A secondary open-circuit protection device for a current transformer
By connecting an ammeter in series with a thyristor and a Zener diode in parallel to form a resistor-capacitor absorption circuit, the structural complexity and safety hazards of the secondary open-circuit protection device for current transformers are solved, thus achieving safe and reliable protection for current transformers.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- GANSU JIU STEEL GRP HONGXING IRON & STEEL CO LTD
- Filing Date
- 2025-06-12
- Publication Date
- 2026-06-30
AI Technical Summary
Existing open-circuit protection devices for current transformers have complex structures, are difficult to maintain, and pose safety hazards, which can easily lead to equipment damage and electric shock risks.
A current transformer is connected in series with an ammeter, and first and second thyristors are connected in parallel. A voltage-regulating diode and a current-limiting resistor form a resistor-capacitor absorption circuit to limit the voltage and bypass the current, thus preventing high voltage from being generated.
It achieves a simple structure, is easy to process and maintain, is safe and reliable, avoids the generation of high voltage in current transformers, and protects the safety of maintenance personnel.
Smart Images
Figure CN224438559U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of power protection technology, specifically to a secondary open-circuit protection device for a current transformer. Background Technology
[0002] Current transformers, as an important type of power equipment, convert large currents into smaller ones for easier measurement and protection. However, the secondary side of a current transformer must not be open-circuited, as this can lead to a series of serious consequences. When the secondary side of a current transformer is open-circuited, the induced current in the secondary winding disappears, and the magnetic flux in the primary winding cannot be released through the magnetic reluctance of the secondary winding, resulting in magnetic saturation of the primary winding. Magnetic saturation can cause the iron core of the current transformer to overheat or even burn out. When the secondary side is open-circuited, according to Faraday's law of electromagnetic induction, the voltage in the secondary winding will rise sharply, potentially reaching several kilovolts or even higher. This poses a serious threat to equipment and personnel, and can also cause abnormal currents, potentially leading to power system failures. Therefore, an open-circuit secondary side of a current transformer can lead to equipment damage and the risk of electric shock to maintenance personnel, resulting in serious safety accidents. Thus, designing a protection device for an open-circuit secondary side of a current transformer is of paramount importance.
[0003] The patent application, CN119448167A, entitled "A Secondary Open-Circuit Protector for a Current Transformer," specifically includes: a first current transformer, a second current transformer, a central processing unit (CPU), a nonlinear resistor, and a switch. The switch is connected to the circuit under test via the primary winding of the first current transformer. The CPU senses whether an open circuit has occurred on the primary side of the second current transformer and outputs an action signal based on the signal sensed from the second current transformer. This action signal controls the switch to close. The nonlinear resistor is connected in parallel between the primary winding of the first current transformer and the ground wire, and it limits the overvoltage generated when the primary side of the current transformer is open. This limits the overvoltage generated when the secondary circuit of the protected circuit is open.
[0004] The aforementioned secondary open-circuit protector for current transformers has a complex structural design, which is not conducive to later maintenance and requires a large investment. Utility Model Content
[0005] The purpose of this utility model is to provide a current transformer secondary open circuit protection device with reasonable structural design, ingenious concept, easy processing, low processing and manufacturing cost, convenient operation, and safe and reliable operation. It solves the problem of high voltage generated by open circuit of current transformer by limiting AC voltage and expanding the current carrying capacity of voltage limiting device, so as to fully ensure the safe operation of personnel and avoid safety accidents.
[0006] This utility model discloses a secondary open-circuit protection device for a current transformer, comprising a current transformer, an ammeter connected in series with the current transformer, a first thyristor and a second thyristor connected in parallel on the secondary side of the current transformer, and a first Zener diode and a second Zener diode connected in series between the first thyristor and the second thyristor.
[0007] The first and second thyristors are connected in parallel to the two anode and cathode terminals of the current transformer circuit in opposite directions, respectively; the first and second Zener diodes are connected in series in opposite directions to the ports between the first and second thyristors.
[0008] The ammeter is used to measure the current in the circuit and can provide a reference for circuit maintenance, troubleshooting, and performance evaluation. The first and second thyristors are connected in parallel with the anode and cathode of the current transformer circuit, respectively, in opposite directions. The first and second Zener diodes are connected in series in reverse, connected to the ports between the first and second thyristors. When the ammeter experiences an open circuit, the voltage across the secondary terminals of the current transformer will increase due to the open circuit in the current detection circuit. When the voltage rises to the Zener diode's voltage regulation value, the higher voltage on the secondary side of the current transformer will be released through the cathode and gate internal resistance of the first thyristor, and the forward... The first Zener diode is turned on, the second Zener diode is reverse-broken in the operating region, and the gate and cathode of the second thyristor are connected. In this way, the second thyristor is triggered to conduct by the flow of a forward trigger current. Similarly, when the AC current is in the negative half-cycle, the first thyristor is triggered to conduct. In this way, the high voltage on the secondary side of the current transformer is limited to the preset voltage value, making it safe and reliable to use. When the current circuit on the secondary side of the current transformer is open, the voltage limiting protection device connected in parallel to the secondary side terminals of the current transformer bypasses the secondary current of the current transformer to the protection branch, thereby avoiding the generation of high voltage on the current transformer, protecting the safety of maintenance personnel, and preventing electric shock accidents.
[0009] The first thyristor is connected to a second current-limiting resistor and a non-polarized capacitor thyristor.
[0010] The second current-limiting resistor and the non-polarized capacitor thyristor connected to the first thyristor can form a RC snubber circuit. When the current loop rises, excessively high voltages will be generated at a1 and a2 across the current transformer, which could cause the first thyristor to break down and be damaged. The RC snubber circuit suppresses the increased voltages at a1 and a2 across the current transformer. Furthermore, when excessively high voltages are generated in the secondary current loop of the current transformer, the RC snubber circuit formed by the second current-limiting resistor and the non-polarized capacitor thyristor can bypass the secondary current of the current transformer to the protection branch, thereby preventing the generation of high voltages at a1 and a2 across the current transformer, protecting the safety of maintenance personnel, and preventing electric shock accidents.
[0011] A first current-limiting resistor is connected between the second thyristor and the second Zener diode.
[0012] The first current-limiting resistor is set to limit the current of the trigger branch, preventing the trigger current from impacting the first and second thyristors and causing them to burn out. This further reduces the current intensity in the circuit and prevents the circuit from being burned out.
[0013] The beneficial effects of this utility model are:
[0014] 1) The ammeter is used to measure the current in the circuit and can provide a reference for circuit maintenance, troubleshooting, and performance evaluation. The first and second thyristors are connected in parallel to the two anode and cathode terminals of the current transformer circuit, respectively, in opposite directions. The first and second Zener diodes are connected in series in reverse, respectively, to the ports between the first and second thyristors. When the ammeter experiences an open circuit, the voltage across the secondary terminals of the current transformer will increase due to the open circuit in the current detection circuit. When the voltage rises to the Zener diode's voltage regulation value, the higher voltage on the secondary side of the current transformer will be released through the cathode and gate internal resistance of the first thyristor. The first Zener diode conducts through the reverse breakdown of the operating area, and the gate and cathode of the second thyristor. Thus, the second thyristor is triggered to conduct by the flow of a forward trigger current. Similarly, when the AC current is in the negative half-cycle, the first thyristor is triggered to conduct. This limits the high voltage on the secondary side of the current transformer to a preset voltage value, ensuring safe and reliable operation. If an open circuit occurs in the secondary current loop of the current transformer, a voltage-limiting protection device connected in parallel to the secondary terminals of the current transformer bypasses the secondary current to a protection branch, preventing the generation of high voltage in the current transformer, protecting maintenance personnel, and avoiding electric shock accidents.
[0015] 2) The second current-limiting resistor and the non-polarized capacitor thyristor connected to the first thyristor can form a RC snubber circuit. When the current loop rises, the voltages a1 and a2 across the current transformer will be too high, which will cause the first thyristor to break down and be damaged. The RC snubber circuit suppresses the voltage rise at a1 and a2 across the current transformer. Furthermore, when the secondary current loop of the current transformer generates too high a voltage, the RC snubber circuit formed by the second current-limiting resistor and the non-polarized capacitor thyristor can bypass the secondary current of the current transformer to the protection branch, thereby avoiding the generation of high voltages at a1 and a2 across the current transformer, protecting the safety of maintenance personnel, and preventing electric shock accidents.
[0016] 3) The first current-limiting resistor is set to limit the current of the trigger branch, prevent the trigger current from impacting the first and second thyristors, causing the first and second thyristors to burn out, further reduce the current intensity in the circuit, and avoid the circuit being burned out.
[0017] 4) The protection device has a reasonable structural design, ingenious concept, is easy to process, has low processing and manufacturing costs, is convenient to operate, and is safe and reliable to operate. By limiting AC voltage and expanding the current capacity of the voltage limiting device, it solves the problem of high voltage generated by open circuit of current transformer secondary circuit, fully ensuring the safe operation of personnel and avoiding safety accidents. The device has been put into field use and the effect is good. It is worth promoting and applying it on a large scale. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the structure of this utility model.
[0019] In the diagram: First thyristor 1, Second thyristor 2, First Zener diode 3, Second Zener diode 4, First current limiting resistor 5, Current transformer 6, Non-polarized capacitor thyristor 7, Ammeter 8, Current transformer 9. Detailed Implementation
[0020] Example 1.
[0021] The present invention will be further described below with reference to the accompanying drawings.
[0022] This utility model includes a first thyristor 1, a second thyristor 2, a first Zener diode 3, a second Zener diode 4, an ammeter 8, and a current transformer 9. The specific structure includes a current transformer 9, with the ammeter 8 connected in series with the current transformer 9. The secondary side of the circuit of the current transformer 9 is connected in parallel to the first thyristor 1 and the second thyristor 2, respectively. The first Zener diode 3 and the second Zener diode 4 are connected in series between the first thyristor 1 and the second thyristor 2.
[0023] The first thyristor 1 and the second thyristor 2 are connected in parallel to the two anode and cathode terminals of the current transformer 9 circuit in opposite directions, respectively; the first Zener diode 3 and the second Zener diode 4 are connected in series in opposite directions to the port between the first thyristor 1 and the second thyristor 2.
[0024] In use: When ammeter 5 experiences an open circuit, the voltage across the secondary terminals of current transformer 6 will increase due to the open circuit in the current detection circuit. When the voltage rises to the Zener diode's stabilizing value, the higher voltage on the secondary side of current transformer 9 will flow through the internal resistance between the cathode and gate of the first thyristor 1, the forward-conducting first Zener diode 3, the reverse-broken second Zener diode 4 in the operating region, and the gate and cathode of the second thyristor 2. Thus, the second thyristor 2 is triggered to conduct by the forward trigger current flowing through it. Similarly, when the AC current is in the negative half-cycle, the first thyristor 1 is triggered to conduct. In this way, the high voltage on the secondary side of current transformer 9 is limited to the preset voltage value, ensuring safe and reliable operation. When the current circuit on the secondary side of current transformer 9 becomes open, the voltage limiting protection device connected in parallel to the secondary side terminals of current transformer 9 bypasses the secondary current of current transformer 9 to the protection branch, thereby preventing the generation of high voltage in current transformer 9, protecting the safety of maintenance personnel, and avoiding electric shock accidents.
[0025] Example 2.
[0026] This utility model includes a first thyristor 1, a second thyristor 2, a first Zener diode 3, a second Zener diode 4, a current transformer 6, a non-polarized capacitive thyristor 7, an ammeter 8, and a current transformer 9. The specific structure includes a current transformer 9, with the ammeter 8 connected in series with the current transformer 9. The secondary side of the circuit of the current transformer 9 is connected in parallel to the first thyristor 1 and the second thyristor 2, respectively. The first Zener diode 3 and the second Zener diode 4 are connected in series between the first thyristor 1 and the second thyristor 2.
[0027] The first thyristor 1 and the second thyristor 2 are connected in parallel to the two anode and cathode terminals of the current transformer 9 circuit in opposite directions, respectively; the first Zener diode 3 and the second Zener diode 4 are connected in series in opposite directions to the port between the first thyristor 1 and the second thyristor 2.
[0028] The first thyristor 1 is connected to a second current-limiting resistor 6 and a non-polarized capacitor thyristor 7.
[0029] In use: When ammeter 5 experiences an open circuit, the voltage across the secondary terminals of current transformer 6 will increase due to the open circuit in the current detection circuit. When the voltage rises to the Zener diode's stabilizing value, the higher voltage on the secondary side of current transformer 9 will flow through the internal resistance between the cathode and gate of the first thyristor 1, the forward-conducting first Zener diode 3, the reverse-broken second Zener diode 4 in the operating region, and the gate and cathode of the second thyristor 2. Thus, the second thyristor 2 is triggered to conduct by the forward trigger current flowing through it. Similarly, when the AC current is in the negative half-cycle, the first thyristor 1 is triggered to conduct. In this way, the high voltage on the secondary side of current transformer 9 is limited to the preset voltage value, ensuring safe and reliable operation. When the current circuit on the secondary side of current transformer 9 becomes open, the voltage limiting protection device connected in parallel to the secondary side terminals of current transformer 9 bypasses the secondary current of current transformer 9 to the protection branch, thereby preventing the generation of high voltage in current transformer 9, protecting the safety of maintenance personnel, and avoiding electric shock accidents.
[0030] The second current-limiting resistor 6 and the non-polarized capacitor thyristor 7 connected to the first thyristor 1 can form a RC snubber circuit. When the current loop rises, the voltages a1 and a2 across the current transformer 9 will be too high, which will cause the first thyristor 1 to break down and be damaged. The RC snubber circuit suppresses the voltage rise at a1 and a2 across the current transformer 9. Furthermore, when the secondary current loop of the current transformer 9 generates too high a voltage, the RC snubber circuit formed by the second current-limiting resistor 6 and the non-polarized capacitor thyristor 7 can bypass the secondary current of the current transformer 9 to the protection branch, thereby avoiding the generation of high voltages at a1 and a2 across the current transformer 9, protecting the safety of maintenance personnel, and preventing electric shock accidents.
[0031] Example 3.
[0032] This utility model includes a first thyristor 1, a second thyristor 2, a first Zener diode 3, a second Zener diode 4, a first current-limiting resistor 5, a current transformer 6, a non-polarized capacitive thyristor 7, an ammeter 8, and a current transformer 9. The specific structure includes a current transformer 9, with an ammeter 8 connected in series with the current transformer 9. The secondary side of the circuit of the current transformer 9 is connected in parallel to the first thyristor 1 and the second thyristor 2, respectively. The first Zener diode 3 and the second Zener diode 4 are connected in series between the first thyristor 1 and the second thyristor 2.
[0033] The first thyristor 1 and the second thyristor 2 are connected in parallel to the two anode and cathode terminals of the current transformer 9 circuit in opposite directions, respectively; the first Zener diode 3 and the second Zener diode 4 are connected in series in opposite directions to the port between the first thyristor 1 and the second thyristor 2.
[0034] The first thyristor 1 is connected to a second current-limiting resistor 6 and a non-polarized capacitor thyristor 7.
[0035] A first current-limiting resistor 5 is connected between the second thyristor 2 and the second Zener diode 4.
[0036] In use: When ammeter 5 experiences an open circuit, the voltage across the secondary terminals of current transformer 6 will increase due to the open circuit in the current detection circuit. When the voltage rises to the Zener diode's stabilizing value, the higher voltage on the secondary side of current transformer 9 will flow through the internal resistance between the cathode and gate of the first thyristor 1, the forward-conducting first Zener diode 3, the reverse-broken second Zener diode 4 in the operating region, and the gate and cathode of the second thyristor 2. Thus, the second thyristor 2 is triggered to conduct by the forward trigger current flowing through it. Similarly, when the AC current is in the negative half-cycle, the first thyristor 1 is triggered to conduct. In this way, the high voltage on the secondary side of current transformer 9 is limited to the preset voltage value, ensuring safe and reliable operation. When the current circuit on the secondary side of current transformer 9 becomes open, the voltage limiting protection device connected in parallel to the secondary side terminals of current transformer 9 bypasses the secondary current of current transformer 9 to the protection branch, thereby preventing the generation of high voltage in current transformer 9, protecting the safety of maintenance personnel, and avoiding electric shock accidents.
[0037] The second current-limiting resistor 6 and the non-polarized capacitor thyristor 7 connected to the first thyristor 1 can form a RC snubber circuit. When the current loop rises, the voltages a1 and a2 across the current transformer 9 will be too high, which will cause the first thyristor 1 to break down and be damaged. The RC snubber circuit suppresses the voltage rise at a1 and a2 across the current transformer 9. Furthermore, when the secondary current loop of the current transformer 9 generates too high a voltage, the RC snubber circuit formed by the second current-limiting resistor 6 and the non-polarized capacitor thyristor 7 can bypass the secondary current of the current transformer 9 to the protection branch, thereby avoiding the generation of high voltages at a1 and a2 across the current transformer 9, protecting the safety of maintenance personnel, and preventing electric shock accidents.
[0038] The first current-limiting resistor 5 limits the current of the trigger branch to prevent the trigger current from impacting the first thyristor 1 and the second thyristor 2, causing the first thyristor 1 and the second thyristor 2 to burn out, and further reduces the current intensity in the circuit to avoid the circuit being burned out.
Claims
1. A secondary open-circuit protection device for a current transformer, characterized in that: Includes a current transformer (9), an ammeter (8) connected in series on the current transformer (9), and the second side of the circuit of the current transformer (9) is connected in parallel to the first thyristor (1) and the second thyristor (2), and the first Zener diode (3) and the second Zener diode (4) are connected in series between the first thyristor (1) and the second thyristor (2).
2. The current transformer secondary open-circuit protection device as described in claim 1, characterized in that: The first thyristor (1) and the second thyristor (2) are connected in parallel to the two anode and cathode terminals of the current transformer (9) circuit in opposite directions, respectively; the first Zener diode (3) and the second Zener diode (4) are connected in series in opposite directions to the port between the first thyristor (1) and the second thyristor (2).
3. The current transformer secondary open-circuit protection device as described in claim 2, characterized in that: The first thyristor (1) is connected to a second current-limiting resistor (6) and a non-polarized capacitor thyristor (7).
4. The current transformer secondary open-circuit protection device as described in claim 3, characterized in that: A first current-limiting resistor (5) is connected between the second thyristor (2) and the second Zener diode (4).