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
  • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
  • G01R15/186—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using current transformers with a core consisting of two or more parts, e.g. clamp-on type
• • 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
  • G01R15/142—Arrangements for simultaneous measurements of several parameters employing techniques covered by groups G01R15/14 - G01R15/26
• • 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
  • G01R15/185—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 with compensation or feedback windings or interacting coils, e.g. 0-flux sensors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
  • G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
  • G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
  • G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
  • G01R31/52—Testing for short-circuits, leakage current or ground faults

Definitions

• the invention relates to a partial discharge sensor, specifically to a broadband current inductive partial discharge signal sensor.
• the good condition of the insulation of electrical circuits is a basic condition for their proper function.
• the condition of the insulation is threatened by various factors, such as chemical, electrical or production imperfections.
• the end state of the insulation is an electric field breakdown and this breakdown is always built up of partial discharges, no matter what impairment of the state of the insulation is created by whichever degradation mechanism, for example degradation of the insulation due to inhomogeneities in production of the insulation, the formation of so-called cavities.
• sensors for sensing partial discharges are known, which are physically two types, namely, voltage sensors for partial discharges and current sensors for partial discharges.
• CZ 25229 From utility model CZ 25229 is known the use of a detector for evaluating the probability of the occurrence of partial discharges in the body of an encased transformer, which extends into the inner space of the transformer and which consists of an antenna and is connected to a measuring device.
• the detector has an antenna provided with a reflector which is joined to the antenna power connector, with at least one detector being located on the transformer housing and extending inside the transformer via the non-metallic design of the bushing housing.
• the disadvantage of this sensor is that it can only be used with a transformer, it cannot be used anywhere else for other sources of discharges.
• a meter which consists of a load impedance and a broadband or narrowband amplifier, evaluation circuits connected to the amplifier output, and control and synchronisation units, or a display at the output of the evaluation circuits.
• Evaluation circuits connected to the output of a broadband or narrowband amplifier consist of a charge converter for time, the output of which is connected to the input of the time converter of the converted charge and to the input of the counter defining the position of that impulse on the basic measuring voltage period, where the outputs of these counters are connected to the memory, which is further connected to the indication circuits.
• To the output of the time charge converter can also be connected the sum of all times of partially discharged charges during the measuring voltage period, its output being connected to the memory and/or a counter of the number of partial discharge impulses in the measured period, the output of which is connected to the memory.
• a partial discharge sensor is furthermore known from patent document US20080174320, which comprises a primary current transformer having an opening. Inside the opening of the primary current sensor and close to it is located a conductive shield. The concentric openings of the primary current sensor and the conductive shield are arranged to receive the first high voltage power conductor.
• the second conductor is electrically connected to the conductive shield.
• the second conductor is structured to be electrically connected to ground.
• the second sensor interacts with the second conductor and is structured to sense signals associated with partial discharge activity.
• the output of the second sensor is received by an electronic monitoring circuit.
• the electronic monitoring circuit is arranged to provide on-line monitoring of the partial discharges occurring in the primary high voltage power conductor.
• the disadvantage of this sensor is its complex construction, very complicated assembly and above all its lower sensing sensitivity.
• the object of the invention is a simple and variable construction of a broadband current inductive sensor with a very wide frequency range, which will be able to capture a partial discharge.
• a partial discharge sensor specifically a broadband current inductive partial discharge signal sensor, comprising a magnetic core housed in a casing and at least one secondary circuit arranged on the magnetic core, characterised by that the magnetic core is made of an amorphous magnetic material, with there being a maximum of 10 threads of one secondary circuit mounted on the magnetic core.
• the advantage is that the partial discharge sensor allows monitoring with a high frequency range.
• Another advantage is the very high permeability of the magnetic core.
• Another great advantage is that, thanks to the material used, various sensor sizes can be assembled without limiting their functionality.
• the value of the secondary winding is a maximum of 10 threads and thus the optimal inductance is set, guaranteeing a very small to negligible effect on the shape of the transmitted impulse, which means maintaining the steepness of the sensed partial discharge.
• the advantage of this arrangement is simple production without the need for special winding machines.
• the secondary circuit is provided with a shield. If the secondary circuit were not shielded and the shield not grounded, ambient interference could begin to be induced in the secondary circuit because the unshielded secondary circuit can act as a receiving antenna for surrounding interference. Although the sensor itself is relatively resistant to undesirable noise phenomena, the use of shielding further significantly increases this resistance.
• the casing with the magnetic core is designed to be transversely divided into two parts.
• the magnetic core with the casing are split in half.
• the casing is provided with at least two insertion pins which are arranged within the casing.
• the advantage is that the two halves are easily fit together by means of the insertion pins in the protrusions of the side walls of the sensor casing, which results in a very simple and undemanding assembly and thus to a reduction in costs.
• the secondary circuit is to advantage joined to the connector via terminals.
• the advantage is that during production it is not necessary to create sensors with a terminal, but according to needs, more precisely according to the location of the sensor, the supply wires can be made to measure thanks to the connector joining.
• the casing is provided with a connector chamber.
• the advantage is the simplification of the assembly of the connector, where the conductors have a winding space apart from the threads, where they are folded up in after attaching the conductors to the connector.
• the housing is preferably made of a self-extinguishing material, which is to greatest advantage polyethylene terephthalate glycol (PETG).
• PETG polyethylene terephthalate glycol
• the magnetic core is designed as toroidal.
• the advantage is that the toroidal core has excellent magnetic properties, above all very low magnetic losses and high resistance to external magnetic fields, while it can be easily mechanically adjusted, for easy assembly, during production and end use as well.
• the magnetic core is made of an amorphous magnetic material, which is wound with nanoplate of a thickness of about 10pm. Thanks to its very fine structure, the wound nanoplate has very favourable frequency parameters, from 0 Hz to 2 MHz.
• the advantage is that the use of nanoplates significantly amplifies the signal, which is excited by only the small primary current generated by the current of the partial discharge.
• the magnetic core is made of an amorphous Fe-based magnetic material.
• the advantage is the excellent magnetic properties of such a material.
• a resin is arranged in the free space in the cavity of the magnetic core casing.
• the casing is provided on its surface with at least one cable tie, which holds the two halves of the housing together simply in such a way that the sensor performs its function safely and securely.
• the advantage of this solution is its cost-effectiveness.
• the main advantage of the partial discharge sensor according to the invention is that it allows monitoring with a high frequency range. It is also to advantage that the use of nanoplates significantly amplifies the signal, which is excited by only the small primary current generated by the current of the partial discharge. Due to the small number of threads of the primary and secondary windings, the intrinsic inductance of the entire magnetic circuit is very small (approx. ⁇ 30mH). As a result, this does not affect the course of the primary current impulse and is transmitted very faithfully to the secondary side. Thanks to the divided design, the sensor can be easily mounted on the measured conductor. It is divided transversely into two halves, which fit together and encircle the measured conductor and secure against its own decomposition and spontaneous displacement.
• the sensor is primarily intended for sensing partial discharges in high voltage cables, where the discharge activity is mainly related to shielding braiding, which is used in all modern HV cables. Since this shield is grounded at the starting points of the cable ends, a current impulse from a specific discharge in a particular monitored cable passes through a grounding connection to ground.
• an inductive sensor Because there is very little space in modern substations, it is very advantageous to use an inductive sensor, due to its small size ( ⁇ 80 x 30mm), which allows one to read information about partial discharges of the monitored device from the grounding conductor, which is connected from the cable to the grounding network of the object. There is no need to connect directly to the voltage supply level with a voltage sensor, which is usually of much larger dimensions (eg ⁇ 200 x 380 mm) and mass. This leads to a very significant saving of space, and this inductive sensor can be placed into all substations without complications and restrictions.
• fig.1 shows a cross-sectional perspective view of the arrangement of individual parts of the sensor
• fig. 2 shows a frontal view of the sensor ready for mounting at the measuring point
• fig. 3 shows a perspective view of the whole sensor
• fig. 4 shows a circuit diagram of the individual parts of the sensor
• fig. 5 shows a perspective view of the partial discharge sensor installed on a conductor.
• the broadband current inductive sensor 10 of the partial discharge signal (fig.1, fig. 2, fig. 3, fig. 4, fig. 5) comprises a magnetic core 1 housed in a casing 2 and on the magnetic core 1 a secondary circuit 3 is mounted.
• the magnetic core 1 is made of an amorphous magnetic material.
• threads 4 of the secondary circuit 3 are mounted on the magnetic core 1 .
• threads 4 of the secondary circuit 3 can be mounted on the magnetic core 1 .
• the secondary circuit 3 is provided with a shield 5.
• the casing 2 with the magnetic core 1 is designed as transversely divided into two parts 6,7, the casing 2 being provided with four insertion pins 8, which are arranged in the fitting 9 of the casing 2.
• the secondary circuit 3 is joined via terminals H to a connector 12, which is connectable by a cable 13 to an external computer evaluation device.
• the connector 11 has IP 68 protection.
• the casing 2 is provided with a chamber 14 of the connector 12, being made of a self-extinguishing material which is polyethylene terephthalate glycol (PETG).
• PETG polyethylene terephthalate glycol
• the magnetic core 1 is made to be toroidal from an amorphous magnetic material, which is a wound nanoplate.
• the magnetic core 1 is made of an amorphous magnetic material based on Fe, which amorphous material can be any of the materials listed in the following table:
• the casing 2 with the magnetic core 1 contains a free space in which a resin is arranged.
• the casing 2 is provided on its surface with two cable ties 15, which are arranged in the end grooves 16 of the casing 15.
• the partial discharge sensor 10 operates in such a way that the current flowing through the primary conductor T7 generates an electromagnetic field which induces a magnetic flux in the magnetic circuit.
• This magnetic flux in the magnetic core 1 in the secondary circuit 3 induces a voltage which is an image of the primary current and its parameters of are transmitted for further processing by an external evaluation computer device to determine the presence of a partial discharge.
• the partial discharge sensor according to the invention can specifically be used to detect partial discharges in high-voltage cables. List of Reference Marks

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Testing Relating To Insulation (AREA)
• Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (6)

• 2021
  • 2021-02-10 CZ CZ2021-60A patent/CZ202160A3/cs unknown
• 2022
  • 2022-02-02 WO PCT/CZ2022/000005 patent/WO2022171216A1/en not_active Ceased

Patent Citations (6)

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