KR100644142B1 - An apparatus for sensing open state of the secondary terminal of a current transformer - Google Patents

Abstract

The present invention is a device for detecting the opening (CT) of the secondary terminal of the current transformer (CT), more specifically, when the secondary terminal is opened by directly connected to the secondary terminal of the current transformer to operate the relay circuit, etc. using this as an input signal By shorting the secondary terminal of the current transformer to prevent the current transformer burnout, electric shock, and the like.

Current transformer opening detection device of the present invention is connected to the current transformer secondary terminal, reducing the open circuit voltage of the secondary terminal to cut off the overvoltage, rectifier for rectifying the voltage signal passing through the circuit protection, the output from the rectifier A comparison unit for comparing the voltage signal with a value of a predetermined reference voltage and outputting a voltage signal for opening the current transformer secondary terminal and a function of shorting the open secondary terminal by operating the voltage signal output from the comparison unit. It comprises a short circuit section to perform.

The short circuit unit may be configured using a relay contact circuit, a transistor capable of performing a similar switching function, a triac, an SCR, a photo relay, or the like.

In addition, the current transformer opening detection device of the present invention can stably short the secondary terminal of the current transformer (CT) in the operation, such as inspection, repair and replacement of various devices such as an ammeter, power meter, recorder connected to the electrical equipment. It includes a check switch that can be used.

Current transformer, secondary terminal, relay, sensing circuit, magnetic induction

Description

Opening detection device of current transformer secondary terminal {AN APPARATUS FOR SENSING OPEN STATE OF THE SECONDARY TERMINAL OF A CURRENT TRANSFORMER}             

1 is a circuit diagram of a relay current transformer opening detection apparatus according to an embodiment of the present invention.

2 is a circuit diagram of a power supply unit supplied to a sensing circuit of the present invention.

Figure 3 is a circuit diagram of the electronic current transformer opening detection apparatus according to an embodiment of the present invention.

Figure 4 is a circuit diagram of a current transformer open detection device according to an embodiment of the present invention.

Figure 5 is a block diagram of the electrical installation configuration implemented current transformer open detection device of the present invention.

The present invention is a device for detecting the opening (CT) of the secondary terminal of the current transformer (CT), more specifically, the secondary circuit is connected directly to the secondary terminal of the current transformer when the secondary terminal is opened as the input signal relay circuit, etc. It is a device for preventing current transformer burnout and electric shock by shorting the secondary terminal of the current transformer by operating.

Current transformers (CTs) are transformers used to extend the measuring range of an alternating current ammeter by obtaining a small current proportional to that of a large current of alternating current. The structure of the current transformer is a winding of a primary coil with a small number of windings and a secondary coil with a large number of windings on a stratified core such as a transformer. The secondary coil connects a measuring device such as an ammeter, a power meter, and a relay. In addition, the rated current of the primary current of the current transformer varies from several tens of amps to several thousand A. However, the rated current of the secondary current is mostly 5 A and the current ratio of the primary and secondary coils is determined by the number of coil turns. Inversely

On the other hand, the secondary terminal of the current transformer is safe to short it, but it is very dangerous to open it. If the secondary coil is opened while current flows in the primary coil of the current transformer, This is because the current acts to magnetize all the iron cores so that the iron cores saturate and generate heat, which may cause damage to the coil or explosion risk of the current transformer and electric shock. Therefore, if the internal circuit of the instrument such as the ammeter or power meter connected to the secondary coil of the current transformer is opened or other reasons, the secondary coil of the current transformer is opened and immediately detects that it is shut off, that is, the open secondary side. It is necessary to connect a circuit to the secondary side of the current transformer with the function of shorting the terminal immediately.

On the other hand, after the open sensing circuit detects an open and shorts the terminal, the open sensing circuit must maintain the short circuit state until the administrator finds the cause of the opening of the current transformer and removes it. do. If the short-circuit status is incomplete and the manager suddenly switches to the open state during repair work, an electric shock may occur.

Even though there is such a risk, there is almost no countermeasure for preventing accidents due to the opening of the secondary coil of the current transformer. Therefore, the development of a device for preventing this is required.

In addition, when inspecting or repairing current measuring instruments and other measuring devices connected to electrical equipment, such as ammeters, wattmeters, relays, recorders, etc., it is necessary to stably short-circuit the secondary terminals of the current transformer during the work to prevent electric shock. Needs to be.

In this case, there were many inconveniences in the prior art because there was no separate device for simply shorting the secondary terminal of the current transformer. In other words, there is always a risk of electric shock because the secondary terminal of the current transformer must be shorted while the power is continuously supplied without stopping the operation of the entire electric equipment.

Accordingly, the present invention is to provide a sensing device for preventing damage to the current transformer and electric shock accident by detecting a short circuit of the secondary terminal when the secondary terminal of the current transformer is open.                         

Another object of the present invention is to further include a separate check switch in the sensing circuit to provide a sensing device capable of stably maintaining a short circuit of the current transformer secondary terminal just by pressing the check switch.

It is still another object of the present invention to provide a sensing device that can be constituted by a transistor, a triac, an SCR, a photo relay, or the like having a relay contact or similar function in a short circuit that short-circuits the secondary terminal of the current transformer. It is.

Still other objects of the present invention will become apparent from the following detailed description and the accompanying drawings.

The sensing device of the present invention for achieving the above object, a circuit protection unit for connecting the current transformer secondary terminal to reduce the open voltage of the secondary terminal to cut off the overvoltage, rectification unit for rectifying the voltage signal passed through the circuit protection unit, A comparison unit for comparing the voltage signal output from the rectifying unit with a value of a predetermined reference voltage and outputting a voltage signal for opening of the current transformer secondary terminal, and operating by the voltage signal output from the comparison unit It comprises a short circuit section for performing the function of shorting the ruler.

Here, the short-circuit part for shorting the open secondary terminal of the current transformer may include a relay type using an induction coil or an electronic type using an integrated circuit (IC), and may include a transistor, an SCR, a photo relay, and the like. Let's look at in detail.

First Embodiment Relay Detection Circuit

The configuration of the relay type sensing circuit is shown in FIG. Looking at the composition,

 A circuit protection unit connected to the secondary transformer current transformer to reduce the open voltage of the secondary terminal to block overvoltage, a rectifier for rectifying the voltage signal passing through the circuit protection unit, a voltage signal output from the rectifier and a value of a predetermined reference voltage A comparison unit for outputting a voltage signal for opening the current transformer secondary terminal, a relay coil for generating magnetic induction by a current flowing by a voltage signal for opening the secondary terminal output from the comparison unit, and the relay coil It can be seen that it comprises a short-circuit switch to short-circuit the current transformer secondary terminal by magnetic induction of.

Referring to the accompanying drawings, the operation principle of the circuit is as follows. As shown in FIG. 1, the input terminal of the circuit is connected to the secondary terminal of the current transformer so that the voltage induced when the current transformer secondary terminal is opened is received as an input signal.

On the other hand, since the input voltage generally has a high voltage value, it is necessary to block such overvoltage in order to protect the sensing circuit. In the embodiment of FIG. 1, an overvoltage is cut off by inserting a TNR as a circuit protection unit.

In this way, in order to use the voltage passed through the circuit protection unit as a signal source, after rectifying in the diode D1, the capacitor C1 is smoothed and converted into direct current. In this case, the resistor R1 prevents the discharge of the capacitor and the opening of the input of the op amp.

The rectified signal is input to the comparison amplifier, and the comparison amplifier compares the voltage of the input signal with the reference voltage and outputs a result value, that is, a low (L) or high (H) value depending on whether the current transformer is open. In this embodiment, the positive voltage is output when the current transformer is opened, that is, when the voltage of the input signal is higher than the reference voltage, and the negative voltage is output when the current transformer is higher than the reference voltage.

When a positive signal is output from the comparison amplifier due to the opening of the current transformer, the output signal is applied to the base of the transistor TR by limiting the current through the resistor R5. In this way, when a voltage is applied to the base of the transistor, the current of the collector flows to the emitter so that the current flows to the relay coil.

As such, when a current flows through the relay coil, the first interlock switch S1 is operated by magnetic induction to ground one potential of the relay (GND) so that the relay self-maintains and limits the current through the resistor R6. In addition, the second interlock switch, that is, the alarm switch (S2) is connected to the alarm system so that the alarm is generated during the relay operation to inform the administrator of the open state of the current transformer. When the third interlock switch, that is, the short switch S3, is operated, the open terminal of the current transformer is immediately shorted. Meanwhile, in this embodiment, a separate light emitting diode (LED) is connected to display an operation state while the relay is operating.

The recovery switch (RESET-SW) is for releasing the self-maintenance of the relay. When the recovery switch is pressed, the voltage of the relay is turned off, so the self-maintenance function disappears and the relay returns to its original state. Therefore, the administrator checks the cause of the current transformer opening, and after completing the repair work, operates the recovery switch to reset the relay status.

The circuit of this embodiment further includes a separate check switch (TEST-SW) for artificially operating the relay even if the current transformer is not opened. As shown in the figure, when the test switch (TEST-SW) is pressed, one side of the relay is grounded so that a current flows in the relay coil, and the secondary terminal of the current transformer maintains a short circuit due to magnetic induction. Such a check switch is used in the case where it is necessary to stably short-circuit the secondary terminal of the current transformer in order to check a measuring device connected to the rear end of the current sensing circuit or the current transformer, such as an ammeter or a power meter.

On the other hand, the circuit configuration of the power supply unit supplied to the sensing circuit of the present invention is shown in FIG. As shown, AC power is connected to the primary side of the transformer so that the reduced voltage is induced on the secondary side, and the reduced voltage is rectified through the diodes D2 and D3 and then smoothed by the capacitors C2 and C3. It is designed to supply the sensing circuit.

Second Embodiment

As a second embodiment, an electronic sensing circuit will be described.

Figure 3 is an embodiment of a circuit diagram of the electronic sensing device according to the present invention. The operation principle of the circuit is basically the same as the relay circuit described above, except that the integrated circuit is used instead of the relay coil.

The open circuit voltage of the current transformer secondary terminal is used as an input signal, a TNR is inserted to protect the sensing circuit from overvoltage, and the rectification of the input signal and the output process of the comparison voltage by the comparison amplifier are the same as the relay type described above.

When the open voltage signal is output from the comparison amplifier due to the opening of the current transformer, the output signal is input to the input portion of the integrated circuit IC through the diode D4. Resistor R8 was used to prevent the input of the integrated circuit from opening.

When the input signal comes in, the output Q of the integrated circuit IC goes high (H) to turn on the light emitting diode (LED) through the resistor (R6), while the triac (TRIAC) through the resistor (R5). It is input to the gate of and shorts both ends of the current transformer. The output of the integrated circuit remains high until the reset switch (RESET-SW) is pressed, which causes the triac to remain on.

On the other hand, in case of abnormality, it outputs alarm signal through alarm switch for automatic operation of other equipment. In this embodiment, a transistor is used as the alarm switch.

Like the relay circuit described above, the check switch is included in this embodiment. Pressing the check switch to check this sensing circuit and equipment such as ammeter and power meter at the back of the current transformer will operate the integrated circuit and keep the output high (H), so that the secondary terminal of the current transformer can maintain the short circuit status. It can make repair and inspection work safe. After the work is completed, press the recovery switch to return to the normal state. On the other hand, the power supply unit supplied to the electronic sensing circuit of the present invention can also use the same as the relay circuit.

4 is another embodiment of the sensing device of the present invention. The basic configuration is similar to the sensing apparatus of FIGS. 1 and 3 described above. However, it can be seen that the buffer amplifier further amplifies the DC voltage output from the rectifier. The buffer amplifier is used to increase the input impedance for the purpose of reducing the influence on the current transformer output. An amplifier uses an OP-AMP. In FIG. 4, the buffer amplifier unit is composed of an OP-AMP and an applied power supply (+ 12V) for supplying power thereto. Looking at the specific operation of the circuit of Figure 4 as follows.

When the current transformer secondary terminal (b-b ') is opened in a state where current flows in the primary coil of the current transformer, a high value of the open voltage V1 is applied to the secondary terminal kl, and such an applied voltage. V1 becomes the input voltage of the open sensing circuit.

The voltage V1 of this open terminal is generally very large. Therefore, the circuit protection unit 10 is configured to protect the open sensing circuit of the present invention from such an overvoltage V1. Inserting the varistor (TNR) into the circuit protection unit 10 to protect the first stage, and secondly limiting the current in the resistor R1 and once again in the first zener diode (D10) and the second zener diode (D11). By cutting off the overvoltage, it outputs a safe voltage (V2) (hereinafter referred to as 'safe voltage') that will not damage the sensing circuit. As such, the circuit protection unit 10 receives the overvoltage V1 and outputs a 'safe voltage V2'. In FIG. 4, the circuit protection unit 10 includes a varistor TNR, a resistor R1, a first zener diode ZD1, and a second zener diode ZD2.

As described above, since the open detection circuit of the present invention uses the secondary open voltage as an input signal unlike the case in which the open current on the secondary side of the current transformer is an input signal, the rated value of the current transformer secondary current (5A in most cases). Accurate detection is always possible without being limited by the range of.

The safety voltage V2 output by the circuit protection unit 10 is converted into a DC voltage through the rectifier 20. That is, the rectifier 20 receives the safety voltage V2 output by the circuit protection unit, rectifies it through the diode D4, smoothes it in the capacitor C12, and converts it to the DC voltage V3. The converted DC voltage V3 is input to the buffer amplifier 30. In FIG. 4, the rectifier 20 includes a diode D4, a resistor R11, and a capacitor C11.

The buffer amplifier 30 amplifies the DC voltage V3 output from the rectifier 20 using an externally applied power supply 12V. The buffer amplifier unit is for increasing the input impedance for the purpose of reducing the influence on the current transformer output, and uses an op-amp as an ultra-short amplifier. In FIG. 4, the buffer amplifier 30 is composed of an OP-AMP and an applied power supply 12V supplying power thereto.

The voltage signal V4, which is amplified by the first stage OP-AMP1 and passed through the resistor R4, is input to the comparison amplifier OP-AMP2 together with the reference voltage V5, and in this case, the comparison unit ( +) Voltage is output.

Looking at this in detail as follows. That is, the signal of the output voltage V4 of the buffer amplifier 30 is input to the (+) terminal of the OP-AMP2 through the resistor R5. On the other hand, a reference voltage V5 generated by a separate DC applied power supply Vcc (+ 12V), resistor R2, resistor R3, and variable resistor S-VR is applied to the negative terminal of the comparative amplifier OP-AMP2. When the secondary side of the current transformer is opened, when the voltage V4 input to the comparison amplifier becomes higher than the reference voltage V5, the output V6 of the comparison amplifier is outputted with a positive voltage and the resistance R6 direction of the relay driver 50 is output. Current flows. On the other hand, in the usual case in which the secondary side of the current transformer is not opened, the input voltage V4 is not higher than the reference voltage V5. Therefore, the output V6 of the comparative amplifier is outputted with a negative voltage so that the relay circuit part does not operate. . In FIG. 4, the comparator 40 has a configuration in which an applied power source Vcc 400 is applied to the resistors R2, R3, R4, and R5 and the comparative amplifier OP-AMP2.

As described above, when the secondary terminal kl of the current transformer is opened, the output V6 of the comparative amplifier is applied to the base terminal of the transistor TR through the current limiting of the resistors R6 and R7 in the relay driver 50. The capacitor C11 maintains the voltage value applied to the base terminal of the transistor TR for a predetermined time. At this time, the capacitor C11 can be quickly charged by the diode D5, and is discharged through the resistors R6, R7, and R8 during discharge.

When a voltage is applied to the base terminal of the transistor TR, a current flows from the collector toward the emitter, so that the relay circuit unit 60 operates.

While the relay circuit unit 60 is operating, the light-emitting diode LED is turned on by limiting the current through the resistor R9 to serve as an alarm display, and the self-maintaining switch S1 operates so that the potential of one of both terminals of the relay coil is activated. By grounding the relay coil, it retains its magnetism. In addition, when alarm switch S2 is closed, the alarm system circuit is operated to inform the manager, etc. that the current transformer secondary terminal is open, and when the short switch S3 is closed, the secondary coil of the current transformer is shorted. The switching operations of the switches S1, S2, and S3 can cause each switch to be closed at the same time as the current flows through the relay coil by the electromagnetic induction phenomenon by the relay circuit unit 60. FIG.

On the other hand, when the current flows to the relay circuit unit 60, the magnetism is generated to close the short-circuit switch S3. During this time, the manager finds an abnormal part of the current transformer and repairs it. Press to release the self hold. In other words, when the recovery switch (RESET-SW) is pressed, it is in an open state in relation to the applied power (+ 12V), so the switches S1, S2, and S3 return to their original states. That is, the self-holding state of the relay is released by the return of S1, the alarm system circuit is stopped by the return of S2, and the short circuit state of the secondary terminal of the current transformer is released by the return of S3.

Meanwhile, as described above, it is possible to use various electronic components such as transistors, triacs, SCRs, and photo relays that function similar to relay contacts as switches for operating a short switch or an alarm switch instead of the relay circuit part on the left side.

4 also installs a check switch that connects power to the short circuit section, the administrator can press the check switch if necessary to operate the short circuit section so that the secondary terminal of the current transformer until the required work is completed Stable short circuit can be maintained.

5 is a view of an embodiment in which the sensing device described so far is connected to an electrical installation and implemented. As shown, a general power supply and a load are connected to the primary side of the current transformer, and various measuring instruments such as an ammeter, a power meter, a relay, and a recorder are connected to the secondary side of the current transformer.

When the secondary terminal of the current transformer is open, the open voltage becomes the input signal of the sensing device, and the protection unit cuts off the overvoltage, the rectifier converts the signal to direct current, the comparator and the short circuit switch for comparing the value of the reference voltage and the rectified signal. After passing through the short circuit portion containing a short circuit the secondary terminal of the current transformer.

On the other hand, when the check switch is pressed, the power is supplied to the short circuit section, and the short circuit section is operated accordingly to short-circuit the secondary terminal of the current transformer. That is, even if no open signal is input from the comparator, it is possible to maintain a stable short-circuit state of the secondary transformer current transformer whenever necessary through the check switch.

While specific embodiments of the present invention have been described and illustrated, it is obvious that the present invention may be modified and practiced by those skilled in the art. However, such modified embodiments should not be understood individually from the technical spirit or viewpoint of the present invention, but should be interpreted as being included in the claims of the present invention.

According to the current transformer opening detection device of the present invention, even if the current transformer secondary terminal is open, it is possible to immediately short circuit it, it is possible to prevent damage to the current transformer and electric shock.

In addition, by including a check switch in the open detection device, the secondary terminal of the current transformer can be stably maintained during the inspection or repair work of various measuring devices such as the current transformer connected to the electrical equipment, thus enabling safe operation without an electric shock accident.

The sensing device of the present invention provides an electronic operation method in addition to the relay operation method, and may also be configured in various ways such as transistors, triacs, SCRs, photo relays, etc. in addition to the relay switch as an electric element for shorting the secondary terminals. The sensing circuit can be configured flexibly.

Claims (8)

In the device for detecting the opening of the secondary terminal of the current transformer, A circuit protection unit connected to the current transformer secondary terminal to block an overvoltage by reducing an open voltage of the secondary terminal; A rectifier for rectifying the voltage signal passing through the circuit protection unit; A comparator for comparing the voltage signal output from the rectifier with a value of a predetermined reference voltage and outputting a voltage signal for opening the second transformer terminal; A short circuit unit operating by a voltage signal output from the comparison unit to short-circuit the open secondary terminal; And And a check switch capable of short-circuiting the secondary terminal of the current transformer by connecting a power supply to the short circuit unit to operate the secondary current detection device of the current transformer. The method of claim 1, wherein the short circuit portion, A relay coil for generating magnetic induction by flowing a current by a voltage signal for opening of the secondary terminal output from the comparing unit; And And a shorting switch to short-circuit the current transformer secondary terminal by magnetic induction of the relay coil. The method of claim 1, wherein the short circuit portion, An integrated circuit which receives a voltage signal for opening the secondary terminal output from the comparator and outputs an operation signal; And And a triac (TRIAC) connected to the current transformer secondary terminal and receiving an output signal of the integrated circuit to short-circuit the current transformer secondary terminal. The method of claim 1, wherein the short circuit portion, A transistor, triac, SCR, photorelay comprising any one of, the secondary open detection device of the current transformer. The alarm switch according to any one of claims 1 to 4, further comprising an alarm switch for operating the alarm system for opening of the secondary terminal by a voltage signal for opening of the secondary terminal output from the comparing unit. Second open detection device of the current transformer. delete The secondary open sensing device of claim 1, further comprising a buffer amplifier configured to amplify the signal rectified by the rectifier. The secondary open detection device of the current transformer according to any one of claims 1 to 4, further comprising a recovery switch for releasing the operating state of the short circuit portion operated by the opening of the secondary terminal. .

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