DETECTOR FOR HIGH INTENSITY ELECTRICAL CURRENTS

Abstract: The invention discloses a detection- and recording system for high intensity electric currents such as lightning currents in a lightning conductor in a wind turbine. The system comprises a detector (6) containing a power supply (7), a measuring circuit (8), and a converter means (9) and furthermore a recording means (11) non-galvanically coupled to said converter means (9) and a measuring coil (5) to be inductively coupled to an electric conductor (2) carrying the high intensity electric current. The power supply (7) receives its electrical energy directly from the lightning current via the power coil (4) which makes the system non-sensitive to mains supply drop-outs.

Description: DETECTOR FOR HIGH INTENSITY ELECTRICAL CURRENTS TECHNICAL FIELD The present invention relates generally to detection and recording of high intensity electrical currents and more particularly to detection and recording of lightning currents flowing in a lightning conductor for instance in a wind turbine BACKGROUND ART In order to guarantee adequate maintenance of systems which could potentially be subjected to unwanted high intensity electric currents flowing through the system, for instance if the system forms part of the lightning current path in a lightning conductor, it is often required continuously to monitor the system and to measure and record the intensity of lightning currents, the date of the lightning current and the number of the occurrences of lightning currents within a given period of time A method and an apparatus for measuring and recording a lightning current in a lightning conductor is disclosed in EP-0,757,797 ("Method for monitoring lightning protection equipment") This apparatus basically comprises a magnetic core around the lightning conductor such that a lightning current flowing in the lightning conductor will generate a magnetic field in the core A winding is disposed around said core such that said magnetic field by means of induction will generate an electric current in the winding The winding is coupled to a measuring circuit and a recording circuit which records the intensity of the lightning current and the date of the lightning current These circuits are powered by means of a power supply Furthermore, the recorded data can be forwarded to a telephone line via a non- galvanic coupling (for security reasons) In order to guarantee un-interrupted operation of a monitoring system for lightning protectors, it is important that the power supply which supplies monitoring circuits with electric energy should be protected against failure for instance caused by a power line drop-out, a failure which might remain unnoticed for a period of time One method of circumventing such problems is to provide the system with some kind of power supply backup means, but a more advantageous solution would be to be able to avoid a power-line-dnven power supply altogether The present invention addresses this possibility DISCLOSURE OF THE INVENTION It is the object of the present invention to provide a detector for high intensity electric currents such as lightning currents in a lightning conductor, for instance in a wind turbine, said detector continuously monitoring lightning currents in the lightning conductor where said detector provides improved reliability, in that the power needed by the detector means is provided by the lightning current itself instead of by a power supply coupled to the mains supply This object is achieved by the aid of a system comprising the features set forth in the characterising clause of claim 1 One specific embodiment hereof is defined in claim 2 It is a further object of the present invention to provide a safe and reliable transmission of data from said detector to succeeding recording and/or processing equipment located at a remote position relative to the detector This object is achieved according to the features set forth in the characterising clause of claim 3 Further advantageous embodiments of the invention are described in the remaining independent claims The advantageous effect of the present invention is that the operation of the detector is independent of external power supply, so that its operation remains unaffected by for instance drop-outs of mains voltage Such drop-outs are typical in connection with lightning activity and in some places mains supply is even deliberately shut down during lightning activity Drop-outs of mains supply during lightning activity is thus a typical situation BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of exemplifying embodiments hereof and with reference to the accompanying drawing in which Figure 1 is a schematic block diagram of a lightning current path and associated lightning detector connected to a computer as used in a wind turbine according to the invention DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows an embodiment of the present invention specifically to be used in a wind turbine The Figure schematically shows a lightning conductor 2 located inside each of the blades of the wind turbine and connecting the tip of the blade 1 in a manner known per se via parts of the mechanical components of the wind turbine (not shown on the drawing) to ground 3 The detector 6 comprises an internal power supply 7 for the detector itself, a measuring circuit 8 which measures the intensity of the lightning current flowing in the lightning conductor 2 located in the blade of the wind turbine and a converter means 9 receiving the output signal from the measuring circuit 8 and converting this signal into a suitable form to be transmitted via the non-galvanic connection to a recording and/or processing means, here shown as the computer 11 One suitable means of transmission of signals between the detector 6 and the recording/procession means 11 would be by means of an optical fibre In this case the converter means 9 should convert for instance the electrical output signal from the measuring circuit 8, being a function of the intensity of the lightning current, into a light signal of an intensity and spectral composition suitable for the following optical fibre 10 A corresponding inverse converter means (not shown) would then be provided at the recording/processing means 11 The input to the measuring circuit 8 consists in the embodiment shown in Figure 1 of an electrical signal provided by a measuring coil 5 placed in close proximity to the lightning conductor 2, such that a lightning current flowing in the lightning conductor 2 by way of induction generates a voltage across the two terminals of the measuring coil 5 A construction of the measuring coil resembling the arrangement shown in above-mentioned EP-0,757,797 could for instance be used, although many other layouts could be conceived by somebody skilled in the art A very essential part of the present invention is the power supply 7 which in the present embodiment is being provided with electrical energy from the lightning current via the power coil 4, across the terminals of which a voltage is rapidly built up, as soon as a lightning current begins to flow through the lightning conductor The power supply 7 provides DC voltages to the measuring circuit 8 and the converter means 9 The power supply 7 is capable of providing DC voltages and maintaining the necessary DC voltage throughout the period of time, in which the measuring circuit 8 and the converter means 9 should be functioning The dynamics of the power supply 7 and its power coil 4 must thus be optimised to the dynamics of the measuring circuit 8 and the converter means 9 In the embodiment shown in Figure 1 and described above, two separate coils, the power coil 4 and the measuring coil 5 are used It is also possible in an alternative embodiment of the invention to replace these two coils with one common coil providing both the necessary energy for the power supply 7 and the measuring signed for the measuring circuit 8 This solution is, however, technically more complicated, and hence two separate coils 4,5 have been employed in the embodiment shown in Figure 1 The present invention has been described above with reference to one specific embodiment hereof, but it should be understood that other embodiments, for instance of the connection means between the lightning current and the power supply 4 and/or between the converter means 9 and the recording/processing means 11 , which would be conceivable by somebody skilled in the art, would also fall within the scope of the present invention

Claims: CLAIMS 1 Detection- and recording system for high intensity electric currents comprising a detector (6) containing at least a power supply (7), a measuring circuit (8), and a converter means (9) where said system furthermore comprises a recording means (11) non-galvanically coupled to said converter means (9) and a measuring coil (5) to be inductively coupled to an electric conductor (2) carrying said high intensity electric current, characterized in that said power supply (7) receives its electric energy from said high intensity current via a non-galvanic coupling (4) 2 System according to claim 1 , characterized in that said non-galvanic coupling between said power supply (7) and said electric conductor (2) is an inductive coupling provided via a power coil (4) 3 System according to any of the preceding claims, characterized in that said non-galvanic coupling between said converter means (9) and said recording means (11) is accomplished by the aid of fibre optics (10) 4 System according to any of the preceding claims, characterized in that said high intensity current is the lightning current flowing in a lightning conductor (2) 5 System according to claim 4, characterized in that said measuring circuit (8) measures the intensity of said high intensity electric current 6 System according to claim 4, characterized in that said recording means (11) records the intensity of said high intensity electric current and furthermore records the number of lightnings and the time of occurrence of these lightnings 7 System according to any of the preceding claims, characterized in that said measuring coil (5) and said power coil (4) is combined into one common coil

Inventors: FAERCH HENRIK, KLEMAR BENNY AARIS, FAERCH, HENRIK, KLEMAR, BENNY, AARIS
Applicants: FAERCH HENRIK, KLEMAR BENNY AARIS, VESTAS WIND SYS AS, FAERCH, HENRIK, KLEMAR, BENNY, AARIS, VESTAS WIND SYSTEMS A/S
Application year: 1999
Main classification: G01R29
IPC codes: F03D11, G01R19, G01R29