An oil-immersed mutual inductor end screen grounding monitoring and protection system
By designing a grounding monitoring and protection system for the end screen of an oil-immersed instrument transformer with photoelectric signals, the grounding status of the end screen is monitored in real time. The grounding status is displayed using photoelectric signals and combined with surge arrester protection, which solves the problem of poor grounding of the end screen of the oil-immersed instrument transformer and improves equipment safety and operating efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHWEST BRANCH OF CHINA DATANG CORP SCI & TECH RES INST
- Filing Date
- 2023-02-24
- Publication Date
- 2026-06-19
Smart Images
Figure CN116500492B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of instrument transformer technology, and more particularly to an oil-immersed instrument transformer. Background Technology
[0002] Instrument transformers are used for measuring and metering current and voltage. In existing technology, when an instrument transformer is operating normally, its end screen needs to be reliably grounded to ensure safe operation of the equipment. During maintenance, the end screen grounding wire needs to be disconnected for preventative testing. After the test, the end screen is restored to a reliable grounding state. As the equipment ages, the end screen grounding wire gradually ages and may even break, causing unreliable grounding. Furthermore, if the maintenance personnel do not restore the end screen grounding after maintenance, a high floating potential will appear at the end screen after the equipment is put back into operation, causing the end screen to break down and be damaged, affecting the safe operation of the equipment. Therefore, an oil-immersed instrument transformer end screen grounding monitoring and protection system is needed to monitor the grounding status of the end screen. Summary of the Invention
[0003] The purpose of this invention is to address the above-mentioned problems by proposing a grounding monitoring and protection system for the end screen of an oil-immersed instrument transformer with photoelectric signals. The system includes an oil-immersed instrument transformer end screen grounding electrical signal monitoring circuit, an oil-immersed instrument transformer end screen grounding optical signal monitoring circuit, and an oil-immersed instrument transformer end screen grounding protection circuit. It can monitor the end screen grounding status, the end screen grounding status, the end screen ungrounded status, and the power outage maintenance status.
[0004] Furthermore, in an oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signals, when the end-screen grounding is good during operation, the ammeter shows a reading, the voltmeter shows no reading, and the green LED D1 is lit.
[0005] Furthermore, in an oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signals, when the end-screen grounding is faulty during operation, the ammeter shows a reading, the voltmeter shows a reading, and the green LED D1 lights up.
[0006] Furthermore, in an oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signals, when the end-screen is not grounded during operation, the ammeter shows no reading, the voltmeter shows a reading, and the LED red D2 is lit.
[0007] Furthermore, in an oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signals, during power outage maintenance, the ammeter and voltmeter show no readings, and the LED red D2 is lit.
[0008] The oil-immersed instrument transformer end screen grounding signal monitoring circuit includes an oil-immersed instrument transformer, an end screen, an end screen grounding wire, a current transformer, a relay JDQ with a set of normally open and a set of normally closed auxiliary contacts, a resistor R1, an ammeter, a capacitor divider composed of C1 and C2, and a voltmeter.
[0009] Furthermore, a grounding monitoring and protection system for the end screen of an oil-immersed instrument transformer with photoelectric signals is provided. The primary side of the oil-immersed instrument transformer is led out through the end screen, and the e-terminal of the end screen is directly grounded through a grounding wire. A current transformer is installed on the grounding wire to collect the current in the grounding loop.
[0010] Furthermore, in an oil-immersed current transformer end-screen grounding monitoring and protection system with photoelectric signal, the secondary wire of the current transformer is connected to the A1 terminal of a relay, the A2 terminal of the relay is connected to a resistor R1 and then to an ammeter, and the other end of the ammeter is grounded.
[0011] Furthermore, in an oil-immersed current transformer end-screen grounding monitoring and protection system with photoelectric signal, the e-end and f-end of the end-screen are separated by a nut, the f-end of the end-screen is connected to capacitor C1, capacitor C2 is connected to the other end of capacitor C1 to form a capacitor voltage divider, and the other end of capacitor C2 is grounded.
[0012] Furthermore, in an oil-immersed transformer end-screen grounding monitoring and protection system with photoelectric signal, the voltage signal at the connection point of capacitor C1 and capacitor C2 is sent to a voltmeter, and the other end of the voltmeter is grounded.
[0013] The oil-immersed current transformer end screen grounding light signal monitoring circuit includes a VCC DC power supply, a protection resistor R2, a normally open auxiliary contact of a relay, a normally closed auxiliary contact of a relay, a green LED, and a red LED.
[0014] Furthermore, in an oil-immersed transformer end-screen grounding monitoring and protection system with photoelectric signal, the protection resistor R2 is connected to the VCC DC power supply, and the other end is connected to the normally open auxiliary contact a and normally closed auxiliary contact c of the relay. The normally open auxiliary contact b of the relay is connected to the anode of the green LED D1, and the cathode of the green LED D1 is grounded.
[0015] Furthermore, in an oil-immersed current transformer end-screen grounding monitoring and protection system with photoelectric signal, the normally closed auxiliary contact d of the relay is connected to the anode of the light-emitting diode red D2, and the cathode of the light-emitting diode red D2 is grounded.
[0016] The oil-immersed instrument transformer end screen grounding protection circuit includes a surge arrester, one end of which is connected to the f terminal of the end screen, and the other end is grounded.
[0017] The beneficial effects of this invention are as follows: This solution provides an oil-immersed instrument transformer end screen grounding monitoring and protection system with photoelectric signal. During operation, it can monitor the grounding status of the end screen, eliminating the need for on-site inspection by existing power outage maintenance personnel. This avoids situations such as inadequate grounding by maintenance personnel or poor grounding during operation. Furthermore, when the end screen is not grounded, the surge arrester protects the end screen to prevent damage. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of an oil-immersed instrument transformer end-screen grounding monitoring and protection system.
[0019] In the diagram: 1-current transformer, 2-end screen, 3-surge arrester, 4-current transformer, 5-monitoring backend. Detailed Implementation
[0020] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.
[0021] As shown in the attached figure, the oil-immersed instrument transformer end screen grounding monitoring and protection system with photoelectric signal includes an oil-immersed instrument transformer end screen grounding electrical signal monitoring circuit, an oil-immersed instrument transformer end screen grounding optical signal monitoring circuit, and an oil-immersed instrument transformer end screen grounding protection circuit.
[0022] The oil-immersed instrument transformer end screen grounding signal monitoring circuit includes an oil-immersed instrument transformer, an end screen, an end screen grounding wire, a current transformer, a relay JDQ with a set of normally open and a set of normally closed auxiliary contacts, a resistor R1, an ammeter, a capacitor divider composed of C1 and C2, and a voltmeter.
[0023] Furthermore, the primary side tail end of the oil-immersed transformer is led out through the end screen, and the e-end of the end screen is directly grounded through the grounding wire. A current transformer is installed on its grounding wire to collect the current in the grounding circuit.
[0024] Furthermore, the secondary wire of the current transformer is connected to terminal A1 of the relay, terminal A2 of the relay is connected to resistor R1 and then to an ammeter, and the other end of the ammeter is grounded.
[0025] Furthermore, the e-terminal and f-terminal of the end screen are separated by a nut to prevent the f-terminal from being affected when the e-terminal is removed. The f-terminal of the end screen is connected to capacitor C1, and capacitor C2 is connected to the other end of capacitor C1 to form a capacitor voltage divider. The other end of capacitor C2 is grounded.
[0026] Furthermore, the voltage signal at the connection point of capacitors C1 and C2 is sent to a voltmeter, and the other end of the voltmeter is grounded.
[0027] The oil-immersed current transformer end screen grounding light signal monitoring circuit includes a VCC DC power supply, a protection resistor R2, a normally open auxiliary contact of a relay, a normally closed auxiliary contact of a relay, a green LED, and a red LED.
[0028] Furthermore, the protection resistor R2 is connected to the VCC DC power supply, and its other end is connected to the normally open auxiliary contact a and normally closed auxiliary contact c of the relay. The normally open auxiliary contact b of the relay is connected to the anode of the green LED D1, and the cathode of the green LED D1 is grounded.
[0029] Furthermore, the normally closed auxiliary contact d of the relay is connected to the anode of the LED red D2, and the cathode of the LED red D2 is grounded.
[0030] The oil-immersed instrument transformer end screen grounding protection circuit includes a surge arrester, which is connected to the f-terminal of the end screen, and the other end is grounded.
[0031] In this embodiment, an oil-immersed instrument transformer end-screen grounding monitoring and protection system can monitor the end-screen grounding status, the end-screen grounding status, the end-screen ungrounded status, and the power outage maintenance status.
[0032] When the final screen is properly grounded, the ammeter shows a reading, the voltmeter shows no reading, and the green LED D1 is lit.
[0033] When the grounding of the last screen is faulty, the ammeter and voltmeter show readings, and the green LED D1 lights up.
[0034] When the end screen is not grounded, the ammeter shows no reading, the voltmeter shows a reading, and the LED red D2 is lit.
[0035] During the power outage maintenance, the ammeter and voltmeter showed no readings, and the LED D2 was lit.
[0036] Monitoring process for good grounding of the last screen:
[0037] When the current transformer is operating normally, the primary side of the current transformer and the grounding of the end screen form a loop. Current flows through the grounding wire of the end screen, and the current transformer collects the current signal, so that the ammeter located at the monitoring backend shows a reading.
[0038] The grounding of terminal e of the end screen is good. There is no voltage in the two circuits of the surge arrester and the capacitor divider connected in parallel with it, so the voltmeter shows no reading.
[0039] Current flows through the circuit from the current transformer to the ammeter, and the relay JDQ operates normally, closing its normally open auxiliary contacts a and b, and opening its normally closed auxiliary grounds c and d. This completes the circuit consisting of VCC DC voltage, resistor R2, normally open auxiliary grounds a and b, and LED green D1, causing LED green D1 in the monitoring backend to light up. Conversely, the circuit consisting of VCC DC voltage, resistor R2, normally closed auxiliary grounds c and d, and LED red D2 is disconnected, causing LED red D2 in the monitoring backend to turn off.
[0040] Monitoring process for poor grounding of the last screen:
[0041] When the grounding of the end screen is poor during the operation of the current transformer, a loop can still be formed between the primary side of the current transformer and the grounding of the end screen, and current still flows through the grounding wire of the end screen. However, the current value is smaller than the current during normal operation. At the same time, the current transformer collects the current signal, so that the ammeter located at the monitoring backend has a reading. However, the ammeter reading is smaller than the ammeter reading during normal operation. Therefore, the operators can judge whether the grounding of the end screen is good based on the deviation value of the ammeter reading.
[0042] The grounding of the e-terminal of the last screen is poor. There is voltage in the two circuits of the surge arrester and the capacitor divider connected in parallel with it, so the voltmeter shows a reading.
[0043] Current flows through the circuit from the current transformer to the ammeter, and the relay JDQ operates normally, closing its normally open auxiliary contacts a and b, and opening its normally closed auxiliary grounds c and d. This completes the circuit consisting of VCC DC voltage, resistor R2, normally open auxiliary grounds a and b, and LED green D1, causing LED green D1 on the monitoring backend to light up. Conversely, the circuit consisting of VCC DC voltage, resistor R2, normally closed auxiliary grounds c and d, and LED red D2 is disconnected, causing LED red D2 on the monitoring backend to turn off.
[0044] Monitoring process for ungrounded screen:
[0045] When the end screen of the current transformer is not grounded during operation, a loop cannot be formed between the primary side of the current transformer, the end screen, and the ground. No current flows through the grounding wire of the end screen, and the current transformer cannot collect the current signal, resulting in the ammeter reading at the monitoring backend being zero.
[0046] The e-terminal of the final shield is not grounded. Voltage exists in the two circuits connected in parallel with it: the surge arrester and the capacitor divider. Therefore, the voltmeter shows a reading, which is higher than when the final shield is poorly grounded during transformer operation. The lack of grounding at the e-terminal of the final shield causes a floating voltage at the final shield. When this floating voltage exceeds the surge arrester's power frequency reference voltage, the surge arrester conducts, pulling the voltage at the final shield down to the arrester's residual voltage, thus protecting the final shield.
[0047] No current flows through the circuit from the current transformer to the ammeter, so the relay JDQ stops working. Its normally open auxiliary contacts a and b open, and its normally closed auxiliary ground contacts c and d close. This disconnects the circuit consisting of VCC DC voltage, resistor R2, normally open auxiliary ground contacts a and b, and LED green D1, causing LED green D1 in the monitoring system to turn off. Meanwhile, the circuit consisting of VCC DC voltage, resistor R2, normally closed auxiliary ground contacts c and d, and LED red D2 becomes conductive, illuminating LED red D2 in the monitoring system.
[0048] During power outage maintenance:
[0049] When the current transformer is shut down for maintenance, there is no voltage on the primary side of the current transformer. Therefore, no current flows through the grounding wire of the end screen, and the current transformer cannot collect the current signal, resulting in the ammeter reading at the monitoring backend being zero.
[0050] Since there is no voltage on the primary side of the instrument transformer, there is no voltage at the end panel, and the voltmeter reading is zero. A nut separates the e-terminal and f-terminal of the end panel to prevent the f-terminal from being affected when the e-terminal is removed. When maintenance personnel need to remove the grounding wire of the end panel for instrument transformer testing, only the e-terminal of the end panel needs to be removed. Due to the presence of the surge arrester and capacitive voltage divider, the testing of the insulation resistance of the end panel and the dielectric loss factor and capacitance of the instrument transformer itself will not be affected.
[0051] No current flows through the circuit from the current transformer to the ammeter, so relay JDQ stops working. Its normally open auxiliary contacts a and b open, and normally closed auxiliary grounds 3 and 4 close. This disconnects the circuit consisting of VCC DC voltage, resistor R2, normally open auxiliary grounds a and b, and LED D1, causing LED green D1 in the monitoring backend to turn off. Meanwhile, the circuit consisting of VCC DC voltage, resistor R2, normally closed auxiliary grounds c and d, and LED red D2 becomes conductive, illuminating LED red D2 in the monitoring backend.
[0052] After the instrument transformer maintenance is completed, if the end screen grounding is in good condition, the instrument transformer will return to normal operation. If the end screen grounding is not restored after maintenance, the instrument transformer will be in a state where the end screen is not grounded during operation. The operating personnel can promptly identify any problems missed during maintenance based on photoelectric signal prompts, thus avoiding damage to the end screen of the instrument transformer.
[0053] This solution employs an oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signals. During operation, the voltage and current signals at the end-screen are transmitted to the monitoring backend, enabling timely detection of poor or ungrounded end-screen grounding. After maintenance personnel shut down the power to inspect the instrument transformer, they can use lights to determine the end-screen grounding status and introduce surge arresters to protect the end-screen. When the end-screen is not grounded during operation, if the floating voltage of the end-screen exceeds the surge arrester's power frequency reference voltage, the surge arrester will conduct, pulling the voltage at the end-screen down to the arrester's residual voltage, thus protecting the end-screen.
[0054] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. An oil-immersed mutual inductor end screen grounding monitoring protection system with photoelectric signals, characterized in that, It includes a monitoring circuit for the grounding electrical signal of the end screen of the oil-immersed instrument transformer, a monitoring circuit for the grounding optical signal of the end screen of the oil-immersed instrument transformer, and a grounding protection circuit for the end screen of the oil-immersed instrument transformer; the system can monitor: the end screen grounding good status, the end screen grounding poor status, the end screen ungrounded status, and the power outage maintenance status. The oil-immersed instrument transformer end screen grounding signal monitoring circuit includes an oil-immersed instrument transformer (1), an end screen (2), an end screen grounding wire, a current transformer (4), a relay JDQ with a set of normally open and a set of normally closed auxiliary contacts, a resistor R1, an ammeter A, a capacitor divider composed of capacitors C1 and C2, and a voltmeter V. The primary side of the oil-immersed transformer (1) is led out through the end screen (2). The e end of the end screen is directly grounded through the grounding wire. A current transformer (4) is installed on its grounding wire to collect the current in the grounding circuit. The secondary wire of the current transformer (4) is connected to the A1 end of the relay. The A2 end of the relay is connected to the resistor R1 and then to the ammeter A. The other end of the ammeter is grounded.
2. The oil-immersed transformer screen grounding monitoring protection system with photoelectric signal according to claim 1, characterized in that, The oil-immersed current transformer end screen grounding light signal monitoring circuit includes a VCC DC power supply, a protection resistor R2, a normally open auxiliary contact of a relay, a normally closed auxiliary contact of a relay, a green LED D1, and a red LED D2.
3. The oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signal according to claim 1, characterized in that, The oil-immersed transformer end screen grounding protection circuit includes a surge arrester (3), which is connected to the f terminal of the end screen (2) and the e terminal is grounded.
4. The oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signal according to claim 1, characterized in that, When the oil-immersed transformer (1) is in operation and the end screen (2) is well grounded, the ammeter A shows a reading, the voltmeter V shows no reading, and the green LED D1 is lit. When the oil-immersed transformer (1) is in operation and the end screen (2) is poorly grounded, the ammeter A shows a reading, the voltmeter V shows a reading, and the green LED D1 is lit.
5. The oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signal according to claim 1, characterized in that, When the oil-immersed transformer (1) is in operation and the end panel (2) is not grounded, the ammeter A shows no reading, the voltmeter V shows a reading, and the LED red D2 is lit. When the oil-immersed transformer (1) is in a power outage maintenance state, the ammeter A shows no reading, the voltmeter V shows no reading, and the LED red D2 is lit.
6. The oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signal according to claim 1, characterized in that, The e-end and f-end of the end screen (2) are separated by a nut. The f-end of the end screen (2) is connected to capacitor C1, and capacitor C2 is connected to the other end of capacitor C1 to form a capacitor voltage divider. The other end of capacitor C2 is grounded.
7. The oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signal according to claim 1, characterized in that, The voltage signal at the connection point of capacitors C1 and C2 is sent to voltmeter V. The other end of voltmeter V is grounded. The protective resistor R2 is connected to the VCC DC power supply, and the other end is connected to the normally open auxiliary contact a and normally closed auxiliary contact c of the relay. The normally open auxiliary contact b of the relay is connected to the anode of the green LED D1, and the cathode of the green LED D1 is grounded.
8. The oil-immersed instrument transformer end-screen grounding monitoring and protection system with photoelectric signal according to claim 2, characterized in that, The normally closed auxiliary contact d of the relay is connected to the anode of the LED red D2, and the cathode of the LED red D2 is grounded.