JP2002247748A - Short-circuit detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of facilitating the determination of a short-circuited section by measuring a resistance value by combining two phases among three phases of a three-phase cable and using only the obtained data of the resistance value. SOLUTION: In a short-circuit detector 10, terminals 11a to 11c connected to each phase of the three-phases cable are disposed via a switching part 12. Energizing is carried out between the selected two phases from an AC signal generating part 15 by a command of a main control circuit 13. A resistance component detection part 16 obtains resistance value data, displays the data of the resistance value on a display device 17, and specifies the position of a short circuit in accordance with the volume of the data of the indicated resistance value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus used for detecting a short circuit on a high voltage side or a secondary side of a transformer in a private high voltage electric facility or the like.

[0002]

2. Description of the Related Art In general, in private high-voltage electrical equipment and the like, when performing construction or inspection of electrical equipment on the private side,
For example, a day when the facilities do not operate, such as a holiday, is selected, and the required work is performed with a power cut in the construction section. Then, after conducting the construction and inspection of the electric equipment on the private side, when energizing the constructed section, it is necessary to confirm that there is no short circuit or the like in the high-voltage side and the low-voltage side electric circuit, and then receive the power. There is. Therefore, when receiving power after the above-mentioned work, the installation location of the short-circuit grounding device, the jumper wire, etc., the number of installations, etc. are checked using a check table and the like. Means are used.

[0003]

However, even when the check is made using the check table or the like, there is a problem that a short circuit sometimes occurs due to omission of check or the like, and a serious short circuit accident may occur. is there. This is because the detection of the short-circuit is performed manually, but in order to completely prevent the occurrence of the short-circuit accident as described above, more strict confirmation is required, Need to be done. However, even if the checklist is used many times, it is not possible to completely avoid an accident such as a short circuit at the time of receiving power again when the check worker's beliefs etc. work, and more efficient At present, the development of a good confirmation method is desired.

An object of the present invention is to solve the above-described conventional problem of checking the short-circuit of an electric circuit, and a method for easily ensuring the safety of electric equipment by confirming the resistance value data of the electric circuit. It is intended to provide a device.

[0005]

SUMMARY OF THE INVENTION According to the present invention, an electric resistance including a high-voltage side and a low-voltage side electric circuit is connected to a high voltage side of a power receiving facility, and a detection of a short circuit or the like of the electric circuit is detected from the obtained data. Related to the device to perform. The invention according to claim 1 of the present invention is provided in the measurement terminal switching unit, and sequentially selects two terminals from among the terminals connected to each phase of the polyphase AC circuit and the two phases of the polyphase AC circuit, and selects the two phases. Voltage applying means for applying a measuring AC voltage between terminals, measuring means for sequentially measuring a resistance value between the two phases, and means for determining a short circuit based on data obtained by the measuring means based on the resistance value only; It is characterized by having.

A second aspect of the present invention is characterized in that a short-circuit of an electric circuit is detected before power supply is started again from a power failure state of the power receiving equipment.

According to a third aspect of the present invention, in the means for determining a short circuit based on data obtained by the measuring means, the short circuit of the high voltage side bus, the secondary short circuit of the transformer and the secondary short circuit of the instrument transformer are provided. It is characterized in that three types of judgments can be made.

[0008] With the above-described configuration, in the device of the present invention, short-circuiting is performed based on the measured value obtained by repeatedly measuring the resistance value by combining two phases of the polyphase AC circuit. The determination of the site can be easily performed. Since the data obtained by the device is only the resistance value, the determination of the short-circuit state can be easily performed. Therefore, it is possible to prevent serious accidents from occurring beforehand. Serious accidents can be prevented from occurring.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of the present invention will be described according to the illustrated example. As shown in FIG. 2, the short-circuit detector 10 shown in FIG.
Terminals 11a, 11c connected to each of 2b, 2c
b, 11c, and the three terminals are provided to be connected to the measurement terminal switching circuit 12. The measurement terminal switching circuit 12 includes:
The main control circuit 13 is connected to the main control circuit 13 and the resistance component detection circuit 16, and is provided with a circuit for inputting control / storage and operation information of the apparatus. The main control circuit 13 includes a display 17 and a resistance component detection circuit 1.
6 and an AC signal generating circuit 15 is connected to the resistance component detecting circuit 16, and the display 17 displays the operating status of the device and the measured resistance value between each line. Make up. As a power source of the device 10, since the power consumption of the device described below is very small, a battery or the like can be used.
In addition, 100
It may be supplied with V and used as a power supply for the device.

In each of the circuits arranged in the short-circuit detector 10, the main controller 13 comprises a control, storage and operation circuit, and performs operations such as outputting control information for each component (circuit). It is configured as a combination of a control means for instructing and obtaining data by operation of each circuit, a CPU and a memory for storing data, operation buttons and the like, and performs comprehensive control of the apparatus. The AC signal generation circuit 15 includes an oscillation circuit for generating a measurement frequency, a voltage amplification circuit, a constant current generation circuit, and the like, and generates a voltage and a current to be applied to the high-voltage bus 2 as an object to be detected.

The main control circuit 13 and the AC signal generating circuit 1
5 has three terminals 11a, 11b, 11c as described above, and a signal from the main control circuit 13 combines two of those terminals. While switching, the resistance between the selected two terminals is measured. The terminal switching operation in the measurement terminal switching circuit 12 is performed while automatically switching the measurement terminals based on a program set in the control / storage / operation unit provided in the main control circuit.
The resistance value between each of the two terminals is measured, and the detected information is transmitted to the resistance component detection circuit 16. The order of the operation of switching terminals in the measurement terminal switching circuit 12 is as follows.
An operation of measuring a resistance value between terminals while sequentially switching between terminals of a multi-phase electric circuit or a multi-wire electric circuit, such as between terminals 11a and 11b, between terminals 11b and 11c, and between terminals 11a and 11c. Is repeated.

In the resistance component detection circuit 16, a resistance value is detected by detecting a resistance component current I 'flowing through the detection object 1 by a synchronous detection circuit or a correction current [Id] described later, and performing an arithmetic processing or the like. , And sends data to the main control circuit 13. The circuit shown as the object to be detected is shown in the equivalent circuit diagram of FIG. 3 and is intended for a circuit including all of the high-voltage side bus 2, the transformer of the private power receiving equipment, and the low-voltage side electric circuit. In the apparatus shown in FIG. 1, the flow of signals between circuits is indicated by a solid line, and the flow of control signals is indicated by a dotted line. Further, the timing at which the resistance value is detected by the resistance component detection circuit 16 is configured to be synchronized with the operation of switching the measurement terminals in the measurement terminal switching circuit 12. As described above, the short-circuit detector 10 according to the present embodiment is a device that can be connected between two-phase terminals to perform an operation of measuring a resistance value. Instead, both the multi-wire circuit and the multi-phase circuit are configured as capable of detecting a short circuit between two phases.

The basic principle of the operation of detecting a short circuit in the short-circuit detector 10 can be described first with reference to an equivalent circuit shown in FIG. For example, an electric circuit of a private electric facility or the like can be represented by an equivalent circuit such as a capacitance C such as a power capacitor, a resistance R such as a transformer or an electric wire, and an inductance X. Then, terminals a and b of the object 1 are detected.
When an AC voltage V is applied from the short-circuit detector 10 during that time, a current I flows through the detection target 1. The phase relationship between the applied voltage V and the current I flowing, as shown in the example of the graph of FIG.
Is generated. The relationship between the phases changes depending on the correlation between the capacitance C and the inductance X of the electric circuit.

In the vector relationship shown in FIG. 4, when a voltage V is applied from the short-circuit detector 10, a necessary condition for detecting a short-circuit is as shown in the graph of FIG. Assuming that the current flowing through the sensing object is I, the current I has a magnitude and a phase φ related to the values of R, C, and X in the equivalent circuit. This current I changes in magnitude and phase due to C and X, which are unrelated to the short circuit,
It is difficult to detect a short circuit in an electric circuit only by detecting I and V. Therefore, the data relating to C and X of the equivalent circuit is ignored as much as possible, and only the resistance component of the equivalent circuit is measured, whereby the short circuit can be reliably detected.

In view of the above, in the graph of FIG. 5, changes in the vector depending on the values and positions of the R, C, and X are shown.
The applied voltage vector V, the current flowing through the object to be detected (hereinafter referred to as “measured current”) is I, and the phase difference between both is φ. The angle of the phase shift φ changes depending on the mutual values of R, C, and X of the electric circuit. Further, when the position of R, C, or X in FIG. May be the position of the vector Ia indicated by the broken line.

Further, in order to detect a short circuit, it is necessary to detect the resistance component R of the electric circuit as described above. In the graph of FIG. 5, the current vector component I ′ in the same direction as the applied voltage vector V includes a large resistance component of the electric circuit,
It can be seen that the current vector component I ″ having a phase difference of 90 ° from the applied voltage vector V contains many components related to C and X. Therefore, in order to detect the measured current I ′ component, a synchronous detection circuit uses I ′. = I cos φ, and as shown in FIG. 6, a correction current Id having a phase difference of 90 ° from the applied voltage V is added to the current vector component I to perform vector correction, and the magnitude of the correction current Id is made variable. There is also a method for obtaining I 'by an operation for obtaining a point at which the combined current value becomes the smallest, and since I' obtained by these methods has a small C and X component and a large resistance component, I ' It is suitable for use as data for detecting a short circuit.

The applied voltages V and I 'obtained from the above operation
Is converted to a resistance value (hereinafter, referred to as “Rs”) that makes it easy to determine the short-circuit state of the electric circuit. The value of Rs can be calculated by a simple Ohm's law operation (Rs = V / I ') or, if a circuit using a constant current power supply is adopted, by converting the magnitude of I' into a resistance value. Ask.

Next, a short-circuit detection portion and an equivalent circuit in the device of the present invention will be described. First, in the present embodiment, the short-circuit of the high-voltage side and the low-voltage side electric circuit of the private electric equipment can be detected collectively. That is, when it is detected using the short-circuit detector 10, (a) a short-circuit in the high-voltage side bus or the like. (B) Transformer secondary side short circuit (low voltage side electric circuit short circuit): The measured value is the sum of the primary conversion resistance value of the transformer secondary circuit and the primary circuit resistance value. (C) Instrument transformer (hereinafter referred to as "VT") secondary-side short circuit (low-voltage side electric circuit short-circuit): The measured value is the sum of the primary conversion resistance value and the primary circuit resistance value of the transformer secondary circuit.

The equivalent circuit and data at the time of short-circuiting of the high-voltage side bus and the like in (a) will be described. The short-circuit of the high-voltage side bus is represented by a short circuit between terminals a and b in the equivalent circuit shown in FIG. be able to. In the short-circuit state between the terminals a and b in the equivalent circuit of FIG. 7, the phase of the applied voltage V and the measurement current I in the short-circuit detector 10 becomes the same (φ is 0), and the resistance component of the circuit can be easily detected. When a short circuit occurs in the high-voltage side bus or the like, the measured value is substantially 0 [Ω]. In the circuit of FIG. 7 showing the equivalent circuit of the transformer and VT, the excitation admittance of the transformer is a very small value.
It is described as an equivalent circuit ignoring the value. In the description of the circuit, r1: primary resistance, r2: secondary resistance,
x1: Primary leakage reactance, x2: Secondary leakage reactance.

It is assumed that the equivalent circuit at the time of short-circuiting on the transformer secondary side in (b) and (c) is as shown in FIG. In this case, the relationship between the applied voltage V and the measured current I is similar to that shown in FIG. Then, from the measurement principle of the apparatus shown in this embodiment, C, X1 and the primary conversion value X2 'of the secondary leakage reactance in FIG. 8 are ignored, and the measured values are the primary resistance r1 and the primary conversion resistance of the secondary resistance. The equivalent circuit and data when the secondary side such as the transformer or VT of the above (b) and (c), in which the sum of r2 'is displayed, will be described. The equivalent circuit is a transformer, VT
A circuit as shown in FIG. 9 is formed by the back electromotive force.
As shown in this circuit, the phase difference between the applied voltage V and the measurement current I becomes 90 ° (I advances by 90 ° from V), and when measured by a short-circuit detector from the primary terminals a and b (high voltage side), To ignore the capacitance C of the high-voltage capacitor, the primary leakage reactance x1 of the transformer, and the primary resistance component r1,
The measured resistance value becomes infinite.

In this embodiment based on the above-described operation principle, the measurement frequency, the measurement current, and the voltage are set as described below. In other words, the measurement accuracy is
It is susceptible to noise due to electromagnetic induction, electrostatic induction, and the like of the electric circuit, and is further greatly affected by the capacitance C of the electric circuit. Therefore, the following conditions are set to perform the measurement work. * As the measurement frequency, a frequency smaller than the commercial frequency, for example, is adopted as a frequency that is hardly affected by the capacitance C of the electric circuit and noise. * Although a sine wave alternating current is generally used for the measurement waveform, a square waveform may be employed for the purpose of simplifying the circuit, increasing the power efficiency of the electronic circuit, and the like. * The current and the voltage are set to appropriate values that are not easily affected by the noise of the electric circuit of the object to be detected, that are hardly affected by the electric equipment, and that have a small risk of electric shock.

When the short-circuit detector 10 having the above configuration is connected to a high-voltage bus or the like of a private electric facility to detect a short circuit of an object to be detected, first, the private electric facility is set to a power outage state. After performing predetermined work and before re-energizing, it is necessary to confirm that there is no short circuit or the like in the high-voltage side and low-voltage side electric circuits, and then receive power. Therefore, as described in the above-mentioned conventional example, the installation location and the number of installation of the short-circuit grounding device, the jumper wire and the like are confirmed using a check table or the like. Further, when various members such as the short-circuit grounding device are removed, means for confirming the removal by a check table or the like is used. In parallel with the above-mentioned checking operation or after checking by a conventional method, the terminals of the short-circuit detector 10 are connected to three high-voltage buses of three-phase AC as shown in the example of FIG. To short-circuit detector 10
While the measurement terminals are switched by the measurement terminal switching circuit 12, the resistance value between the two phases is measured. Then, by performing the above-described confirmation work, it is performed whether or not it is possible to perform the power transmission after the power outage, or to confirm that the safety of the electric circuit is ensured.

When the resistance value is measured by the short-circuit detector 10, for example, (a) in the case of a short-circuit on the high-voltage side bus, etc., the value becomes 0Ω; and (b) a short-circuit on the secondary side of the transformer. In the case of (short circuit on the low voltage side), a value of about 1 to 100Ω can be obtained, but it has been found that the larger the rated capacity of the transformer, the smaller the measured value. (C) In the case of a short circuit on the secondary side of VT (instrument transformer),
A measured value of about 1000 to 1500 Ω is obtained. (D) In a state where there is no short circuit in the electric circuit of the detected object, that is, in a normal state, the measured value as the resistance value data is an infinite value.

Further, by using the apparatus of the present invention,
The resistance measurement function using the AC voltage and the current can use the mechanism shown in the above-described embodiment for the following measurement in addition to the short-circuit detection.・ Detection of rare short circuit etc. of transformer: Rare short circuit can be detected by shorting the secondary side of the transformer and displaying the resistance value between each phase measured from the primary side.・ Short circuit detection of high voltage capacitor: Short circuit can be detected by measurement between high voltage buses.

When it is confirmed that there is no short circuit on the high voltage side and the low piezoelectric path side after the construction or inspection of the private electric equipment using the apparatus of the present embodiment, the short circuit detector 10-3 is used.
One terminal is connected to the three-phase high voltage side. Then, by selecting two phases from the three-phase cables and measuring the electric resistance including the high-voltage side and the low-voltage side electric circuit, a short circuit of the electric circuit can be detected from the data. Further, the checking operation which conventionally relies only on humans can be more reliably performed by using the checking method based on the resistance value data or by using the conventional method and the method for obtaining the resistance value data. Therefore, by using the method of the present invention, in addition to detecting short-circuiting due to forgetting to remove a short-circuited part of an electric circuit after inspection of private electric equipment, etc., confirmation of disconnection of a transformer, interlayer short-circuit (rare short), power It can also be applied to the confirmation of a short circuit of a capacitor.

When the apparatus shown in the present embodiment is used, the following features can be exhibited. -Prevention of serious accidents: A short-circuit accident caused by forgetting to remove a short-circuited part of an electric circuit prevents a major accident such as a power outage of a large number of electrical equipment connected to the power transmission and distribution system, equipment damage due to short-circuit current, and personal injury. be able to. -Since the data obtained by the device is only the resistance value, it is possible to easily determine the state of the short circuit. The determination of the short-circuit site can be easily performed based on the obtained measurement values. That is, the high voltage side bus short circuit (0Ω), the transformer secondary side short circuit (the larger the rated capacity, the smaller the measured value is, generally about 1 to 100Ω), and the VT secondary side short circuit (about 1000 to 1500Ω). On the other hand, when there is no short circuit, the resistance value becomes infinite. In order to individually display the resistance values between the respective phases (three-phase RS, ST, TR, etc.), the short-circuit phase is determined from the obtained resistance value data.・ In one operation, short circuit from high voltage side to low piezoelectric path side
Can be detected all together.・ Since the measured voltage and current are small, there is no electric shock or damage to the device under test.・ Compact and lightweight, and easy to use. -Since a measurement circuit with low power consumption can be configured, a battery can be used as a power supply, and a device with good workability can be configured.

[0027]

As described above, in the apparatus of the present invention, the resistance value is measured by combining two phases of the three-phase cable, and the short-circuited portion is determined based on the measured value. The determination can be made easily. Since the data obtained by the device is only the resistance value, the determination of the short-circuit state can be easily performed. Therefore, it is possible to prevent serious accidents from occurring, and to prevent short-circuit accidents caused by forgetting to remove short-circuited parts of the electric circuit, such as power outages of a large number of electrical equipment connected to the transmission and distribution system, equipment damage due to short-circuit current, personal injury, etc. Serious accidents can be prevented from occurring.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a device of the present invention.

FIG. 2 is an explanatory diagram of a state in which the device is connected to a high-voltage side bus.

FIG. 3 is an equivalent circuit diagram in a state where the device of the present invention is connected.

FIG. 4 is a vector diagram showing a relationship between an applied voltage and a flowing current.

FIG. 5 is a vector diagram showing an example of an Ia component.

FIG. 6 is a vector diagram showing a relationship between correction currents Id and I ′.

FIG. 7 is an equivalent circuit diagram of a transformer.

FIG. 8 is an explanatory diagram of an equivalent circuit when the secondary side is short-circuited.

FIG. 9 is an explanatory diagram of an equivalent circuit when a secondary side such as a transformer is opened.

[Explanation of symbols]

2 High voltage side busbar, 10 Short circuit detector, 11
Terminal, 12 measurement terminal switching section 13 main control circuit,
15 AC signal generation circuit, 16 Resistance component detection circuit, 17 Display.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02H 7/26 H02H 7/26 A F term (Reference) 2G014 AA03 AB04 AB33 AC19 2G028 AA02 BB09 BB10 BB20 BE05 BF03 CG02 DH05 DH06 EJ02 FK02 GL02 5G004 AA02 AB01 BA03 CA01 CA02 GA01 5G058 BB05 BC08 BD10 BD11 CC01 CC09

Claims (3)

[Claims] 1. An apparatus which is connected to a high voltage side of a power receiving facility, measures electric resistance including a high voltage side and a low voltage side electric circuit, and detects a short circuit or the like of the electric circuit from the obtained data. A terminal provided in the switching unit and connected to each phase of the polyphase AC circuit; and a voltage application for sequentially selecting two phases of the polyphase AC circuit and applying a measurement AC voltage between the two phase terminals. Means for measuring a resistance value between the two phases in sequence, and means for determining a short circuit based on data obtained by the measurement means based on only the resistance value. 2. The short-circuit detector according to claim 1, wherein a short-circuit of an electric circuit is detected before the power supply is restarted from a power failure state. 3. The means for judging a short circuit based on data obtained by the measuring means includes three kinds of judgments: a high voltage side bus short circuit, a transformer secondary side short circuit, and an instrument transformer secondary side short circuit. The short-circuit detector according to claim 1, wherein the short-circuit detector can perform the following.