JP2023176968A - Surge current measuring device - Google Patents

Abstract

To provide a surge current measuring device capable of measuring a magnitude of a surge current by a non-power supply system that requires neither a battery nor an AC power supply and with a relatively simple circuit configuration.SOLUTION: A surge current measuring device includes: a current transformer 1 for detecting a surge current flowing in a ground wire of a lightning arrester; a rectifying unit 2 for full-wave rectifying a secondary current of the current transformer 1; a capacitor 3 charged by a current rectified by the rectifying unit 2; a signal output unit 4 for generating an output signal based on a current discharged from the capacitor 3; and a surge current calculation unit 5 for measuring output time of the output signal output from the signal output unit 4 to calculate a magnitude of the surge current based on the output time of the output signal.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surge current measuring device that measures surge current caused by lightning strikes and the like.

2. Description of the Related Art A surge current measuring device that determines the magnitude of a surge current using a power-free method that does not require batteries or an AC power source is disclosed in Patent Document 1 listed below. The surge current measuring device of Patent Document 1 includes a current transformer that detects a surge current flowing through a grounding wire such as a lightning arrester, a rectifier circuit that full-wave rectifies the secondary current of the current transformer, and a device that is charged by the output of the rectifier circuit. A level detection circuit detects the peak value of the secondary current of the current transformer, and a microcomputer driven by the output of the capacitor. A level detection circuit that detects the peak value of the secondary current is composed of a plurality of thyristors, a peak hold circuit, or an A/D conversion circuit, and is driven by the output of a capacitor. Based on the output of the level detection circuit, the number of surge current intrusions and the peak value for each intrusion are recorded in the microcomputer. In the embodiment of Patent Document 1, the level detection circuit is configured with three thyristors having different operating threshold currents, and the magnitude of the surge current is determined based on the threshold currents of the three thyristors.

Japanese Patent Application Publication No. 2020-177775

In the surge current measuring device of Patent Document 1, in order to determine the magnitude of the surge current, a level detection circuit composed of a plurality of thyristors, a peak hold circuit, or an A/D conversion circuit measures the surge current (secondary current). ), the circuit configuration tends to be complicated.

An object of the present invention is to provide a surge current measuring device that can measure the magnitude of a surge current using a power-free method that does not require batteries or an AC power source, and with a relatively simple circuit configuration.

In order to solve the above problems, the present invention includes a current transformer that detects a surge current flowing in a line to be detected such as a lightning arrester, a rectifier that performs full-wave rectification of the secondary current of the current transformer, and a rectifier that a capacitor that is charged by a rectified current; a signal output section that generates an output signal based on the current discharged from the capacitor; and a signal output section that measures the output time of the output signal output from the signal output section. A surge current measuring device is provided, including a surge current calculation section that calculates the magnitude of the surge current based on output time.

According to the present invention, it is possible to provide a surge current measuring device that can measure the magnitude of a surge current using a power-free system that does not require batteries or an AC power source, and with a relatively simple circuit configuration.

FIG. 1 is a circuit diagram showing a surge detection device according to a first embodiment of the present invention. FIG. 2 is a circuit diagram showing a surge detection device according to a second embodiment of the present invention. FIG. 3 is a circuit diagram showing a surge detection device according to a third embodiment of the present invention. It is a circuit diagram showing a surge detection device concerning a 4th embodiment of the present invention.

Hereinafter, a surge current measuring device according to an embodiment of the present invention will be described with reference to the drawings. In the embodiment described below, the detection target line for detecting a surge current due to a lightning strike or the like is, for example, a grounding line of a lightning arrester.

FIG. 1 is a circuit diagram showing a surge current measuring device according to a first embodiment. The surge current measuring device of this embodiment includes a current transformer 1 that detects surge current flowing through a grounding wire, a rectifier 2 that performs full-wave rectification of the secondary current of the current transformer 1, and a rectifier 2 that performs full-wave rectification of the secondary current of the current transformer 1. A capacitor 3 that is charged by the current, a signal output section 4 that generates an output signal based on the current discharged from the capacitor 3, and an output time of the output signal output from the signal output section 4 are measured and the output signal is determined. The main element is a surge current calculation section 5 that calculates the magnitude of the surge current based on the output time. In this embodiment, a constituent circuit including a rectifier 2, a capacitor 3, and a signal output section 4 is mounted on a wiring board and housed inside a casing C shown by a two-dot chain line in the figure. The housing C is provided with input terminals 6 and 7 and output terminals 8 and 9, the rectifying section 2 is arranged on the input terminals 6 and 7 side, and the signal output section 4 is arranged on the output terminals 8 and 9 side. The current transformer 1 and the surge current calculation unit 5 are located outside the housing C, and the secondary coil wound around the iron core (not shown) of the current transformer 1 is connected to the input terminals 6 and 7, and the surge current calculation unit 5 is located outside the housing C. Section 5 is connected to output terminals 8 and 9. Furthermore, a varistor 10 is interposed between the input terminals 6 and 7 and the rectifier 2 in order to protect the above-mentioned constituent circuits and the like from surge currents.

The rectifier 2 is formed of, for example, a bridge circuit, and is connected to the input terminals 6 and 7 in parallel with the varistor 10. When a surge current flows through a grounding wire due to a lightning strike or the like, a secondary current corresponding to the surge current is induced in the secondary coil of the current transformer 1. This secondary current flows from the input terminals 6 and 7 to the rectifier 2, where it is full-wave rectified.

The secondary current that has been full-wave rectified by the rectifier 2 flows into a capacitor 3 connected to the output side of the rectifier 2 . The capacitor 3 is charged by the secondary current flowing from the rectifier 2 and stores electrical energy.

The signal output section 4 is connected to the capacitor 3 and is driven by the electrical energy stored in the capacitor 3 (no power supply system). In this embodiment, the main components of the signal output section 4 include a thyristor 4a connected to the capacitor 3 and a transistor 4b (for example, an NPN transistor) connected to the cathode side of the thyristor 4a.

The thyristor 4a is connected to the capacitor 3 in parallel with the variable resistor 4c, and the movable contact of the movable resistor 4c is connected to the gate of the thyristor 4a. The gate current of the thyristor 4a is adjusted by the variable resistor 4c, and thereby the conduction (gate ON voltage) between the anode and cathode of the thyristor 4a is variably adjusted. Further, a resistor R1 is provided on the cathode side of the thyristor 4a, so that the current flowing from the anode to the cathode of the thyristor 4a flows to the transistor 4b side.

The base of transistor 4b is connected between the cathode of thyristor 4a and resistor R1 via resistor R2. For example, in order to lengthen the output time (for example, several seconds to several tens of seconds) of the output signal output from the signal output section 4, a resistor R2 having a large resistance value (for example, ten kΩ to several MΩ) can be used. When the charging voltage of the capacitor 3 reaches the gate ON voltage of the thyristor 4a, a gate current flows to the gate of the thyristor 4a via the variable resistor 4c, and the thyristor 4a becomes conductive. When the current that conducts through the thyristor 4a flows to the base of the transistor 4b via the resistor R2, a collector current flows from the collector to the emitter of the transistor 4b. An output signal is generated by the collector current of the transistor 4b, and this output signal is outputted from the output terminals 8 and 9 to the surge current calculation section 5.

The surge current calculation unit 5 has a timer function that measures the output time of the output signal output from the signal output unit 4, and a calculation function that calculates the magnitude of the surge current based on the output time of the output signal. . The output time of the output signal output from the signal output section 4 changes depending on the electrical energy stored in the capacitor 3, and the electrical energy stored in the capacitor 3 changes depending on the surge current detected by the current transformer 1. Varies depending on size. That is, since the output time of the output signal output from the signal output section 4 changes depending on the magnitude of the surge current detected by the current transformer 1, the magnitude of the surge current is measured from the output time of the output signal. be able to. For example, the correlation (proportional relationship) between the magnitude of the surge current detected by the current transformer 1 and the output time of the output signal output from the signal output section 4 is determined in advance by an experiment, and the surge current calculation section 5 calculates the Store it in the function. Then, the calculation function calculates the magnitude of the surge current based on the output time of the output signal measured by the timer function and the correlation (proportional relationship) described above.

FIG. 2 is a circuit diagram showing a surge current measuring device according to a second embodiment. The surge current measuring device of the second embodiment differs from the surge current measuring device of the first embodiment in that a second capacitor 4d is added to the gate side of the thyristor 4a. By adding the capacitor 4d, the signal output section 4 starts operating when the charging voltage of the capacitor 4d reaches the gate ON voltage of the thyristor 4a, so the capacitor 3 stores a large amount of electrical energy and outputs the signal. The driving force of the output section 4 can be increased. Further, by adding the capacitor 4d, noise prevention effects can also be obtained.

FIG. 3 is a circuit diagram showing a surge current measuring device according to a third embodiment. The surge current measuring device of the third embodiment differs from the surge current measuring device of the first embodiment in that a second transistor 4e is added to the signal output section 4. The second transistor 4e is Darlington connected to the first transistor 4b. In this way, by providing two or more stages of Darlington circuits in the signal output section 4, the driving force of the signal output section 4 can be increased (a large load current can flow).

FIG. 4 is a circuit diagram showing a surge current measuring device according to a fourth embodiment. The surge current measuring device of the fourth embodiment has polarity-specific measuring circuits (positive polarity current measuring circuit Y and negative polarity current measuring circuit Z) added to the component circuit X of the surge current measuring device of the first embodiment. It is something. The positive current measurement circuit Y and the negative current measurement circuit Z are each branch-connected to the input side of the rectifier 2 (between the rectifier 2 and the varistor 10). A diode 11 is connected so that a positive secondary current flows from the current transformer 1, and a diode 12 is connected to the negative current measuring circuit Z so that a negative secondary current flows from the current transformer 1. There is. The circuits downstream of the diodes 11 and 12 in the positive current measurement circuit Y and the negative current measurement circuit Z are the same as the circuits downstream of the rectifier 2 in the circuit X of the first embodiment. However, the configuration circuit may be the same as that of the second or third embodiment.

The positive polarity current measurement circuit Y includes a capacitor 3 that is charged by the positive polarity secondary current of the current transformer 1, a signal output section 4 that generates an output signal based on the current discharged from the capacitor 3, and a signal output section 4 that generates an output signal based on the current discharged from the capacitor 3. The surge current calculating section 5 measures the output time of the output signal output from the section 4 and calculates the magnitude of the positive surge current based on the output time. Further, the negative polarity current measurement circuit Z includes a capacitor 3 charged by the negative secondary current of the current transformer 1, a signal output section 4 that generates an output signal based on the current discharged from the capacitor 3, The surge current calculation unit 5 measures the output time of the output signal output from the signal output unit 4 and calculates the magnitude of the negative surge current based on the output time.

The positive polarity current measuring circuit Y can measure the magnitude of a surge current having a positive polarity charge, and the negative polarity current measuring circuit Z can measure the magnitude of a surge current having a negative polarity charge. be able to. Moreover, the component circuit X can measure the magnitude (absolute value) of a surge current having charges of both positive and negative polarities. In this way, the surge current measuring device according to the fourth embodiment can measure the magnitude of the surge current according to its polarity (bipolarity, positive polarity, negative polarity), so that the flow of the surge current can be measured. By knowing the direction and size of the surge current, it is possible to identify the route of surge entry based on the direction and size of the surge current flow, and to clarify areas where lightning countermeasures, etc., need to be strengthened.

In the embodiments described above, the surge current calculation unit 5 can be configured as an accessory device of the surge current measuring device, or can be incorporated into the software of a remote monitoring device, a PC terminal, or a smart phone terminal. Alternatively, the surge current calculation section 5 can be built into the housing C of the surge current measuring device.

1 Current transformer 2 Rectifier 3 Capacitor 4 Signal output section 4a Thyristor 4b Transistor 4d Second capacitor 4e Second transistor X Bipolar component circuit Y Positive polarity current measurement circuit Z Negative polarity current measurement circuit

Claims (5)

A current transformer that detects surge current flowing in the detection target line,
a rectifier that full-wave rectifies the secondary current of the current transformer;
a capacitor charged by the current rectified by the rectifier;
a signal output unit that generates an output signal based on the current discharged from the capacitor;
A surge current measuring device comprising: a surge current calculation section that measures an output time of the output signal output from the signal output section and calculates a magnitude of the surge current based on the output time. The surge current measuring device according to claim 1, wherein the signal output section includes a thyristor connected to the capacitor and a transistor connected to the cathode side of the thyristor. The surge current measuring device according to claim 2, wherein the signal output section further includes a second capacitor connected to the gate of the thyristor. The surge current measuring device according to claim 2 or 3, wherein the signal output section further includes a second transistor connected to the transistor. further comprising a polarity measurement circuit that measures the surge current according to its polarity,
The polarity measurement circuit includes a positive polarity current measurement circuit and a negative polarity current measurement circuit that are branch-connected to the input side of the rectifier,
The positive current measurement circuit includes a capacitor charged by a positive secondary current of the current transformer, a signal output section that generates an output signal based on a current discharged from the capacitor, and the signal output section. and a surge current calculation unit that measures the output time of the output signal output from and calculates the magnitude of the positive surge current based on the output time,
The negative polarity current measurement circuit includes a capacitor charged by a negative secondary current of the current transformer, a signal output section that generates an output signal based on a current discharged from the capacitor, and the signal output section. 2. The surge current measurement unit according to claim 1, further comprising a surge current calculation unit that measures the output time of the output signal output from and calculates the magnitude of the negative polarity surge current based on the output time. Device.

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