JPH0145803B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides multiple installations on a distribution line, and when an overcurrent occurs,
The present invention relates to an overcurrent display device that displays this.

Conventionally, when an overcurrent occurs in a distribution line due to a short circuit, etc., this is detected by an overcurrent relay installed at a substation, and the substation's switch is tripped.
The re-closing relay recloses the breaker after a certain period of time, and if the re-closing is successful, power is supplied as is, and if the re-closing is not successful, that is, the breaker trips again, the circuit is turned off at that point. A method has been adopted for distribution lines in which the faulty sections are selected and disconnected in order to separate the faulty sections, and the power is transmitted to the healthy sections by repeating the disconnection, thereby reducing the power outage area. ing. However, as power distribution lines have become insulated wires in recent years, if a short circuit accident due to lightning occurs, arcs will concentrate and even if the distribution line melts, it will be insulated by the insulation coating, making it impossible to detect a ground fault. When the circuit breaker is reclosed, power is supplied in a state of successful reclosing as if it were healthy, leading maintenance personnel to believe that it is a temporary short circuit, and the power supply continues. If this continues, there is a problem in that there is a risk of electric shock due to the disconnected power distribution line, resulting in 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 forces. In terms of maintenance and management of power distribution lines, it is necessary to lock the closed circuit and restore faults in power distribution lines where overcurrent has occurred. However, on the other hand,
Locking the automatic reclosing circuit when an overcurrent occurs
Since the power outage will be widespread over a wide area until the accident is restored, there is a problem in that it will lead to a decline in service in terms of power supply.

To deal with this, some systems have installed overcurrent indicators on distribution lines to quickly find the fault point when an overcurrent occurs, to quickly recover from the fault, and to shorten the duration of the power outage. This overcurrent indicator operates a relay when an overcurrent flows, releases the lock on the display piece, and projects the display outside the device.
In the case of a device configured in this way, it is necessary to manually return to the position on the pole each time after the display operation, which requires a lot of effort such as going up and down on the pole, returning operation with live wires, etc. It had the disadvantage of being dangerous.

The present invention has been made in view of the above-mentioned points, and its purpose is to provide a simplified structure that accurately detects and displays overcurrent, and automatically returns after holding this for a predetermined period of time. Our goal is to provide the following.

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 that is detachably attached to the distribution line 1, and is a through-type current transformer that is divided into two parts and is inserted through the distribution line 1 from both sides.
It consists of 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. A display section 4 connected to the output end of the control section 3
It consists of a display element called an electrochromic display (ECD). This involves placing a display electrode P ₁ and a counter electrode P ₂ facing each other in the container substrate.
Electrolyte for hydrogen ions to move between these two electrodes
EL is sealed and formed, and when a voltage of (-) polarity is applied to the display electrode P ₁ and a voltage of (+) polarity is applied to the counter electrode P ₂ , hydrogen ions in the electrolytic solution EL are transferred to the display electrode.
It adheres to P ₁ and displays a blue color, and the above electrode P ₁ ,
By applying a voltage with a polarity opposite to that described above to _P2 and causing a current to flow in the opposite direction, the hydrogen ions attached to the display electrode _P1 are ionized and the blue colored display is erased. Furthermore, as shown in Figure 3, which shows the relationship between the applied voltage time and the amount of electricity written, the display element ECD exhibits a characteristic in which the amount of electricity written increases with the passage of time, and color develops within a few seconds after voltage is applied. It has an electromotive force due to an increase in the amount of electricity written, and has a memory function so that the display state can be maintained even if the applied voltage is removed.

Next, the control section 3 will be explained. A rectifier circuit DB ₁ in which diodes are bridge-connected to perform full-wave rectification is connected to the secondary side of _{the current transformer CT 1 ,} and a plurality of diodes (for example, 11 A voltage non-linear element NLE connected in series in the forward direction and a low-resistance fixed resistor _R1 for voltage conversion are inserted in series, and a variable resistor _VR1 for overcurrent detection is inserted between the terminals of this resistor _R1 . and temperature compensation circuit
A circuit in which CC ₁ and are inserted in series and a constant voltage circuit
CVC ₁ and a display capacitor C ₁ are connected in parallel to the output terminal of this constant voltage circuit CVC ₁ via a diode D ₁ for reverse current blocking and a charging resistor R ₂ , and a voltage is connected between the terminals of the capacitor C ₁ . The display section 4 is connected to the emitter-collector of a PNP type main transistor _Q1 via a protective resistor _R3 connected to this collector, and the charging voltage of the capacitor _C1 is transferred to the main transistor.
A discharge is applied to the display element ECD via _Q1 . Between the terminals of the display section 4, there is a circuit in which overvoltage protection diodes D ₂ and D ₃ are connected in series in the forward direction, a discharge resistor R ₄ , and a collector-emitter circuit of a display recovery transistor Q ₂ . are inserted in parallel, and the connection point (point a) of voltage dividing resistors R ₅ and R ₆ inserted in series between the output terminals of the constant voltage circuit CVC ₁ is connected to the base of this transistor Q ₂ . The collector of the transistor Q ₃ for recovery control is connected, and the emitter of this transistor Q ₃ is commonly connected to the emitter of the above transistor Q ₂ , so that when the transistor Q ₃ becomes non-conductive,
The transistor Q ₂ is made conductive to short-circuit the terminals of the display element ECD of the display section 4, and a constant voltage circuit is connected to the base of the transistor Q ₃ .
Between the output terminal of CVC ₁ is an N-type field effect transistor (hereinafter abbreviated as FET) between the drain and source of Q ₄ , a variable resistor VR ₂ for release control, and a temperature compensation circuit.
The above variable resistor VR ₂ of the circuit inserted in series with CC ₂
The slider of FETQ 4 is connected through the base resistor R ₇ , and the gate of the above FETQ ₄ is connected to the collector of the main transistor Q ₁ to form FETQ ₄ as a source follower, and the source voltage changes according to the change of the gate voltage. Vary this through the variable resistor VR ₂ transistor
When the terminal voltage V _ECD of the display element ECD becomes lower than the level of the base-emitter voltage V _BE3 of the transistor _{Q 3 ,} the transistor Q ₃ is turned off and the transistor Q ₂ is turned off. It has become conductive. Therefore, when a predetermined time (for example, 4 hours) has elapsed since the main transistor _Q1 became non-conductive and the display element ECD started discharging the electromotive force due to the written amount of electricity through the discharge resistor _R4 , the variable resistor VR The discharge resistor R ₄ and the variable resistor VR ₂ are set so that the output of the transistor Q ₂ is lower than the base-emitter voltage V _BE3 of the transistor Q ₃ . In addition, the base of a transistor Q ₅ whose emitter is grounded is connected to the output terminal (slider) of the variable resistor VR ₁ through a base resistor R ₈ , and a low resistance discharge is established between the collector and emitter of this transistor Q ₅ . Insert a capacitor C ₂ through a charging resistor R ₉ and connect the output terminals of the rectifier circuit DB ₁ between the terminals of this capacitor C ₂ through a charging resistor R ₁₀ to connect the capacitor C ₂ to DB ₁ → Charge with the circuit R ₁₀ → C ₂ → DB ₁ ,
It is designed to discharge using the circuit C ₂ → R ₉ → Q ₅ → C ₂ . The resistance values of the discharging resistor R ₉ and the charging resistor R ₁₀ are set in the relationship R ₉ ≪ R ₁₀ (for example, 1/1000), so that the discharging time constant of the capacitor C ₂ is extremely smaller than the charging time constant. It's becoming more and more like that. Furthermore, the base and emitter of a transistor _Q6 are connected between the terminals of the capacitor _C2 through a base resistor _R11 , and the collector of this transistor _Q6 is connected to the base of a transistor _Q7 whose emitter is grounded. The charging voltage of the capacitor _C2 makes the transistor _Q6 conductive and lowers the base potential of the transistor _Q7 . Then, the output terminal of the variable resistor VR ₁ is connected to the base of the transistor Q ₇ through the base resistor R ₁₂ , and the main transistor Q ₁ has its emitter connected through the resistor R ₁₃ and a resistor R ₁₄ inserted between the emitter and the base. Connect the collector of a PNP transistor Q ₈ connected to the base of the transistor Q 8 , and connect the base of this transistor Q ₈ to the collector of the transistor Q ₇ to make the transistors Q ₇ and Q ₈ conductive due to the non-conduction of the transistor Q ₆ . The collector current of transistor _Q8 flows into the base of transistor _Q7 to create a variable resistor.
A switching circuit with a latch function that maintains conduction even when the output V _OC of VR ₁ becomes zero is formed by transistors Q ₇ and Q ₈ , and by maintaining conduction, the main transistor Q ₁ becomes conductive. hold and keep the discharge circuit of capacitor _C1 closed, display element
The charging voltage of the capacitor _C1 is applied to the ECD by discharging it to produce a colored display. or,
The temperature compensation circuit CC ₁ connected to the variable resistor VR ₁ is formed by connecting a thermistor Th ₁ and a resistor R ₁₅ in parallel, and the base-emitter voltage V of the transistors Q ₅ and Q ₇ forming the switching circuit is _BE5 ,
The output V _OC of the variable resistor VR ₁ is compensated in response to the temperature change of V _BE7 with respect to room temperature (for example, 25°C). And the output of the variable resistor VR ₁ above
V _OC at normal temperature (e.g. 25°C)
When an overcurrent (e.g. 600A current) flows through the
Base-emitter voltage of transistors Q ₅ and Q ₇
It is set to reach the level of V _BE5 and V _BE7 . In addition, a protective constant voltage element CVE is inserted between the terminals of the resistor _R1 , which has multiple diodes (two in this example) connected in series in a forward direction relative to the output of the rectifier circuit _DB1 . When the voltage across the terminals of resistor _R1 becomes equal to or higher than the forward voltage of the constant voltage element CVE (for example, if the forward voltage of one diode is 0.6 V, then in this example 1.2 V), the constant voltage element CVE conducts to maintain the forward voltage to protect the output side of the variable resistor VR ₁ , and also to protect the output side of the variable resistor VR 1.
Constant voltage circuit due to conduction between NLE and constant voltage element CVE
It protects the CVC ₁ by suppressing the voltage applied to it from rising above a certain value. Further, the voltage regulator circuit CVC ₁ has a voltage regulator diode ZD ₁ inserted in series between the collector and base of a transistor Q ₉ between the output terminals of the rectifier circuit DB ₁ , and a resistor R ₁₆ inserted between the collector and base. The output V _S1 is then sent from the emitter of the transistor _Q9 . Furthermore, a temperature compensation circuit CC ₂ connected to the variable resistor VR ₂ is formed by connecting a thermistor Th ₂ and a resistor R ₁₇ in parallel, and is configured to compensate for temperature changes in the base-emitter voltage V _BE3 of the transistor Q ₃ . variable resistance
It is designed to compensate the output of VR ₂ .

The control unit 3 and display unit 4 are housed in a box (not shown), and a display window is provided at the bottom of the box so that the colored display of the display unit 4 can be accurately identified from the ground, and The present device is formed by integrally attaching a current detection unit 2 to the top of the box, in which a two-split through-type alternator CT ₁ is removably clamped and connected to both sides of the distribution line 1. , which are suspended from a plurality of locations on the distribution line 1 to indicate fault points by overcurrent display.

Next, the overcurrent display operation will be explained. Now, all transistors Q ₁ to _{Q 9} of the control unit 3 are non-conducting.
Capacitors C ₁ and C ₂ are all at zero, and when current transformer CT ₁ is clamped and connected to distribution line 1 in this state, the secondary current of AC transformer CT ₁ becomes a current that has been full-wave rectified by rectifier circuit DB ₁ . and capacitor _C2 is the charging resistor
Charged through R ₁₀ with C ₂ R ₁₀ time constant. At the same time, the current flows through the resistor R ₁₆ of the constant voltage circuit CVC ₁ to turn on the transistor Q ₉ , and its output charges the display capacitor C ₁ via the diode D ₁ . Then, due to the rise in the charging voltage of the capacitor _C2 , the base potential of the transistor _Q6 also rises, and the transistor _Q6 becomes conductive. As a result, the base and emitter of transistor Q ₇ are short-circuited, and transistors Q ₇ and Q ₈ forming the switching circuit are maintained in a non-conducting state. On the other hand, when voltage nonlinear element NLE is applied with a voltage higher than the forward voltage of its multiple diodes, it becomes conductive and a current flows, and this current flows through resistor R ₁ and variable resistor VR _1.
and the circuit connected to the temperature compensation circuit _CC1 . At this time, the output V _OC of the variable resistor VR ₁ which receives the voltage between the terminals caused by the current flowing through the resistor R ₁ is smaller than the base-emitter voltage V _BE5 of the transistor Q ₅ (V _OC < V _BE5 ), so the transistor Q ₅ is not conductive. Further, since the gate voltage of FET _{Q 4 is} zero, transistor Q 3 is in a non-conductive state, and therefore transistor Q ₂ is conductive and short-circuits the terminals of display element ECD.

In this state, if a short-circuit accident occurs in the distribution line 1 due to a lightning strike, etc., and an overcurrent flows, the output V _OC of the variable resistor VR ₁ increases, and the voltage between the base and emitter of the transistor Q ₅ reaches the level of the base-emitter voltage V _BE5 , for example. At time t ₀ in FIG. 2, transistor Q ₅ conducts (the second
Figure _Q5 ).

This makes capacitor C ₂ C ₂ → R ₉ → Q ₅ → C ₂
is instantaneously discharged in the circuit, lowering the base potential of transistor Q ₆ and making transistor Q ₆ non-conductive, which makes transistor Q ₇ conductive and lowering the base potential of transistor Q ₈ , causing transistor Q ₈ to become non-conductive. Conducts (Figure 2, Q ₇ , Q ₈ ). When the transistor Q ₈ becomes conductive, the collector current of the transistor Q ₈ flows into the base of the transistor Q ₇ , and the transistors Q ₇ and Q ₈ are latched.
The output V _OC of the variable resistor VR ₁ is connected to the base of the transistor Q ₅ by the full-wave rectified waveform output of the rectifier circuit DB ₁ .
Once the emitter voltage _VBE5 drops below the level,
Even if the transistor Q ₅ becomes non-conductive, the charging time constant of the capacitor C ₂ is set to be much larger than the discharging time constant (C ₂ R ₁₀ ≫C ₂ R ₉ ), so
Even if the capacitor _C2 is repeatedly charged and discharged, its charging voltage will never reach the level of the base-emitter voltage _VBE6 of the transistor _Q6 , and the transistors _Q7 and _Q8 forming the switching circuit will become conductive. The state is maintained (C ₂ , Q ₇ Q ₈ in Figure 2). Then, due to the conduction of the transistors Q ₇ and Q ₈ , the base potential of the main transistor Q ₁ decreases, and the transistor
_Q1 conducts and holds it. Due to this conduction, the charging voltage V _C1 of capacitor C ₁ is applied to the gate of FETQ ₄ .
is applied, and a variable resistor that divides the source voltage
The output of VR ₂ makes the transistor Q ₃ conductive, which lowers the base potential of the transistor Q ₂ and makes the transistor Q ₂ non-conductive, and the capacitor C ₁ changes from C ₁ →Q ₁ →R ₃ →ECD→C ₁ discharge in the circuit of
The charging voltage V _C1 is applied to the display element ECD with the polarity shown. The display element ECD that received this is an electrolyte solution.
Hydrogen ions in the EL adhere to the display electrode _P1 due to reduction and develop a blue color to indicate the occurrence of an overcurrent.

On the other hand, in a substation (not shown), distribution line 1
The overcurrent that occurs is detected by the overcurrent relay, the circuit breaker trips (t _CB in Figure 2), and the circuit recloses after a certain period of time (for example, one minute). If the breaker trips again due to this re-closing, the fault section of the distribution line 1 is separated at that point, and the breaker closes again after a certain period of time to supply power to the healthy section.
Due to the occurrence of this overcurrent, maintenance personnel locate the fault point on the distribution line 1 using the overcurrent display of this device, and the fault is quickly restored. After the fault is restored, power is supplied to the faulty section.

On the other hand, when the shield circuit breaker trips due to the occurrence of the above-mentioned overcurrent, the power supply to this device will be stopped. (before tripping 3 cycles later), the transistor
Since Q ₇ and Q ₈ are kept conductive, the main transistor Q ₁ is kept conductive, and the capacitor
The discharge of C ₁ continues. Then, the charging voltage V _C1 of the capacitor C ₁ decreases due to discharging, and the amount of electricity written to the display element ECD increases as the applied voltage elapses, causing the terminal voltage V _ECD to rise. When the charging voltage V _C1 becomes smaller than the voltage V _ECD , the transistor Q ₁ becomes non-conductive,
Furthermore, when the charging voltage V _C1 becomes less than the level of the sum of the base-emitter voltages of transistors Q ₇ and Q ₈ (V _BE7 + V _BE8 ), transistors Q ₇ and Q ₈ also become non-conductive. Due to the non-conduction of the transistor _Q1 , the display element ECD discharges the electromotive force due to the written amount of electricity through the discharge resistor _R4 (that is, a current flows in the opposite direction to the display element ECD). Due to this discharge, the voltage V _ECD between the terminals of the display element ECD becomes as shown in Fig. 4.
As the gate voltage of FET Q ₄ decreases, its source voltage also decreases, and when a predetermined period of time (for example, 4 hours) has elapsed since the main transistor Q ₁ became non-conductive (Fig. 4).
T ₁ ), a variable resistor that divides the source voltage and outputs it.
When the output voltage of VR ₂ becomes lower than the base-emitter voltage V _BE3 of transistor Q ₃ , transistor Q ₃
becomes non-conductive, and the specified time (e.g. 4 hours)
If the accident has been recovered by then and power is being supplied, the base potential of transistor Q ₂ will rise, transistor Q ₂ will become conductive, and the terminals of display element ECD will be short-circuited. As a result, the display element ECD rapidly discharges its superpower, and the hydrogen ions adhering to the display electrode _P1 of the display element ECD are ionized in a voluminous manner, and the colored display is erased. That is, the overcurrent display is automatically restored. In other words, even if the fault caused by overcurrent is restored and power is supplied to the distribution line 1, the display element ECD maintains its colored display for a predetermined period of time, and the recovery control transistor _Q3
The overcurrent display is automatically reset by controlling the conduction of the display reset transistor _Q2 .

When power is supplied to the distribution line 1 after the accident is restored, the capacitor C ₁ is charged via the constant voltage circuit CVC ₁ , but at the same time, the capacitor C ₂ is charged via the resistor R ₁₀ , and its charging voltage increases. Transistor _Q6 becomes conductive due to the rise in
The switching circuit consisting of _Q7 and _Q8 is maintained in a non-conductive state, and the main transistor _Q1 is maintained in a non-conductive state 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 temperature compensation circuit
Thermistors Th ₁ and Th ₂ of CC ₁ and CC ₂ detect this and change the resistance value according to the temperature change, thereby varying the output of variable resistors VR ₁ and VR ₂ according to the temperature change. Therefore, variations in the operating current value due to temperature changes in the base-emitter voltages V _BE5 and V _BE3 of the transistors Q ₅ and Q ₃ are compensated for, and the overcurrent detection value of the distribution line 1 set in advance (for example, the current transformer CT ₁ 600A on the primary side) and a specified time (e.g. 4 hours)
It works accurately. The display operation is the same as described above, so the explanation will be omitted.

According to the present invention, when an overcurrent occurs in a power distribution line, it is quickly detected before the substation circuit breaker trips, and the display capacitor charged during normal operation is discharged, and the display capacitor charged during normal operation is discharged. The overcurrent is indicated by applying a voltage to the display element and displaying it in color, so even if the circuit breaker trips and the power supply stops, the occurrence of an overcurrent will be accurately indicated. be able to. Moreover, since the display element maintains its display based on the written amount of electricity, the overcurrent display can be maintained, and the distribution line in which the overcurrent has occurred can be easily found. In addition, the overcurrent display time is determined by discharging the electromotive force due to the amount of write electricity accumulated in the display element itself through the discharge resistor, and reducing the voltage between the terminals of the display element that decreases due to this discharge.
Set based on the time it takes for the display reset transistor inserted between the terminals of the display element to become conductive due to the disconnection of the reset control transistor applied to the base via the reset control variable resistor. Therefore, the display time can be arbitrarily set by the set value of the variable resistor. This means that when an overcurrent occurs, even if the time required for maintenance personnel to locate the fault point and the time required for fault recovery differs greatly between the transmission end and the end of the distribution line, the corresponding display time will be This has the great advantage of being able to be set in advance.

Moreover, since the variable resistor for reset control is equipped with a transient compensation circuit, the temperature inside the box changes depending on the outside temperature, which causes variations in the operating current value of the voltage between the base and emitter of the transistor for reset control. Even if this occurs, it can be compensated for and the display can be operated accurately within the set display time. After the display time has been reached, the display recovery transistor is made conductive by supplying power to the accident section after the accident is restored and the recovery control transistor is made non-conductive, thereby shorting the terminals of the display element. Since the electromotive force of the display element is rapidly discharged, the colored display can be rapidly faded, clearly distinguishing between the display state and the reset state, preventing maintenance personnel from misidentifying the information during inspection, and reducing the risk of errors. Current display can be accurately identified,
Moreover, since the display is automatically reset, there is no need to perform a reset operation on the pole, which reduces labor and further contributes to streamlining the maintenance management of power distribution lines.
In addition, the occurrence of overcurrent is indicated by applying the charging voltage of the display capacitor to the display element by discharging, and recovery is performed by discharging the display element itself, so it is easy to use at substations. Overcurrent indication and recovery can be performed regardless of the reclosing or reclosing locking operation of the disconnector, and the range of its application can be expanded.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a time chart explaining the operation of FIG. FIG. 4 is a discharge characteristic diagram of the display element shown in FIG. 1. 1: Distribution line, CT ₁ : Current transformer, Q ₁ : Main transistor, Q ₂ : Display recovery transistor, Q 3: Recovery control transistor, _{Q 4 :} Field effect transistor, R ₄ : Discharge resistor.

Claims (1)

[Claims] 1. A constant voltage circuit connected to the secondary side of a current transformer connected to the distribution line via a rectifier circuit, and an indicating capacitor connected to the output end of this constant voltage circuit via a diode for blocking reverse current. , a display element is connected between the terminals of this display capacitor via the emitter and collector of a PNP type main transistor, and displays a color by applying a voltage and maintains it; A variable resistor for overcurrent detection whose output is output to the base of the transistor is provided, and when an overcurrent occurs, the main transistor is turned on and the display capacitor is discharged to cause the display element to display color, A discharge resistor and the collector-emitter of a display reset transistor are inserted in parallel between the terminals of the display element, and the output terminal of the constant voltage circuit and the reset control transistor are connected between the base and emitter of the display reset transistor. The collector and emitter of the transistor are connected, and the base of the reset control transistor is connected to the above-mentioned field effect transistor whose drain and source are connected to the output terminal of the constant voltage circuit and whose gate is connected to the collector of the main transistor. source,
A temperature compensation circuit consisting of a thermistor and a resistor arranged in parallel is connected to the variable resistor for reset control, and the display element is colored by the reset control transistor. An overcurrent display device for a power distribution line, characterized in that the device is controlled to rapidly erase the color after a predetermined period of time.