Device for suppressing transformer inrush current and its usage method

Abstract

The present invention relates to a switch device with a closing resistor for suppressing transformer excitation inrush current and a method of using the switch device, comprising a closing resistor tank and a switch device tank, wherein a closing resistor unit is installed in the closing resistor tank, and two ends of the closing resistor unit are respectively connected to two bushings through a connecting bus, and a static contact assembly and a moving contact assembly are installed in the switch device tank, and the static contact assembly and the moving contact assembly are respectively connected to the two ends of the closing resistor unit, and also include an operating mechanism for driving the moving contact assembly to extend and retract to realize opening and closing, and a current transformer for detecting excitation inrush current is installed on the outside of the connecting bus, and the operating mechanism adjusts the closing speed of the moving contact and the static contact according to the size of the excitation inrush current detected by the current transformer. The switch device can not only achieve the purpose of suppressing the transformer excitation inrush current, but also accurately control the input time of the closing resistor, so as to prevent the closing resistor from causing the thermal capacity to exceed the tolerance value of the closing resistor due to too long an input time.

Description

Technical Field

[0001] The invention relates to the field of electrical switches, and in particular to a switch device with a closing resistor for suppressing transformer excitation surge current and a use method thereof. Background Art

[0002] Transformers are the hubs connecting the power grid and users, and are indispensable in the power system. Their operating status also affects the stable operation of the power system. When the transformer is closed without load, the closing time is random, which often leads to saturation of the transformer core. Because the core material has nonlinear characteristics, it will generate an excitation inrush current, which can reach ten times the rated current.

[0003] Transformer excitation inrush current will cause the transformer differential protection to not work correctly, causing the transformer to not work properly. In addition, excessive excitation inrush current will damage other electrical components such as circuit breakers connected to the transformer, causing large-scale grid stagnation and huge losses, which will have a great impact on the stable operation of the grid. Therefore, it is very necessary to suppress the transformer excitation inrush current, which can greatly reduce unnecessary power outages and the scope of power outages. The existing suppression technologies are generally not ideal, and the use of open equipment will occupy a large area, and it is impossible to achieve millisecond-level control accuracy. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a switch device with a closing resistor for suppressing transformer excitation inrush current and a use method thereof.

[0005] The present invention is achieved through the following technical scheme, which provides a switch device with closing resistor for suppressing transformer excitation inrush current, including a closing resistor tank and a switch device tank, wherein a closing resistor unit is installed in the closing resistor tank, and the two ends of the closing resistor unit are respectively connected to two bushings through a connecting bus, and a static contact assembly and a moving contact assembly are installed in the switch device tank, and the static contact assembly and the moving contact assembly are respectively connected to the two ends of the closing resistor unit, and also include an operating mechanism for driving the moving contact assembly to extend and retract to realize opening and closing, and a current transformer for detecting excitation inrush current is installed on the outside of the connecting bus, and the operating mechanism adjusts the closing speed of the static contact assembly and the moving contact assembly according to the size of the excitation inrush current detected by the current transformer.

[0006] In this scheme, when the current flows from the bushing assembly at one end into the parallel switch device with closing resistance, the moving and static contacts of the switch device unit are in the open state at first, and the switch device unit circuit is in the open state. Therefore, the current flows through the closing resistance unit circuit. The closing resistance unit resistance value is in the kilo-ohm level, so the excitation surge current energy will be converted into resistance heating; when the moving contact in the switch device unit moves to connect with the static contact, the switch device unit is closed, and the switch device unit circuit changes from open circuit to open circuit. Because the circuit resistance of the switch device circuit is much smaller than that of the closing resistance circuit after the circuit is opened, the closing resistance unit circuit will be short-circuited by the switch device unit circuit, so that the current can pass through the switch device unit circuit instead of flowing through the closing resistance unit circuit. Because the resistance value of the switch device circuit is in the milliohm level, the heat generated is very small, which meets the rated current flow requirement after the excitation surge current disappears.

[0007] The closing time of the switching device must be no less than the duration of the excitation surge current to ensure that the excitation surge current passes through the closing unit. After the excitation surge current disappears, the closing device circuit is closed and the current flows through the closing device.

[0008] As an optimization, the operating mechanism includes a driving cylinder, a high-pressure cylinder body, a high-pressure cylinder piston installed in the high-pressure cylinder body, and a disc spring that pushes the high-pressure cylinder piston into the high-pressure cylinder body to form a high-pressure oil chamber. The piston rod of the driving cylinder is connected to the moving contact assembly through an insulating pull rod. The high-pressure oil chamber is connected to the rod chamber of the driving cylinder. It also includes a reversing valve, a low-pressure oil chamber, and an oil pump that pumps oil in the low-pressure oil chamber into the high-pressure oil chamber. The low-pressure oil chamber, the high-pressure oil chamber and the rodless chamber of the driving cylinder are respectively connected to the reversing valve, and a closing speed regulating valve is installed on the oil pipe of the low-pressure oil chamber, and an opening speed regulating valve is installed on the oil pipe of the rodless chamber of the driving cylinder.

[0009] As an optimization, the disc spring sleeve is mounted on the driving oil cylinder, and a disc spring push plate is provided between the disc spring and the high-pressure cylinder piston. In this solution, the disc spring sleeve plays a guiding role on the driving oil cylinder, and the disc spring push plate realizes the thrust of the disc spring on the high-pressure cylinder piston.

[0010] As an optimization, the moving contact assembly includes a moving side connection seat connected to one end of the closing resistor unit and a moving main contact sliding in the moving side connection seat, and the static contact assembly includes a static side connection seat connected to the other end of the closing resistor unit and a static main contact fixed to the static side connection seat, and a static arc contact is installed in the static main contact. The moving main contact in this solution is inserted into the static main contact and wraps the static arc contact, so that the static arc contact can play the role of arc initiation while achieving connection.

[0011] As an optimization, a moving contact shielding cover is installed on the moving side connection seat, and a static contact shielding cover is installed on the static side connection seat. The moving contact shielding cover and the static contact shielding cover in this solution play a shielding role.

[0012] As an optimization, the closing resistor tank body and the switch device tank body are connected and separated by two pot-type insulators, and the static contact assembly and the moving contact assembly are respectively connected to the two ends of the closing resistor unit through connecting conductors, and the connecting conductors pass through the pot-type insulators and the passing places are sealed. In this solution, the pot-type insulator realizes the sealed separation of the closing resistor tank body and the switch device tank body.

[0013] The method for using a switch device with a closing resistor for suppressing transformer excitation inrush current comprises the following steps:

[0014] a. Energy storage: The oil pump pumps the oil in the low-pressure oil chamber into the high-pressure oil chamber, pushing the high-pressure cylinder piston to move, thereby compressing the disc spring, so that the high-pressure oil chamber is filled with high-pressure oil;

[0015] b. Closing: Adjust the reversing valve to connect the high-pressure oil chamber with the rodless chamber of the oil cylinder. Since the high-pressure oil chamber is connected with the rod chamber of the driving oil cylinder and the areas at both ends of the oil cylinder piston of the driving oil cylinder are different, the piston rod of the driving oil cylinder is pushed out, and the moving contact assembly is connected with the static contact assembly through the insulating pull rod to achieve closing. Adjusting the size of the closing speed regulating valve can control the oil flow size and thus control the closing speed;

[0016] c. When closing, the closing time needs to meet the flow requirements of the excitation current, that is, the switch unit cannot be closed during the excitation current passing time. After the excitation current disappears, the switch unit should be closed quickly to avoid long-term flow of current through the closing resistor unit, which may cause overheating of the resistor.

[0017] d. Opening the gate: Adjust the reversing valve to connect the low-pressure oil chamber with the rodless chamber of the oil cylinder. The high-pressure oil will drive the oil cylinder piston to move to open the gate. Adjusting the size of the opening gate speed regulating valve can control the oil flow rate and thus control the opening gate speed.

[0018] The beneficial effects of the present invention are as follows: the switch device with closing resistor for suppressing transformer excitation inrush current and the use method of the present invention adopt a linear transmission structure, eliminating the intermediate transmission link, so that the contact closing time can be achieved in the millisecond level, the switch device is accurately controlled and the transmission is stable, which can not only achieve the purpose of suppressing the transformer excitation inrush current, but also accurately control the input time of the closing resistor, prevent the closing resistor from causing the thermal capacity to exceed the tolerance value of the closing resistor due to too long an input time, and at the same time can adjust the closing speed of the static contact assembly and the moving contact assembly according to the size of the excitation inrush current detected by the current transformer.

[0019] The device adopts SF6 insulating gas, which greatly reduces the insulation distance of the equipment, reduces the volume of the equipment, reduces the floor space of the equipment, and reduces the equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the installation structure of the present invention;

[0021] Figure 2 For the present invention Figure 1 Schematic diagram of the internal structure in the middle A direction;

[0022] Figure 3 This is a schematic diagram of the structure of the moving contact assembly of the present invention;

[0023] Figure 4 It is a schematic diagram of the structure of the static contact assembly of the present invention;

[0024] Figure 5 This is a schematic diagram of the operating mechanism of state 1 of the present invention;

[0025] Figure 6 This is a schematic diagram of the operating mechanism of state 2 of the present invention;

[0026] Figure 7 This is a schematic diagram of the operating mechanism of state 3 of the present invention;

[0027] Figure 8 It is the structural principle diagram of the present invention;

[0028] As shown in the figure:

[0029] 1. Bushing assembly, 2. Connecting busbar, 3. Closing resistor tank, 4. Closing resistor unit, 5. Connecting conductor, 6. Switchgear tank, 7. Static contact assembly, 71. Static side connection seat, 72. Static contact shielding cover, 73. Static main contact, 74. Static arc contact, 8. Moving contact assembly, 81. Moving contact shielding cover, 82. Support plate, 83. Moving side connection seat, 84. Moving main contact, 85. Band contact finger, 86. Conductor To ring, 9, connecting rod, 10, insulating pull rod, 11, iron pull rod, 12, operating mechanism, 13, pot insulator, 14, operating mechanism housing, 15, driving cylinder, 16, cylinder piston, 17, piston rod, 18, disc spring, 19, disc spring push plate, 20, high-pressure cylinder body, 21, high-pressure cylinder piston, 22, low-pressure oil chamber, 23, reversing valve, 24, opening speed regulating valve, 25, closing speed regulating valve, 26, high-pressure oil chamber. DETAILED DESCRIPTION

[0030] In order to clearly illustrate the technical features of this solution, this solution is described below through a specific implementation method.

[0031] like Figures 1 to 8 As shown, the switching device with closing resistor for suppressing transformer excitation inrush current of the present invention comprises a closing resistor tank body 3 and a switch device tank body 6, wherein a closing resistor unit 4 is installed in the closing resistor tank body 3, and both ends of the closing resistor unit 4 are respectively connected to two bushing assemblies 1 through connecting busbars 2, and the closing resistor tank body 3 and the switch device tank body 6 are arranged side by side between the two connecting busbars 2.

[0032] The switch device tank body 6 contains a stationary contact assembly 7 and a moving contact assembly 8, and the stationary contact assembly 7 and the moving contact assembly 8 are respectively connected to the two ends of the closing resistor unit 4. The closing resistor tank body 3 and the switch device tank body 6 are connected and separated by two pot-type insulators 13, and the stationary contact assembly 7 and the moving contact assembly 8 are respectively connected to the two ends of the closing resistor unit 4 through the connecting conductor 5, and the connecting conductor 5 passes through the pot-type insulator 13 and the passing place is sealed.

[0033] The moving contact assembly 8 includes a moving side connection seat 83 connected to one end of the closing resistor unit 4 and a moving main contact 84 slidingly connected in the moving side connection seat 83. The end of the moving main contact 84 is connected to the insulating pull rod 10 through a connecting rod 9, one end of the iron pull rod 11 is connected to the insulating pull rod 10, and the other end of the iron pull rod 11 is connected to the operating mechanism 12. At the same time, the outer side of the moving main contact 84 is connected to the moving side connection seat 83 through a strap contact finger 85, and the moving side connection seat 83 is connected to the pot insulator 13 through a connecting conductor 5. A guide ring 86 is installed between the moving main contact 84 and the moving side connection seat 83.

[0034] The moving side connecting seat 83 is provided with a moving contact shielding cover 81, and a supporting plate 82 is installed inside the moving contact shielding cover 81. When the switch is opened, the moving main contact 84 of the switch device is retracted inside the moving contact shielding cover 81. At this time, the switch device is opened, the switch device circuit is disconnected, and the closing resistance unit circuit is connected.

[0035] The static contact assembly 7 includes a static side connection base 71 connected to the other end of the closing resistor unit 4 and a static main contact 73 fixed to the static side connection base 71. The static main contact 73 contains a static arc contact 74. The static side connection base 71 is connected to the pot insulator 13 through the connecting conductor 5.

[0036] A static contact shielding cover 72 is mounted on the static side connection seat 71 . A static main contact 73 is located inside the static contact shielding cover 72 .

[0037] It also includes an operating mechanism 12 for driving the moving contact assembly 8 to extend and retract to achieve opening and closing. The operating mechanism 12 is installed at one end outside the switch device tank 6 and is used to drive the moving contact assembly 8 to achieve opening and closing, thereby realizing the opening and closing of the switch device circuit.

[0038] A current transformer for detecting the excitation surge current is installed outside the connecting busbar 2, and the operating mechanism 12 adjusts the closing speed of the static contact assembly 7 and the moving contact assembly 8 according to the magnitude of the excitation surge current detected by the current transformer.

[0039] When the current flows from the bushing assembly at one end into the parallel switch device with closing resistance, the moving and static contacts of the switch device unit are in the open state at first, and the switch device unit circuit is in the open state, so the current flows through the closing resistance unit circuit. The closing resistance unit resistance value is in the kilo-ohm level, so the excitation surge current energy will be converted into resistance heating; when the moving contact in the switch device unit moves to connect with the static contact, the switch device unit is closed, and the switch device unit circuit changes from open circuit to open circuit. Because the circuit resistance of the switch device circuit is much smaller than that of the closing resistance circuit after the circuit is opened, the closing resistance unit circuit will be short-circuited by the switch device unit circuit, so that the current can pass through the switch device unit circuit instead of flowing through the closing resistance unit circuit. Because the resistance value of the switch device circuit is in the milliohm level, the heat generated is very small, which meets the rated current flow requirement after the excitation surge current disappears.

[0040] When closing, the closing time needs to meet the flow requirements of the excitation current, that is, the switch device unit cannot be closed during the time when the excitation current passes. After the excitation current disappears, the switch device unit should be closed quickly to avoid long-term flow of current through the closing resistor unit, causing overheating of the resistor.

[0041] The operating mechanism 12 includes a driving oil cylinder 15 , a high-pressure cylinder body 20 , a high-pressure cylinder piston 21 installed in the high-pressure cylinder body 20 , and a disc spring 18 that pushes the high-pressure cylinder piston 21 into the high-pressure cylinder body 20 to form a high-pressure oil chamber 26 .

[0042] The high-pressure cylinder body 20 is fixedly connected to the outside of the driving cylinder 15 . The disc spring 18 is sleeved on the driving cylinder 15 . A disc spring push plate 19 is provided between the disc spring 18 and the high-pressure cylinder piston 21 . The disc spring push plate 19 pushes the high-pressure cylinder piston 21 .

[0043] The piston rod 17 of the driving cylinder 15 is connected to the moving contact assembly 8 through the insulating pull rod 10, and the high-pressure oil chamber 26 is connected to the rod chamber of the driving cylinder 15. It also includes a reversing valve 23, a low-pressure oil chamber 22 and an oil pump that pumps the oil in the low-pressure oil chamber 22 into the high-pressure oil chamber 26. The low-pressure oil chamber 22, the high-pressure oil chamber 26 and the rodless chamber of the driving cylinder 15 are respectively connected to the reversing valve 23, and the oil pipe of the low-pressure oil chamber 22 is equipped with a closing speed regulating valve 25, and the oil pipe of the rodless chamber of the driving cylinder 15 is equipped with an opening speed regulating valve 24.

[0044] The operating mechanism 12 further comprises an operating mechanism housing 14 , in which various parts of the operating mechanism 12 are mounted.

[0045] The closing resistor tank 3 and the switch device tank 6 are filled with SF6 as an insulating medium, which greatly reduces the space required to meet the insulation requirements, saves construction area and reduces equipment investment.

[0046] The method for using a switch device with a closing resistor for suppressing transformer excitation inrush current comprises the following steps:

[0047] a. Energy storage: The oil pump pumps the oil in the low-pressure oil chamber 22 into the high-pressure oil chamber 26, pushing the high-pressure cylinder piston 21 to move, thereby compressing the disc spring 18, so that the high-pressure oil chamber 26 is filled with high-pressure oil. Figure 5 As shown, the black part in the figure is high-pressure oil, and the grid part is low-pressure oil;

[0048] b. Closing: Adjust the reversing valve 23 to make the high-pressure oil chamber 26 communicate with the rodless chamber of the oil cylinder 15. Since the high-pressure oil chamber 26 is connected with the rod chamber of the driving oil cylinder 15, and the areas at both ends of the oil cylinder piston 16 of the driving oil cylinder 15 are different, the piston rod 17 of the driving oil cylinder 15 is pushed out, and the moving contact assembly 8 is connected with the static contact assembly 7 through the insulating pull rod 10 to achieve closing. Adjusting the size of the closing speed regulating valve 25 can control the oil flow size and thus control the closing speed, such as Figure 6 As shown, the black part in the figure is high-pressure oil, and the grid part is low-pressure oil;

[0049] c. When closing, the closing time needs to meet the flow requirements of the excitation current, that is, the switch unit cannot be closed during the excitation current passing time. After the excitation current disappears, the switch unit should be closed quickly to avoid long-term flow of current through the closing resistor unit, which may cause overheating of the resistor. Figure 7 As shown, the black part in the figure is high-pressure oil, and the grid part is low-pressure oil;

[0050] d. Opening: Adjust the reversing valve 23 to connect the low-pressure oil chamber 22 with the rodless chamber of the oil cylinder 15. The high-pressure oil will drive the oil cylinder piston 16 to move and realize opening. Adjusting the size of the opening speed regulating valve 24 can control the oil flow size and thus control the opening speed.

[0051] Of course, the above description is not limited to the above examples. Technical features not described in the present invention can be achieved by or by using existing technologies, which will not be described here. The above embodiments and drawings are only used to illustrate the technical scheme of the present invention and are not limitations of the present invention. The present invention is described in detail with reference to the preferred implementation methods. Ordinary technicians in this field should understand that changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention do not depart from the purpose of the present invention, and should also fall within the scope of protection of the claims of the present invention.

Claims

1. A switch device with closing resistor for suppressing transformer excitation inrush current, characterized in that: The invention comprises a closing resistor tank (3) and a switch device tank (6), wherein the closing resistor tank (3) contains a closing resistor unit (4), and the two ends of the closing resistor unit (4) are respectively connected to two bushing assemblies (1) via a connecting busbar (2), and the switching device tank (6) contains a stationary contact assembly (7) and a moving contact assembly (8), and the stationary contact assembly (7) and the moving contact assembly (8) are respectively connected to the two ends of the closing resistor unit (4), and further comprises an operating mechanism (12) for driving the moving contact assembly (8) to extend and retract to realize opening and closing, and a current transformer for detecting an excitation inrush current is installed outside the connecting busbar (2), and the operating mechanism (12) adjusts the closing speed of the stationary contact assembly (7) and the moving contact assembly (8) according to the magnitude of the excitation inrush current detected by the current transformer; The operating mechanism (12) includes a driving cylinder (15), a high-pressure cylinder body (20), a high-pressure cylinder piston (21) installed in the high-pressure cylinder body (20), and a disc spring (18) for pushing the high-pressure cylinder piston (21) into the high-pressure cylinder body (20) to form a high-pressure oil chamber (26). The piston rod (17) of the driving cylinder (15) is connected to the moving contact assembly (8) via an insulating pull rod (10). The high-pressure oil chamber (26) is connected to the driving cylinder (15). ), further comprising a reversing valve (23), a low-pressure oil chamber (22), and an oil pump for pumping oil in the low-pressure oil chamber (22) into the high-pressure oil chamber (26); the low-pressure oil chamber (22), the high-pressure oil chamber (26), and the rodless chamber of the driving oil cylinder (15) are respectively connected to the reversing valve (23); a closing speed regulating valve (25) is installed on the oil pipe of the low-pressure oil chamber (22), and an opening speed regulating valve (24) is installed on the oil pipe of the rodless chamber of the driving oil cylinder (15); The method for using the switch device with closing resistance for suppressing transformer excitation inrush current comprises the following steps: a. Energy storage: The oil pump pumps the oil in the low-pressure oil chamber (22) into the high-pressure oil chamber (26), pushing the high-pressure cylinder piston (21) to move, thereby compressing the disc spring (18), so that the high-pressure oil chamber (26) is filled with high-pressure oil; b. Closing: adjusting the reversing valve (23) so that the high-pressure oil chamber (26) is connected to the rodless chamber of the oil cylinder (15). Since the high-pressure oil chamber (26) is connected to the rod chamber of the driving oil cylinder (15), and the areas of the two ends of the oil cylinder piston (16) of the driving oil cylinder (15) are different, the piston rod (17) of the driving oil cylinder (15) is pushed out, and the moving contact assembly (8) and the static contact assembly (7) are connected through the insulating pull rod (10) to achieve closing. By adjusting the size of the closing speed regulating valve (25), the oil flow size can be controlled, thereby controlling the closing speed; c. When closing, the closing time needs to meet the flow requirements of the excitation current, that is, the switch unit cannot be closed during the excitation current passing time. After the excitation current disappears, the switch unit should be closed quickly to avoid long-term flow of current through the closing resistor unit, which may cause overheating of the resistor. d. Opening: Adjust the reversing valve (23) to connect the low-pressure oil chamber (22) with the rodless chamber of the oil cylinder (15). The high-pressure oil will drive the oil cylinder piston (16) to move and open the gate. Adjusting the size of the opening speed regulating valve (24) can control the oil flow and thus the opening speed.

2. The switch device with closing resistor for suppressing transformer excitation inrush current according to claim 1 is characterized in that: The disc spring (18) is sleeved on the driving oil cylinder (15), and a disc spring push plate (19) is provided between the disc spring (18) and the high-pressure cylinder piston (21).

3. The switch device with closing resistor for suppressing transformer excitation inrush current according to claim 1 is characterized in that: The moving contact assembly (8) comprises a moving side connection seat (83) connected to one end of the closing resistor unit (4) and a moving main contact (84) slidably connected in the moving side connection seat (83); the stationary contact assembly (7) comprises a stationary side connection seat (71) connected to the other end of the closing resistor unit (4) and a stationary main contact (73) fixedly connected to the stationary side connection seat (71); a stationary arc contact (74) is installed in the stationary main contact (73).

4. The switch device with closing resistor for suppressing transformer excitation inrush current according to claim 3 is characterized in that: The movable side connection seat (83) is provided with a movable contact shielding cover (81), and the movable side connection seat (71) is provided with a movable contact shielding cover (72).

5. The switch device with closing resistor for suppressing transformer excitation inrush current according to claim 3 is characterized in that: The closing resistor tank body (3) and the switch device tank body (6) are connected and separated by two pot-type insulators (13); the stationary contact assembly (7) and the moving contact assembly (8) are respectively connected to two ends of the closing resistor unit (4) via a connecting conductor (5); the connecting conductor (5) passes through the pot-type insulator (13) and the passing portion is sealed.

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