of the conventional solution relies on a hypothesis, i.e.
  • the earth pin of the socket or the enclosure is earthed well, and thus the threshold voltage is set relatively low.
  • the threshold voltage is set relatively low.
  • object of the present application is to improve detection accuracy of electrical shock hazard on an electrical equipment, in particular a metal enclosure of an alternating current, AC, equipment.
  • a first aspect of the present invention provides a circuit for detecting electrical shock hazard on a metal enclosure of an alternating current, AC, equipment, the circuit comprising a voltage sample and rectifying module and a voltage comparison module, wherein
  • the voltage sample and rectifying module is connected between a line conductor (L) and the metal enclosure, and is configured to:
  • the voltage comparison module is configured to compare the rectified line-to-enclosure sample voltage (VR.LE) with a first threshold voltage, and to detect an electrical shock hazard on the metal enclosure when the rectified line-to-enclosure sample voltage (VR.LE) is lower than the first threshold voltage. Since the line-to-enclosure sample voltage is not affected by the earthing, regardless of whether the metal enclosure of the AC equipment is earthed well or not, the correct line-to- enclosure sample voltage (VS.LE) is sampled, and an electrical shock hazard on the metal enclosure can be detected when the rectified line-to-enclosure sample voltage (VR.LE) is lower than the first threshold voltage, thus the detection accuracy can be improved or ensured, and the operators' safety requirement can be met.
  • the first threshold voltage (V re f) is chosen from a range which is higher than 0 and lower than the predefined voltage value, the predefined voltage value being proportional to a calculated line-to-enclosure voltage (VLE.C) value between the line conductor L and the metal enclosure when a minimum line-to-neutral voltage value (Vi.N.min) among a set of predefined main voltages between the line conductor L and a neutral conductor N is used. Therefore, the limit scenario is considered for defining the predefined voltage value, and the first threshold voltage (V re f) is chosen from a range which is higher than 0 and lower than the predefined voltage value.
  • the circuit further includes a voltage divider circuit, connected between a neutral conductor N and the metal enclosure and being configured to divide a current main voltage (VL-N) between the line conductor L and the neutral conductor N, so that a line-to-enclosure voltage (VL-E) between the line conductor L and the metal enclosure and a neutral-to-enclosure voltage (VN-E) between the neutral conductor N and the metal enclosure are a fraction of the main voltage (VL-N).
  • VL-N current main voltage
  • the line-to-enclosure voltage VL-E and the neutral-to-enclosure voltage VN-E can be definite. Once the line-to-enclosure voltage VL-E and the neutral-to-enclosure voltage VN-E are known, these can be used to define the predefined voltage value, thereby allowing a more efficient choice of the first threshold voltage.
  • the voltage sample and rectifying module comprises a voltage sample module and a voltage rectification module;
  • the voltage sample module includes a first string of resistors comprising a first sample resistor and a second sample resistor connected in series with each other, a first end of the first string of resistors being connected to the line conductor L and a second end of the first string of resistors being connected to the metal enclosure,
  • the line-to-enclosure sample voltage (VS.LE) is a voltage across the second sample resistor, and the voltage sample module being configured to output the line-to-enclosure sample voltage (VS.LE) to the voltage rectification module;
  • a first end of the voltage rectification module is connected to the common end between the first sample resistor and the second sample resistor, and a second end of the voltage rectification module is connected to the voltage comparison module, the voltage rectification module being configured to rectify the line-to-enclosure sample voltage (VS.LE); and the voltage comparison module is configured to compare the rectified line-to-enclosure sample voltage (VR.LE) with the first threshold voltage and output an alarm signal when the rectified line-to-enclosure sample voltage (VR.LE) is lower than the first threshold voltage.
  • the first string of resistors has two functions: firstly it is used to sample a line-to- enclosure sample voltage across the second sample resistor and secondly it can be used to ensure an insulation between the line conductor L and the enclosure. In this manner even through the operators touch one or more parts of the AC equipment, the electric current passing through the body of the operators will be reduced compared with the used main voltage, thereby further increasing the safety of the circuit.
  • the voltage divider circuit is further configured to output a neutral-to- enclosure sample voltage (VS.NE) to the voltage sample and rectifying module, the neutral-to- enclosure sample voltage (V S.NE) being a fraction of the neutral-to-enclosure voltage (VN-E) between the neutral conductor N and the metal enclosure;
  • VS.NE neutral-to- enclosure sample voltage
  • V S.NE neutral-to- enclosure sample voltage
  • VN-E neutral-to-enclosure voltage
  • the voltage sample and rectifying module is further configured to rectify the neutral-to- enclosure sample voltage (VS.NE) and output the rectified neutral-to-enclosure sample voltage (VR.NE) to the voltage comparison module; and
  • the voltage comparison module is further configured to compare the rectified neutral-to- enclosure sample voltage (VR.NE) with a second threshold voltage, and to detect an electrical shock hazard on the metal enclosure when the rectified line-to-enclosure sample voltage (V R.LE) is lower than the first threshold voltage and the rectified neutral-to-enclosure sample voltage (V R.NE) is higher than the second threshold voltage. Therefore, a double check is done, thereby improving the detection accuracy and allowing fulfilling the operators' safety requirement with a higher degree of accuracy compared with conventional methods.
  • the voltage sample and rectifying module comprises a voltage sample module and a voltage rectification module;
  • the voltage sample module includes a first string of resistors comprising a first sample resistor and a second sample resistor connected in series with each other, a first end of the first string of resistors being connected to the line conductor L and a second end of the first string of resistors being connected to the metal enclosure,
  • the voltage sample module is configured to output the line-to-enclosure sample voltage (VS.LE) to the voltage rectification module, the line-to-enclosure sample voltage (VS.LE) being a voltage across the second sample resistor;
  • the voltage divider circuit includes a second string of resistors comprising a first divider resistor and a second divider resistor connected in series with each other, a first end of the second string of resistors being connected to the neutral conductor N and a second end of the second string of resistors being connected to the metal enclosure, wherein the voltage divider circuit is configured to output the neutral-to-enclosure sample voltage (VS.NE) to the voltage rectification module, the neutral-to-enclosure sample voltage (VS.NE) being a voltage across the second divider resistor;
  • a first end of the voltage rectification module is connected to the common end between the first sample resistor and the second sample resistor, a second end of the voltage rectification module is connected to the voltage comparison module, and a third end of the voltage rectification module is connected to the common end between the first divider resistor and the second divider resistor, the voltage rectification module is configured to rectify the line-to- enclosure sample voltage (VS.LE) and the neutral-to-enclosure sample voltage (VS.NE), and output the rectified line-to-enclosure sample voltage and the rectified neutral-to-enclosure sample voltage (VR.LE, VR.NE) to the voltage comparison module; and
  • the voltage comparison module is configured to compare the rectified line-to-enclosure sample voltage (VR.LE) with the first threshold voltage and the rectified neutral-to-enclosure sample voltage (VR.NE) with the second threshold voltage, and to output an alarm signal when the rectified line-to-enclosure sample voltage (VR.LE) is lower than the first threshold voltage and the rectified neutral-to-enclosure sample voltage (VR.NE) is higher than the second threshold voltage.
  • the first string of resistors has two functions: firstly it is used to sample a line-to- enclosure sample voltage across the second sample resistor (VS.LE) and secondly it can be used to ensure an insulation between the line conductor L and the enclosure. In this manner, even though the operators touch one or more parts of the AC equipment, the electric current passing through the body of the operators will be reduced compared with the used main voltage, thereby further increasing the safety of the circuit;
  • the second string of resistors has three functions: firstly it is used to divide or split the main voltage (VL-N) between the line conductor L and the neutral conductor N, secondly it can be used to ensure an insulation between the neutral conductor N and the enclosure. In this manner, even though the operators touch one or more parts of the AC equipment, the electric current passing through the body of the operators will be reduced compared with the used main voltage, thereby further increasing the safety of the circuit, and thirdly it is used to sample a neutral-to-enclosure sample voltage (VS.NE) across the second divider resistor.
  • a second aspect of the present invention provides an AC equipment, comprising a metal enclosure and a circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment described above.
  • a third aspect of the present invention provides a communication system comprising an AC equipment described above and a power system for supplying power to the AC equipment.
  • a fourth aspect of the present invention provides a base station system, BSS, comprising an AC base station and a power system for supplying power to the AC base station, wherein the AC base station comprises a metal enclosure and a circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment described above, wherein the AC base station is deployed on a tower of the BSS.
  • BSS base station system
  • the AC equipment, the communication system and the base station system of the present invention achieves the same advantages as described above for the circuit for detecting electrical shock hazard on a metal enclosure of an alternating current equipment.
  • Figure 1 illustrates an exemplary block diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment according to an embodiment of the present invention
  • Figure 2 illustrates an exemplary block diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment according to another embodiment of the present invention
  • Figure 3a illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 1 ;
  • Figure 3b illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 1 ;
  • Figure 4 illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 1 ;
  • Figure 5 illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 1 ;
  • Figure 6a illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 2;
  • Figure 6b illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 2;
  • Figure 6c illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 2;
  • Figure 6d illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 2;
  • Figure 7 illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 2;
  • Figure 8 illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 1 ;
  • Figure 9 illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 1 ;
  • Fig. 10 illustrates an exemplary block diagram of AC equipment according to an embodiment of the present invention
  • Fig. 11 illustrates an exemplary block diagram of a communication system according to an embodiment of the present invention
  • Fig. 12 illustrates an exemplary block diagram of a base station system, BSS, according to an embodiment of the present invention.
  • line conductor L is meant a conductor which is energized in normal operation and capable of contributing to the transmission or distribution of electric energy but which is not a neutral or mid-point conductor.
  • neutral conductor N is meant a conductor electrically connected to the neutral point and capable of contributing to the distribution of electric energy.
  • protective earthing conductor PE is meant a conductor provided for purposes of safety, for example protection against electric shock; protective conductor provided for protective earthing.
  • line-to-neutral voltage is meant a voltage between a line conductor and the neutral conductor at a given point of an a.c. electric circuit.
  • electric shock is meant a physiological effect resulting from an electric current through a human or animal body.
  • Fig. 1 illustrates an exemplary block diagram of a detecting circuit 100 for detecting electrical shock hazard on a metal enclosure 10 of an AC equipment according to an embodiment of the present invention.
  • the detecting circuit 100 includes a voltage sample and rectifying module 110 and a voltage comparison module 120.
  • the voltage sample and rectifying module 1 10 is connected between a line conductor L and the metal enclosure 10, and is configured to sample a line-to-enclosure sample voltage VS.LE between the line conductor and the metal enclosure (called in the following description also line-to-enclosure sample voltage), rectify the line-to-enclosure sample voltage (VS.LE), and output the rectified line-to-enclosure sample voltage VR.LE (also in short rectified L2E sample voltage) to the voltage comparison module 120.
  • the voltage comparison module 120 is configured to compare the rectified L2E sample voltage (VR.LE) with a first threshold voltage, and to detect an electrical shock hazard on the metal enclosure when the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage.
  • any module described to in the description may also be referred to as circuit.
  • the voltage sample and rectifying module 1 10 and the voltage comparison module 120 may be as well referred to as a sample and rectifying circuit and a voltage comparison circuit.
  • the voltage sample and rectifying module 1 10 samples a line-to-enclosure sample voltage between the line conductor and the metal enclosure.
  • the first threshold voltage is pre-defined to detect electrical shock hazard on a metal enclosure of an alternating current (AC) equipment.
  • the judge criterion is that, if the rectified L2E sample voltage (VR.LE) is higher than the first threshold voltage, the metal enclosure is considered to be no electrical shock hazard. If the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage, the metal enclosure is considered to be electrical shock hazard.
  • the first threshold voltage (V re f) is chosen from a range which is higher than 0 and lower than the predefined voltage value, the predefined voltage value being proportional to a calculated line-to-enclosure voltage (VLE. C ) value between the line conductor L and the metal enclosure when a minimum line-to-neutral voltage value (Vi_N,min) among a set of predefined main voltages between the line conductor L and the neutral conductor N is used.
  • the set of predefined main voltages may, for instance include, several voltages, which are available in the network and which depend on the standard used for the power supply network, such as but not limited to 220V, 1 10V and the like. A more detailed example will be given below.
  • the predefined voltage value may be defined by taking into account a limit (most unfavorable) scenario, in which the circuit can be used.
  • the AC equipment uses the minimum line-to-neutral voltage value (Vi_N,min) between the line conductor L and the neutral conductor N and it will be assumed that the metal enclosure is not earthed well.
  • a minimum line-to-enclosure voltage value (VLE.min) between the line conductor L and the metal enclosure is a fraction of the minimum line-to-neutral voltage value VLN.min .
  • VLE.min the minimum line-to-enclosure voltage value
  • VNE.min the minimum neutral-to-enclosure voltage
  • the calculated line-to-enclosure voltage may be a fraction of the minimum line-to-enclosure voltage (Vi_E,min).
  • the proportionality factor may be a conversion ratio for rectifying half-wave AC to direct current (DC).
  • the set of predefined main voltages may be ⁇ 100V to 240V ⁇ ; the main voltage between the line conductor L and the neutral conductor N varies from country to country throughout the world.
  • a widely used voltage choice is either 1 10-volt AC (1 10V) or 220-volt AC (220V). Note that 1 10 volts and 220 volts are averages, since the voltage does fluctuate during usage.
  • the minimum line-to-neutral voltage value (VLN.min) is 110V and the metal enclosure is not earthed well
  • the minimum line- to-enclosure voltage (VLE.min) and the minimum neutral-to-enclosure voltage (V N E.min) are a fraction of the minimum line-to-neutral voltage value (VLN.min).
  • the minimum line-to-enclosure voltage (Vi_E.min) and the minimum neutral-to-enclosure voltage (VNE.min) may be 55V respectively.
  • VLE.min minimum line-to-enclosure voltage
  • V N E,min minimum neutral-to-enclosure voltage
  • the limit scenario is considered for defining the predefined voltage value, and the first threshold voltage (V re f) is chosen from a range which is higher than 0 and lower than the predefined voltage value.
  • the AC equipment is used in the normal case (i.e. no hazard voltage is connected to the metal enclosure)
  • the rectified L2E sample voltage (VR,LE) is lower than the first threshold voltage (V re f).
  • the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage
  • there must be an electrical shock hazard on the metal enclosure thus the detection accuracy can be further improved or ensured, and the operators' safety requirement can be met.
  • FIG. 2 illustrates an exemplary block diagram of a detecting circuit 200 for detecting electrical shock hazard on a metal enclosure of AC equipment according to another embodiment of the present invention.
  • the detecting circuit 200 is a further development of the detecting circuit 100 and components therein, which are common between the two circuits will be indicated with same reference signs and will not be described again.
  • the circuit includes a voltage sample and rectifying module 110 and a voltage comparison module 120 as already described above.
  • the detecting circuit 200 includes a voltage divider circuit 230.
  • the voltage sample and rectifying module 110 is connected between a line conductor L and the metal enclosure, and is configured to sample the line-to-enclosure sample voltage (VS.LE) between the line conductor and the metal enclosure and rectify the line-to-enclosure sample voltage (VS.LE) (in short L2E sample voltage), and output the rectified L2E sample voltage (VR.LE) to the voltage comparison module 120.
  • the voltage comparison module 120 is configured to compare the rectified L2E sample voltage (VR.LE) with a first threshold voltage, and to detect an electrical shock hazard on the metal enclosure when the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage.
  • the voltage divider circuit 230 is connected between the neutral conductor N and the metal enclosure and is configured to divide a current line-to-neutral main voltage VL-N (in short main voltage) between the line conductor L and the neutral conductor N, so that a line-to-enclosure voltage (VL-E) between the line conductor L and the metal enclosure and a neutral-to-enclosure voltage (VN-E) between the neutral conductor N and the metal enclosure are a fraction of the main voltage (VL-N).
  • VL-E line-to-enclosure voltage
  • VN-E neutral-to-enclosure voltage
  • the line-to-enclosure voltage (VL-E) and the neutral-to-enclosure voltage VN-E can be definite. Once the line-to- enclosure voltage V L -E and the neutral-to-enclosure voltage VN-E are known, these can be used to define the predefined voltage value, thus it is more efficient to choose the first threshold voltage.
  • the voltage divider circuit 230 may be further configured to output a neutral-to-enclosure sample voltage VS.NE between the neutral conductor N and the metal enclosure (also called in the following neutral- to-enclosure sample voltage) to the voltage sample and rectifying module 110, wherein the neutral-to-enclosure sample voltage (VS.NE) is a fraction of the neutral-to-enclosure voltage (VN-E) between the neutral conductor N and the metal enclosure.
  • VS.NE neutral-to-enclosure sample voltage
  • VN-E neutral-to-enclosure voltage
  • the voltage sample and rectifying module 110 is further configured to rectify the neutral-to-enclosure sample voltage (VS.NE) and output the rectified neutral-to- enclosure sample voltage VR.NE (in short rectified N2E sample voltage) to the voltage comparison module 120.
  • the voltage comparison module 120 is further configured to compare the rectified N2E sample voltage VR.NE with a second threshold voltage and to detect an electrical shock hazard on the metal enclosure when the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage and the rectified N2E sample voltage (VR.NE) is higher than the second threshold voltage.
  • the second threshold voltage may be chosen to be higher than a limit voltage value, the limit voltage value being proportional to a calculated neutral-to- enclosure voltage (VNE. C ) value between the neutral conductor N and the metal enclosure when a maximum line-to-neutral voltage value (Vi_N,max) among a set of predefined main line-to- neutral voltages between the line conductor L and the neutral conductor N (in short main voltage) is used.
  • the limit voltage value may be defined by taking into account a limit (most unfavorable) scenario, in which the circuit can be used.
  • the maximum line-to-neutral voltage value Vi_N,max between the line conductor L and the neutral conductor N is used, and it will be assumed that the metal enclosure is not earthed well.
  • the maximum line-to-neutral voltage value is chosen among a set of predefined main voltages between the line conductor L and the neutral conductor N as described above with reference to the implementation of Figure 1.
  • a maximum neutral-to-enclosure voltage value (VNE.max) is a fraction of the maximum line-to-neutral voltage value (Vi_N,max).
  • V E.max The specific value of the maximum neutral-to-enclosure voltage value (V E.max) depends on how the maximum line-to-neutral voltage value (VLN.max) is shared by the maximum line-to- enclosure voltage (VLE.max) and the maximum neutral-to-enclosure voltage (V E.max).
  • the calculated neutral-to-enclosure voltage may be a fraction of the maximum neutral-to-enclosure voltage (VNE.max), and the proportionality factor may be a conversion ratio for rectifying half-wave AC to DC.
  • Figure 3a or 3b illustrates an exemplary circuit schematic diagram of a detecting circuit 300 for detecting electrical shock hazard on a metal enclosure of the AC equipment of Fig. 1.
  • a voltage sample and rectifying module 1 10 of the circuit of Fig. 1 includes a voltage sample module 311 and a voltage rectification module 312.
  • the voltage sample module 311 comprises a first string of resistors comprising a first sample resistor (Rn ) and a second sample resistor (Ri 2 ) connected in series with each other. A first end of the first string of resistors is connected to the line conductor L and a second end of the first string of resistors is connected to the metal enclosure.
  • the line-to-enclosure sample voltage (VS.LE) is a voltage across the second sample resistor (R12)
  • the voltage sample module 31 1 is configured to output the line-to-enclosure sample voltage (VS.LE) to the voltage rectification module 31 2.
  • the voltage sample module 31 1 comprises a first sample resistor (Rn) and a second sampie resistor (R12), according to further embodiments two or more resistors may be alternatively used.
  • a first end of the voltage rectification module 31 2 is connected to a common end between the first sample resistor (Rn) and the second sample resistor (R12).
  • a second end of the voltage rectification module 31 2 is connected to the voltage comparison module 1 20, the voltage rectification module 31 2 being configured to rectify the line-to- enclosure sample voltage VS.LE.
  • the voltage comparison module 1 20 is configured to compare the rectified L2E sample voltage (VR.LE) with the first threshold voltage and output an alarm signal when the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage. Specifically, the voltage comparison module 1 20 outputs an output signal having a first value when the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage. The first value indicates an electrical shock hazard on the metal enclosure of the AC equipment. The output signal may be seen as an alarm signal. Furthermore, the voltage comparison module 1 20 may output an output signal having a second value when the rectified L2E sample voltage (VR.LE) is higher than the first threshold voltage. The second value indicates no electrical shock hazard on the metal enclosure of the AC equipment.
  • the first threshold voltage, Vrefi may be represented by the following formula:
  • Vi.E,efr represents an effective voltage between the line conductor L and the metal enclosure when the minimum line-to-neutral voltage value (Vi_N,min) among the set of predefined main voltages between the line conductor L and the neutral conductor N is used.
  • the voltage V L E,eff is a fraction of the minimum line-to-neutral voltage value (VLN.min), and a represents a conversion ratio for rectifying half-wave AC to DC.
  • the third sample resistor may be connected in series to the first sample resistor, an end of the third sample resistor being connected to the line conductor L.
  • the limit scenario in which the minimum line-to-neutral voltage value (Vi_N,min) is used and the metal enclosure of the AC equipment is not earthed well, is considered.
  • the effective voltage VLE.eff is a fraction of the minimum line-to-neutral voltage value (V L N,min), for example, the voltage Vi_E,eff may be half of the minimum line-to-neutral voltage value
  • the first string of resistors in the voltage sample module 311 may consists of a first sample resistor and a second sample resistor connected in series with each other.
  • a first end of the first sample resistor is connected to the line conductor L and a second end of the second sample resistor is connected to the metal enclosure, and the first threshold voltage, V ie ii is represented by the following formula:
  • Ru and Rn represent the resistance of the first and second sample resistor in the voltage sample module 311 , respectively.
  • the total resistance of the first string of resistors in the voltage sample module 311 is larger than 1 ⁇ to limit the current.
  • the first string of resistors in the voltage sample module 311 may include more than two resistors to ensure safety also in case that one of the resistors fails.
  • the detection circuit may further include an alarm module 140.
  • the alarm module 140 is configured to generate an alarm based on the alarm signal, wherein the alarm is any one or combination of the following: buzzer, light and vibration.
  • the voltage comparison module 120 comprises any one or combination of the following: Silicon Controlled Rectifier (SCR), metallic oxide semiconductor field effect transistor (MOSFET), operational amplifier, Comparators, Relay and voltage regulator diode.
  • SCR Silicon Controlled Rectifier
  • MOSFET metallic oxide semiconductor field effect transistor
  • operational amplifier Comparators
  • Relay Relay and voltage regulator diode.
  • the voltage rectification module 412 includes a rectify diode D1 , a filter capacitor C1 and a discharge resistor F3 ⁇ 4, wherein the filter capacitor C1 is used for filtering a voltage waveform of the line-to-enclosure sample voltage VS.LE , and the discharge resistor is used for discharging the current from the filter capacitor C1 .
  • the anode of the rectify diode D1 is connected to the common end between the first sample resistor and the second sample resistor, and the cathode of the rectify diode D1 is connected to the voltage comparison module 420.
  • the filter capacitor C1 and the discharge resistor F3 ⁇ 4 are connected in parallel, and both the filter capacitor C1 and the discharge resistor R3 are connected between the cathode of the rectify diode D1 and the metal enclosure.
  • the anode of the rectify diode D1 correspond to the first end of the voltage rectification module 412
  • the cathode of the rectify diode D1 corresponds to the second end of the voltage rectification module 412.
  • Fig.4 illustrates a possible realization of a voltage comparison module, which can be used in the detection circuit according to the implementations of the invention described so far.
  • the voltage comparison module 420 of the detection circuit 400 illustrated in Fig. 4 includes an operational amplifier 421 .
  • a non-inverting input 422 of the operational amplifier 421 is connected to the cathode of the rectify diode D1 , or more generally to the output of the rectifying module 412.
  • An inverting input 423 of the operational amplifier 421 is connected to the source of the first threshold voltage; a positive power supply of the operational amplifier 421 is connected to GND; a negative power supply of the operational amplifier 421 is connected to Vcc (i.e. the supply voltage for the operational amplifier 421 ).
  • an output of the operational amplifier 421 is connected to the alarm module 140.
  • the alarm signal which may be a low electrical level signal (e.g. 0), is output when the rectified L2E sample voltage (VR, LE ) is lower than the first threshold voltage, and a high electrical level signal (e.g. 1 ) is output when the rectified L2E sample voltage (VR.LE) is higher than the first threshold voltage.
  • the inverting input of the operational amplifier 421 may be connected to the cathode of the rectify diode D1 and the non-inverting input of the operational amplifier 421 may be connected to the source of the first threshold voltage.
  • the positive power supply of the operational amplifier 421 is connected to Vcc; a negative power supply of the operational amplifier 421 is connected to GND.
  • an output of the operational amplifier 421 is connected to the alarm module 140.
  • the alarm signal being a high electrical level signal (e.g. 1 ) is output when the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage, and a low electrical level signal (e.g. 0) is output when the rectified L2E sample voltage (VR.LE) is higher than the first threshold voltage.
  • the voltage sample module 31 1 , the voltage rectification module 312 and the voltage comparison module 320 have a common terminal connected to a common voltage reference GND.
  • the voltage sample module 31 1 , the voltage rectification module 412 and the voltage comparison module 420 have a common terminal connected to a common voltage reference GND.
  • 31 1 may be different from a common voltage reference of the voltage rectification module
  • the first string of resistors (including a first sample resistor and a second sample resistor) being connected between the line conductor L and the metal enclosure actually has two functions: firstly it is used to sample a line-to- enclosure sample voltage across the second sample resistor and secondly it can be used to ensure an insulation between the line conductor L and the enclosure.
  • the electric current passing through the body of the operators will be reduced compared with the used main voltage, thereby further increasing the safety of the circuit.
  • FIG. 5 illustrates a schematic diagram of an example of a detecting circuit 500 for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 1.
  • a voltage sample and rectifying module includes a voltage sample module 511 and a voltage rectification module 412.
  • the voltage sampie module 511 comprises a string of components comprising a first resistor F3 ⁇ 4i and a transformer T1 connected in series with each other, a first end of the string of components being connected to the line conductor L and a second end of the string of components being connected to the metal enclosure.
  • the line-to-enclosure sample voltage (VS.LE) is a voltage output from the transformer T1 , and the voltage sample module 511 is configured to output the line-to-enclosure sample voltage (VS.LE) to the voltage rectification module 512.
  • the voltage sample module 511 comprises a first resistor R51 configured to limit the current, according to further embodiments two or more resistors may be also used. In the implementation depicted in Fig.
  • a voltage rectification module 412 includes a rectify diode D1 , a filter capacitor C1 and a discharge resistor F3 ⁇ 4.
  • the anode of the rectify diode D1 is connected to an output of the transformer T1
  • the cathode of the rectify diode D1 is connected to the voltage comparison module 420;.
  • the filter capacitor C1 and the discharge resistor F3 ⁇ 4 are connected in parallel, and both the filter capacitor C1 and the discharge resistor R3 are connected between the cathode of the rectify diode D1 and the metal enclosure.
  • the anode of the rectify diode D1 corresponds to the first end of the voltage rectification module 412, and the cathode of the rectify diode D1 corresponds to the second end of the voltage rectification module 412.
  • the transformer T1 has a primary winding on a primary side of the transformer T1 and a secondary winding on a secondary side of the transformer T1.
  • the primary winding's circle number and the secondary winding's circle number are represented by N1 and N2 respectively.
  • the first threshold voltage, V re fi may be represented by the following formula:
  • R51, R52, and Rn represent the resistance of the first resistor, the second resistor and the transformer T1 in the voltage sample module 511 respectively, represents an effective voltage between the line conductor L and the metal enclosure when the minimum line-to-neutral voltage value (Vi_N.min) among the set of predefined main voltages between the line conductor L and the neutral conductor N is used.
  • the voltage VLE.etf is a fraction of the minimum line-to-neutral voltage value (VLN.min), and a represents a conversion ratio for rectifying half-wave AC to DC.
  • Figure 6a, 6b, 6c, 6d or 7 illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 2.
  • a voltage sample and rectifying module 1 10 of the circuit of Fig. 2 includes a voltage sample module 311 and a voltage rectification module 312.
  • the voltage sample module 311 comprises a first string of resistors comprising a first sample resistor and a second sample resistor connected in series with each other. A first end of the first string of resistors is connected to the line conductor L and a second end of the first string of resistors is connected to the metal enclosure.
  • the line-to-enclosure sample voltage (VS.LE) is a voltage across the second sample resistor R12, and the voltage sample module 311 is configured to output the line-to-enclosure sample voltage (VS.LE) to the voltage rectification module 312.
  • the voltage sample module 311 comprises a first sample resistor Rn and a second sample resistor R12, according to further embodiments two or more resistors may be also used.
  • a first end of the voltage rectification module 312 is connected to the common end between the first sample resistor Rn and the second sample resistor R12 and a second end of the voltage rectification module 12 is connected to the voltage comparison module120.
  • the voltage rectification module 312 is configured to rectify the line-to-enclosure sample voltage (VS.LE) across the second sample resistor, and output the rectified L2E sample voltages (VR.LE) to the voltage comparison module 120.
  • the voltage divider circuit 630 comprises a second string of resistors comprising a first divider resistor R21 and a second divider resistor R22 connected in series with each other. A first end of the second string of resistors is connected to the neutral conductor N and a second end of the second string of resistors is connected to the metal enclosure.
  • the voltage divider circuit 630 comprises the first divider resistor, R21 and the second divider resistor, R22, according to further embodiments two or more resistors may be also used. According to a further embodiment, as shown in FIG. 6c or 6d, the voltage divider circuit 630 is configured to output a neutral-to-enclosure sample voltage (VS.NE) to the voltage rectification module 312, the neutral-to-enclosure sample voltage (VS.NE) being a voltage across the second divider resistor R22.
  • VS.NE neutral-to-enclosure sample voltage
  • a third end of the voltage rectification module 312 may be connected to the common end between the first divider resistor R21 and the second divider resistor, R22 of the voltage divider circuit 630.
  • the voltage rectification module 312 is further configured to rectify the neutral-to-enclosure sample voltage (VS.NE) across the second divider resistor R22, and output the rectified neutral-to-enclosure sample voltages (VR.NE) to the voltage comparison module 120.
  • the voltage comparison module 120 is configured to compare the rectified line-to-enclosure sample voltage VR.LE (in short rectified L2E sample Voltage) with the first threshold voltage and to compare the rectified neutral-to-enclosure sample voltage (VR.NE) with the second threshold voltage.
  • the voltage comparison module 20 is further configured to output an alarm signal when the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage and the rectified N2E sample voltage (VR.NE) is higher than the second threshold voltage.
  • the alarm signal indicates the electrical shock hazard on the metal enclosure of the AC equipment.
  • the alarm signal which may be a high electrical level signal (e.g.
  • a normal signal which may be a low electrical level signal (e.g. 0) is output when the rectified L2E sample voltage (VR.LE) is higher than the first threshold voltage and the rectified N2E sample voltage (VR.NE) is lower than the second threshold voltage.
  • a normal signal which may be a low electrical level signal (e.g. 0) is output when the rectified L2E sample voltage (VR.LE) is higher than the first threshold voltage and the rectified N2E sample voltage (VR.NE) is lower than the second threshold voltage.
  • the alarm signal which may be a low electrical level signal (e.g. 0) is output when the rectified L2E sample voltage (VR,LE) is lower than the first threshold voltage and the rectified N2E sample voltage (VR.NE) is higher than the second threshold voltage; while a normal signal, which may be a high electrical level signal (e.g. 1 ), is output when the rectified L2E sample voltage (V R , L E) is higher than the first threshold voltage and the rectified N2E sample voltage (VR.NE) is lower than the second threshold voltage.
  • a low electrical level signal e.g. 0
  • a normal signal which may be a high electrical level signal (e.g. 1 ) is output when the rectified L2E sample voltage (V R , L E) is higher than the first threshold voltage and the rectified N2E sample voltage (VR.NE) is lower than the second threshold voltage.
  • the voltage sample module 311 may include a number m of sample resistors connected in series
  • the voltage divider circuit 630 may include a number n of divider resistors connected in series, where m or n is an integer and m, n>-2.
  • the first threshold voltage, V re » may be represented by the following formula:
  • VLE.eff represents an effecitive voltage between the line conductor L and the metal enclosure when the minimum line-to-neutral voltage value (VLN.min) among a set of predefined main voltages between the line conductor L and the neutral conductor N is used.
  • the voltage is a fraction of the minimum line-to-neutral voltage value (VL .mm), and a represents a conversion ratio for rectifying half-wave AC to DC.
  • the voltage Vi_E,eff may be given by:
  • R21, ..., 3 ⁇ 4 > represent the resistance of the first divider resistor, the second divider resistor,... and the nth divider resistor of the second string of resistors in the voltage divider circuit 630 respectively.
  • V L N,min a minimum line-to-neutral voltage value between the line conductor L and the neutral conductor N is used and the metal enclosure of the AC equipment is not earthed well.
  • the voltage Vi_E,eff is a fraction of the minimum line-to-neutral voltage value ( min)
  • the voltage Vi_E,eff is a half of the minimum line-to-neutral voltage value (VLN.min) if the resistance of the voltage sample module 311 are the same with the resistance of the voltage divider circuit 630.
  • the first string of resistors in the voltage sample module 311 may consist of a first sample resistor and a second sample resistor connected in series with each other. According to this configuration, a first end of the first sample resistor is connected to the line conductor L and a second end of the second sample resistor is connected to the metal enclosure.
  • the first threshold voltage, V rS fi will be given by the following formula:
  • the first string of resistors in the voltage sample module 311 may consist of a third sample resistor Ri 3 (dashed in the figures), a first sample resistor Rn and a second sample resistor R12 connected in series with each other. According to this configuration, an end of the third sample resistor R13 is connected to the iine conductor L and a second end of the second sample resistor R12 is connected to the metal enclosure.
  • the first threshold voltage, V re n is represented by the following formula:
  • Ru, R12 and R13 represent the resistance of the first sample resistor, the second sample resistor and the third sample resistor in the voltage sample module 311 respectively.
  • V N E,eff represents an effective voltage between the neutral conductor N and the metal enclosure when a maximum line-to-neutral voltage value (VLN.max) among a set of predefined main voltages between the line conductor L and the neutral conductor N is used.
  • the effective voltage VNE.eff is here a fraction of the maximum line-to-neutral voltage value (VLN.ma ), and or represents a conversion ratio for rectifying half-wave AC to DC.
  • VNE.eff The effective voltage VNE.eff is given by:
  • VNE.eff V LN n * wherein R21 R ⁇ n represent the resistance of the first divider resistor, the second divider resistor,... and the nth divider resistor of the second string of resistors in the voltage divider circuit 630 respectively.
  • the limit scenario where not only the maximum line-to-neutral voltage value (VLN.max) between the line conductor L and the neutral conductor N is used and the metal enclosure is not earthed well, is considered.
  • the effective voltage V E.eff is a fraction of the maximum line-to-neutral voltage value (VLN.max), for example, the voltage V E.eff is a half of the maximum line-to-neutral voltage value (Vi_N,max) if the resistance of the voltage sample module 311 are the same with the resistance of the voltage divider circuit 630.
  • the second string of resistors in the voltage divider circuit 630 may consist of a first divider resistor F1 ⁇ 2 and a second divider resistor F1 ⁇ 2 connected in series with each other.
  • a first end of the first divider resistor R21 is connected to the neutral conductor N and a second end of the second divider resistor R22 is connected to the metal enclosure.
  • the second threshold voltage, V r0 f2 is represented by the following formula:
  • R21 and R22 represent the resistance of the first divider resistor and the second divider resistor in the second string of resistors in the voltage divider circuit 630 respectively.
  • the second string of resistors may include a third divider resistor, a first divider resistor and a second divider resistor connected in series with each other in the voltage divider circuit 630.
  • an end of the third divider resistor being connected to the neutral conductor N and a second end of the second divider resistor is connected to the metal enclosure.
  • the second threshold voltage, V re f2 is represented by the following formula:
  • R + R n + R 23 wherein R21, R22 and R23 represent the resistance of the first divider resistor, the second divider and the third divider resistor in the voltage divider circuit 630 respectively.
  • the total resistance of the first string of resistors in the voltage sample module 311 or the total resistance of the second string of resistors in the voltage divider circuit 630 is larger than 1 ⁇ to limit the current.
  • the respective string of resistors in the voltage sample module 311 or the voltage divider circuit 630 includes more than two resistors to ensure safety in case one or more of the remaining resistors fails.
  • the total resistance of the first string of resistors in the voltage sample module 311 is the same as the total resistance of the second string of resistors in the voltage divider circuit 630.
  • the detecting circuit further includes an alarm module 140, configured to generate an alarm based on the alarm signal, wherein the alarm is any one or combination of the following: buzzer, light and vibration.
  • the alarm module 140 outputs the alarm to alert an operator of a failure which may cause an electrical hazard.
  • the voltage comparison module 120 comprises any one or combination of the following: Silicon Controlled Rectifier (SCR), metallic oxide semiconductor field effect transistor (MOSFET), operational amplifier, Comparators, Relay and voltage regulator diode.
  • SCR Silicon Controlled Rectifier
  • MOSFET metallic oxide semiconductor field effect transistor
  • a voltage rectification module 412 may include a rectify diode D1 , a filter capacitor C1 and a discharging resistor R 3 .
  • the anode of the rectify diode D1 is connected to the common end between the first sample resistor and the second sample resistor, and the cathode of the rectify diode D1 is connected to the voltage comparison module 420. Further, the filter capacitor C1 and the discharging resistor are connected in parallel, and both the filter capacitor C1 and the discharging resistor are connected between the cathode of the rectify diode D1 and the metal enclosure.
  • the anode of the rectify diode D1 corresponds to the first end of the voltage rectification module 412
  • the cathode of the rectify diode D1 corresponds to the second end of the voltage rectification module 412.
  • the voltage comparison module 420 may include an operational amplifier 421.
  • a non-inverting input 422 of the operational amplifier 421 is connected to the cathode of the rectify diode D1 ; an inverting input 423 of the operational amplifier 21 is connected to the source of the first threshold voltage V re fi ; a positive power supply of the operational amplifier 421 is connected to GND (i.e. ground); a negative power supply of the operational amplifier 421 is connected to Vcc (i.e. the supply voltage for the operational amplifier 421 ).
  • an output of the operational amplifier 421 is connected to an alarm module 140.
  • the alarm signal being a low electrical level signal (e.g 0) is output when the rectified L2E sample voltage (VFUE) is lower than the first threshold voltage
  • the normal signal being a high electrical level signal (e.g 1 ) is output when the rectified L2E sample voltage (VFUE) is higher than the first threshold voltage
  • a inverting input 423 of the operational amplifier 421 is connected to the cathode of the rectify diode D1 ; an non-inverting input 422 of the operational amplifier 421 is connected to the source of the first threshold voltage V re fi ; a positive power supply of the operational amplifier 421 is connected to Vcc; a negative power supply of the operational amplifier 421 is connected to GND; preferably, an output of the operational amplifier 421 is connected to an alarm module 140.
  • the alarm signal being a high electrical level signal (e.g 1 ) is output when the rectified L2E sample voltage (VR.LE) is lower than the first threshold voltage
  • the normal signal being a low electrical level signal (e.g 0) is output when the rectified L2E sample voltage (VR.LE) is higher than the first threshold voltage.
  • the common terminal of the voltage sample circuit 311 , the voltage division circuit 630, the voltage rectification module 312 and the voltage comparison module 120 is a common voltage reference.
  • the common terminal of the voltage sample circuit 311 , the voltage division circuit 630, the voltage rectification module 412 and the voltage comparison module 420 is a common voltage reference.
  • a common voltage reference of the voltage sample circuit 311 and the voltage division circuit 630 is different from a common voltage reference of the voltage rectification module 312 and the voltage comparison module 120.
  • a common voltage reference of the voltage sample circuit 311 , the voltage division circuit 630 and the voltage rectification module 312 is different from a voltage reference terminal of the voltage comparison module 120.
  • the first string of resistors (including a first sample resistor and a second sample resistor) connected between the line conductor L and the metal enclosure has two functions: firstly it is used to sample a line-to- enclosure sample voltage across the second sample resistor (VS.LE) and secondly it can be used to ensure an insulation between the line conductor L and the enclosure.
  • VS.LE second sample resistor
  • the second string of resistors (including a first divider resistor and a second divider resistor) connected between the neutral conductor N and the metal enclosure has three functions: firstly it is used to divide or split the main voltage (VL-N) between the line conductor L and the neutral conductor N, secondly it can be used to ensure an insulation between the neutral conductor N and the enclosure. In this manner, even through the operators touch one or more parts of the AC equipment, e.g. the circuit along the bold line shown in Fig.
  • the electric current passing through the body of the operators will be reduced compared with the used main voltage, thereby further increasing the safety of the circuit, and thirdly it is used to sample a neutral-to-enclosure sample voltage (VS.NE) across the second divider resistor R22.
  • VS.NE neutral-to-enclosure sample voltage
  • the rectified L2E sample voltage (VR,LE) across the second sample resistor is compared with a first threshold voltage
  • the rectified N2E sample voltage (VR.NE) across the second divider resistor is compared with a second threshold voltage.
  • an electrical shock hazard on the metal enclosure is detected when the rectified sample voltage (V R.LE) is lower than the first threshold voltage and the rectified sample voltage (V R.NE) is higher than the second threshold voltage.
  • a double check is done, thereby improving the detection accuracy and allowing fulfilling the operators' safety requirement with a higher degree of accuracy compared with standard methods.
  • Figure 8 or 9 illustrates an exemplary circuit schematic diagram of a circuit for detecting electrical shock hazard on a metal enclosure of AC equipment of Fig. 1.
  • a voltage sample and rectifying module 810 includes: a rectify diode D1 , a first resistor R 8 i and a second resistor Rs2 connected in series with each other.
  • the anode of the rectify diode D1 is connected to the line conductor L and an end of the second resistor Rs2 is connected to the metal enclosure.
  • a filter capacitor C1 and a discharging R3 resistor are connected in parallel, and both the filter capacitor C1 and the discharging resistor R3 are connected between the common end between the first resistor Rsi and the second resistor Rs2, and the metal enclosure.
  • the voltage sample and rectifying module 810 is configured to output the rectified L2E sample voltage (VR.LE) to the voltage comparison module 420, the rectified L2E sample voltage (VR, L E) being a voltage across the second resistor Rs2.
  • the voltage comparison module 420 is connected to the common end between the first resistor R 8 i and the second resistor Rs2.
  • a voltage sample and rectifying module 910 includes a first resistor R91 , a rectify diode D1 and a second resistor R92 connected in series with each other, an end of the first resistor R91 being connected to the line conductor L and an end of the second resistor R92 being connected to the metal enclosure.
  • a filter capacitor C1 and the discharging resistor f3 ⁇ 4 are connected in parallel, and both are connected between the common end between the cathode of the rectify diode D1 and the second resistor R92, and the metal enclosure.
  • the voltage sample and rectifying module 910 is configured to output the rectified L2E sample voltage (VR.LE) to the voltage comparison module 420, the rectified L2E sample voltage (VR,LE) being a voltage across the second resistor R92.
  • the voltage comparison module 420 is connected to the common end between the cathode of the rectify diode D1 and the second resistor R92.
  • Fig. 10 illustrates an exemplary block diagram of AC equipment according to an embodiment of the present invention.
  • the AC equipment includes a metal enclosure 10 which is a device housing and a detection circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment as described above.
  • the AC equipment includes a power supply unit (PSU) 150 being configured to convert an input AC voltage (for example, 220Vac or 110Vac) to a DC voltage (for example, 3.3Vdc or 5Vdc) being a power supply for internal use in the AC equipment.
  • PSU power supply unit
  • the AC equipment may be an AC base station, the detection circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment may be deployed in an area which is provided by a power supply unit (PSU) included in the AC base station.
  • circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment of this embodiment may be specifically implemented according to the above embodiments; reference may be made to related description in the above embodiment, which is not repeated herein.
  • FIG. 11 illustrates an exemplary block diagram of a communication system according to an embodiment of the present invention.
  • the communication system includes an AC equipment 1100 and a power system 1101 for supplying power to the AC equipment.
  • the power system 1101 may be deployed at a distance away from a foundation of a tower of the communication system, for example, the distance may be larger than 300 meter, and the AC equipment 1100 is deployed on a tower of the communication system (for example, deployed on a top of the tower of the communication system), the power system 1101 is configured to convert the high voltage A.C. (e.g 10KVac) from the electricity distribution system to a normal low mains voltage A.C. (for example, 220Vac or 1 0Vac) for supplying power to the AC equipment 1100.
  • A.C. e.g 10KVac
  • A.C. normal low mains voltage
  • A.C. for example, 220Vac or 1 0Vac
  • the AC equipment 1 100 includes a metal enclosure and a detection circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment as described above.
  • the AC equipment 1 100 further includes a power supply unit (PSU) being configured to convert an input AC voltage (for example, 220Vac or 110Vac) to a DC voltage (for example, 3.3Vdc or 5Vdc) being a power supply for internal use in the AC equipment.
  • PSU power supply unit
  • the detection circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment of this embodiment may be specifically implemented according to the above embodiments; reference may be made to related description in the above embodiment, which is not repeated herein.
  • Fig. 12 illustrates an exemplary block diagram of a base station system (BSS) according to an embodiment of the present invention. As shown in FIG.
  • the base station system comprising an AC base station 1200 and a power system 1201 for supplying power to the AC base station, wherein the AC base station 1200 comprises a metal enclosure and a detection circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment described above, wherein the AC base station is deployed on a tower of the BSS.
  • the power system is deployed at a distance away from a foundation of a tower of the BSS, for example, the distance may be larger than 300 meter, and the AC base station is deployed on a top of the tower of the BSS, the power system is configured to convert the high voltage A.C. (e.g 10KVac) from the electricity distribution system to a normal low mains voltage (for example, 220Vac or 110Vac) for supplying power to the AC base station.
  • A.C. e.g 10KVac
  • a normal low mains voltage for example, 220Vac or 110Vac
  • the AC equipment may further includes a power supply unit (PSU) being configured to convert an input AC voltage (for example, 220Vac or 110Vac) to a DC voltage (for example, 3.3Vdc or 5Vdc) being a power supply for internal use in the AC equipment.
  • PSU power supply unit
  • an input AC voltage for example, 220Vac or 110Vac
  • DC voltage for example, 3.3Vdc or 5Vdc
  • the base station system further comprises a base station controller 1202; reference may be made to the known prior art, which is not repeated herein.
  • the power system is further configured to convert the high voltage A.C. (e.g 10KVac) from the electricity distribution system to a normal low mains voltage (for example, -48Vdc) for supplying power to the base station controller 1202.
  • A.C. e.g 10KVac
  • a normal low mains voltage for example, -48Vdc
  • the detection circuit for detecting electrical shock hazard on the metal enclosure of the AC equipment of this embodiment may be specifically implemented according to the above embodiments; reference may be made to related description in the above embodiment, which is not repeated herein. It can seen from the above, regardless of whether the metal enclosure of the AC equipment is earthed well or not, the line-to-enclosure sample voltage (VS.LE) between the line conductor and the metal enclosure is sampled, and an electrical shock hazard on the metal enclosure can be detected when the rectified L2E sample voltage (V R.LE) is lower than the first threshold voltage, thus the detection accuracy can be improved or ensured, and the operators' safety requirement of the BSS can be met.
  • V R.LE rectified L2E sample voltage
  • sample resistor divider resistor
  • divider resistor are used for identifying the different resistors based on their location in the circuit.
  • sample divider resistor
  • divider is not intended to limit the resistor to any specific type of resistors.

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Abstract

L'invention concerne un circuit pour détecter un risque de choc électrique sur une enveloppe métallique d'un équipement à courant alternatif. Le circuit comprend un module d'échantillonnage et de redressement de tension et un module de comparaison de tension, le module d'échantillonnage et de redressement de tension étant connecté entre un conducteur de ligne et l'enveloppe métallique, et étant configuré pour échantillonner une tension d'échantillonnage de ligne vers enveloppe, et redresser la tension d'échantillonnage de ligne vers enveloppe (VR,LE) ; et délivrer en sortie la tension d'échantillonnage de ligne vers enveloppe redressée (VR,LE) au module de comparaison de tension. Le module de comparaison de tension est configuré pour comparer la tension d'échantillonnage de ligne vers enveloppe redressée (VR,LE) avec une première tension de seuil, et pour détecter un risque de choc électrique sur l'enveloppe métallique lorsque la tension d'échantillonnage de ligne vers enveloppe redressée (VR,LE) est inférieure à la première tension de seuil.
PCT/EP2015/081174 2015-12-23 2015-12-23 Circuit pour détecter un risque de choc électrique WO2017108134A1 (fr)

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CN201580083343.1A CN108027399B (zh) 2015-12-23 2015-12-23 用于检测电击危险的电路、ac设备、通信系统和基站系统
PCT/EP2015/081174 WO2017108134A1 (fr) 2015-12-23 2015-12-23 Circuit pour détecter un risque de choc électrique

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