SE507933C2 - Method, apparatus and sensor for capacitively detecting fields and voltages and their use - Google Patents

Abstract

A measuring device (10) for measuring voltage in a high-voltage part (22) surrounded by an electric field comprises a capacitive sensor (11) and a signal converter (13). The sensor includes an inner electrode (12) with a surrounding screen electrode (14). In the screen electrode, which is connected to a controllable reference potential, an opening (16) is provided which, during measurement, is directed towards the high-voltage part (22). By sensing a directed part of the electric field penetrating through the opening of the screen electrode into the inner electrode, the voltage of the high-voltage part (22) is measured at insulation distance.

Description

sleep 933 10 15 20 25 30 35 40 be used either flush with the ground plane by placing it in a hole dug in the ground covered by a metal protective plate with an opening for the device. The device can also be placed so that it protrudes above the ground.

The above-mentioned article also shows a device for measuring above ground level of the electric field under high voltage conductors. The device comprises two metal cylinders, each lengthwise divided into two insulated halves, which metal cylinders have equal or different radii, but different lengths and they rotate at different speeds. From a mechanical point of view, it is desirable that the metal cylinders rotate in opposite directions. The calibration of this device takes place in two steps.

The devices shown above are both sensitive to undesirable fields, and both have a relatively complicated construction.

US-4,328,46l discloses an apparatus for measuring electric fields without contact. The apparatus is shown in three different embodiments, the apparatus comprising a measuring electrode and electronics in the form of a sensor and signal generator. In a first embodiment, the measuring electrode consists of two hemispherical conductors or electrodes of electrically conductive material and the sensor and signal generator is arranged inside and shielded by the measuring electrode. In a second embodiment, the measuring electrode consists of two circular plates of conductive metal which form a pair of conductors or electrodes and the sensor and signal generator is arranged between and at least partially shielded by said plates. In a third embodiment, the measuring electrode consists of two sub-cylindrical conductors and the sensor and signal generator is arranged between and at least partially shielded by said conductor. Although the embodiment with the measuring electrode in the form of plates shows a certain directional sensitivity, a significant disadvantage of these solutions is their lack of directional effect, which means that the devices are sensitive to undesirable fields.

SUMMARY OF THE INVENTION The object of the present invention is to provide a sensor for non-contact measurement of a directional part of an electric field according to the preamble of claim 1, and a voltage measuring device of the preamble of claim 7 specified stroke. A further object of the present invention is a method for non-contact measurement of voltage according to the type stated in the preamble of claim 17. In addition, the object of the present invention is encompassed by a use of a measuring device according to claims 14 - 16, and the use of a method according to claims 25-27.

The basis of the present invention is a device for measuring the alternating voltage at a distance from conductors, as well as detecting transients and ionic discharge.

The device comprises at least one capacitive sensor means and an electrode means arranged around the capacitive sensor means for shielding electric fields. The electrode means is also provided with an opening intended to be directed towards the conductor, the capacitive sensor means sensing a directed part of the electric field. With this device, a simple, inexpensive and reliable equipment is obtained for measuring alternating voltage at a distance from conductors. An additional advantage is that the device is broadband, which means that you can measure within a large frequency range.

The present invention further relates to a voltage measuring device for measuring alternating voltage, harmonics, and detecting transients and ionic discharge at a distance from conductors. The voltage measuring device comprises an air-filled, elongate, hollow insulator and a high-voltage electrode arranged at one short end of the insulator.

The voltage measuring device further comprises a device of the above-mentioned type, which is arranged at the other short end of the insulator, the device sensing a directed part of the electric field on the primary side. A voltage measuring device of this type is simple, inexpensive, reliable and economically very competitive.

The present invention further relates to the use of devices of the above-mentioned type for measuring 3-phase alternating voltage in an encapsulated switchgear, wherein 3 devices are arranged in a housing and directed towards each phase.

The present invention further relates to the use of a device of the type indicated above for measuring alternating voltage in a housing comprising a phase, wherein the device is connected to earth potential and is directed towards the phase.

The present invention further relates to the use of devices of the above type for measuring 1-phase, 2-phase or 3-phase alternating voltage on a power line pole, wherein 1 device, 2 devices or 3 devices are arranged on a power line pole and connected to earth. potential and aimed at each phase.

The present invention further relates to the use of devices of the type indicated above for measuring alternating voltage in an encapsulated or unencapsulated switchgear, wherein at least two devices are arranged directed towards each phase for increasing the measuring accuracy.

The present invention further relates to a means for measuring DC voltage at a distance from conductors.

The means comprises a device of the kind indicated above. At the opening of the device a metal plate is arranged.

This metal plate is rotatable around a point located next to the device. This causes the metal plate to rotate in front of the opening, so that the metal plate alternately covers and does not cover the opening. With this device you get a simple, cheap and reliable equipment for measuring DC voltage at a distance from conductors.

A further advantage of the device according to the present invention is that its areas of use are varied.

The invention will now be further elucidated by the following description of preferred embodiments thereof with reference to the accompanying drawings.

Brief Description of the Drawings Fig. 1 shows a view, partly in section, of a first embodiment of a device for directional voltage measurement according to the present invention; Fig. 2 shows a view, partly in section, of a second embodiment of the device for directional voltage measurement according to the present invention; Fig. 3 shows a field distribution obtained using a device according to Fig. 2; Fig. 4 shows a view, partly in section, of a third embodiment of the device for directional voltage measurement according to the present invention; Fig. 5 shows a cross-sectional view of a first embodiment of a voltage measuring device according to the present invention; Fig. 6 shows a cross-sectional view of a second embodiment of the voltage measuring device according to the present invention; Fig. 7 shows a schematic diagram of a first use of devices according to Fig. 1 according to the present invention for measuring 3-phase alternating voltage in an encapsulated switchgear; Fig. 8 shows a schematic diagram of a second use of a device according to Fig. 1 according to the present invention for measuring alternating voltage in a housing comprising a phase; Fig. 9 shows a schematic diagram of a third use of devices according to Fig. 1 according to the present invention for measuring 3-phase alternating voltage on a power line pole; Fig. 10 shows a principle sketch of a fourth use of devices according to Figure 1 or 2, according to the present invention, for measuring alternating voltage in an encapsulated switchgear by means of several devices; and Fig. 11 shows a view, partly in section, of a means for measuring DC voltage at a distance from conductors without contact according to the present invention.

Detailed Description of Embodiments of the Present Invention Figure 1 shows a view, partly in section, of a device 10 for directional voltage measurement according to the present invention. The device 10 is intended to measure the alternating voltage at a distance from conductor 22 without contact. The device 10 comprises a capacitive sensor means 12 and an electrode means 14 arranged around the capacitive sensor means 12, which is provided with an opening 16 intended to be directed towards the conductor 22. The capacitive sensor means 12 is by means of a lead device 18, e.g. in the form of a coaxial cable, connected to a measuring and detecting device 20 for processing signals obtained from the capacitive sensor means 12. The capacitive sensor means 12 is constituted by a plate 12 which is arranged substantially perpendicularly in relation 507 šzz 10 15 20 25 30 The capacitive sensor means 12 is adjustable so that the distance between the capacitive sensor means 12 and the opening 16 of the electrode means 14 can be changed, as indicated by the arrow A in Figure 1. The capacitive sensor means 12 can also be fixedly mounted so that said adjustment is not possible. The capacitive sensor means 12 and the electrode means 14 form a capacitor constellation 12, 14. The electrode means 14 is made of a conductive material and is also connected to ground potential as shown in Figure 1. The electrode means 14 has, for example, the shape of a "bucket". It should also be pointed out that i.e. one and one neither the electrode 14 nor the plate 1 must necessarily have circular cross-sections. For example, one may have a square cross-section. Figure 1 shows the electrode 14 with a first portion 24, of constant diameter, arranged closest to the "bottom", adjacent to the first portion 24 and having a continuous and a second portion 26, which is device reducing diameter from the first portion 24 to said opening 16. The device 10 may further comprise a amplifier means (not shown) arranged at the electrode means 14 for amplifying signals from the plate capacitor 12, 14. The advantage of an amplifier means arranged at the electrode the odor means 14 is that one becomes independent of the length of the line device 18. The amplifier means is constituted, for example, by a video amplifier. At the electrode means 14 there are a plurality of different filter means (not shown) for filtering the signals 14. The reason why it is practical to have several different filter means is that from the capacitor constellation 12, one can use, i.e. connect, different filter means for different applications. The filter means are often, but not necessarily, bandpass type filters.

The device 10 may further comprise a phase release circuit (not shown) arranged at the electrode means 14. This phase locking circuit (PLL circuit) makes it possible that in e.g. a three-phase system locks the device 10 on the phase it is intended to measure in such a way that the influence of the other phases is not visible in the output signal from the device 10, which results in an increased measurement accuracy. 10 15 20 25 30 35 40 iso? 933 When using the device 10 to measure the AC voltage at a distance from a high voltage conductor 22, the device 10 is directed towards the conductor 22 so that the opening 16 and thus the capacitor constellation 12, 14 face the conductor 22. Before starting the measurement itself, the device 10 is calibrated in place. The calibration takes place by applying a known voltage, after which measurement with the device 10 takes place. The device 10 is thus calibrated to give the known voltage as a measured value. When this is done, the measurement itself can be performed. The shielded capacitive sensor means 12 senses and measures a certain directional part of the electric field E from the conductor 22. 14 is then amplified by the signal from the capacitor constellation 12, arranged at the electrode means 14 by the amplifier means and transmitted via the lead device 18 to the measuring and detecting device 20 where the signal is processed, for later reading of the AC voltage. An advantage of the device 10 according to the present invention is that the device 10 does not have to be put in galvanic contact with the conductor on which the measurement is to be performed, but the measurement can take place at a distance from the conductor 22. Thus, it is not necessary to come into contact with the conductor 22. is that it is very sensitive to direction. Device- Another advantage of the device 10 is also very cheap to manufacture and is reliable. The device 10 of the present invention can further be used to detect transients and ionic discharge. A further advantage is that the device 10 is broadband, which means that one can measure within a large frequency range. Further applications with the device 10 are that the measurement can be the basis for charging, as well as for relay protection.

Fig. 2 shows a view, partly in section, of a second embodiment of a device 10 'for directional voltage measurement according to the present invention. The device 10 'is correspondingly intended for measuring alternating voltage at a distance from conductor 22. The device 10 'comprises a capacitive sensor means 12' and an electrode means 14 'arranged around the capacitive sensor means 12', which is provided with an opening 16 'intended to be directed towards the conductor 22. The main difference with this device 10' in 507 933 10 15 20 25 30 35 40 comparison with the device 10 according to figure 1 is that the device 10 'has a spherically shaped electrode member 14' and that the capacitive sensor member 12 'is constituted by a spherically curved plate 12'. The spherically curved plate 12 'has its concave surface facing the opening 16'. The advantage of this geometry is that the field distribution inside the device 10 'becomes smoother and the design of the capacitive sensor member 12' in the form of a spherically curved plate 12 'means that all field lines fall perpendicular to the plate 12'.

(Compare Fig. 3). This provides further advantages with a stronger output signal from the device 10 'while maintaining the shielding properties of the device 10'.

Fig. 3 shows an electric field distribution obtained using a device 10 'shown in Fig. 2. Figure 3 shows how the field lines (indicated by arrows) fall perpendicular to the capacitive sensor means 12 '(only a part of the sensor means 12' is shown). Otherwise, the device 10 'according to Figures 2 and 3 functions in the same way as the device 10 according to Figure 1.

Figure 4 shows a view, partly in section, of a third embodiment of the device 10 for directional voltage measurement according to the present invention. In the case shown, the starting point is a device 10 according to Figure 1, but the principle can also be applied to a device 10 'according to Figure 2. In the device 10 shown in Figure 4, the capacitive sensor member 12 is divided into two sections 121, 122. These sections 12h both sections 12h 122 have the same shape, as shown in Figure 4. The 122 are bridge-connected and the sections are intended to be placed symmetrically under the high voltage source, capacitances, C1 and C2, which are experienced between the sections e.g. a conductor 22. This means that the 121, 122 and the conductor 22 are equal in size and thereby the bridge coupling is balanced, ie the voltage between the two sections 121, 122 is zero. reason would be moved laterally so that the sections If the conductor 22 of any 121, 122 is not symmetrically below the conductor 22, the capacitances C1 and C2 will change differently, which will result in a voltage different from zero between the sections 121, 122. Also a change in the external electric field from surrounding apparatus) (eg 10 15 20 25 30 35 40 S 507 933 will give rise to a change in the voltage between sections 121, 122. An advantage of this device 10 is that one can detect changes in the outer field or lateral displacements and compensate for the measurement signal for such disturbances.Another advantage of this device 10 is that one obtains two measurement values (one measurement value from each 12fl improves the measurement accuracy. section 12h from the same device 10, thereby device 10 is constructed in the same way as the device 10 according to figure 1, i.e. it comprises an electrode member 14, with an opening 16, a lead device 18 connected to a measuring and detecting device 20 (not shown in figure 4). Of course, the capacitive sensor means 12 may be divided into more than two sections. The sensor means 12 can e.g. be divided into n sections 121 ... 12n, where n 2 2, corresponds to an angular segment of 360 ° / n. Also a device where all sections are equal in size and 10 'according to figure 2 can have the capacitive sensor means 12' divided into n sections l2'1, ..., 12'n where n 2 2 in a corresponding manner. This type of device 10, 10 'is especially valuable in applications where geometric variations in height can be ruled out.

Figure 5 shows a cross-sectional view of a first embodiment of a voltage measuring device 30 according to the present invention. The voltage measuring device 30 comprises an air-filled, elongate, the voltage 30 further comprises a high voltage electrode 34 hollow insulator 32. Voltage measuring device arranged at one short end of the insulator 32. The high voltage electrode 34 consists in the example shown in Figure 5 of a ball-shaped part the insulator 32 and a rod-shaped part connected to the spherical part, which is arranged both in the insulator 32 and outside the insulator 32.

The high voltage electrode 34 may, of course, have other suitable configurations than that shown in Figure 5. At the other short end of the insulator 32, a device 10 for directed voltage measurement of the type shown in Figure 1 is arranged.

The device 10 for directional voltage measurement is arranged inside the insulator 32 and consists of similar parts which function in the same way as the device 10 shown in figure 1 or the device 10 'shown in figure 2. 507 šzs 10 15 20 25 30 35 10 The device 10 in Figure 5 has therefore not been provided with reference numerals regarding its various components, but is only shown schematically. The electrode member of the device 10 is connected to ground via one short end of the voltage measuring device 30, as shown in Figure 5. For a description of its function, reference is made to Figure 1 or 2.

The capacitive sensor means (compare Figure 1) in the device 10 senses and measures a certain directional part of the electric field, in addition to measuring the voltage one can also easily measure harmonics (PD-E. With this type of voltage measuring device 30 can also detect lightning strikes and ionic partial discharge). The voltage measuring device 30 shown can be a replacement for today's voltage transformers.

Figure 6 shows a cross-sectional view of a second embodiment of the voltage measuring device 30 'according to the present invention. Parts of the voltage measuring device 30 'in Figure 6 which correspond to parts of the voltage measuring device 30 in Figure 5 have been provided with the same reference numerals. This voltage measuring device 30 'also includes an insulator 32, a high voltage electrode 34 and a device 10 for directional voltage measurement such as a voltage measuring device 30 according to Figure 5. As shown in Figure 6, the first part of the voltage electrode 34 is not spherical but shaped like an ellipsoid. The voltage measuring device 30 'further comprises two shield rings 36 arranged at the two short ends and arranged around the insulator 32. The purpose of the outer shield rings 36 is to absorb any disturbances from surrounding equipment. Any interference signals will be capacitively coupled to the shield rings 36 instead of to the high voltage electrode 34. In Fig. 6, the electrode means of the device 10 has obtained the design shown in Fig. 1, arranged i.e. with a first portion, of constant diameter, closest to the "bottom", and a second portion, which is arranged at the first portion and can have a continuously decreasing diameter from the first portion to the opening of the device 10. Otherwise, the voltage measuring device 30 operates in the same way as the voltage measuring device 30, i.e. it can, in addition to measuring the voltage according to Figure 5, also detect lightning strikes and ionic discharge.

Figure 7 shows a schematic diagram of a first use of devices 10 according to Figure 1 according to the present invention for measuring in a encapsulated switchgear 3-phase gear- As shown in Figure 7, three devices 102, 103; 10'1, 10'2, measurement according to figure 1 or 2 placed in the same housing 40 in a switchgear, voltage. The different devices 101, 102, 103, 10'1, 10'2, 10'3 are directed towards respective phases 42 '(R), 42 "(S), 42 "'(T). The device 101, 10'1 is directed towards and measures the voltage of the phase 42 '(R), the device 102, 10'2 is directed towards and measures the voltage of the phase 42 "(S) and the device 103, 10'3 is directed towards and measures the voltage of phase 42 "'(T). In Figure 7, the devices 101, 102, 103; 10'1, 10'2, 10'3 for directional voltage measurement have only been indicated schematically, but the design and function are the same as in the device 10 shown in Figure 1 or as in the device 10 'shown in Figure 2. This type of use of devices 10; 10' for directional voltage measurement saves, among other things, assembly time and space in the cabinets.

Figure 8 shows a schematic diagram of a second use of a device 10; 10 'according to Figure 1 or 2 according to the present invention for measuring alternating voltage in a housing comprising a phase. As shown in Figure 8, a device 10; 10 'for directional voltage measurement according to Figure 1 or 2 placed inside a housing 50 comprising an alternating voltage (a phase) 52 which it is desired to measure on.

The device 10; 10 'directed towards the phase 52. When the distance to the high voltage conductor is connected to ground potential and is 52 as the device 10; 10 'is constant and no field-disturbing geometry changes in the device 10; 10 'proximity is made, no insulator is needed between the device 10; 10 'and high voltage.

Figure 9 shows a schematic diagram of a third use of devices for directional voltage measurement according to Figure 1 or 2 for measuring 3-phase alternating voltage on a power line pole. In this use, three devices are 101, 102, 103; 10'1, l0'2, l0'3 placed on a power line 507 šsz 10 15 20 25 30 35 40 12 12 and are directed towards each phase. The devices 10h 102, 103; 10'1, 10'2, then the distance to the high voltage conductors as the devices 101, 102, 103; 10'1, 10'2, no field-disturbing geometry changes in the devices 101, 102, 103; 10'1, 10'2, isolant between the device 10h 10'3 are connected to ground potential. 10'3 directed towards is constant and 103 proximity is made, no 102, 103 is needed; 10'1, 10'2, 10'3 and high voltage. It should be noted that the voltage measuring device is not connected to the insulator. However, they do not have to be separated. The 102, 103 obtained in the voltage measurements; 10'1, 10''3 via wireless telephony to a suitable location for the values can be transmitted from the devices 10h 10 '@ collection of measured values. With this solution, by 102, 103; 10'3 along a network perform measurements and collect have a number of permanently installed devices 10h 10'1, 10 '@ measurement values about the network.

The measured values can also be transmitted from the devices 10; 10 'by means of optical fiber (not shown) to a place intended for collecting measured values. Of course, with the use shown, it is also possible to measure 1-phase or 2-phase alternating voltage, either with three devices 101, 102, 103; 10'1, 10 '@ with one or two devices 10; 10 '10'3 arranged on the power line pole 60 or arranged on the power line pole 60 (not shown in Figure 9).

Figure 10 shows a schematic diagram of a fourth use of devices 10, 10 'according to Figure 1 or 2 according to the present invention for in a nested switchgear by means of several devices 10; 10 'measure alternating voltage. Figure 10 shows an encapsulated switchgear comprising a mound 64 with a phase or high voltage part 621. In each corner of the housing 64 a device 101h 10n, 103, 10M, 10'n, 10'n, 10'n, 10 ' M directed toward phase 621. Devices 1011, 1012, 10n, 1014; 10'11, 10'12, 10'1 @ 10'm are arranged symmetrically with respect to said phase 621. With this use it is possible to accurately detect if the high voltage part 621 is moved. When the devices 101; 10'1 are symmetrically arranged in relation to the phase 621, the same measured values are obtained from the different 10 '@ ideal positions, the different measured values of the devices 101 are obtained; On the other hand, should the phase 621 move from the shown 10 10 'of standard type, one can calculate the new position of the phase 621 from the devices 101; By geometric calculations and / or compensate for the movement to obtain a correct (corrected) measured value. This can be done by going to the devices 101; 10'1. This use can also be used to connect a detector and compensation means (not shown) to detect and compensate for change in background field, which gives asymmetric change in the measured 10'L one can have a higher measuring accuracy only by the introduction of several. this use is also applied to an unencapsulated switchgear In the unencapsulated switchgear it is particularly valuable to be able to compensate for the changed signals from the devices 101; In addition, devices 101; 10'1 which measures on the same phase 621. (not shown). background field. The devices 101; 10'1 are connected to ground potential. This principle can be applied with n number l01n, '10'11, ..., lÛ'1I'1 Il 2 2 AND the devices are symmetrically arranged in relation to devices 10n. ..., phase 621. The use of several devices provides greater measurement accuracy.

Figure 11 shows a view, partly in section, of a means 70 for measuring DC voltage at a distance from conductors without contact according to the present invention. The means 70 comprises a device 10 for directional voltage measurement according to Figure 1.

The means 70 thus comprises, like the device 10 according to Figure 1, a capacitive sensor means 12 and an electrode means 14 arranged around the capacitive sensor means 12, which is provided with an opening 16 intended to be directed towards the conductor (not shown). The capacitive sensor means 12 is by means of a coaxial cable in the form of a coaxial cable 18, e.g. connected to a measuring and detecting device (not shown) for processing signals obtained from the capacitive sensor means 12. The capacitive sensor means 12 is constituted, for example, by a round plate 12 which is arranged substantially perpendicular to the electrode means 14. The plate 12 is adjustable so that the distance between the plate 12 and the opening 16 of the electrode member 14 can be changed. The electrode member 14 is made of a conductive material and is also connected to ground potential. Otherwise, the device 10 operates in the same manner as described in connection with Figure 1. The member 70 further comprises a metal plate 72 arranged at the opening 16 which is rotatable (shown by arrow A in Figure 11) located around a shaft 74 next to the device 10. The rotation of the shaft 74 is illustrated by the arrow B in Figure 11. Because the metal plate 72 is fixed to the shaft 74 in the manner shown, when the shaft 74 is rotated in the direction of the arrow B, the metal plate 72 will alternately cover and not covering the opening 16. By placing a rotating metal plate 72 in front of the opening 16 of the device 10, an alternating electric field is created incident on the capacitive sensor means 12 which makes it possible to capacitively measure the signal from the voltage source even though it is a direct voltage source (DC source ).

The device 10 shown in figure 11 can be replaced by a The function becomes in both cases device 10 'according to figure 2. the same.

The invention is not limited to the embodiments shown, but several variations are possible within the scope of the appended claims.

Claims (27)

K 507 933 15 PATENT REQUIREMENTS Capacitive sensor (II) for detecting a directional part of an electric field comprising an inner electrode (12) and a shield electrode (14), characterized in that the shield electrode (14) encloses the inner electrode (12) leaving an opening (16), wherein when the sensor is directed towards a field generating object, the inner electrode detects a part of the electric field penetrating through the opening. Sensor according to Claim 1, characterized in that the inner electrode (12) and the shield electrode (14) are insulated from one another by a gaseous dielectric. Sensor according to Claim 1 or 2, characterized in that the inner electrode (12) is adjustably fixed in the shield electrode (14). Sensor according to one of the preceding claims, characterized in that the inner electrode (12) has a substantially planar propagation, the propagation plane of which is substantially perpendicular to a normal to the opening (16) in the shield electrode (14). Sensor according to one of the preceding claims, characterized in that the inner electrode (12) is cup-shaped. Sensor according to one of the preceding claims, characterized in that the inner electrode (12) comprises a plurality of electrically insulated sub-electrodes (12a, 12b) from one another. Measuring device (10) for measuring the voltage of a high-voltage component (22) surrounded by an electric field, characterized in that the measuring device (10) comprises a capacitive sensor (11), including an internal electrode ( 12) and a shield electrode (14) connected to a controllable reference potential, the shield electrode being arranged to shield the inner electrode from a disturbing electric field, the sensor by sensing a directed part of the electric electrode penetrating into the inner electrode the field at insulation distance measures the voltage of the high voltage part. Measuring device according to Claim 7, characterized in that the shield electrode (14) and the inner electrode (12) are insulated from one another by a gaseous dielectric. Measuring device according to Claim 7 or 8, characterized in that the shield electrode (14) encloses the inner electrode (12) and is provided with an opening (16) through which the inner electrode senses a directed part of an electric field. Measuring device according to one of Claims 7 to 9, characterized in that the inner electrode (12) includes a plurality of sub-electrodes (12a, 12b). Measuring device according to one of Claims 7 to 10, characterized in that the measuring device comprises a signal converter (13) which is arranged in the vicinity of the sensor (11) and comprises means for amplifying and impedance converting the measuring signal. Measuring device according to claim 11, characterized in that the signal converter (13) includes means for phase welding of the shield electrode (14) and / or the inner electrode (12). Measuring device according to one of Claims 7 to 12, characterized in that the measuring device (10) is arranged at the earthed part of an insulator. 17 Use of a measuring device (10) according to claims 7 - 13 in switchgear. Use of a measuring device (10) according to claims 7 - 13 in electric power networks for charging for consumed energy. Use of a measuring device (10) according to claims 7 - 13 in electric power networks for establishing relay functionalities. Method for measuring voltage of a high-voltage component (22) surrounded by an electric field, characterized in that a directional part of the electric field is sensed at insulating distance with at least one capacitive sensor (11). Method according to claim 17, characterized in that the sensor (11) is arranged to comprise an inner electrode (12) and a shielding electrode (14) connected to a controllable potential, the shielding electrode being arranged to shield the inner electrode from interfering electric fields, so that the electric field generated from the high voltage part is sensed by the inner electrode. Method according to Claim 17 or 18, characterized in that the shield electrode (14) is arranged to be insulated from the inner electrode (12) by a gaseous dielectric. Method according to claims 17 - 19, characterized in that a shield electrode (14) is arranged to enclose the inner electrode (12) leaving an opening (16), through which a directed part of an electric field is sensed by the inner electrode. 507 953 18 Method according to Claims 17 to 20, characterized in that a means for phase locking is connected to the sensor (11), whereby the potential of the shield electrode (14) and / or the inner electrode (12) is read in relation to the high voltage part, so that the influence of interfering electric fields are suppressed. Method according to claims 17 - 21, characterized in that the inner electrode (12) is caused to include a fletal sub-electrodes (12a, 12b), wherein by comparing the signals from the sub-electrodes a change in the incident electric field caused by a displacement of the high voltage part is detected. Method according to Claims 17 to 22, characterized in that the sensor (II) is arranged in relation to the high-voltage part (22) at a fixed distance. Method according to Claims 17 to 23, characterized in that the sensor (11) is caused to be alternately shielded from a directed static electric field at a known frequency, whereby a varying electric field is created in the sensor, from which DC voltage of a high-voltage element is measured ( 22). Use of a method according to claims 17 - 24 in switchgear. Use of a method according to claims 17 - 24 in electricity power networks for charging for consumed energy. Use of a method according to claims 17 - 24 in electric power grids for establishing relay functionalities.