JPH0227888B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overcurrent indicating device for a power distribution line.

Conventionally, when an overcurrent occurs in a distribution line due to a short-circuit accident, this is detected by an overcurrent relay, the breaker at the substation is tripped, and a re-closing relay causes the breaker to reclose after a certain period of time. If the re-closing is successful, power is supplied as is, but if the re-closing is not successful, that is, the circuit breaker trips again, the distribution line is divided into multiple sections and the sections are sequentially supplied from the transmitting end. A method is adopted in which the faulty section is isolated using a so-called faulty section detection device that detects the faulty section and the power is transmitted to the healthy section by re-closing the disconnector. However, in recent years, as insulated wires have come to be used for power distribution lines, in the case of a short circuit caused by a lightning strike, even if the distribution line melts due to a concentrated arc, it is still insulated by the insulation coating. The ground fault could not be detected, and therefore, when the circuit breaker was reclosed, the circuit was successfully reclosed as if it were healthy, and power was supplied, allowing maintenance personnel to detect a temporary short circuit. There is a problem in that if it is made to seem like an accident and continues as it is, there is a risk of electric shock due to the broken distribution line and personal injury.
In addition, even if the distribution line does not melt, the damage caused by the concentration of the arc can be severe and the wire may break due to subsequent mechanical external force.If the circuit breaker trips due to overcurrent, In terms of maintenance and management of distribution lines, it is absolutely necessary to lock the automatic reclosing operation, quickly find the point of fault in the distribution line where overcurrent has occurred, and promptly restore the fault.

In order to solve this problem, we installed an overcurrent indicator on the distribution line, and when an overcurrent flows through the distribution line, a relay is operated to unlock the indicator piece and cause the indicator piece to protrude outside the device. Some display devices are designed to detect abnormalities during inspection, but these types of indicators must be manually reset on the pole each time after the display has been activated, making it difficult to climb up and down the pole or perform reset operations while the wires are live. This method requires a lot of effort and is also dangerous.

The present invention has been made in view of the above-mentioned points, and its purpose is to accurately detect and display overcurrent with a simple configuration, and to enable automatic recovery after recovery from an accident. Our mission is to provide what we believe in.

Embodiments of the present invention will be described below with reference to the drawings.
1 is a distribution line, 2 is a current detection unit detachably attached to the distribution line 1, and is a through-type current transformer formed in two parts.
It is formed by CT ₁ . Reference numeral 3 denotes a control section connected to the current detection section 2 and configured to cause the display section 4 to display when an overcurrent flows through the distribution line 1. The display unit 4 connected to the output terminal of the control unit 3 is an electrochromic display (ECD).
It consists of a display element called. this is,
It consists of a display electrode, a counter electrode, and an electrolyte through which ions move. When a voltage with a (-) polarity is applied to the display electrode and a (+) polarity is applied to the counter electrode, hydrogen ions in the electrolyte adhere to the display electrode. By applying a voltage of opposite polarity to the electrodes and passing a current in the opposite direction to that described above, the hydrogen ions are ionized and the above display is erased, and the memory function is activated. The display state is maintained even if the voltage is removed, and the memory has an electromotive force.

Next, the control section 3 will be explained. DB ₁ is a rectifier circuit connected to the secondary side of current transformer CT ₁ , and is designed to perform full-wave rectification by bridge-connecting diodes. At the output end of this rectifier circuit DB ₁ , a voltage non-linear element NLE consisting of multiple diodes (six in this example) connected in series in the forward direction and a low resistance fixed resistor R ₁₂ for overcurrent detection are connected. A variable resistor for overcurrent detection is connected in series between the terminals of this fixed resistor _R12 .
A circuit in which VR ₁ and temperature compensation circuit CC are inserted in series,
The display capacitor C 1 is connected in parallel with the display capacitor C ₁ via the constant voltage circuit CVC, and the display section 4 is connected between the terminals of the capacitor C ₁ and the emitter-collector of the PNP type main transistor Q ₁ and the protective resistor R ₁₃ . and a circuit in which overvoltage protection diodes D ₁ and D ₂ are connected in series in the forward direction between the terminals of the display unit 4.
Insert the collector and emitter of the display recovery transistor Q ₂ in parallel, and connect the (+) side output terminal of the rectifier circuit DB ₁ to the base of this transistor Q ₂ via the charging resistor R ₃ and the base resistor R ₄ . and connect
A bias resistor _R5 is inserted between the emitter and base of the main transistor _Q1 , and the discharge circuit of the capacitor _C1 is closed by conduction of the transistor _Q1 ,
The discharge of the capacitor _C1 causes the display section 4 to display a colored display, and the conduction of the transistor _Q2 erases the colored display.
In addition, the base of a discharging transistor Q ₃ whose emitter is connected to the (-) side output terminal of the rectifier circuit DB ₁ is connected to the output terminal (slider) of the variable resistor VR ₁ through the base resistor R ₆ . Connect this transistor
Insert the display recovery capacitor C ₃ between the collector and emitter of Q ₃ via the low resistance discharge resistor R ₇ .
The base of control transistor Q ₄ is connected to the connection point between resistor R ₇ and capacitor C ₃ via base resistor R ₉ , and the (+) side output terminal of rectifier circuit DB ₁ is connected via resistor R ₃ . The capacitor C ₃ is charged along the path DB ₁ →R ₃ →C ₃ →DB ₁ , and also through the path C ₃ →R ₃ →Q ₃ →C ₃ . The discharging resistor R ₇ and the charging resistor R ₃ are set in a relationship such that R ₇ <<R ₃ , so that the discharging time constant of the capacitor C ₃ is much smaller than the charging time constant. The transistor _Q4 has its collector connected to the output terminal of the variable resistor _VR1 via the resistor _R8 , and its emitter connected to the emitter of the transistor _Q3 , and is normally charged by charging the capacitor _C3 . Transistors Q ₂ and Q ₄ are made conductive by voltage, and when an overcurrent occurs, transistor Q ₃ is made conductive and capacitor C ₃ is instantaneously discharged, lowering the base potential of transistors Q ₂ and Q ₄ , and transistors Q ₂ and It is designed to ensure that Q ₄ becomes non-conductive. In addition, a capacitor _C2 for noise absorption is inserted between the collector and emitter of the transistor _Q4 , and the collector of the transistor _Q4 is connected to the base of the first transistor _Q5 , and the emitter is connected to the emitter of the transistor _Q5 . , the above transistor Q ₅ has its collector connected to the base of the second transistor Q ₆ of PNP type,
In addition, the bases are connected to the collectors of the transistors _Q6 , and the emitters of the transistors _Q6 are connected to the bases of the main transistor _Q1 via the resistor _R10 , and when the transistor _Q4 is turned off, the transistors _Q5 and _Q6 are connected to each other. A switching circuit with a latch function that allows the collector current of transistor Q ₆ to flow into the base of transistor Q ₅ and maintains conduction even if the output voltage V _OC of variable resistor VR ₁ becomes zero is connected to transistors Q ₅ and Q. ₆ , and its conduction maintains the conduction of the main transistor _Q1 and maintains the closure of the discharge circuit of the capacitor _C1 ,
The discharge voltage of the capacitor _C1 is applied to the display section 4 to cause the display elements of the display section 4 to display color to indicate an overcurrent. Also, the above variable resistor VR ₁
The temperature compensation circuit CC connected to the thermistor Th ₁
The output voltage of the variable resistor VR ₁ changes in response to changes in the current operating value due to temperature changes in the base-emitter voltage V _BE1 of _the transistor Q ₅ forming the above-mentioned switching circuit.
It is designed to compensate for V _OC . The low-resistance fixed resistor _R12 inserted at both ends of the circuit connecting the variable resistor VR ₁ and the temperature compensation circuit CC is set to a resistance value of, for example, about 1/100 of that of the variable resistor VR ₁ . , a protective constant voltage element CVE consisting of multiple diodes (two in this example) connected in series in the forward direction is inserted between the terminals of this resistor _R12 , and a variable resistor _VR1 and a temperature compensation circuit CC are inserted. The voltage applied to both ends of the circuit connected in series is the forward voltage of the constant voltage element CVE (for example, the forward voltage of one diode is
When the voltage exceeds 0.6V (1.2V in this example), the constant voltage element CVE is made conductive and held at the forward voltage to protect the output side of the variable resistor VR ₁ , and the voltage nonlinear element NLE and the constant voltage element CVE protects the constant voltage circuit CVC by suppressing the voltage applied to it from rising above a certain value. In addition, the constant voltage circuit CVC is the rectifier circuit.
The collector of a transistor _Q7 is connected to the (+) side output terminal of _DB1 via a resistor _R1 , and the base of the transistor _Q7 is connected via a resistor _R2 ,
The above base is connected to the cathode of a constant voltage diode ZD ₁ , and the emitter of the above transistor Q ₇ is connected to the emitter of the transistor Q ₁ and the capacitor C _1.
The anode of the voltage regulator diode ZD ₁ is connected to the other terminal of the capacitor C ₁ , and the resistor R ₁ is set to, for example, about 1/50 of R ₂ . The charging voltage applied to the capacitor _C1 is kept constant by the constant voltage circuit CVC.

The control section 3 and the display section 4 are housed in a box, and a display window is provided at the bottom of the box so that the colored display on the display section 4 can be accurately identified from the ground. The present device is formed by integrally mounting a current detection unit 2 in which a two-split through-type current transformer CT ₁ is clamped and connected from both sides of the distribution line 1, and this is connected to the distribution line 1. The system is designed to display fault points by displaying overcurrent by hanging the device at multiple locations on the device.

Next, the overcurrent display operation will be explained. now,
All transistors Q ₁ to _{Q 7} of the control unit 3 are non-conducting,
All of the capacitors C ₁ to _{C 3} are at zero, and in this state, when the current transformer CT ₁ of the current detection unit 2 is connected to the distribution line 1 by clamping, the secondary current of the current transformer CT ₁ is transferred to the rectifier circuit DB ₁
This current is full-wave rectified by
C ₃ is charged through resistor R ₃ with C ₃ R ₃ time constant.
At the same time, the current flows through the resistor _R2 of the constant voltage circuit CVC, causing the transistor _Q7 to conduct and charging the capacitor _C1 between the collector and emitter of the transistor _Q7 . Then, due to the increase in the charging voltage of the capacitor C ₃ , the transistors Q ₄ ,
The base potential of Q ₂ rises and transistors Q ₂ and Q ₄ become conductive. On the other hand, the charging voltage of the above capacitor _C1 also increases, and this charging voltage V _C1 becomes the voltage regulator diode.
Zener voltage of ZD ₁ and base of transistor Q _{7
The transistor _ _}
Since Q ₇ becomes non-conductive and the current flows to the circuit of DB ₁ → R ₂ → ZD ₁ → DB ₁ , the constant voltage circuit CVC
As the input voltage increases, this causes a voltage nonlinear element.
When the forward voltage of the NLE exceeds (for example, if the forward voltage of one diode is 0.6V, there are six diodes in this example, so it is 3.6V or more),
The above voltage nonlinear element NLE conducts (resistance R ₁₂
is low resistance). This causes a current to flow through the voltage nonlinear element NLE, and this current flows through the low resistance R ₁₂ and the variable resistance
The current is shunted to VR ₁ and the circuit of the compensation circuit CC. On this occasion,
Since the resistor R ₁₂ is set to a lower resistance (for example, about 1/100) than the variable resistor VR ₁ , the variable resistor VR ₁
The output V _OC is approximately zero, and transistors Q ₃ and Q ₅ are not conductive. Therefore, the transistors Q ₆ and Q ₁ remain non-conductive and the display section 4 is short-circuited and does not display due to the conduction of the transistor Q ₂ . Also, due to the conduction of the voltage non-linear element NLE, the current in the rectifier circuit DB ₁ is shunted to the circuits NLE → R ₁₂ VR ₁ −CC and R ₂ → ZD ₁ , but the resistor R ₂ has a high resistance. Since the current flowing through the circuit R ₂ →ZD ₁ is extremely small (for example, about 1/400) compared to the current flowing through the rectifier circuit DB ₁ , most of the current flowing through the distribution line 1 is due to the voltage. It will flow through the non-linear element NLE. Therefore, the accuracy of overcurrent detection by the variable resistor VR ₁ will not be reduced.

In this state, if a short circuit occurs in the distribution line 1 due to a lightning strike, etc., and an overcurrent flows, _{the output} voltage V _OC of the variable resistor VR ₁ increases, and the base-emitter voltage V _BE1 ( (e.g. 0.6V), transistor _Q3 becomes conductive (Fig. 2).
_Q3 ). As a result, capacitor C ₃ instantly discharges, lowering the base potential of transistors Q ₂ and Q ₄ ,
Transistors Q ₂ and Q ₄ become non-conductive, which causes transistor Q ₅ to become conductive (Q ₂ , Q ₄ and Q ₅ , Q ₆ in FIG. 2). At this time, due to the occurrence of the above-mentioned overcurrent, the voltage between the terminals of the constant voltage element CVE increases to the forward voltage of the constant voltage element CVE (assuming the forward voltage of one diode is 0.6 V, in this example, two diodes Therefore, when the voltage exceeds 1.2V, it becomes conductive and the voltage applied across the circuit of variable resistor VR ₁ and compensation circuit CC is maintained at the forward voltage of constant voltage element CVE. Then, due to the conduction of the transistor _Q5 , the base voltage of the transistor _Q6 decreases,
Transistor Q ₆ becomes conductive. this transistor
When Q ₆ becomes conductive, the collector current of transistor Q ₆ flows into the base of transistor Q ₅ , transistors Q ₆ and Q ₅ are latched, and the output V _OC of variable resistor VR ₁ flows into the base of transistor Q ₅ .
Transistors Q ₅ and Q ₆ remain conductive even when the voltage drops below the level of emitter voltage V _BE1 (Fig. 2).
_Q5 , _Q6 ). As the transistors Q ₅ and Q ₆ become conductive, the base voltage of the transistor Q ₁ decreases, and the transistor Q ₁ becomes conductive. As a result, a discharge circuit of the capacitor C ₁ is formed along a path of C ₁ →Q ₁ →R ₁₃ →4 →C ₁ , and the discharge voltage of the capacitor C ₁ is applied to the display section 4. Upon receiving this, a display element (not shown) of the display section 4 becomes colored as the hydrogen ions in the electrolyte adhere to the display electrode due to reduction, thereby indicating the occurrence of an overcurrent. On the other hand, at a substation (not shown), the distribution line 1
The overcurrent relay will detect the overcurrent and trip the circuit breaker, causing the power supply to stop. Transistors Q ₃ and Q ₅ become conductive (before being cut off after 3 cycles), which makes transistor Q conductive and maintains it, causing transistor Q ₁ to remain conductive.
Capacitor C ₁ continues to discharge, and as the discharge voltage decreases, the voltage between the base and emitter of transistor Q ₁ decreases, and transistor Q ₁ becomes non-conductive.
As a result, the applied voltage is removed from the display section 4, but since the display section 4 has a memory function, the display indicating that an overcurrent has occurred is maintained. The above transistor
Since the discharging current from the capacitor C ₁ flows through the transistor Q ₆ due to the non-conduction of Q ₁ , the transistors Q ₆ and Q ₅ maintain the conduction state. This retention means that the voltage across the terminals of capacitor _C1 is
This continues until the voltage between the bases and emitters of Q ₆ and Q ₅ (for example, 1.2V when the voltage between the bases and emitters is 0.6V) becomes lower than that or until the transistor Q ₄ becomes conductive. At this time, as shown in FIG. 2, the transistor Q ₃ receives the output V _OC of the variable resistor VR ₁ in a full-wave rectified waveform, so that the base-emitter voltage V _BE1 of the transistors Q ₃ and Q ₅ increases. Conducts only while the level is exceeded. That is,
It will repeat ON-OFF. Therefore, capacitor _C3 is repeatedly charged and discharged, but since the charging time constant is extremely large compared to the discharging time constant, the voltage across the terminals of capacitor _C3 is
The level of the base-emitter voltage V _BE2 of Q ₂ and Q ₄ is not reached, and the transistors Q ₂ and Q ₄ remain non-conductive (Q ₂ and Q in FIG. 2).

After an overcurrent occurs (for example, after 3 cycles), the substation circuit breaker trips. As a result, charging of the capacitor C ₁ is stopped, the voltage between its terminals decreases, and the transistors Q ₆ and Q ₅ become non-conductive. In this state, a maintenance worker searches for the fault point, the fault point on the distribution line 1 is detected by the colored display on the display section 4, and the fault is repaired. After the accident is restored, when the above-mentioned circuit breaker is turned on, the secondary current of the current transformer CT ₁ flows through the rectifier circuit DB ₁ to the capacitor C _{3 due to the current flowing in the distribution line 1, and the capacitor C 3 is} charged. be done. Due to this charging, the voltage between the terminals of capacitor C ₃ increases and the voltage between the bases of transistors Q ₂ and Q ₄ increases.
When the emitter voltage V _BE2 is reached, the transistor Q ₂ ,
Q ₄ is conductive. As a result, the display section 4 is short-circuited, the electromotive force of the display element is consumed, hydrogen ions adhering to the display electrodes are ionized, and the colored display is erased.
That is, the overcurrent display is automatically restored. On the other hand, when the circuit breaker is turned on after the accident is recovered, the transistor _Q7 of the constant voltage circuit CVC becomes conductive as described above, and the capacitor _C1 is charged, in preparation for the next occurrence of overcurrent.

In addition, when the temperature inside the box of this device installed on the distribution line 1 rises or falls below normal temperature (for example, 25°C) due to the influence of the outside temperature, the compensation circuit
CC thermistor Th ₁ detects the temperature and its resistance value changes according to the temperature change, and the output of variable resistor VR ₁ is also changed accordingly, resulting in the voltage between the base and emitter of the transistor and the forward voltage of the diode. This corresponds to changes due to the temperature characteristics of.
Therefore, it operates accurately at the initially set distribution line overcurrent detection value (for example, 600 A) in which variations in the current operating value are compensated for by the temperature characteristics of the base-emitter voltage V _BE1 of the transistors Q _{3 and} Q 5 . Since the overcurrent operation operates in the same manner as described above, a description thereof will be omitted.

According to the present invention, when an overcurrent flows through a distribution line, the display capacitor discharge circuit detects the overcurrent through a current transformer before the substation circuit breaker trips, and charges the display capacitor during normal operation. The main transistor inserted in the circuit is made conductive, and the capacitor is discharged, causing the display element to display color to indicate an overcurrent. Even if the power supply stops, the overcurrent can be accurately displayed, and since the display element has a memory function, the overcurrent display can be maintained even if there is no voltage. This makes it possible to easily find the distribution line where overvoltage has occurred, and to speed up accident recovery. In addition, a display reset transistor is inserted between the terminals of the display element, and the output terminal of the rectifier circuit connected to the current transformer is connected to the above capacitor via the charging resistor and the display reset capacitor's charging circuit. When an overcurrent is detected, the capacitor is connected so as to apply a charging voltage of There is nothing wrong with that, and what's more, after the accident is restored, the power supply from the power distribution line turns on the display reset transistor, erases the color display on the display element, and resets the overcurrent display. There is no need for any operation to restore the system, and the system can be restored automatically without any effort. Furthermore, the variable resistor for overcurrent detection is equipped with a temperature compensation circuit, so even if the temperature inside the box rises or falls due to the outside temperature, this device installed on the distribution line will follow this and prevent overheating. Current can be detected accurately, and detection accuracy can be further improved. Furthermore, the display capacitor is charged via a constant voltage circuit, and a constant voltage circuit and a voltage non-linear element are installed in parallel, and the current flowing through the distribution line is passed to the voltage non-linear element via a current transformer. Since most of the current is shunted, it can be applied to distribution lines with different currents (e.g. 1A to several 100A) during steady state, expanding the range of application and being stable against temperature changes. It has remarkable effects such as being able to make it more effective.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a time chart explaining the operation of FIG. 1. 1: Distribution line, 2: Current detection section, 4: Display section,
NLE: Voltage nonlinear element, CVC: Constant voltage circuit,
CC: Temperature compensation circuit, VR ₁ : Variable resistor for overcurrent detection, Q ₁ : Main transistor, C ₁ : Capacitor for display, C ₃ : Capacitor for display recovery, Q ₂ : Transistor for display recovery, R ₁₂ : Overcurrent Fixed resistance for detection.

Claims (1)

[Claims] 1. A voltage nonlinear element consisting of multiple diodes connected in series in the forward direction and a low-resistance fixed resistor for overcurrent detection are connected to the secondary side of the current transformer attached to the distribution line via a rectifier circuit. A circuit consisting of a variable resistor for overcurrent detection and a temperature compensation circuit inserted in series between the terminals of this fixed resistor and a display capacitor via a constant voltage circuit are connected in parallel, and between the terminals of the capacitor, A display section consisting of a display element that displays a colored display in response to an input voltage and a display recovery transistor that erases the colored display by conduction are inserted in parallel through the emitter and collector of a PNP type main transistor, The base and emitter of this transistor are connected between the terminals of the above-mentioned capacitor of a charging circuit consisting of a charging resistor connected to the above-mentioned rectifier circuit and a display reset capacitor, and the output terminal of the above-mentioned variable resistor is connected between the terminals of this capacitor. The collector and emitter of the discharging transistor whose base is connected to The first transistor whose base is connected to the output terminal, and the PNP whose emitter is connected to the base of the above main transistor.
A switching circuit is formed by connecting the collectors of the second transistor and the other transistor to the bases of the other transistor, and connecting the base to the output terminal of the display recovery capacitor between the base and emitter of the first transistor of the switching circuit. The collector and emitter of a control transistor connected to the display are inserted so that when an overcurrent is detected, the display recovery capacitor is discharged to cause the switching circuit to conduct through the control transistor. Overcurrent display device for distribution lines.