METHOD AND MEASURING ASSEMBLY FOR DETECTING FAULTS ON ELECTRICAL LINES

Abstract

A method for detecting faults on an electrical line includes feeding a measurement signal to a first location on the line by using a measuring assembly, receiving a reflected measurement signal at the first location, and determining a fault location on the line on the basis of the period of time until the reflected measurement signal is received while considering a line attenuation. A reflection location on the line where the measurement signal is reflected is used, and the line attenuation is determined on the basis of the level of the reflected measurement signal received at the first location. A corresponding measuring assembly is also provided.

Claims

1-15. (canceled)

16. A method for fault detection on an electrical line, the method comprising: feeding-in a measurement signal at a first location on the line by using a measuring assembly; reflecting the measurement signal at a reflection location on the line; receiving the reflected measurement signal at the first location; determining a fault location on the line based on a time duration until reception of the reflected measurement signal while taking a line attenuation into consideration; and determining the line attenuation based on a level of the reflected measurement signal received at the first location.

17. The method according to claim 16, which further comprises providing an impedance apparatus at the reflection location.

18. The method according to claim 17, which further comprises using a choke coil as the impedance apparatus.

19. The method according to claim 16, which further comprises providing the measurement signal in a kilohertz frequency range.

20. The method according to claim 16, which further comprises providing the measurement signal with a frequency in a frequency range of from 50 kHz to 5 MHz.

21. The method according to claim 16, which further comprises compensating the line attenuation by normalizing the level of the measurement signal reflected from the reflection location to zero decibels, and raising the level of the reflected measurement signal linearly along a length of the line.

22. The method according to claim 21, which further comprises specifying a first threshold value for the level of the normalized reflected measurement signal, and detecting a fault on the line upon exceeding the first threshold value.

23. The method according to claim 21, which further comprises adjusting the compensation of the line attenuation with a regular time cycle, in order to compensate for a change in the line attenuation resulting from a temperature change in an environment of the line.

24. The method according to claim 16, which further comprises determining the reflection location based on the time duration until the reception of the reflected measurement signal and taking the line attenuation into account.

25. The method according to claim 22, which further comprises specifying a second threshold value for the level of the normalized reflected measurement signal, and detecting at least one of a fault in the measuring assembly or a line attenuation being so large that a reliable fault location determination is not possible, when the level falls below the second threshold value.

26. . A measuring assembly for fault detection on an electrical line, the measuring assembly comprising: a signal generator apparatus disposed at a first location on the line and configured to feed a measurement signal into the line; a reception apparatus disposed at the first location and configured to receive a reflected measurement signal reflected from a reflection location on the line; and an evaluation apparatus configured to determine a fault location on the line based on a time duration until reception of the reflected measurement signal while taking a line attenuation into consideration. said evaluation apparatus configured to determine the line attenuation based on a level of the reflected measurement signal received at the first location.

27. The measuring assembly according to claim 26, wherein said evaluation apparatus is configured to compensate the line attenuation by normalizing the level of the measurement signal reflected from the reflection location to zero decibels, and raising the level of the reflected measurement signal linearly along a length of the line.

28. The measuring assembly according to claim 27, wherein said evaluation apparatus is configured to specify a first threshold value for the level of the normalized reflected measurement signal, permitting a fault to be detected on the line upon exceeding the first threshold value.

29. The measuring assembly according to claim 27, wherein said evaluation apparatus is configured to adjust the compensation of the line attenuation with a regular time cycle, to compensate for a change in the line attenuation resulting from a temperature change in an environment of the line.

30. The measuring assembly according to claim 26, wherein said evaluation apparatus is configured to determine the reflection location based on the time duration until reception of the reflected measurement signal and taking the line attenuation into consideration.

Description

[0048] To better explain the invention:

[0049] FIG. 1 shows a first schematic reflection diagram of an electrical line; and

[0050] FIG. 2 shows a second schematic reflection diagram of an electrical line with compensation of the line attenuation; and

[0051] FIG. 3 shows a third schematic reflection diagram of an electrical line with compensation of the line attenuation and a first threshold value for a fault detection; and

[0052] FIG. 4 shows a fourth schematic reflection diagram of an electrical line with changed line attenuation; and

[0053] FIG. 5 schematically shows a measuring assembly.

[0054] FIG. 1 shows a first reflection diagram of an electrical line. The length of the line is here plotted in kilometers on the horizontal axis. The level, or the maximum amplitude of a reflected measurement signal 1 received at the first end of the line—at zero kilometers—is plotted in decibels on the vertical axis A. By definition, a received signal level of zero decibels corresponds to the signal level of the original measurement signal that is fed in. In the illustrated example, the line is 190 km long, so that a high level results for an end reflection 2 at the second end of the line at line length L of 190 km. It can be seen that the level of the reflected signal continues to fall with increasing line length.

[0055] FIG. 2 shows a second reflection diagram of an electrical line with compensation of the line attenuation. The level of the reflection at the line end—the end reflection—is used continuously to determine the line attenuation and to adjust the detection threshold accordingly. The level of the end reflection 2 is determined after each reflection measurement, as for example in FIG. 1. The line attenuation can be compensated making the assumption that the end reflection 2 usually corresponds to a total reflection, and that the line attenuation increases proportionally with the line length. The level of the reflection signal 4 is for this purpose increased linearly with the line length in such a manner that the level of the end reflection 3 in FIG. 2 is at 0 dB.

[0056] FIG. 3 shows that a first threshold value can be placed as a horizontal line 5 with a specified clearance underneath the zero line (zero decibels) as a detection threshold for line faults. A constant sensitivity to faults over the entire line length is achieved in this way, which is a significant advantage of the method of the invention.

[0057] This method is, for example, both applied to the first measurement following installation as well as in further operation in order to determine the line attenuation continuously and to compensate for it at the next measurement.

[0058] FIG. 4 shows a measurement in which the actual line attenuation differs from the previously compensated line attenuation, and should be adjusted in the next measurement. The level of the end reflection lies a few decibels above the zero line. The reflection diagram should again correspond to FIG. 2 after the adjustment.

[0059] A typical frequency range for a reflection measurement with a measurement signal in high-voltage lines lies between 30 kHz and 5 MHz.

[0060] FIG. 5 shows a measuring assembly 7, 8, 9, 10 for fault detection on an electrical line 6, comprising a signal generator apparatus 7 that is arranged at a first end 11 of the line 6 and is designed to feed a measurement signal into the first end 11 of the line 6. A reception apparatus 8 that is arranged at the first end 11 of the line 6 is designed to receive the reflected measurement signal.

[0061] An evaluation apparatus 9 is designed to determine a fault location 13 on the line 6 on the basis of the time duration until reception of the reflected measurement signal while taking a line attenuation into consideration.

[0062] The signal generator apparatus 7 and the reception apparatus 8 are integrated, together with the evaluation apparatus 9, into a first communication device 15 for power line communication over the line 6. The first communication device 15 comprises a choke 16.

[0063] An impedance apparatus 10 that is designed as a choke 10 and is integrated into a second communication device 14 for power line communication over the line 6 is arranged at the second line end 12. The choke 10 is suitable for reflecting the measurement signal.

[0064] The reception apparatus 8 is further designed to receive the end reflection of the measurement signal from the second line end 12. The evaluation apparatus 9 is designed as a conventional computer, and can determine the line attenuation on the basis of the level of the end reflection.