CN210577761U - Open-circuit prevention device for current transformer - Google Patents
Open-circuit prevention device for current transformer Download PDFInfo
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- CN210577761U CN210577761U CN201921704201.4U CN201921704201U CN210577761U CN 210577761 U CN210577761 U CN 210577761U CN 201921704201 U CN201921704201 U CN 201921704201U CN 210577761 U CN210577761 U CN 210577761U
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Abstract
The utility model provides a current transformer prevents open circuit device. The utility model discloses a prevent that open circuit device has set up delay circuit, through the voltage at detection drive circuit detection delay circuit's energy storage capacitor both ends, according to the voltage signal start protection circuit who acquires. When the secondary side of the CT generates an open-circuit fault, the voltage of the energy storage capacitor of the delay circuit rises, the coil of the relay connected in series with the output end of the detection driving circuit is electrified, the first group of normally open contacts connected in series with the protection circuit is closed, and the protection circuit is started; after the protection circuit is started, the circuit of the CT secondary side is in a short-circuit state, so that the secondary high voltage of the CT is restrained, the dangerous high voltage generated on the CT secondary side is effectively restrained when the CT is opened, and the switch is prevented from being refused to operate when in fault.
Description
Technical Field
The utility model relates to an electric power protection technical field especially relates to a current transformer prevents open circuit device.
Background
In an electric power system, a Current Transformer (CT) converts a large current into a predetermined small current, and is widely used for current measurement, control, and protection of a primary line. Current transformers are roughly classified into a current transformer for measurement and a current transformer for protection according to their uses. The current transformer for protection is mainly matched with a relay device, and when a circuit has faults such as short circuit, overload and the like, a signal is provided for the relay device to cut off a fault circuit so as to protect the safety of a power supply system.
When the CT normally works, the secondary side is in an approximate short-circuit state, the output voltage is very low, but if the secondary winding is open-circuited or abnormal current flows through the primary winding during operation, high voltage of thousands of volts or even tens of thousands of volts is generated on the secondary side, which seriously endangers the safety of workers and equipment. At present, various CT anti-open devices exist in the market, but all the CT anti-open devices have the defect that when the CT anti-open devices are applied to a current transformer for protection, when a circuit has faults such as short circuit, overload and the like, the CT anti-open devices can be started preferentially, fault signals collected by a relay device disappear, and therefore a tripping instruction cannot be sent out, and a switch fails to operate when the fault occurs.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a current transformer prevents device of opening a way to when realizing the dangerous high voltage that effectively restraines the CT secondary side and produce when CT opens a way, switch refuses to move when avoiding the trouble.
In order to achieve the above object, the utility model provides a following scheme:
an open-circuit prevention device for a current transformer, the open-circuit prevention device comprising: the device comprises a rectifier bridge, a delay circuit, a detection driving circuit, a protection circuit and a relay;
the output end of the current transformer is connected with the alternating current input end of the rectifier bridge;
the delay circuit is connected in parallel with the output end of the rectifier bridge;
the input end of the detection driving circuit is connected with the energy storage capacitor of the delay circuit in parallel; the output end of the detection driving circuit is connected with a coil of the relay in series and then is connected to the output end of the rectifier bridge in parallel;
the protection circuit is connected with a first group of normally open contacts of the relay in series and then connected with the output end of the rectifier bridge in parallel;
the detection driving circuit is used for detecting the voltage at two ends of the energy storage capacitor, and when the detected voltage signal reaches a voltage threshold value, the detection driving circuit controls the energization of the coil of the relay, so that the first group of normally open contacts of the relay is controlled to be closed, and the protection circuit is started.
Optionally, the second normally open contact of the relay is connected in parallel to the output end of the detection driving circuit.
Optionally, the delay circuit includes a current-limiting resistor and an energy-storing capacitor;
the current-limiting resistor and the energy-storing capacitor are connected in series between the positive pole of the direct-current output end and the negative pole of the direct-current output end of the rectifier bridge.
Optionally, the detection driving circuit includes a first voltage-dividing resistor, a second voltage-dividing resistor, and a triode;
one end of the first divider resistor is connected with the anode of the energy storage capacitor, the other end of the first divider resistor and one end of the second divider resistor are respectively connected with the base electrode of the triode, and the other end of the second divider resistor is connected with the cathode of the direct current output end of the rectifier bridge;
the collector of the triode is connected with the negative electrode of the coil of the relay, and the emitter of the triode is connected with the negative electrode of the direct current output end of the rectifier bridge;
and the positive pole of the coil of the relay is connected with the positive pole of the direct current output end of the rectifier bridge.
Optionally, the protection circuit includes a first diode, a second diode, a third diode, and a fourth diode;
the anode of the first diode and the anode of the second diode are respectively connected with the positive electrode of the direct-current output end of the rectifier bridge;
the cathode of the first diode is connected with the anode of the third diode, and the cathode of the second diode is connected with the anode of the fourth diode;
and the cathode of the third diode and the cathode of the fourth diode are respectively connected with the input contacts of the first group of normally open contacts of the relay, and the output contacts of the first group of normally open contacts of the relay are connected with the negative electrode of the direct-current output end of the rectifier bridge.
Optionally, the protection circuit includes a fifth diode;
the anode of the fifth diode is connected with the anode of the direct-current output end of the rectifier bridge, the cathode of the fifth diode is connected with the input contact of the first group of normally open contacts of the relay, and the output contact of the first group of normally open contacts of the relay is connected with the cathode of the direct-current output end of the rectifier bridge.
According to the utility model provides a concrete embodiment, the utility model discloses a following technological effect:
the utility model provides a current transformer prevents open circuit device, prevent open circuit device includes: the device comprises a rectifier bridge, a delay circuit, a detection driving circuit, a protection circuit and a relay; the output end of the current transformer is connected with the alternating current input end of the rectifier bridge; the delay circuit is connected in parallel with the output end of the rectifier bridge; the input end of the detection driving circuit is connected with the energy storage capacitor of the delay circuit in parallel; the output end of the detection driving circuit is connected with a coil of the relay in series and then is connected to the output end of the rectifier bridge in parallel; the protection circuit is connected with a first group of normally open contacts of the relay in series and then connected with the output end of the rectifier bridge in parallel; a second normally open contact of the relay is connected in parallel with the output end of the detection driving circuit; the utility model discloses set up delay circuit, through the voltage at detection drive circuit detection delay circuit's energy storage capacitor both ends, according to the voltage signal start protection circuit who acquires. When the secondary side of the CT generates an open-circuit fault, the voltage of the energy storage capacitor of the delay circuit rises, the coil of the relay connected in series with the output end of the detection driving circuit is electrified, the first group of normally open contacts connected in series with the protection circuit is closed, and the protection circuit is started; after the protection circuit is started, the circuit of the CT secondary side is in a short-circuit state, so that the secondary high voltage of the CT is restrained, the dangerous high voltage generated on the CT secondary side is effectively restrained when the CT is opened, and the switch is prevented from being refused to operate when in fault.
Meanwhile, after the protection circuit is started, the second group of normally open contacts connected with the output end of the detection driving circuit in parallel are closed, the output end of the detection driving circuit is short-circuited, and only after the CT secondary output open circuit fault disappears, the voltage of a coil of the relay is reduced, the normally open state can be restored by the first group of normally open contacts and the second group of normally open contacts, so that frequent oscillation of a switching device is avoided, and the protection performance of the CT anti-open circuit device is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive labor.
Fig. 1 is a schematic circuit diagram of an open circuit prevention device for a current transformer according to the present invention;
in fig. 1, D1 is a rectifier bridge, D2 is a protection circuit, R1 is a current-limiting resistor, R2 is a first voltage-dividing resistor, R3 is a second voltage-dividing resistor, C1 is an energy-storage capacitor, Q1 is a triode, and K1 is a relay.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
The utility model aims at providing a current transformer prevents device of opening a way to when realizing the dangerous high voltage that effectively restraines the CT secondary side and produce when CT opens a way, switch refuses to move when avoiding the trouble.
In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description.
As shown in fig. 1, the open circuit prevention device of the current transformer includes a rectifier bridge D1, a protection circuit D2, a delay circuit, a detection driving circuit and a relay K1, wherein an ac input terminal of the rectifier bridge D1 is connected in parallel to a CT secondary output terminal CT1 and a CT 2.
The delay circuit is composed of an energy storage capacitor C1 and a current-limiting resistor R1, the anode of the energy storage capacitor C1 is connected with the current-limiting resistor R1 in series and then connected with the anode VDC of the direct-current output end of the rectifier bridge D1, the cathode of the energy storage capacitor is connected with the cathode GND of the direct-current output end of the rectifier bridge D1, a voltage signal sent by the direct-current output end of the rectifier bridge D1 charges the energy storage capacitor C1 through the current-limiting resistor R1, voltage on the capacitor C1 cannot generate sudden change, and therefore the voltage signal is sent to the detection driving circuit. The condition that the switch refuses to move due to the fact that fault signals collected by the relay device are interrupted in advance is avoided.
The detection driving circuit is composed of a first voltage-dividing resistor R2, a second voltage-dividing resistor R3 and a triode Q1, an emitter of the triode Q1 is connected with a negative pole GND of a direct-current output end of a rectifier bridge D1, a base stage of the triode Q1 is connected with a serial connection point of the first voltage-dividing resistor R2 and the second voltage-dividing resistor R3, and when the voltage on the energy-storage capacitor C1 reaches a certain value, the triode Q1 is conducted, and the driving protection circuit is started.
The protection circuit comprises rectifier bridge D2 that four diodes (first diode, second diode and third diode) are constituteed, after triode Q1 switches on, the collecting electrode output low level, drive relay K1's two sets of normally open contact closure, first group normally open contact (normally open contact KA2 and GND) switch on the back, the CT return circuit is in short-circuit state, the production of CT secondary high voltage has been suppressed from this, second group normally open contact (normally open contact KA1 and GND) switch on the back, triode Q1 opens circuit, triode Q1 collecting electrode can only continuously output low level, two sets of normally open contact of relay K1 keep lasting closure, after the CT trouble disappears, relay K1's two sets of normally open contact can resume normally open state, thereby the frequent oscillation of switching device has been avoided, CT prevents open circuit device's protective performance has been improved.
As another embodiment, the protection circuit of the present invention may be composed of a fifth high-power diode.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principle and the implementation of the present invention are explained by applying specific embodiments, the description of the above embodiments is only used to help understand the method and the core idea of the present invention, and the described embodiments are only a part of the embodiments of the present invention, but not all embodiments, and based on the embodiments of the present invention, all other embodiments obtained by the person of ordinary skill in the art without creative work belong to the protection scope of the present invention.
Claims (6)
1. An open-circuit prevention device for a current transformer, comprising: the device comprises a rectifier bridge, a delay circuit, a detection driving circuit, a protection circuit and a relay;
the output end of the current transformer is connected with the alternating current input end of the rectifier bridge;
the delay circuit is connected in parallel with the output end of the rectifier bridge;
the input end of the detection driving circuit is connected with the energy storage capacitor of the delay circuit in parallel; the output end of the detection driving circuit is connected with a coil of the relay in series and then is connected to the output end of the rectifier bridge in parallel;
the protection circuit is connected with a first group of normally open contacts of the relay in series and then connected with the output end of the rectifier bridge in parallel;
the detection driving circuit is used for detecting the voltage at two ends of the energy storage capacitor, and when the detected voltage signal reaches a voltage threshold value, the detection driving circuit controls the energization of the coil of the relay, so that the first group of normally open contacts of the relay is controlled to be closed, and the protection circuit is started.
2. The current transformer open-circuit prevention device according to claim 1, wherein the second normally open contact of the relay is connected in parallel to the output terminal of the detection driving circuit.
3. The current transformer open-circuit prevention device according to claim 1, wherein the delay circuit comprises a current limiting resistor and an energy storage capacitor;
the current-limiting resistor and the energy-storing capacitor are connected in series between the positive pole of the direct-current output end and the negative pole of the direct-current output end of the rectifier bridge.
4. The open circuit prevention device of a current transformer according to claim 3, wherein the detection driving circuit comprises a first voltage dividing resistor, a second voltage dividing resistor and a triode;
one end of the first divider resistor is connected with the anode of the energy storage capacitor, the other end of the first divider resistor and one end of the second divider resistor are respectively connected with the base electrode of the triode, and the other end of the second divider resistor is connected with the cathode of the direct current output end of the rectifier bridge;
the collector of the triode is connected with the negative electrode of the coil of the relay, and the emitter of the triode is connected with the negative electrode of the direct current output end of the rectifier bridge;
and the positive pole of the coil of the relay is connected with the positive pole of the direct current output end of the rectifier bridge.
5. The current transformer open-circuit prevention device according to claim 1, wherein the protection circuit comprises a first diode, a second diode, a third diode, and a fourth diode;
the anode of the first diode and the anode of the second diode are respectively connected with the positive electrode of the direct-current output end of the rectifier bridge;
the cathode of the first diode is connected with the anode of the third diode, and the cathode of the second diode is connected with the anode of the fourth diode;
and the cathode of the third diode and the cathode of the fourth diode are respectively connected with the input contacts of the first group of normally open contacts of the relay, and the output contacts of the first group of normally open contacts of the relay are connected with the negative electrode of the direct-current output end of the rectifier bridge.
6. The current transformer open-circuit prevention device according to claim 1, wherein the protection circuit comprises a fifth diode;
the anode of the fifth diode is connected with the anode of the direct-current output end of the rectifier bridge, the cathode of the fifth diode is connected with the input contact of the first group of normally open contacts of the relay, and the output contact of the first group of normally open contacts of the relay is connected with the cathode of the direct-current output end of the rectifier bridge.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921704201.4U CN210577761U (en) | 2019-10-12 | 2019-10-12 | Open-circuit prevention device for current transformer |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921704201.4U CN210577761U (en) | 2019-10-12 | 2019-10-12 | Open-circuit prevention device for current transformer |
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| Publication Number | Publication Date |
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| CN210577761U true CN210577761U (en) | 2020-05-19 |
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| CN201921704201.4U Active CN210577761U (en) | 2019-10-12 | 2019-10-12 | Open-circuit prevention device for current transformer |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110581531A (en) * | 2019-10-12 | 2019-12-17 | 北京恒源利通电力技术有限公司 | open-circuit prevention device for current transformer |
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2019
- 2019-10-12 CN CN201921704201.4U patent/CN210577761U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110581531A (en) * | 2019-10-12 | 2019-12-17 | 北京恒源利通电力技术有限公司 | open-circuit prevention device for current transformer |
| CN110581531B (en) * | 2019-10-12 | 2024-03-15 | 北京恒源利通电力技术有限公司 | Open-circuit preventing device of current transformer |
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