JP2017173212A - Sensor for current detection and ground fault locating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote communization of a sensor for current detection that is used in a ground fault locating system.SOLUTION: Provided is a sensor for current detection that is used in a ground fault locating system for locating a ground fault point in a utility grid, comprising an annular winding core arranged so that an electric power line of the utility grid penetrates, and a coil wound around the winding core so as to detect a ground fault current occurring in the electric power line when the electric power line is grounded to earth. The winding core is formed so that the flux density of a magnetic flux occurring when the ground fault current flows in the electric power line is less than or equal to a prescribed value that is determined on the basis of the rate of a change of magnetic permeability to a change of the flux density.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a current detection sensor and a ground fault location system.

  In the power system, a ground fault location system is installed to enable quick recovery from a ground fault by quickly locating the ground fault when a ground fault occurs.

  The ground fault location system includes sensors installed at various locations to detect the state of the power system such as current and voltage, and a ground fault location device that identifies the ground fault location using signals from these sensors. , And is configured.

  When a ground fault occurs in the power system, ground fault currents of different sizes flow depending on the power system. For this reason, what has an appropriate detection range is employ | adopted for the sensor for electric current detection used for a ground fault point location system according to the magnitude | size of the ground fault current of each electric power grid | system. Various techniques have been developed for such sensors (see, for example, Patent Document 1).

JP-A-6-314626

  However, in the case of a 22 kV distribution system, for example, even if the 22 kV distribution system is the same, the transformer grounding system provided in the substation connects the neutral point of the transformer and the ground with a conductor through a resistor. There is a grounding resistance grounding method and a non-grounding method that does not perform neutral point grounding, and the grounding current range varies greatly depending on the grounding method of the transformer provided in the substation. . For example, in the case of the resistance grounding method, since the neutral point is grounded by a resistor, the ground fault current is about several hundred A (ampere), but in the case of the non-grounding method, it is about several tens mA (milliampere). is there.

  For this reason, in the ground fault location system for a 22 kV distribution system that is supplied with power by a resistance grounding transformer, a current transformer (CT) capable of measuring a current of several hundred A is installed in each phase of the distribution line. The zero-phase current is detected by synthesizing the currents of these phases. However, in the ground fault location system of the 22 kV distribution system that is supplied with power by a non-grounded transformer, the number of each phase of the distribution line The zero-phase current is detected using a zero-phase current transformer (ZCT) that measures current of about 10 mA collectively.

  In this way, different sensors may be used depending on the neutral point grounding system of the transformer even though they are the same power system, and it is desired to make these common.

  The present invention has been made in view of the above problems, and an object thereof is to promote the common use of current detection sensors used in the ground fault location system.

  A sensor according to one aspect is a current detection sensor used in a ground fault point location system that locates a ground fault point in a power system, and is an annular winding disposed so that a power line of the power system penetrates. A core and a coil wound around the core to detect a ground fault current generated in the power line when the power line is grounded, and the core has the ground fault current in the power line. The magnetic flux density of the magnetic flux generated when flowing is formed to be equal to or less than a predetermined value determined based on the degree of change in magnetic permeability with respect to the change in magnetic flux density.

  In addition, the problems disclosed by the present application and the solutions thereof will be clarified by the description in the column of the embodiment for carrying out the invention and the description of the drawings.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to accelerate | stimulate commonality of the sensor for electric current detection used for a ground fault point location system.

It is a figure which shows the ground fault location system which concerns on this embodiment. It is a figure which shows the sensor box which concerns on this embodiment. It is a figure which shows the sensor for electric current detection which concerns on this embodiment. It is a figure which shows the characteristic of the core which concerns on this embodiment. It is a figure which shows the characteristic of the core which concerns on this embodiment.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

  FIG. 1 shows an overall configuration of a ground fault location system 1000 according to an embodiment of the present invention.

  The ground fault location system 1000 is a system for locating a location (ground fault point P) where a ground fault has occurred when a ground fault occurs in the power system (22 kV distribution system in this embodiment).

  As shown in FIG. 1, the ground fault location system 1000 includes a measuring device 10 and a ground fault location device 300.

  The measuring device 10 is a device that is installed at each of a plurality of locations in the distribution system and measures a physical quantity that varies according to the power state of the distribution system. The measuring device 10 includes a sensor box 100 that houses a sensor 150 that measures a physical quantity that varies in accordance with the power state of the distribution system including the current or voltage of the distribution line 500, and a ground fault location device that indicates the measurement result of the sensor 150. And a measuring terminal 200 that transmits to 300.

  The physical quantity measured by the sensor 150 is a physical quantity that varies depending on the power state of the distribution system including the current or voltage of the distribution line 500, but may include a power factor, a frequency, and the like. In the present embodiment, the individual measuring devices for these physical quantities are collectively referred to as a sensor 150. As will be described in detail later, the sensor 150 also includes a current measurement sensor 150 </ b> A that measures the current flowing through the distribution line 500.

  The ground fault point locating device 300 is a device for locating a ground fault point based on measured values of physical quantities respectively measured by the measurement devices 10 at a plurality of locations.

  Although the distribution line 500 is often three-phase, only one distribution line 500 is shown in FIG. 1 for the sake of simplicity. Therefore, in FIG. 1, each measurement terminal 10 is described as having one sensor box 100, but as shown in FIG. 2, each phase of the distribution line 500 has a sensor box 100. Yes.

  The sensor box 100 is attached to each phase of the distribution line 500, and a physical quantity that varies depending on the power state of the distribution system is measured by the sensor 150 housed in each sensor box 100.

  The sensor box 100 includes a sensor 150, a metal outer box 110 that covers the sensor 150, and a pole fitting 120 that fixes the outer box 110 to the arm metal 620 of the utility pole 600.

  When the sensor box 100 is installed on the power pole 600, the sensor box 100 of each phase is fixed to the arm metal 620 on the ground first, and the whole is integrated, and the arm metal 620 is lifted to a predetermined mounting position on the pole. Then, it may be fixed to the utility pole 600 by the armrest mounting tool 610. For this reason, the installation work of the sensor box 100 can also be easily performed.

  The measurement terminal 200 is a device that transmits the measured value of the physical quantity measured by the sensor 150 of each phase of the distribution line 500 to the ground fault location device 300 via the communication path 400.

  In addition, the measurement terminal 200 uses the physical quantity value (direct measurement value) of each phase of the distribution line 500 that is directly measured by the sensor 150, and the value of another physical quantity that varies depending on the power state of the distribution system (indirect). Measurement value) can be calculated and transmitted to the ground fault location device 300.

  For example, the measurement terminal 200 acquires a current value (direct measurement value) of each phase of the distribution line 500 from the sensor box 100, and calculates a zero-phase current (indirect measurement value) by combining these current values. It can be transmitted to the ground fault location device 300. Alternatively, the measurement terminal 200 acquires the voltage value (direct measurement value) of each phase of the distribution line 500 from the sensor box 100, and calculates the zero-phase voltage (indirect measurement value) by combining these voltage values. It can be transmitted to the ground fault location device 300.

  The measurement terminal 200 receives the current time from the GPS satellite 2000, and transmits the direct measurement value and the indirect measurement value to the ground fault location device 300 in association with the time information.

  The ground fault point locating device 300 is a device for locating the ground fault point P based on the respective measured values measured by the measuring devices 10 installed at a plurality of locations in the distribution system.

  Various methods have been developed as a method for locating the ground fault point P. For example, the ground fault locating device 300 is based on the zero-phase current and the zero-phase voltage transmitted from the measurement terminals 200 in each region. The ground fault point P is determined by specifying the arrival time of the surge current and surge voltage in the measuring device 10.

  By the way, since the distribution system according to the present embodiment is a 22 kV distribution system, the grounding system of the transformer (not shown) provided in the substation (not shown) is a resistance grounding system or a non-grounding system. There is. The resistance grounding method is a method in which the neutral point of the transformer and the ground are connected by a conductor via a resistor and grounded, and the non-grounding method is a method in which neutral point grounding is not performed.

  Therefore, when a ground fault occurs in the distribution line 500, the range of the ground fault current varies greatly depending on the difference in the grounding method of the transformer provided in the substation. For example, in the case of the resistance grounding method, since the neutral point is grounded by a resistor, the ground fault current is about several hundred A (ampere), but in the case of the non-grounding method, it is about several tens mA (milliampere). is there.

  In this regard, the current detection sensor 150A according to the present embodiment is configured to be able to detect a ground fault current regardless of the grounding method.

  FIG. 3 shows a current detection sensor 150A according to this embodiment.

  As shown in FIG. 3, the sensor 150 </ b> A is wound to detect a ground fault current generated in the distribution line 500 when the distribution line 500 is grounded with an annular winding core 151 provided so that the distribution line 500 penetrates. And a coil 152 wound around the core 151.

  When a ground fault current flows through the distribution line 500, the magnetic flux Φ of the winding core 151 changes, and the current flowing through the coil 152 changes accordingly. By detecting the current flowing through the coil 152 by a detector (not shown), the ground fault current flowing through the distribution line 500 can be detected.

  Here, the core 151 of the sensor 150A according to the present embodiment is formed such that the magnetic flux density B of the magnetic flux generated when the ground fault current flows through the distribution line 500 is equal to or less than a predetermined value.

  As will be described below, by forming the sensor 150A so that the magnetic flux density B of the magnetic flux generated in the core 151 is as small as possible, the range of the ground fault current that can be detected by the sensor 150A can be expanded. This makes it possible to detect a ground fault current regardless of whether the transformer grounding system of the 22 kV distribution system is a resistance grounding system or a non-grounding system.

  That is, by reducing the magnetic flux density B of the magnetic flux generated in the winding core 151 to be equal to or less than a predetermined value, as will be described below, variations in measured values of the sensor 150A attached to the distribution line 500 of each phase are reduced. Thus, the ground fault current can be measured over a wide band. Hereinafter, a detailed description will be given with reference to FIGS. 4 and 5.

  First, FIG. 4 shows the relationship between the relative permeability μr of the core 151 and the magnetic flux density B of the magnetic flux generated in the core 151. FIG. 4 illustrates a characteristic curve in the case where the winding core 151 is a permalloy core. It can be seen that the value of the relative permeability μr varies greatly depending on the magnetic flux density B.

  For this reason, in order to suppress variations in the characteristics of the sensor 150A of each phase, it is necessary to generate a magnetic flux density B in a range in which the variation of the relative permeability μr is as small as possible.

  Referring to FIG. 4, it can be seen that the smaller the magnetic flux density B, the smaller the variation in the relative permeability μr. Therefore, FIG. 5 shows an enlarged relationship between the magnetic flux density B and the relative permeability μr when the magnetic flux density B is 3000 gauss or less.

  The change in the relative permeability μr and the change in the magnetic flux density B are in a linear relationship, that is, the increase rate of the magnetic flux density B when the ground fault current flows through the distribution line 500 and the increase rate of the relative permeability μr. For example, the change in the relative permeability μr is stabilized with respect to the change in the magnetic flux density B. The range of the magnetic flux density B where the relative permeability μr is stable is an area where the variation of the sensor 150A of each phase is small.

  Then, referring to FIG. 5, it can be seen that the range in which the relative permeability μr increases linearly as the magnetic flux density B increases is a range in which the magnetic flux density B is a predetermined value or less. In the case shown in FIG. 5, a range where the magnetic flux density B is 1000 gauss or less is preferable.

  Of course, the change in the relative permeability μr and the change in the magnetic flux density B do not have to have a completely linear relationship, and each increase rate or change rate only needs to be within a predetermined range.

  Thus, when the ground fault current flows through the distribution line 500, the magnetic flux density B of the magnetic flux generated in the core 151 is equal to or less than a predetermined value determined based on the degree of change in the relative permeability μr with respect to the change in the magnetic flux density B. By doing so, the range of current that can be detected by the sensor 150A can be expanded, and even if the grounding system of the transformer of the 22 kV distribution system is either the resistance grounding system or the non-grounding system, the ground fault current Can be detected.

  In addition, the material used for the core 151 is shown in FIG. 4 by determining the above-described predetermined value, which is the upper limit value of the magnetic flux density B, based on the degree of change in the magnetic permeability μr with respect to the change in the magnetic flux density B. Based on the characteristics of the relative permeability μr and the magnetic flux density B, the upper limit value of the magnetic flux density B can be determined.

  The magnetic flux density B of the magnetic flux generated in the winding core 151 is proportional to the magnetic flux Φ, but is inversely proportional to the cross-sectional area S and length (circumferential length) L of the winding core 151. Therefore, the winding core 151 has a cross-sectional area S and a length L that are equal to or greater than a predetermined value so that the magnetic flux density B of the magnetic flux generated in the winding core 151 is suppressed to a predetermined value or less when a ground fault current is generated. Need to be configured. However, on the other hand, since there is a certain limit in the enlargement of the core 151, the core 151 has a cross-sectional area S and a magnetic flux density B that are not more than a predetermined value and that are not less than a certain lower limit value. It will be configured to have a length L.

  Further, the current flowing through the coil 152 when the distribution line 500 is grounded is inversely proportional to the number of turns of the coil 152. Therefore, the sensor 150A according to the present embodiment is determined such that the number of turns of the coil 152 is equal to or less than a predetermined value. By setting the number of turns of the coil 152 to a predetermined value or less, even a weak ground fault current can be detected by increasing the secondary current level. It can be expanded.

  For example, when detecting a ground fault in a non-grounded distribution system, the distribution lines for each phase can be obtained without having to pierce the distribution lines 500 for three phases through one winding core 151. Sensors 150A are respectively provided in 500, and a ground fault current of about several tens of mA can be detected.

  For this reason, it is possible to detect a ground fault current regardless of whether the transformer grounding system of the 22 kV distribution system is a resistance grounding system or a non-grounding system.

  The current detection sensor 150A and the ground fault location system 1000 according to the present embodiment have been described above. However, according to the present embodiment, the current detection sensor 150A used in the ground fault location system 1000 is shared. Can be promoted.

  Further, even in an electric power system such as a 22 kV power distribution system having a plurality of neutral point grounding methods, the common current detection sensor 150A can be used, and thus the cost can be reduced.

  The embodiments described above are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and equivalents thereof are also included in the present invention.

DESCRIPTION OF SYMBOLS 10 Measuring apparatus 100 Sensor box 110 Outer box 120 Pillar fitting 150 Sensor 150A Current detection sensor 151 Core 152 Coil 200 Measuring terminal 300 Ground fault location device 400 Communication path 500 Distribution line 600 Electric pole 610 Armrest mounting tool 620 Armrest 1000 Ground fault location system 2000 GPS satellite

Claims (10)

A current detection sensor used in a ground fault location system that locates a ground fault point in a power system,
An annular core disposed so that the power line of the power system penetrates; and
A coil wound around the core to detect a ground fault current generated in the power line when the power line is grounded;
Have
The winding core is formed such that a magnetic flux density of a magnetic flux generated when the ground fault current flows through the power line is equal to or less than a predetermined value determined based on a degree of change in permeability with respect to the change in magnetic flux density. The sensor characterized by becoming. The sensor according to claim 1,
The predetermined value is determined based on a degree of coincidence between an increase rate of the magnetic flux density and an increase rate of the magnetic permeability when the ground fault current flows through the power line. The sensor according to claim 1 or 2,
The core is configured to have a cross-sectional area and a length such that the magnetic flux density is equal to or less than the predetermined value. The sensor according to any one of claims 1 to 3,
A sensor, wherein the number of turns of the coil is determined to be a predetermined value or less. The sensor according to any one of claims 1 to 4,
The power system is a 22 kV special high voltage distribution system. A ground fault location system that locates a ground fault point in a power system,
A sensor that is installed at each of a plurality of locations in the power system and measures a ground fault current flowing through a power line of the power system;
A ground fault point locating device for locating the ground fault point using the measured values of the ground fault current respectively measured by the sensors installed in the plurality of locations;
With
The sensor is
An annular core disposed so as to penetrate the power line; and
A coil wound around the core to detect the ground fault current generated in the power line when the power line is grounded;
Have
The winding core is formed such that a magnetic flux density of a magnetic flux generated when the ground fault current flows through the power line is equal to or less than a predetermined value determined based on a degree of change in permeability with respect to the change in magnetic flux density. A ground fault location system characterized by The ground fault location system according to claim 6,
The ground fault location system is characterized in that the predetermined value is determined based on a degree of coincidence between an increase rate of the magnetic flux density when the ground fault current flows through the power line and an increase rate of the magnetic permeability. The ground fault location system according to claim 6 or 7,
The ground fault location system, wherein the core has a cross-sectional area and a length such that the magnetic flux density is equal to or less than the predetermined value. The ground fault location system according to any one of claims 6 to 8,
A ground fault location system characterized in that the number of turns of the coil is determined to be equal to or less than a predetermined value. The ground fault location system according to any one of claims 6 to 9,
The ground fault location system, wherein the power system is a 22 kV special high voltage distribution system.

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