Dual-power high-capacity transformer pre-magnetizing system

Abstract

The invention discloses a dual-power high-capacity transformer pre-magnetizing system, which comprises a pre-magnetizing main circuit, and the pre-magnetizing main circuit comprises three-phase high-voltage circuit breakers, namely a first circuit breaker and a second circuit breaker; the isolating switches comprise a first isolating switch and a second isolating switch, the first isolating switch is used for isolating the first high-voltage power supply during maintenance, and the second isolating switch is used for isolating the second high-voltage power supply during maintenance; the load switches comprise a first load switch and a second load switch, the first load switch is used for switching the primary winding of the transformer into star connection, and the second load switch is used for switching the primary winding of the transformer into triangular connection. Under the high voltage levels provided by different oil and gas field well sites, the impact current in the no-load starting process of the high-capacity high-voltage transformer can be effectively reduced, and the safety and stability of power-on of the whole system are ensured.

Description

Technical Field

[0001] This invention relates to the field of power technology for oil and gas drilling and production equipment. More specifically, this invention relates to a pre-magnetizing system for a dual-power, high-capacity transformer. Background Technology

[0002] In current oil and gas field drilling and production operations, the power supply networks at well sites mainly consist of two high-voltage systems: 10kV and 6kV. Traditional oil and gas drilling and production equipment is typically designed with a power distribution system that can only connect to a single voltage level of high-voltage power. This single-system design exhibits significant limitations when dealing with well sites using different power systems. Specifically, equipment designed for one power system cannot be directly applied to well sites using another power system. Either complex and costly on-site modifications are required, or the operation opportunity must be abandoned. This greatly limits the versatility and application scope of the equipment, increasing the complexity of equipment deployment and operating costs.

[0003] To address this challenge, the industry has begun adopting pressure-driven skid-mounted dual-power transformer and frequency converter circuits. This solution involves designing a high-voltage switchgear with dual power supply matching, providing high-voltage power to the primary side of the transformer via a common outgoing cabinet, thus enabling a single set of equipment to flexibly adapt to the power supply of different well sites, such as 10kV or 6kV. However, the introduction of this dual-power system has placed new and more complex demands on the structural design of the high-voltage switchgear.

[0004] Meanwhile, to meet the demands of high-power drilling equipment, the system typically requires a large-capacity high-voltage transformer. Such transformers generate a high-amplitude, short-duration inrush current at the moment of no-load switching. This inrush current can reach 6-8 times or even higher than the transformer's rated current, impacting the power grid, causing voltage dips, affecting the stable operation of other equipment on the same grid, and in severe cases, even causing the transformer's own relay protection devices to malfunction, resulting in power-on failure.

[0005] In existing technologies, to address the inrush current problem, a pre-charging system is typically installed at the transformer's upstream end, using a pre-charging resistor or reactor to limit the starting current. However, in this application scenario, the dual-power-input structure makes the design of the pre-charging system exceptionally complex. Designing and integrating a pre-charging system capable of simultaneously matching two different high-voltage power supplies (10kV / 6kV) within a compact high-voltage switchgear that must meet stringent "five-proof" requirements has become a key technological bottleneck ensuring the stable and reliable startup of the entire large-capacity transformer-frequency conversion system. Existing single-power-supply pre-charging solutions cannot be directly applied, as their structural layout and electrical logic cannot meet the requirements for flexible switching and safe isolation between dual power supplies.

[0006] Therefore, there is an urgent need in this field for an innovative solution that can design a high-capacity high-voltage transformer pre-charging system with a reasonable structure, high integration, and adaptability to dual power input without violating the safety specifications of high-voltage switchgear. This system can effectively suppress the no-load starting current of the transformer and ensure that the equipment can achieve stable and smooth power-on in different electrical control well sites. Summary of the Invention

[0007] The purpose of this invention is to provide a dual-power large-capacity transformer pre-magnetization system. This system can effectively reduce the inrush current during the no-load start-up process of large-capacity high-voltage transformers under high voltage levels provided by different oil and gas field well sites, ensuring the safety and stability of the entire system when powered on.

[0008] The technical solution adopted by this invention to solve this technical problem is as follows: A pre-magnetizing system for a dual-power large-capacity transformer, comprising a pre-magnetizing main circuit, wherein the pre-magnetizing main circuit includes: a three-phase high-voltage circuit breaker, namely a No. 1 circuit breaker and a No. 2 circuit breaker; disconnecting switches, namely a No. 1 disconnecting switch and a No. 2 disconnecting switch, wherein the No. 1 disconnecting switch is used to isolate a first high-voltage power supply during maintenance, and the No. 2 disconnecting switch is used to isolate a second high-voltage power supply during maintenance; load switches, namely a No. 1 load switch and a No. 2 load switch, wherein the No. 1 load switch is used to switch the primary winding of the transformer to a star connection, and the No. 2 load switch is used to switch the primary winding of the transformer to a delta connection; The transformer has its primary side connected to either a first or a second high-voltage power supply, and its secondary side outputs the required low-voltage power. There are two high-voltage AC contactors: a No. 1 high-voltage AC contactor and a No. 2 high-voltage AC contactor. The main contacts of the No. 1 high-voltage AC contactor control the connection and disconnection of the power supply circuit between the high-voltage switchgear output line and the transformer primary side, while the main contacts of the No. 2 high-voltage AC contactor control the connection and disconnection of the pre-magnetizing circuit. A high-voltage resistor is connected in series in the pre-magnetizing circuit to limit the inrush current during transformer startup. The pre-magnetizing circuit consists of the main contacts of the No. 2 high-voltage AC contactor connected in series with a high-voltage resistor. One end of the circuit is connected to the outgoing bus of the high-voltage switchgear, and the other end is connected to the primary side of the transformer T. The normal power supply circuit is controlled by the main contacts of the No. 1 high-voltage AC contactor and is connected in parallel with the pre-magnetizing circuit.

[0009] As a further aspect of the present invention, it further includes a pre-magnetization control circuit, which is configured to: Receive status signals from circuit breaker No. 1 / circuit breaker No. 2; In response to the closing command, in the pre-magnetization mode, the second high-voltage AC contactor is first controlled to close to connect the pre-magnetization circuit; After a preset delay, the system automatically controls the first high-voltage AC contactor to close to connect the normal power supply circuit and controls the second high-voltage AC contactor to open.

[0010] As a further aspect of the present invention, the pre-magnetization control circuit includes: The power supply and protection unit is used to provide power to the entire control circuit and implement overcurrent and short-circuit protection; A three-position selector switch for selecting pre-magnetization, stop, or no pre-magnetization mode; Operating buttons (SB1, SB2, SB3, SB4) used to issue closing and opening commands; Status indicator light used to indicate the pre-magnetization process; Relay modules used to implement logic control and delay functions.

[0011] As a further aspect of the present invention, the control power supply and protection unit includes two branches corresponding to the first high-voltage power supply and the second high-voltage power supply respectively. Each branch is connected in series with a low-voltage circuit breaker, and a fuse is provided in the circuit for overcurrent and short-circuit protection.

[0012] As a further aspect of the present invention, the relay module includes: An intermediate relay, which is triggered at the start of pre-magnetization; The time-delay relay's closing control coil is connected to the circuit through the passive normally open contact of the intermediate relay, thereby being activated.

[0013] As a further aspect of the present invention, the three-position changeover switch has a non-pre-magnetizing position. When switched to this position, the closing command can be triggered to directly connect the No. 1 high-voltage AC contactor, skipping the pre-magnetizing process and directly powering the transformer.

[0014] As a further aspect of the present invention, the passive normally closed contact of the No. 1 circuit breaker is connected in series with the power supply circuit of the closing control coil of the No. 2 circuit breaker, and the passive normally closed contact of the No. 2 circuit breaker is connected in series with the power supply circuit of the closing control coil of the No. 1 circuit breaker, thereby realizing electrical interlocking between the two power supply circuits.

[0015] The present invention has at least the following beneficial effects: 1. Compatibility and Flexibility with Multiple High Voltage Levels: This invention integrates two independent high-voltage incoming circuits (QF1 / QS1 and QF2 / QS2) and a load switch (QL1 / QL2) with switchable transformer winding connection methods, successfully enabling a pre-magnetized system to be compatible with multiple high voltage levels, including 10kV and 6kV. This design greatly enhances the system's application flexibility, allowing it to adapt flexibly to oil and gas well sites with different voltage systems. It solves the problem of limited application range of traditional equipment due to voltage mismatch, laying the foundation for equipment standardization and widespread deployment.

[0016] 2. Excellent Inrush Current Suppression and Equipment Protection Capabilities: The core of this invention lies in the innovative introduction of a dedicated pre-charge magnetization circuit composed of a high-voltage AC contactor (KM2) and high-voltage resistors (Ra, Rb, Rc). During transformer no-load startup, the system first establishes a magnetic field on the primary side of the transformer through this current-limiting circuit, effectively suppressing the startup inrush current within a safe range. This process significantly reduces the impact of instantaneous high current on the well site power grid, while greatly reducing electrical stress damage to the transformer itself and upstream high-voltage switchgear and other electrical equipment, comprehensively improving the stability of the entire power supply system and the service life of the equipment.

[0017] 3. Reliable Emergency Bypass Function and System Availability: For emergency scenarios where the pre-magnetizing system itself may fail or the upstream power grid capacity is sufficient, this invention innovatively incorporates a three-position selector switch (S0) in the control circuit, providing a no-pre-magnetizing setting. In this mode, operators can easily switch to instruct the system to skip the pre-magnetizing stage and directly connect the contactor (KM1) of the normal power supply circuit to energize the transformer. This emergency function ensures that even if the pre-magnetizing system temporarily fails during critical operations, the power supply to the well site will not be interrupted, greatly enhancing the system's reliability and emergency response capabilities.

[0018] 4. High Integration and Significant Economic Benefits: Through careful component selection and optimized circuit layout, this invention successfully integrates the pre-magnetization requirements of two high-voltage power supplies into a unified system, achieving hardware resource sharing. This highly integrated design avoids redundant investment in configuring independent pre-magnetization systems for the two voltages, effectively reducing the size and space occupancy of the complete equipment, meeting the well site's requirements for compact equipment, and significantly reducing manufacturing, installation, and maintenance costs, resulting in outstanding economic benefits.

[0019] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the pre-magnetization main circuit of the dual-power transformer of the present invention; Figure 2 This is a schematic diagram of the transformer pre-magnetization control circuit of the present invention; Figure 3 This is a schematic diagram of the 10kV pre-magnetized operation flow of the present invention; Figure 4 This is a schematic diagram of the flow operation after the 10kV pre-magnetization of the present invention is completed; Figure 5This is a schematic diagram of the 6kV pre-magnetized operation flow of the present invention; Figure 6 This is a schematic diagram of the flow operation after the 6kV pre-magnetization of the present invention is completed. Detailed Implementation

[0021] The present invention will now be described in detail and completely with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the accompanying drawings, it should be particularly noted that the technical solutions and features provided in various parts of the present invention, including the following description, can be combined with each other without conflict.

[0022] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows: This invention mainly involves adding high-voltage pre-charging resistors and high-voltage AC contactors between the common outgoing line side of the dual-power high-voltage switchgear and the primary side of the large-capacity dual-power high-voltage transformer. Before the large-capacity dual-power high-voltage transformer is started under no-load conditions, it can effectively establish a stable magnetic field when any high-voltage power source is connected, thereby reducing the inrush current during the no-load start-up of the large-capacity dual-power high-voltage transformer.

[0024] like Figure 1As shown, the present invention provides a pre-magnetizing system for a dual-power high-capacity transformer, including a pre-magnetizing main circuit, which includes: a three-phase high-voltage circuit breaker, a disconnecting switch, a load switch, a high-capacity dual-power high-voltage transformer T, a high-voltage AC contactor, a high-voltage resistor, etc. The three-phase high-voltage circuit breakers are designated as follows: Circuit breaker No. 1 (QF1) and Circuit breaker No. 2 (QF2). QF1 is used for the control and protection of the 10kV power supply circuit, and QF2 is used for the control and protection of the 6kV power supply circuit. The disconnecting switches are designated as follows: Disconnecting switch No. 1 (QS1) and Disconnecting switch No. 2 (QS2). Disconnecting switch No. 1 (QS1) is used to isolate the first type of high-voltage power supply (10kV) during maintenance, and disconnecting switch No. 2 (QS2) is used to isolate the second type of high-voltage power supply (6kV) during maintenance. The load switches are designated as follows: Load switch No. 1 (QL1) and Load switch No. 2 (QL2). Load switch No. 1 (QL1) is used to switch the primary winding of the transformer to a star connection, and load switch No. 2 (QL2) is used to switch the primary winding of the transformer to a delta connection. The transformer T has its primary side connected to either the first type of high-voltage power supply (10kV) or the second type of high-voltage power supply (6kV), and its secondary side outputs the required low-voltage power. For example, it can be converted to the required 600V or 400V low-voltage power supply; high-voltage AC contactors, namely high-voltage AC contactor KM1 and high-voltage AC contactor KM2, wherein the main contacts of high-voltage AC contactor KM1 control the on / off of the power supply circuit between the high-voltage switchgear outgoing line and the primary side of the transformer, and the main contacts of high-voltage AC contactor KM2 control the on / off of the pre-magnetizing circuit; high-voltage resistors, connected in series in the pre-magnetizing circuit, are mainly used to limit the current surge of the large-capacity dual-power high-voltage transformer, protect circuit components, and ensure the smooth start-up of the large-capacity dual-power high-voltage transformer. Specifically, there are three sets of high-voltage resistors, namely Ra, Rb, and Rc; wherein, the pre-magnetizing circuit is composed of the main contacts of high-voltage AC contactor KM2 connected in series with the high-voltage resistors Ra, Rb, and Rc. One end of this circuit is connected to the high-voltage switchgear outgoing bus, and the other end is connected to the primary side of transformer T and the pre-magnetizing circuit. To ensure successful energization of the large-capacity dual-power high-voltage transformer T after pre-magnetization, the pre-magnetization circuit must be connected in parallel with the normal outgoing circuit. The normal outgoing circuit consists of a controllable, flexibly switchable high-voltage AC contactor KM1. The system changes the connection mode of the transformer's primary winding by switching between load switch QL1 (number one) and load switch QL2 (number two) to accommodate different voltage levels of power input. When any high-voltage power source is connected, the pre-magnetization process is initiated by closing the corresponding circuit's isolating switch and load switch, and operating the corresponding circuit breaker closing button. After pre-magnetization is complete, the system automatically switches to the normal power supply circuit, energizing the transformer.

[0025] As attached Figure 2The diagram shows a pre-magnetization control circuit for a high-capacity dual-power high-voltage transformer according to an embodiment of the present invention. This control circuit is configured to: receive status signals from circuit breaker 1 / circuit breaker 2; respond to a closing command, in pre-magnetization mode, first control the second high-voltage AC contactor KM2 to close to connect the pre-magnetization circuit; after a preset delay, automatically control the first high-voltage AC contactor KM1 to close to connect the normal power supply circuit, and control the second high-voltage AC contactor KM2 to open. By sharing a single pre-magnetization main circuit and pre-magnetization control circuit, it is compatible with high-voltage power inputs of two different voltage levels: 10kV and 6kV.

[0026] The pre-magnetization control circuit includes: a control power supply and protection unit, used to provide power to the entire control circuit and implement overcurrent and short-circuit protection; specifically, it includes a low-voltage circuit breaker, a fuse, a circuit breaker electric closing self-reset switch, a circuit breaker electric opening self-reset switch, a circuit breaker closing control coil, a circuit breaker passive normally open contact, a circuit breaker passive normally closed contact, a pre-magnetization process indicator light, a high-voltage AC contactor closing control coil, a high-voltage AC contactor passive normally open contact, a high-voltage AC contactor passive normally closed contact, a three-position changeover switch, an intermediate relay, an intermediate relay passive normally open contact, a time delay relay, and a time delay relay passive normally open contact, etc.

[0027] XF11 is a passive normally open contact of the QF1 high-voltage circuit breaker, mainly used for self-locking of the power supply circuit of the XF1 closing control coil of the QF1 high-voltage circuit breaker, energizing the HL1 pre-magnetizing process indicator, the XM1 closing control coil of the KM1 high-voltage AC contactor, the XM2 closing control coil of the KM2 high-voltage AC contactor, and the KA1 intermediate relay coil in pre-magnetizing mode, and energizing the XM1 closing control coil of the KM1 high-voltage AC contactor in non-pre-magnetizing mode. XF21 is a passive normally open contact of the QF2 high-voltage circuit breaker, mainly used for self-locking of the power supply circuit of the XF2 closing control coil of the QF2 high-voltage circuit breaker, energizing the HL1 pre-magnetizing process indicator, the XM1 closing control coil of the KM1 high-voltage AC contactor, the XM2 closing control coil of the KM2 high-voltage AC contactor, and the KA1 intermediate relay coil in pre-magnetizing mode, and energizing the XM1 closing control coil of the KM1 high-voltage AC contactor in non-pre-magnetizing mode. XF12 is a passive normally closed contact of the QF1 high-voltage circuit breaker, mainly interlocked with the power supply circuit of the XF2 closing control coil of the QF2 high-voltage circuit breaker. XF22 is a passive normally closed contact of the QF2 high-voltage circuit breaker, mainly interlocked with the power supply circuit of the XF21 closing control coil of the QF1 high-voltage circuit breaker. The circuit breaker's electric closing self-reset switches are SB1 and SB2. SB1 is the electric closing self-reset switch for the QF1 high-voltage circuit breaker, mainly energizing the XF1 closing control coil of the QF1 high-voltage circuit breaker; SB2 is the electric operating closing button for the QF2 high-voltage circuit breaker, mainly energizing the XF2 closing control coil of the QF2 high-voltage circuit breaker. SB3 is the electric tripping self-reset switch for the QF1 high-voltage circuit breaker, mainly de-energizing the XF1 closing control coil of the QF1 high-voltage circuit breaker; SB4 is the electric operating closing button for the QF2 high-voltage circuit breaker, mainly de-energizing the XF2 closing control coil of the QF2 high-voltage circuit breaker. The status indicator HL1, used to indicate the pre-magnetization process, displays yellow during normal operation. Relay modules (KA1, KT1) are used to implement logic control and delay functions. The circuit breaker's closing control coils are XF1 and XF2. XF1 is the closing control coil for the QF1 high-voltage circuit breaker, used to control the closing of the main contacts and passive normally open contacts, and the opening of the passive normally closed contacts. XF2 is the closing control coil for the QF2 high-voltage circuit breaker, used to control the closing of the main contacts and passive normally open contacts, and the opening of the passive normally closed contacts. XM1 is the closing control coil of the KM1 high-voltage AC contactor, mainly used to control the closing of the main contacts of the KM1 high-voltage AC contactor and the XM11 passive normally open contact of the KM1 high-voltage AC contactor, and to control the opening of the XM12 passive normally closed contact of the KM1 high-voltage AC contactor; XM2 is the closing control coil of the KM2 high-voltage AC contactor, mainly used to control the opening and closing of the main contacts of the KM2 high-voltage AC contactor.The XM11 passive normally open contact of the KM1 high-voltage AC contactor is mainly used for self-locking of the power supply circuit of the XM1 closing control coil of the KM1 high-voltage AC contactor. The XM12 passive normally closed contact of the KM1 high-voltage AC contactor is mainly used for switching the power supply circuit of the HL1 pre-magnetization process indicator, the XM2 closing control coil of the KM2 high-voltage AC contactor, and the KA1 intermediate relay coil.

[0028] When the S0 three-position changeover switch is turned from the stop position to the non-pre-magnetized position, with a 10kV high-voltage power supply connected, after closing the QL1 load switch and the QS1 isolating switch, pressing the SB1 electric closing self-reset switch of the QF1 high-voltage circuit breaker will cause the QF1 high-voltage circuit breaker to engage, and the main contacts of the KM1 high-voltage AC contactor to engage. The large-capacity dual-power high-voltage transformer can then be successfully energized directly without pre-magnetization. With a 6kV high-voltage power supply connected, after closing the QL2 load switch and the QS2 isolating switch, pressing the SB2 electric closing self-reset switch of the QF2 high-voltage circuit breaker will cause the QF2 high-voltage circuit breaker to engage, and the main contacts of the KM1 high-voltage AC contactor to engage. The large-capacity dual-power high-voltage transformer can then be successfully energized directly without pre-magnetization.

[0029] The dual-power high-capacity transformer pre-magnetization system of this application, when a high-voltage power source is connected to the high-voltage switchgear, closes the load switch corresponding to the primary connection method of the transformer, load switch QL1 or load switch QL2 and the isolating switch of the high-voltage incoming circuit, isolating switch QS1 or isolating switch QS2, and presses the closing button SB1 or SB2 of the corresponding high-voltage incoming circuit breaker, the high-voltage circuit breaker QF1 or QF2 closes, the high-voltage AC contactor closing control coil XM2 of the high-voltage circuit breaker is energized, the main contacts of the high-voltage AC contactor KM2 are attracted, and the high-voltage power source provides power to the high-capacity dual-power high-voltage transformer T through high-voltage resistors Ra, Rb, and Rc. The high-voltage transformer enters the pre-magnetization state, and the pre-magnetization process indicator HL1 lights up yellow. The passive normally open contact KA11 of the intermediate relay closes, and the time delay relay KT1 enters the pre-magnetization countdown according to the set time delay. After the set time delay of the time delay relay KT1 is reached, the passive normally open contact KT11 of the relay KT1 closes, the closing control coil XM1 of the high-voltage AC contactor is energized, the main contacts of the high-voltage AC contactor KM1 close, and at the same time, the passive normally closed contact XM12 of the high-voltage AC contactor opens. The closing control coil XM2 of the high-voltage AC contactor is de-energized, and the main contacts of the high-voltage AC contactor KM2 open. At this time, the pre-magnetization circuit is disconnected, and the entire large-capacity dual-power high-voltage transformer T completes the pre-magnetization and is successfully energized.

[0030] In a preferred embodiment of this application, the control power supply and protection unit includes two branches corresponding to the first type of high-voltage power supply (10kV) and the second type of high-voltage power supply (6kV), respectively. Each branch is connected in series with a low-voltage circuit breaker (QF3, QF4), and a fuse FU1 is installed in the circuit for overcurrent and short-circuit protection. Specifically, circuit breaker QF3 provides control and protection for the pre-magnetization control circuit of the large-capacity dual-power high-voltage transformer when the 10kV power supply is connected; circuit breaker QF4 provides control and protection for the pre-magnetization control circuit of the large-capacity dual-power high-voltage transformer when the 6kV power supply is connected.

[0031] In a preferred embodiment of this application, the passive normally open contact KA11 of the intermediate relay is mainly used to control the energization of the closing control coil of the KT1 time-delay relay. The passive normally open contact of the time-delay relay, KT11, is mainly used to control the energization of the XM1 closing control coil of the KM1 high-voltage AC contactor. The relay module includes: the intermediate relay KA1, which is mainly used to control the opening and closing of the passive normally open contact of the KA11 intermediate relay, and is triggered when pre-magnetization begins; and the time-delay relay KT1, which is mainly used to control the opening and closing of the passive normally open contact of the KT11 time-delay relay, and its closing control coil is activated after the passive normally open contact KA11 of the intermediate relay KA1 is closed. The specific working logic of the relay module is as follows: when pre-magnetization begins, at the same time the XM2 closing control coil of the KM2 high-voltage AC contactor is energized, the coil of the intermediate relay KA1 is also connected in parallel and triggered. After KA1 operates, its passive normally open contact KA11 closes, which connects the closing control coil of time delay relay KT1 to the control power supply circuit. KT1 is energized and starts timing. After timing ends, KT1's own passive normally open contact KT11 closes, thereby connecting the power supply circuit of KM1's closing control coil XM1.

[0032] In a preferred embodiment of this application, the three-position changeover switch S0 has a non-pre-magnetizing position. When switched to this position, triggering the closing command directly connects the first high-voltage AC contactor KM1, skipping the pre-magnetizing process and directly energizing the transformer. The specific internal wiring of the three-position changeover switch S0 in the non-pre-magnetizing position is as follows: this position directly leads the closing command signal (from SB1 or SB2) to the closing control coil XM1 circuit of the first high-voltage AC contactor KM1, while simultaneously disconnecting the control circuits of the second high-voltage AC contactor KM2 and the time-delay relay KT1. Therefore, when the operator presses the closing button, current flows directly through the "direct start" contact of S0, energizing XM1, causing KM1 to immediately close, directly energizing the transformer, and the pre-magnetizing indicator HL1 on the system panel remains off.

[0033] In a preferred embodiment of this application, the passive normally closed contact XF12 of circuit breaker QF1 is connected in series with the power supply circuit of the closing control coil XF2 of circuit breaker QF2, and the passive normally closed contact XF22 of circuit breaker QF2 is connected in series with the power supply circuit of the closing control coil XF1 of circuit breaker QF1, thereby achieving electrical interlocking between the two power supply circuits. Specifically, the passive normally closed contact XF12 of circuit breaker QF1 is connected in series in the power supply circuit of the closing control coil XF2 of circuit breaker QF2. When QF1 is in the closed position, XF12 is open. Even if SB2 is accidentally pressed, XF2 cannot be energized, and QF2 cannot close. Similarly, the normally closed contact XF22 of QF22 is connected in series in the closing control coil XF1 circuit of QF1, achieving reverse interlocking. This design constitutes a hardwired safety logic, fundamentally preventing the extreme danger of two high-voltage power supplies operating simultaneously.

[0034] The operating principle of the above-mentioned dual-power large-capacity high-voltage transformer pre-magnetization system is as follows (taking a 10kV high-voltage power supply as an example): Turn the three-position changeover switch S0 from the stop position to the pre-magnetization position, then close the QL1 load switch and QS1 isolating switch, and then close the QF3 circuit breaker to supply power to the pre-magnetization control circuit of the large-capacity dual-power high-voltage transformer. Press the SB1 electric closing self-reset switch of the QF1 high-voltage circuit breaker, the QF1 high-voltage circuit breaker will close, the main contacts of the KM2 high-voltage AC contactor will close, and the pre-magnetization process will begin. At the same time, the pre-magnetization process indicator HL1 will be energized. At this time, the large-capacity dual-power high-voltage transformer enters the pre-magnetization state. The schematic diagram of the operation flow of the pre-magnetization process of the large-capacity dual-power high-voltage transformer is shown below. Figure 3 As shown, similarly, when a 6kV high-voltage power supply is connected, the schematic diagram of the pre-magnetization process of a large-capacity dual-power high-voltage transformer is as follows: Figure 5 As shown.

[0035] While the large-capacity dual-power high-voltage transformer is undergoing pre-magnetization, the KT1 time-delay relay closing control coil is energized under the control of the KA1 intermediate relay. When the KT1 time-delay relay reaches its preset time limit, the main contacts of the KM1 high-voltage AC contactor close, and the XM12 passive normally closed contact of the KM1 high-voltage AC contactor opens, controlling the main contacts of the KM2 high-voltage AC contactor to open. This disconnects the pre-magnetization circuit, and the large-capacity dual-power high-voltage transformer is successfully, safely, and stably energized. The operational flow diagram after the large-capacity dual-power high-voltage transformer has completed pre-magnetization is shown below. Figure 4 As shown. Similarly, when a 6kV high-voltage power supply is connected, the operational flow diagram after the pre-magnetization of the large-capacity dual-power high-voltage transformer is completed is shown in the figure. Figure 6As shown. When the SB3 electric closing self-reset switch of the QF1 high-voltage circuit breaker is pressed, the QF1 high-voltage circuit breaker opens, and at the same time the main contacts of the KM1 high-voltage AC contactor open, returning to the state before power-on.

[0036] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A dual power large capacity transformer pre-magnetizing system, characterized by, The pre-magnetization main circuit comprises: three-phase high-voltage circuit breakers, namely a first circuit breaker and a second circuit breaker; disconnectors, namely a first disconnector and a second disconnector, wherein the first disconnector is used for isolating a first high-voltage power supply during maintenance, and the second disconnector is used for isolating a second high-voltage power supply during maintenance; load switches, namely a first load switch and a second load switch, wherein the first load switch is used for switching a primary winding of a transformer into a star connection, and the second load switch is used for switching the primary winding of the transformer into a delta connection; The transformer has a primary winding connected to the first high-voltage power supply or the second high-voltage power supply and outputs a required low-voltage power supply; high-voltage AC contactors, namely a first high-voltage AC contactor and a second high-voltage AC contactor, wherein a main contact of the first high-voltage AC contactor controls the on-off of a power supply loop between an outgoing line of a high-voltage switch cabinet and the primary winding of the transformer, and a main contact of the second high-voltage AC contactor controls the on-off of a pre-magnetization loop; and a high-voltage resistor connected in series in the pre-magnetization loop and used for limiting an impact current during starting of the transformer. The pre-magnetization loop is composed of the main contact of the second high-voltage AC contactor and the high-voltage resistor in series, one end of the loop is connected to an outgoing line bus of the high-voltage switch cabinet, and the other end of the loop is connected to the primary winding of the transformer T; and the normal power supply loop is controlled by the main contact of the first high-voltage AC contactor and is connected in parallel to the pre-magnetization loop.

2. The dual supply large capacity transformer pre-magnetizing system as claimed in claim 1, wherein, The pre-magnetization control circuit is configured to: receive a state signal from the first circuit breaker / second circuit breaker; in response to a closing instruction, first control the second high-voltage AC contactor to close to turn on the pre-magnetization loop in a pre-magnetization mode; after a preset delay, automatically control the first high-voltage AC contactor to close to turn on the normal power supply loop and control the second high-voltage AC contactor to open.

3. The dual supply large capacity transformer pre-magnetizing system as claimed in claim 2, wherein, The pre-magnetization control circuit comprises: a control power supply and protection unit for providing power supply for the entire control circuit and implementing overcurrent and short-circuit protection; a three-position switch for selecting a pre-magnetization mode, a stop mode or a non-pre-magnetization mode; operation buttons for issuing closing and opening instructions; status indicator lamps for indicating a pre-magnetization process; a relay module for implementing logic control and delay functions.

4. The dual supply large capacity transformer pre-magnetizing system as claimed in claim 3, wherein, The control power supply and protection unit comprises two branches corresponding to the first high-voltage power supply and the second high-voltage power supply respectively, each branch has a low-voltage circuit breaker connected in series, and a fuse is arranged in the loop for overcurrent and short-circuit protection.

5. The dual supply large capacity transformer pre-magnetizing system as claimed in claim 3, wherein, The relay module comprises: an intermediate relay triggered at the start of pre-magnetization; a delay relay whose closing control coil is connected to the circuit through a passive normally open contact of the intermediate relay and is thus started.

6. The dual supply large capacity transformer pre-magnetizing system as claimed in claim 3, wherein, The three-position switch has a non-pre-magnetization position, when switched to the position, a closing instruction can directly turn on the first high-voltage AC contactor, and the pre-magnetization process is skipped to directly power on the transformer.

7. The dual supply large capacity transformer pre-magnetizing system as claimed in claim 3, wherein, A passive normally closed contact of the first circuit breaker and a power supply loop of a closing control coil of the second circuit breaker are connected in series, and a passive normally closed contact of the second circuit breaker and a power supply loop of a closing control coil of the first circuit breaker are connected in series, thereby realizing electrical interlocking between the two power supply loops.

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