EP3990934A1 - Dispositif et procédé de contrôle de câbles électriques cc blindés - Google Patents

Dispositif et procédé de contrôle de câbles électriques cc blindés

Info

Publication number
EP3990934A1
EP3990934A1 EP20737110.5A EP20737110A EP3990934A1 EP 3990934 A1 EP3990934 A1 EP 3990934A1 EP 20737110 A EP20737110 A EP 20737110A EP 3990934 A1 EP3990934 A1 EP 3990934A1
Authority
EP
European Patent Office
Prior art keywords
circuit
monitoring
shielded
power cables
cable
Prior art date
Legal status (The legal status 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 status listed.)
Pending
Application number
EP20737110.5A
Other languages
German (de)
English (en)
Inventor
Felix BRUCKER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Elpro GmbH
Original Assignee
Elpro GmbH
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 Elpro GmbH filed Critical Elpro GmbH
Publication of EP3990934A1 publication Critical patent/EP3990934A1/fr
Pending legal-status Critical Current

Links

Classifications

    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/16—Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
    • G01R27/18—Measuring resistance to earth, i.e. line to ground
    • 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
    • G01R31/58—Testing of lines, cables or conductors

Definitions

  • the invention relates to a device for monitoring shielded DC power cables with a first circuit, a second circuit, a measuring device for measuring a parameter of the first circuit and a measuring device for measuring a parameter of the second circuit, as well as a corresponding method for monitoring shielded DC Power cables.
  • Such cables are used in particular where high currents at medium voltage (up to 1000 V) are required, e.g. for powering traction systems or in direct current charging devices for battery-operated vehicles.
  • Such a cable is usually shielded by a conductive screen in order to protect the actual conductor from external electromagnetic influences and to prevent electromagnetic radiation from escaping into the environment.
  • the shield usually consists of thin, mostly braided or stranded copper wires and can be supplemented with a foil.
  • the shield is protected from the outside by an insulating, corrosion-resistant and waterproof jacket (external insulation). Between the shield and the conductor there is an insulation (inner insulation), which is usually made of a dielectric.
  • a cable monitoring system measures the insulation resistance of the inner insulation on the one hand and the outer insulation on the other. The insulation resistances are compared with the set threshold values.
  • the stated object is achieved by means of the device for monitoring shielded DC power cables according to claim 1.
  • the device according to the invention for monitoring shielded DC power cables has a first circuit and a second circuit. Each of the two circuits has a measuring device with which a parameter of the respective circuit is measured.
  • the shielded DC power cable to be monitored is part of the first and part of the second circuit.
  • the device according to the invention monitors the insulation resistance between conductor and shield and the insulation resistance between shield and earth by means of the two electrical circuits. For this purpose, a parameter of the respective circuit is measured and updated. This parameter is usually the electrical voltage between the respective insulation.
  • the voltages between conductor and screen and between screen and earth are measured and are therefore known.
  • the insulation resistance between conductor and shield and the insulation resistance between shield and earth of the cable to be monitored are unknown and must be determined. Since there are two unknown parameters, a second formula is needed to solve the equation.
  • a second circuit is used for this, which is also connected to the DC power cable like the first circuit.
  • the device has two connections.
  • the first connection is suitable and intended to be connected to the shielded DC power cable to be monitored.
  • the second connection is suitable and intended to be connected to a return conductor (earth) of the DC power cable to be monitored. Because of this arrangement, the resistance of the insulation of the DC power cable can be detected, e.g. by measuring the voltage between the conductor and the connection.
  • part of the first circuit and part of the second circuit as well as the measuring devices for measuring a parameter of the first circuit and / or the second circuit of the device are arranged in a housing.
  • the housing protects the components arranged in it from the weather.
  • the housing consists of an impact-resistant plastic, e.g. ABS, and offers protection against foreign bodies, dripping water and against access with a tool (protection class IP31).
  • the device has a third connection which is suitable and intended to be connected to the shielding of the shielded DC power cable to be monitored. Due to this arrangement, the resistance of the insulation of the DC power cable is detectable, e.g. by measuring the voltage between the conductor and connection (earth). In addition, the resistance between screen and earth can be recorded.
  • two voltage measuring devices are arranged in each of the two circuits.
  • the first voltmeter records the voltage between conductor and ground
  • the second voltmeter the voltage between shield and ground.
  • electrical components of the first circuit are also part of the second circuit. Only a few additional components are therefore required for the second circuit, and the costs and effort involved in production are therefore limited.
  • the electrical components which are arranged in the first circuit and in the second circuit include voltage measuring devices and / or resistors. In particular, the voltage measuring devices are part of the first and the second circuit, which limits the effort and costs of cable monitoring.
  • At least one electrical component is arranged in only one of the two circuits.
  • This electrical component is suitable for changing the voltage in the second circuit with respect to the voltage in the first circuit.
  • a switching element is arranged in the second circuit which is provided and suitable for closing the second circuit.
  • the switching element is usually a PhotoMOS relay that does not require cooling and works without wear. In addition, such a switching element is not disturbed by external magnetic fields.
  • the method according to the invention has three method steps: In the first method step (a), a first measured value is recorded in a first circuit for cable monitoring. In the second method step (b), a second measured value is recorded in a second circuit for cable monitoring. In the third method step c), a calculation is carried out using the first and second measured values.
  • the insulation resistance between conductor and shield and the insulation resistance between shield and earth is determined using the monitored on both circuits.
  • a parameter of the respective circuit is measured and updated.
  • This parameter is usually the electrical voltage between the respective insulation.
  • the voltages between conductor and earth and between shield and earth are measured and are therefore known.
  • the insulation resistance between conductor and shield and the insulation resistance between shield and earth of the cable to be monitored are unknown and must be determined. Since there are two unknown parameters, a second formula is needed to solve the equation.
  • a second circuit is used for this, which is also connected to the DC power cable like the first circuit, and records a second measured value.
  • a current is passed through the first circuit and through the second circuit.
  • the first circuit for cable monitoring and the second circuit for cable monitoring differ structurally.
  • the second circuit has additional components. Therefore, the measured values that are recorded by the first circuit differ from the measured values that are recorded by the second circuit.
  • a current is passed through the first circuit and through the second circuit.
  • the first circuit and the second circuit differ in at least one characteristic value.
  • the second circuit has additional components that change a characteristic value of the second circuit compared to the first circuit. Therefore, the measured values that are recorded by the first circuit differ from the measured values that are recorded by the second circuit. It is therefore possible to calculate the electrical resistances of the outer and inner insulation.
  • the second circuit is closed in a further method step and / or the second circuit is opened in a further method step. The two circuits are used alternately and current flows through them. In this way it is possible to equip both circuits with only a few different components, which limits the costs of the device for cable monitoring.
  • the first measured value is recorded in the first circuit for cable monitoring while the second circuit is open.
  • the second measured value is recorded in the second circuit for cable monitoring while the first circuit is open. The two circuits are used alternately, measured values from the first and second circuits are recorded alternately.
  • the method steps are carried out in the order a), 1), b), 2), c). So first a first measured value of a first circuit is recorded, then a second circuit is closed, then a second measured value of a second circuit is recorded, then the second circuit is opened and, at the end of the process, the resistance of the inner and outer insulation is calculated below Use of the recorded measured values. Due to the difference between the two circuits in at least one characteristic value, it is possible to calculate the resistance of the inner and outer insulation.
  • the method steps are repeated in the order a), 1), b), 2), c) at regular time intervals. So first a first measured value of a first circuit is recorded, then a second circuit is closed, then a second measured value of a second circuit is recorded, then the second circuit is opened and, at the end of the process, the resistance of the inner and outer insulation is calculated below Use of the recorded measured values.
  • the repetition of the process steps ensures a continuous Acquisition of the measured values and thus continuous monitoring of the cable to be monitored.
  • the size of the time intervals is between 0.1 s and 1 h, preferably between 0.5 s and 1 min.
  • the size of the time intervals is particularly dependent on the frequency with which a second circuit can be closed or reopened.
  • the size of the time intervals can be adapted to the available storage capacity, if the measured values of both circuits and the resistance values calculated from them are saved over time.
  • the resistances of the outer and inner insulation of the DC power cable are calculated from the recorded measured values.
  • the voltages between conductor and screen and between screen and earth are measured and are therefore known.
  • the insulation resistance between conductor and shield and the insulation resistance between shield and earth of the cable to be monitored are unknown and must be determined. Since there are two unknown parameters, a second formula is needed to solve the equation. A second circuit is used for this, which is also connected to the DC power cable like the first circuit, and records a second measured value.
  • the calculated values and / or the recorded measured values are compared with previously stored values.
  • the stored values can be adjusted and changed by a user at any time.
  • the stored values then form a setpoint value for an intact external or internal insulation of the cable to be monitored.
  • a signal is output as a function of the result of the comparison of the calculated values and / or the recorded measured values.
  • a comparison of the calculated and / or recorded values with the target values of the resistance for the intact outer or inner insulation of the cable to be monitored leads to an error message if the recorded measured value deviates from the stored target valuea.
  • the error message can take place on the cable monitor itself and / or via wireless contact to a central control device, for example.
  • Fig. 1 A circuit diagram of an embodiment of the cable monitoring
  • Fig. 2 An embodiment of the arrangement of the invention
  • Fig. 3 A detailed circuit diagram of an embodiment of the cable monitoring
  • the cable 2 to be monitored is a direct current traction power supply cable 2.
  • the traction power supply cable 2 to be monitored supplies the contact line with electrical direct current at a voltage of 750 V.
  • the screen voltage between the screen and return conductor is measured using the voltage measuring device UMS on the one hand and the conductor voltage between the conductor and return conductor is measured using the voltage measuring device UMI.
  • the external and internal insulation are calculated from the measured voltages.
  • the cable monitoring device 1 has several voltage dividers.
  • the resistors R sa (50 k ⁇ ) and R si (1200 k ⁇ ) are arranged in the cable monitoring device 1.
  • the cable monitoring device 1 has a control device 3 for the calculation.
  • the resistances R ki (internal insulation) and R ka (external insulation) are calculated, which are shown in this and the following figures as equivalent resistances.
  • the resistance values change and thus the voltage measured by means of the UM S and UMI voltage measuring devices (see table).
  • the control device 3 calculates from the recorded voltages UM S and UMI using the following two equations: and:
  • the voltages UMI and UM S are measured and are therefore known.
  • the resistance value of the traction power supply cable 2, consisting of R ki and R ka is unknown and must be determined. Since there are two unknown parameters, a second equation is needed to solve the equation. For this purpose, the circuit is expanded and a test resistor R ma (45.5 k ⁇ ) is switched on and off periodically by means of the switch S. A second circuit with a different resistance value is thus temporarily added to cable monitoring 1. This second circuit has mostly the same components as the first circuit, only the T est resistance R ma is also available. This changes the resistance of the second circuit.
  • the control device 3 has a computer program with which such a calculation is carried out.
  • Fig. 2 shows an embodiment for the use of the device 1 according to the invention for monitoring a DC traction power supply cable 2.
  • the traction power supply cable 2 to be monitored supplies the contact line 8 of a train 9 with electrical direct current with a voltage of 750 V.
  • the cable monitoring device 1 has three electrical connections A1, A2, A3 each with a power line. All three electrical connections lead from the cable monitoring 1 to the traction power supply cable 2 to be monitored.
  • the first connection A1 is arranged on the outer insulation of the direct current traction power supply cable 2, the second connection A2 on the shield of the direct current traction power supply cable 2.
  • the third connection A3 is on the Grounding of the direct current traction power supply cable 2 arranged, in this embodiment on track 10 of the train.
  • the connections A1, A2, A3 are each connected to the cable monitor 1 via power lines and form a circuit.
  • the cable monitor 1 is arranged in a housing.
  • the housing is made of impact-resistant plastic, e.g. ABS, and offers protection against foreign bodies, dripping water and against access with a tool (protection class IP31).
  • the screen voltage between the screen and the return conductor is measured using the UM S voltage measuring device on the one hand and the conductor voltage between the conductor and the return conductor is measured using the UMI voltage measuring device.
  • the voltages between conductor and earth and between shield and earth are measured and are therefore known.
  • the insulation resistance between conductor and shield and the insulation resistance between shield and earth of the cable to be monitored are unknown and must be determined. Since there are two unknown parameters, a second formula is needed to solve the equation.
  • the power supply of the device 1 according to the invention is provided by the current-carrying conductor 2 to be monitored.
  • the device 1 according to the invention therefore does not require a separate power supply for operation.
  • FIG. 3 A detailed schematic structure of the device 1 according to the invention is shown in Fig. 3.
  • the screen voltage between the screen and return conductor by means of the voltage measuring device UM S on the one hand and the conductor voltage between conductor and return conductor by means of the voltage measuring device UMI measured.
  • the cable monitoring device 1 has several voltage dividers.
  • the second circuit, periodically closed and opened by switch S1, has the resistance R ma .
  • the resistors R sa (50 k ⁇ ) and R si (1200 k ⁇ ) and R ma (45.5 k ⁇ ) are arranged in the cable monitoring device 1.
  • the power supply of the cable monitoring device 1 takes place through the current-carrying conductor 2 to be monitored and provided with a shield 2.1 and a Graetz bridge arranged in the power supply.
  • the power consumption of cable monitoring 1 is a maximum of 10 W.
  • a 16-bit A / D converter 4 is used to convert the voltages UM S and UMI recorded by the voltage measuring devices, which is connected to the microcontroller via a data bus connection (preferably SPI) 3 is connected.
  • the limit values for the inner and outer insulation are set using rotary switches 6, which are arranged on the cable monitor 1. If the calculated resistances fall below the set limit value for a certain time, a cable fault is displayed.
  • the setting range of the threshold values is 200 kQ ⁇ R ki ⁇ 2 MW and 0 kQ ⁇ R ka ⁇ 500 kQ. These parameters are specified in 16 steps and are read in directly by the micro-controller.
  • a fault in the inner and / or the outer insulation of the traction power supply cable 2 is indicated in this exemplary embodiment by LEDs on the cable monitoring device 1 itself. Additionally or optionally, an error can also be sent to a remote central monitoring device in a wired or wireless manner.
  • three outputs A connected by means of a driver T each extend from the microcontroller 3.
  • a test button PT and an interface I are provided
  • the cable monitoring device 1 is designed to determine and output a measured value of the shield voltage between the shield and the return conductor by means of the voltage measuring device U MS on the one hand and the conductor voltage between the conductor and return conductor by means of the voltage measuring device UMI every second.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Resistance Or Impedance (AREA)

Abstract

L'invention concerne un dispositif de contrôle de câbles électriques CC blindés, lequel dispositif de contrôle comporte un premier circuit, un second circuit, un dispositif de mesure servant à mesurer un paramètre du premier circuit et un dispositif de mesure servant à mesurer un paramètre du second circuit, le câble électrique CC blindé à contrôler étant une partie du premier circuit et une partie du second circuit. La présente invention concerne également un procédé correspondant de contrôle de câbles électriques CC.
EP20737110.5A 2019-06-28 2020-06-26 Dispositif et procédé de contrôle de câbles électriques cc blindés Pending EP3990934A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102019004666 2019-06-28
PCT/EP2020/068172 WO2020260674A1 (fr) 2019-06-28 2020-06-26 Dispositif et procédé de contrôle de câbles électriques cc blindés

Publications (1)

Publication Number Publication Date
EP3990934A1 true EP3990934A1 (fr) 2022-05-04

Family

ID=71523117

Family Applications (1)

Application Number Title Priority Date Filing Date
EP20737110.5A Pending EP3990934A1 (fr) 2019-06-28 2020-06-26 Dispositif et procédé de contrôle de câbles électriques cc blindés

Country Status (3)

Country Link
EP (1) EP3990934A1 (fr)
DE (1) DE102020116973A1 (fr)
WO (1) WO2020260674A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4089422A1 (fr) * 2021-05-12 2022-11-16 Schneider Electric Industries SAS Dispositif et procédé d estimation de l impédance d'isolation d'un réseau tt ou tn

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2264288A1 (en) * 1974-03-14 1975-10-10 Feuillassier Robert Insulation and resistance control for heating cable - has two transistor amplifier detectors connected to alarms
DE19725611C2 (de) * 1997-06-17 2001-03-08 Siemens Ag Überwachungsverfahren und Überwachungsgerät für ein Kabel
FR2805349B1 (fr) * 2000-02-23 2002-04-26 Socrat Procede de mesure des caracteristiques electriques d'un cable de telecommunication

Also Published As

Publication number Publication date
WO2020260674A1 (fr) 2020-12-30
DE102020116973A1 (de) 2020-12-31

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