Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
  • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
  • G01R15/146—Measuring arrangements for current not covered by other subgroups of G01R15/14, e.g. using current dividers, shunts, or measuring a voltage drop
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
  • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
  • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
  • G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core

Definitions

• the invention relates to a current transformer according to the preamble of claim 1.
• current transformers which have a toroidal core which comprises the conductor carrying the high voltage and on whose secondary winding the measuring signal is taken;
• the core is located on the inside of the encapsulation and includes the inner conductor, as has already been described many times. This so-called conventional current transformers are normally used to measure currents whose frequency is in the range of the mains frequency.
• Newer network protection systems can improve error detection because they can process measurement signals that have significantly higher frequencies.
• the so-called conventional transducers have relatively inadequate high-frequency transmission properties and often also lack linearity, the advantages of the new network protection systems cannot be fully exploited, see Schwab, Hochhardsmeßtechnik, Springer Verlag, Berlin, Heidelberg, New York, 1981, 2nd edition, page 176, first paragraph. In this reference further problems are explained which can occur with the so-called conventional current transformers.
• Non-conventional transducers have been developed, which are based on electro-optical and magneto-optical effects. For example, it has become known from DE-OS 39 24 369 to use a so-called Pockels cell which is penetrated by an electric field generated by the short-circuit current. With this arrangement, higher-frequency, transient short-circuit currents can also be detected.
• DE-OS 39 24 369 it has become known from DE-OS 39 24 369 to use a so-called Pockels cell which is penetrated by an electric field generated by the short-circuit current. With this arrangement, higher-frequency, transient short-circuit currents can also be detected.
• Pipe section is electrically conductively connected to the radial step walls of the circumferential depression.
• the conductor carries the operating current in the inner region of the depression and, due to the so-called skin effect, a high-frequency current flows in the region of the outer circumference of the conductor and thus through the pipe piece, so that such transient and high-frequency overcurrents can be measured without problems .
• the interior can be filled with the gas or the liquid that is used as the insulating medium within the encapsulation. If air is used, the depression can also be filled with air. There is also the possibility of filling the cavity with solid insulating material.
• the pipe section can be formed as a thin film, the thickness of the film also being dependent on the frequencies occurring.
• An advantageous embodiment of the invention can be gathered from the features of claim 5, whereby the analog measured voltage signals on the pipe section are preferably converted into digital signals which are transmitted from a light transmitter directly or onto a light guide and to the outside by means of the light guide Evaluation unit are emitted or executed.
• the supply of the converter circuit arrangement takes place according to the characterizing features of claim 7 by means of a capacitive voltage converter.
• the transmission circuit arrangement which is in the form of a converter circuit arrangement with a light transmitter, is at a high potential in the current-carrying inner conductor.
• the temperature of the inner conductor can reach over 80 ° C. Temperature rises up to 130 C cannot be excluded.
• microelectronics and the associated optoelectronics are, however, only guaranteed up to limit values of the operating temperature; these limit values are around 75 ° C, in special cases they can reach up to 125 ° C.
• Cooling of the electronics can be achieved with the measures according to the characterizing features of patent claim 8.
• a Peltier element is therefore used to cool the converter circuit arrangement with the light transmitter, that is to say the transmission circuit arrangement;
• Peltier elements of this type are known per se, see, for example, Meyers Lexicon of Technology and the Exact Natural Sciences, Volume 3, 1970, bibliographisches Institut Mannheim / Vienna / Zurich.
• FIG. 1 shows a sectional view through a pipe conductor of an encapsulated system with an embodiment of the invention
• Figure 2 shows the arrangement of Figure 1 with a cooling element
• a metal-encapsulated gas-insulated high-voltage system has an outer encapsulation 10 and an inner conductor 11.
• the outer encapsulation 10 is composed of two encapsulation parts 12 and 13, the ends of which face one another and have flanges 14 and 15 between which a disk-shaped support insulator 16 for the inner conductor 11 is fastened.
• the inner conductor 11 is provided with a recess 17, so that the inner conductor 11 is continuously carried on or through with a reduced wall thickness.
• a thin-walled tube piece 22 is arranged on the inner conductor 11 above the recess 17, the outer diameter of which is approximately equal to the outer diameter of the inner conductor 11.
• the length of the pipe section 22 depends on the desired current measurement sensitivity. At the end faces, the pipe section 22 is connected to the radially extending boundary walls of the recess 17, so that the high-frequency currents flow through the pipe section 22 due to the skin effect.
• the voltage drop across the pipe section 22, measured along its jacket line, is a measure of the current flowing through the pipe section 22.
• the pipe section 22 is expediently manufactured from the stand material typical of measuring resistors, for example manganin or Isaohm.
• the voltage drop across the pipe section 22 is tapped by lines of the connecting conductors 23 and 24 and an i inside the inner conductor 11 located converter circuit voltage 25, in which the analog measurement signals are converted into digital signals.
• the circuit arrangement 25 ha is accordingly an analog / digital converter.
• At this converter 25 there is a light transmitter 26 which, after being converted into light signals, transmits the digital signals to a conductor arrangement 27 which, as shown schematically in FIG. 1, is led out spirally through the post insulator 16 to the outside.
• the individual cross sections of the light guide arrangement 27 can be seen in FIG. 1.
• the light guide arrangement 27 is included ner evaluation circuit 28 connected in which the light signals are evaluated.
• the converter 25 is supplied with voltage from a capacitor arrangement or a capacitive voltage converter 29.
• the inner conductor 11 has a depression 30, on the bottom of which webs 31 and 32 are applied, which in connection with an electrode 33 and the bottom of the depression 30 form a supply capacitor 34.
• the capacitance located between the electrode 33 and the outer conductor 12 has the reference number 35.
• the electrode 33 on the one hand and the inner conductor 11 on the other hand are connected to the converter 25 by means of electrical lines 36 and 37.
• This embodiment of the invention takes advantage of the fact that higher-frequency currents only flow in the outermost circumferential region of a conductor due to the so-called skin effect. It is therefore sufficient to measure the voltage drop across the pipe section; the signals that are detected here correspond to the high-frequency short-circuit current components and short-circuit current peak values.
• the depth of the recess 17 is smaller, the greater the frequency of the short-circuit current. The following applies:
• d distance between the bottom surface of the recess and d opposite inner surface of the pipe piece 22
• the depression or groove 17 is covered on the outside by the circumferential electrically conductive tube piece 22 made of resistance material, the ends of which are connected to the inner conductor 11 in an electrically conductive manner.
• the between the pipe section 2 and the bottom of the groove can be filled with a solid insulating material in thin-walled pipe sections.
• the depth of this depression, which is denoted by d, may be chosen to be smaller, the higher the frequency of a transient short-circuit current to be measured.
• the voltage drop U en long of the pipe section 22 is measured; at the ends of the pipe section 22, the lines 23 and 24 are connected, which are connected to the value circuit 25, which further process the voltage signals U s, that they can be transmitted from the inner conductor 11 located at the high voltage potential by means of the light guide arrangement 2 to earth potential.
• the voltage drop tapped with the two lines 23 and 24 can additionally be supplied to a photodiode, the analog light signal of which can then be transmitted to the evaluation unit 28 via a further light guide. This gives an exact phase-angle measurement.
• the light guides are connected to a further evaluation circuit for display and further processing. This evaluation circuit can be used, for example, to generate switch-off signals for a circuit breaker located in the switchgear.
• the signals which can be taken as voltage value U, are precisely analogous to the short-circuit currents.
• the light signals that are received by the evaluation circuit 28 then also correspond precisely to the short-circuit currents to be measured.
• the tube piece 22 can also be a part forming a partial arc segment; the recess is not circumferential on the outside, but is introduced over a partial area of the circumference into the inner conductor 11.
• the material from which the pipe section is formed is a usual measuring resistor material.
• the light signals can thus, as shown, be transmitted to the outside via the light conductors. However, they can also be emitted to the outside via a light beam.
• the light path is designated by the reference number 40.
• i are inner conductors 11 and in the outer conductors 12 or 13 radial bores 41 and 42 are provided through which the light is emitted from the inside out. That the bore 42 on the outer conductor 13 in particular must of course be sealed, for example by means of a suitable transparent mass, is self-evident.
• the invention can also be used in high-voltage outdoor systems.
• FIG. 2 shows an embodiment in which the electronic components are cooled.
• the Peltier element 61 has, as is known, conductive materials of different electrical conductivity, as is known, for example, from Meyers Lexicon of Technology and the Exact Natural Sciences, volume 3, page 1916, so that the composition need not be discussed in more detail here.
• the transmission circuit arrangements are or are thermally contacted with the cold surface of the pel element 61.
• the Peltier element 61 is supplied with current by means of a suitably dimensioned current transformer 62 which provides the inner conductor 11 via lines 63 and 64, so that a sufficient cooling effect can be achieved for the transmission circuit arrangement 25/26.
• a suitably dimensioned current transformer 62 which provides the inner conductor 11 via lines 63 and 64, so that a sufficient cooling effect can be achieved for the transmission circuit arrangement 25/26.
• the power supply 29 could also be used. It goes without saying that a rectifier must be provided and is not shown in more detail in FIG. 2.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Transformers For Measuring Instruments (AREA)
• Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
• Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
• Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=6423520

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Country Status (4)

Cited By (1)

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• 1991
  • 1991-01-23 DE DE19914101859 patent/DE4101859C1/de not_active Expired - Lifetime
• 1992
  • 1992-01-21 EP EP19920905578 patent/EP0521147A1/de not_active Withdrawn
  • 1992-01-21 WO PCT/EP1992/000113 patent/WO1992013277A1/de not_active Application Discontinuation
  • 1992-01-21 JP JP92504885A patent/JPH05507392A/ja active Pending

Non-Patent Citations (1)

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