METHOD AND DEVICE FOR IDENTIFYING AND LOCATING CYCLIC MOMENTARY INSULATION FAULTS IN AN UNDERGROUND POWER SUPPLY SYSTEM

Abstract

The invention relates to a method and a device for identifying and locating cyclic momentary insulation faults in an ungrounded power supply system, the method comprising the steps: detecting a fault current caused by the momentary insulation fault as a differential current in the branch circuit to be monitored and displaying the temporal progression of the differential current via a differential current signal by means of a differential current sensor; providing a processing signal which temporally describes a process sequence of a process taking place in the consumer; correlating the differential current signal with the processing signal in a computing unit in order to yield a correlation signal as a measure for a temporal match between the differential current signal and the processing signal; signaling the momentary insulation fault via the computing unit by means of a signaling signal if the correlation signal shows the temporal match. The device according to the invention has a differential current sensor and a computing unit so that it can implement the method according to the invention.

Claims

1-10. (canceled)

11. A method for identifying and locating cyclic momentary insulation faults in an ungrounded power supply system having a consumer connected via a branch circuit, the method comprising the steps: detecting a fault current caused by the momentary insulation fault as a differential current in the branch circuit being monitored and displaying the temporal progression of the differential current via a differential current signal by means of a differential current sensor, providing a processing signal which temporally describes a process sequence of a process taking place in the consumer, correlating the differential current signal with the processing signal in a computing unit in order to yield a correlation signal as a measure for a temporal match between the differential current signal and the processing signal, and signaling the momentary insulation fault via the computing unit by means of a signaling signal if the correlation signal shows the temporal match.

12. The method according to claim 11, further including generating the processing signal by means of a sensor device by detecting a process parameter related to the process and by displaying the temporal progression of the process parameter.

13. The method according to claim 12, further including detecting as a process parameter a physical variable describing the process sequence or a variable derived therefrom.

14. The method according to claim 13, further including correlating as a process signal a control signal leading the process sequence.

15. The method according to claim 14, further including detecting, by means of a voltage measuring device, between an active conductor of the underground power supply system and ground, the temporal progression of a displacement voltage as a residual voltage signal and correlating with the differential current signal in the computing unit.

16. The method according to claim 11, further including correlating as a process signal a control signal leading the process sequence.

17. The method according to claim 12, further including correlating as a process signal a control signal leading the process sequence.

18. The method according to claim 11, further including detecting, by means of a voltage measuring device, between an active conductor of the underground power supply system and ground, the temporal progression of a displacement voltage as a residual voltage signal and correlating with the differential current signal in the computing unit.

19. The method according to claim 12, further including detecting, by means of a voltage measuring device, between an active conductor of the underground power supply system and ground, the temporal progression of a displacement voltage as a residual voltage signal and correlating with the differential current signal in the computing unit.

20. The method according to claim 13, further including detecting, by means of a voltage measuring device, between an active conductor of the underground power supply system and ground, the temporal progression of a displacement voltage as a residual voltage signal and correlating with the differential current signal in the computing unit.

21. A device configured for identifying and locating cyclic momentary insulation faults in an ungrounded power supply system having a consumer connected via a branch circuit, comprising a differential current sensor configured for detecting a fault current caused by the momentary insulation fault as a differential current in the branch circuit being monitored and displaying the temporal progression of the differential current via a differential current signal, a computing unit configured for (a) receiving a processing signal which temporally describes a process sequence of a process taking place in the consumer, (b) correlating the differential current signal with the processing signal in order to yield a correlation signal as a measure for a temporal match between the differential current signal and the processing signal, and (c) signaling a momentary insulation fault by means of a signaling signal if the correlation signal shows the temporal match.

22. The device according to claim 21, further including a sensor device configured to generate the processing signal by detecting a process parameter related to the process and by displaying the temporal progression of the process parameter.

23. The device according to claim 22, wherein the sensor device is configured for detecting a physical variable describing the process sequence or a variable derived therefrom as a process parameter.

24. The device according to claim 23, wherein the processing signal is a control signal operating the process sequence.

25. The device according to claim 24, further including a voltage measuring device configured for detecting the temporal progression of a displacement voltage between an active conductor of the ungrounded power supply system and ground as a displacement voltage signal, which is correlated with the differential current signal in the computing unit.

26. The method according to claim 21, further including correlating as a process signal a control signal leading the process sequence.

27. The method according to claim 22, further including correlating as a process signal a control signal leading the process sequence.

28. The method according to claim 21, further including detecting, by means of a voltage measuring device, between an active conductor of the underground power supply system and ground, the temporal progression of a displacement voltage as a residual voltage signal and correlating with the differential current signal in the computing unit.

29. The method according to claim 22, further including detecting, by means of a voltage measuring device, between an active conductor of the underground power supply system and ground, the temporal progression of a displacement voltage as a residual voltage signal and correlating with the differential current signal in the computing unit.

30. The method according to claim 23, further including detecting, by means of a voltage measuring device, between an active conductor of the underground power supply system and ground, the temporal progression of a displacement voltage as a residual voltage signal and correlating with the differential current signal in the computing unit.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0046] FIG. 1 shows a method sequence according to the invention,

[0047] FIG. 2 shows a device according to the invention for identifying and locating cyclic momentary insulation faults in an ungrounded three-phase (3AC) power supply system, and

[0048] FIG. 3 shows a device according to the invention for identifying and locating cyclic momentary insulation faults in an ungrounded direct voltage (DC) power supply system.

DETAILED DESCRIPTION

[0049] With an ungrounded power supply system 2 having a connected consumer 6 as its base, FIG. 1 shows the interaction according to the invention between method steps S1 to S4 of the method for identifying and locating cyclic momentary insulation faults.

[0050] In step S1, a differential current ΔI is detected in a branch circuit 4 to be monitored and forwarded to a computing unit 16 as a differential current signal Id by means of a differential current sensor 12.

[0051] Simultaneously in step S2, a process parameter 8 of a process taking place in consumer 6 is detected by means of a sensor device 14 and also transmitted to computing unit 16 as a processing signal Ip in its temporal progression. As a supplementing or alternative processing signal Ip, computing unit 16 can receive a control signal Ix directly from a process sequence control system 7.

[0052] In step S3, differential current signal Id is correlated with (compared to) processing signal Ip in computing unit 16 to identify to what extent the temporal progressions show a match (similarity), i.e., have a temporal synchronicity. For this purpose, a correlation signal Ic is computed and a signaling signal Is is generated if correlation signal Ic shows a temporal match between differential current signal Id and processing signal Ip, e.g., by certain threshold values or signal patterns having distinct maxima, as a measure for the similarity of both signals.

[0053] In FIG. 2, a device 10 according to the invention for identifying and locating cyclic momentary insulation faults Rf is shown in a functional block diagram.

[0054] As the system environment for the application of the invention, a single-phase or multiphase IT system 2 is generally presumed. FIG. 2 shows a three-phase ungrounded power supply system 2 having active conductors L1, L2, L3 and branch circuits 4, which are to be monitored and to which consumer 6 is connected.

[0055] A differential current sensor 12 detects differential current ΔI in branch circuit 4 and generates differential current signal Id, which is supplied to computing unit 16.

[0056] A process sequence control system 7 (not part of the invention) controls the process taking place in consumer 6, process parameter 8 being detected simultaneously by means of sensor device 14 by monitoring differential current ΔI. Sensor device 14 generates a processing signal Ip, which corresponds to the temporal progression of detected parameter 8 and is forwarded to computing unit 16.

[0057] Sensor device 14 can be a current measuring device for measuring a load current as a process parameter 8, for example for a physical or chemical process operated by means of an electric machine, or a motion sensor for detecting a motion sequence for a mechanical process. Furthermore, optical and acoustic sensor devices 14, in particular with regard to a preventive maintenance, are also possible for measuring further physical variables.

[0058] Additionally or alternatively to processing signal Ip generated by sensor device 14, analog or digital information is supplied to computing unit 16 directly from process sequence control system 7 via processing signal Ix operating the process sequence.

[0059] In computing unit 16, differential current signal Id correlates with at least one of the supplied processing signals Ip, and a correlation signal Ic is computed as a result.

[0060] If correlation signal Ic shows a temporal match between differential current signal Id and processing signal Ip, for example in the form of synchronous artifacts or concurring periodicities, a momentary insulation fault Rf is signaled via signaling signal Is.

[0061] In the case of detecting a load current signal as processing signal Ip, a displacement voltage ULx can be additionally detected between one or several active conductors L1, L2, L3 and ground PE by means of a voltage measuring device 20 and is forwarded to computing unit 16 as displacement voltage signal Uv in order to make possible more reliably detecting a cyclic momentary insulation fault Rf by taking into consideration displacement voltage signal Uv with another correlation computation.

[0062] FIG. 3 shows device 10 according to the invention for detecting and locating cyclic momentary insulation faults Rf in conjunction with an ungrounded direct voltage power supply system 2, which has active conductors L+ and L−. The circuit structure of device 10 according to the invention is implemented in the same manner as in FIG. 2. Besides being suitable for detecting a direct differential current ΔI, differential current sensor 12 is also configured for detecting a direct differential current ΔI to derive differential current signal Id.