CN218498822U - Grounding current limiting device for power transformer and power transformer - Google Patents
Grounding current limiting device for power transformer and power transformer Download PDFInfo
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- CN218498822U CN218498822U CN202222604367.7U CN202222604367U CN218498822U CN 218498822 U CN218498822 U CN 218498822U CN 202222604367 U CN202222604367 U CN 202222604367U CN 218498822 U CN218498822 U CN 218498822U
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Abstract
The utility model discloses a ground current limiting device and power transformer for power transformer. Ground current limiting device for a power transformer, comprising: a switch unit connected between an outgoing terminal of an iron core of the power transformer and a ground terminal; and a current limiting unit connected between an outgoing terminal of the iron core of the power transformer and a ground terminal, wherein the switching unit is closed when a ground current of the iron core of the power transformer is less than a predetermined threshold value, the outgoing terminal of the iron core of the power transformer is connected to the ground terminal via the switching unit, and the current limiting unit is bypassed; when the grounding current of the iron core of the power transformer is greater than or equal to a predetermined threshold value, the switching unit is turned off, and the leading-out terminal of the iron core of the power transformer is connected to the grounding terminal via the current limiting unit. The grounding current limiting device is directly installed without the aid of oil filtering equipment and energy storage devices, and is low in cost, high in efficiency, short in construction period and simple to operate.
Description
Technical Field
The utility model belongs to the technical field of the power transformer technique and specifically relates to a ground current limiting device and power transformer for power transformer is related to.
Background
When a large transformer operates, the operation safety regulation monitoring has strict limitation on the grounding current of the transformer core, and the grounding current of the transformer core is required to be less than a certain threshold, such as 300mA. The large transformer has large capacity, high voltage, large current, high corresponding cooling capacity, and high oil flow speed compared with the conventional transformer, so that the insulating oil of the transformer (oil sludge sediment which can be separated out in the insulating oil affects the insulation of the iron core of the transformer to the ground, thereby causing the insulation resistance of the iron core to be reduced, the grounding current to be increased and exceeding the regulation limit value, and the grounding current of the iron core of the transformer is increased, thereby leading to the following problems that 1, the grounding current of the iron core exceeds the regulation and does not accord with the operation condition, and 2, certain safety risk exists in the operation of the transformer.
Therefore, in order to solve the above problems, the following solutions exist in the prior art:
1) When the transformer is stopped and has overhaul conditions, the oil filter equipment is communicated with the oil pipe to carry out hot oil circulation filtration on the transformer to remove partial sludge deposits. The scheme has the advantages that: is removed from the source. However, there are the following disadvantages: tight link location cleanup is not thorough; the equipment is more and the cost is high; the construction period is long.
2) When the transformer is shut down and has maintenance conditions, the energy storage element is charged to discharge to the iron core of the transformer instantly, and the electric arc blows the oil sludge bridged by the iron core. The scheme has the advantages that: the equipment is less and the cost is low; the construction period is short. However, there are the following disadvantages: the local ablation and removal of the oil sludge are not thorough; the input energy (charging voltage and charging time) is not well controlled, and if the input energy is too large, secondary accidents of iron core insulation damage can be caused.
SUMMERY OF THE UTILITY MODEL
In view of this, the utility model provides a ground current limiting device and power transformer for easily realize ground current and be less than predetermined threshold value through slide-wire varistor in the adjusting device.
According to the utility model discloses an embodiment provides a ground current limiting device for power transformer, a serial communication port, include: a switching unit connected between a lead-out terminal (112) of an iron core of the power transformer and a ground terminal of the power transformer; and a current limiting unit connected between an outgoing terminal of an iron core of the power transformer and a ground terminal, wherein the switching unit is turned off, the outgoing terminal of the iron core of the power transformer is connected to the ground terminal via the current limiting unit, a ground current of the power transformer flows through the current limiting unit, and the current limiting unit limits the ground current of the power transformer within a predetermined range.
The grounding current limiting device is connected between the outgoing line of the transformer core and the cement foundation of the transformer in series, so that the grounding current smaller than the preset threshold value is easily realized through the inner slide wire type rheostat in the adjusting device.
Preferably, the current limiting unit includes a first resistor having a fixed resistance value.
Preferably, the current limiting unit further includes a second resistor having an adjustable resistance value, and the second resistor is connected in series with the first resistor.
The resistance value of the structure can be automatically adjusted according to the size of the grounding current, the current-limiting requirement is met, the iron core potential is prevented from being raised, frequent switching of the device caused by reduction of the grounding current after the current-limiting resistor is put into the device is avoided, normal operation of the transformer is not affected, and the technical economy is high.
Preferably, the ground current limiting device further includes a surge arrester connected between the lead-out terminal of the iron core of the power transformer and the ground terminal and connected in parallel with the current limiting unit, the surge arrester protecting a winding of the power transformer.
The structure can prevent the iron core of the transformer from generating higher suspension potential and prevent the damage of the power transformer caused by instantaneous over-voltage loaded on the power transformer.
Preferably, the current limiting unit further includes a third resistor connected between the outgoing terminal of the iron core of the power transformer and a ground terminal, and connected in parallel with the second resistor and the first resistor, the third resistor making the ground current of the power transformer greater than a lower limit of the predetermined range.
The structure enables the third resistor to shunt a part of current, thereby preventing the open circuit caused in the use process of adjusting the resistance of the rheostat and ensuring that the grounding electrode is permanently and firmly grounded.
Preferably, the third resistor comprises a resistor having a fixed resistance value.
Preferably, the ground current limiting apparatus further includes a current measuring unit that measures a ground current of the power transformer in a conductive state of the switching unit.
Preferably, the ground current limiting device further includes a control unit that receives the ground current measured by the current measuring unit and compares the measured ground current with an upper limit of the predetermined range, and when the measured ground current is greater than or equal to the upper limit, the control unit generates a first control signal and a second control signal and transmits the first control signal to the switching unit and transmits the second control signal to the current limiting unit, the switching unit switches from an on state to an off state according to the first control signal, and the current limiting unit increases a resistance value of the second resistor according to the second control signal so that the ground current flowing through the current limiting unit is lower than the upper limit.
Furthermore, according to another embodiment of the present invention, there is provided a power transformer including the ground current limiting device for a power transformer as described above.
According to the scheme, the grounding current is easily smaller than the preset threshold value through the slide wire type rheostat in the adjusting device, so that the direct installation does not need oil filtering equipment and energy storage devices, the cost is low, the efficiency is high, and the construction period is short. In addition, the grounding current limiting device is provided with a protection circuit for preventing open circuit and overvoltage, so that the grounding electrode is ensured to be permanently and firmly grounded and can be recovered after instantaneous overvoltage.
Drawings
The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings, in which:
fig. 1 is a functional block diagram of a ground current limiting device for a power transformer according to the present invention.
Fig. 2 is a schematic circuit diagram of a ground current limiting device for a power transformer according to an embodiment of the present invention.
Fig. 3 is a schematic circuit diagram of a ground current limiting device for a power transformer according to another embodiment of the present invention.
In the above figures, the reference numerals used are as follows:
10: grounding current limiting device
102: a switch unit;
112: a lead-out terminal;
114: a ground terminal;
104: a current limiting unit;
104-1: a first resistor;
104-2: a second resistor;
104-3: a third resistor;
106: a lightning arrester;
108: a current measuring unit;
110: a control unit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention is further described in detail by referring to the following embodiments.
In order to avoid conflict, the embodiments and features of the embodiments of the present application may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
It is to be noted that, unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
In the present application, where the contrary is not intended, the use of directional words such as "upper, lower, top and bottom" is generally with respect to the orientation shown in the drawings, or with respect to the component itself in the vertical, perpendicular or gravitational direction; likewise, for ease of understanding and description, "inner and outer" refer to the inner and outer relative to the profile of the components themselves, but the above directional words are not intended to limit the invention.
Fig. 1 is a functional block diagram of a ground current limiting device for a power transformer according to the present invention. As shown in fig. 1, the ground current limiting apparatus includes: a switch unit 102; a current limiting unit 104; an arrester 106; a current measuring unit 108; a control unit 110. Specifically, the switching unit is connected between an outgoing terminal of an iron core of the power transformer and a ground terminal of the power transformer. The current limiting unit 104 is connected between the lead terminal of the iron core of the power transformer and the ground terminal. The switching unit 102 is turned off, the lead-out terminal of the iron core of the power transformer is connected to the ground terminal via the current limiting unit 104, the ground current of the power transformer flows through the current limiting unit 104, and the current limiting unit 104 limits the ground current of the power transformer within a predetermined range. The surge arrester 106 is connected between the lead-out terminal of the iron core of the power transformer and the ground terminal, and is connected in parallel with the current limiting unit 104, and the surge arrester 106 protects the winding of the power transformer. The current measuring unit 108 measures the ground current of the power transformer in which the switching unit 102 is in a conductive state. The control unit 110 receives the ground current measured by the current measuring unit 108 and compares the measured ground current with an upper limit of a predetermined range, and when the measured ground current is greater than or equal to the upper limit, the control unit 110 generates a first control signal and a second control signal, and transmits the first control signal to the switching unit 102, and transmits the second control signal to the current limiting unit 104, the switching unit 102 switches from the on state to the off state according to the first control signal, and the current limiting unit 104 increases the resistance value according to the second control signal, so that the ground current flowing through the current limiting unit 104 is lower than the upper limit.
Fig. 2 is a schematic circuit diagram of a ground current limiting device for a power transformer according to the present invention.
As shown in fig. 2, the ground current limiting device 10 includes: a switch unit 102 connected between a lead-out terminal 112 and a ground terminal 114 of an iron core of a power transformer; a surge arrester 106 connected between a lead-out terminal 112 and a ground terminal 114 of an iron core of the power transformer; the current limiting unit 104 is connected between a lead terminal 112 of the iron core of the power transformer and a ground terminal 114. Here, when the switching unit is turned off, the lead-out terminal of the iron core of the power transformer is connected to the ground terminal via the current limiting unit, the ground current of the power transformer flows through the current limiting unit, and the current limiting unit limits the ground current of the power transformer within a predetermined range. Further, although not shown in the drawings, the ground current limiting device 10 may further include a current measuring unit that measures a ground current of the core of the power transformer in which the switching unit is in a conductive state in real time. The ground current limiting device 10 may further include a control unit that controls the switching unit 102 to switch between off and on based on a comparison result between a ground current of the core of the power transformer (e.g., a measured current output from the current measuring unit) and an upper limit of the predetermined range, and the control unit may further adjust an internal resistance value of the current limiting unit 104 based on the ground current of the core of the power transformer.
The grounding current limiting device 10 can monitor the grounding current of the iron core in real time, and when the iron core is grounded at two points (or multiple points), a current limiting unit is connected to limit the grounding current to a safe value, so that the accident is prevented from being enlarged, and the transformer can still run safely. Meanwhile, the grounding current limiting device is provided with an overvoltage arrester, so that the winding of the power transformer is protected.
Hereinafter, the operation principle of the ground current limiting apparatus for a power transformer in fig. 2 will be described in detail.
The ground current limiting device 10 operates on the following principle:
when the transformer normally operates, the switch unit 102 is in a closed state, and a grounding down lead led out from a leading-out terminal 112 of a grounding wire of the iron core is directly connected with a shell of the transformer, so that the iron core of the transformer is in a direct grounding operation state, and at the moment, the current measurement unit directly and continuously indicates the grounding current of the iron core of the transformer in the state; when the iron core is grounded in two points (or multiple points), the grounding current is increased, when the grounding current is larger than the upper limit of the threshold value of the preset range of the device, the switch unit 102 is switched off in response to the control signal sent by the control unit, and the current limiting unit 104 is automatically switched on, so that the running state of the transformer iron core which is directly grounded through the switch unit 102 is immediately converted into the current limiting grounding state through the current limiting unit 104, the grounding current of the transformer iron core is limited to a small value, and the further extension of the grounding fault is prevented. The resistance and power parameters of the ground current limiting device 10 can be designed according to the over-transformer structure, the number of winding turns and the internal resistance.
The main functions of the arrester 106 are: when the grounding current of the iron core of the power transformer is too large, the lightning arrester 106 can generate breakdown discharge, and the protection branch formed by the lightning arrester 106 is conducted in a short time, so that the too high voltage and/or current is discharged from the protection branch, and the winding of the power transformer is prevented from being damaged. For example, the lightning arrester 106 may include a varistor.
Fig. 3 is a schematic circuit diagram of a ground current limiting device for a power transformer according to another embodiment of the present invention. In fig. 3, the same reference numerals are given to the same components as those in fig. 1 and 2.
As shown in fig. 3, the ground current limiting device 10 includes: a switch unit 102 connected between a lead-out terminal 112 and a ground terminal 114 of an iron core of a power transformer; a surge arrester 106 connected between a lead-out terminal 112 and a ground terminal 114 of an iron core of the power transformer; the current limiting unit 104 comprises a first resistor 104-1, a second resistor 104-2 and a third resistor 104-3, wherein the first resistor 104-1 with a fixed resistance value and the second resistor 104-2 with an adjustable resistance value are connected in series between the leading-out terminal 112 and the grounding terminal 114 of the iron core of the power transformer, the third resistor 104-3 with a fixed resistance value is connected in parallel with the second resistor and the first resistor, and the third resistor enables the grounding current of the power transformer to be larger than the lower limit of the preset range. Further, although not shown in the drawings, the ground current limiting device 10 may further include a current measuring unit that measures the ground current of the iron core of the power transformer in real time. The ground current limiting device 10 may further include a control unit that controls the switching unit 102 to switch between off and on based on a comparison result between the ground current of the core of the power transformer (e.g., the measured current output from the current measuring unit) and an upper limit of a predetermined threshold, and the control unit may further adjust the resistance value of the second resistor 104-2 based on the ground current of the core of the power transformer.
When the transformer normally operates, the switch unit 102 is in a closed state, and a grounding down lead led out from a leading-out terminal 112 of a grounding wire of the iron core is directly connected with a shell of the transformer, so that the iron core of the transformer is in a direct grounding operation state, and then the current measurement unit directly and continuously indicates the grounding current of the iron core of the transformer in the state; when the iron core is grounded in two points (or multiple points), the grounding current is increased, when the grounding current is larger than the upper limit of the threshold value of the preset range of the device, the switch unit 102 is switched off in response to the control signal sent by the control unit, and the current limiting unit 104 is automatically switched on, so that the running state of the transformer iron core which is directly grounded through the switch unit 102 is immediately converted into the current limiting grounding state through the current limiting unit 104, the grounding current of the transformer iron core is limited to a small value, and the further extension of the grounding fault is prevented. The resistance and power parameters of the ground current limiting device 10 can be designed according to the over-transformer structure, the number of winding turns and the internal resistance. For example, in the series connection of the first resistor 104-1 and the second resistor 104-2, a non-inductive resistor having a fixed resistance value of 1.5k Ω may be used as the first resistor 104-1, and a sliding adjustable resistor may be used as the second resistor 104-2 to adjust the internal resistance to reduce the ground current limit of the power transformer to less than the upper limit of the predetermined range. According to actual requirements, the total operating resistance range of the grounding current limiting device 10 is regulated steplessly at 0.750 kOmega-0.857 kOmega, the total resistance heat capacity is 309W, and the rated current is 600mA. The numerical values of the above cases are only used for reference and are not used as the principle for designing and selecting the device.
The grounding current limiting device 10 can monitor the grounding current of the iron core in real time, and when the iron core is grounded at two points (or multiple points), the current limiting unit is connected to limit the grounding current to a safe value, so that the accident is prevented from being enlarged, and the safe operation of the transformer is ensured. Meanwhile, the grounding current limiting device is provided with an overvoltage arrester and a third resistor for preventing open circuit, so that the grounding electrode is ensured to be permanently and firmly grounded and can be recovered after instantaneous overvoltage.
According to the above technical scheme, according to the utility model provides a power transformer's ground current limiting device, through the light ground current that realizes of slide-wire type rheostat less than predetermined threshold value in the adjusting device, consequently, direct mount need not with the help of oil strain equipment and energy storage device, with low costs, efficient, the time limit for a project weak point. In addition, the grounding current limiting device is provided with a protection circuit for preventing open circuit and overvoltage, so that the grounding electrode is ensured to be permanently and firmly grounded and can be recovered after instantaneous overvoltage.
The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. An earth current limiting device for a power transformer, comprising:
a switching unit (102) connected between a lead-out terminal (112) of the iron core of the power transformer and a ground terminal (114) of the power transformer; and
a current limiting unit (104) connected between an outgoing terminal (112) of the iron core of the power transformer and a ground terminal (114),
wherein, when the switching unit is turned off, the lead-out terminal of the iron core of the power transformer is connected to the ground terminal via the current limiting unit, the ground current of the power transformer flows through the current limiting unit, and the current limiting unit (104) limits the ground current of the power transformer within a predetermined range.
2. An earth current limiting device for a power transformer according to claim 1, characterized in that the current limiting unit (104) comprises a first resistor (104-1) with a fixed resistance value.
3. The ground current limiting device for a power transformer according to claim 2, characterized in that the current limiting unit (104) further comprises a second resistor (104-2), the resistance value of the second resistor (104-2) is adjustable, and the second resistor (104-2) is connected in series with the first resistor (104-1).
4. A ground current limiting device for a power transformer according to claim 1, characterized in that it further comprises a surge arrester (106) connected between an outgoing terminal (112) of the iron core of the power transformer and the ground terminal (114) and in parallel with the current limiting unit (104), the surge arrester (106) protecting the windings of the power transformer.
5. A ground current limiting device for a power transformer according to claim 3, characterized in that the current limiting unit (104) further comprises a third resistor (104-3), the third resistor (104-3) being connected between an outgoing terminal (112) and a ground terminal (114) of the iron core of the power transformer, and the third resistor (104-3) being connected in parallel with the second resistor, the first resistor, the third resistor (104-3) making the ground current of the power transformer larger than the lower limit of the predetermined range.
6. An earth current limiting device for a power transformer according to claim 5, characterized in that the third resistor (104-3) comprises a resistor with a fixed resistance value.
7. A ground current limiting device for a power transformer according to claim 3, characterized in that it further comprises a current measuring unit (108) measuring the ground current of the power transformer with the switching unit (102) in a conducting state.
8. The ground current limiting apparatus for a power transformer according to claim 7, further comprising a control unit (110) receiving the ground current measured by the current measuring unit and comparing the measured ground current with an upper limit of the predetermined range, when the measured ground current is greater than or equal to the upper limit, the control unit generating a first control signal and a second control signal and transmitting the first control signal to the switching unit (102) and transmitting the second control signal to the current limiting unit (104), the switching unit switching from an on state to an off state according to the first control signal, and the current limiting unit (104) increasing the resistance value of the second resistor (104-2) according to the second control signal so that the ground current flowing through the current limiting unit is lower than the upper limit.
9. A power transformer comprising a ground current limiting device for a power transformer according to any one of claims 1-8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222604367.7U CN218498822U (en) | 2022-09-29 | 2022-09-29 | Grounding current limiting device for power transformer and power transformer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222604367.7U CN218498822U (en) | 2022-09-29 | 2022-09-29 | Grounding current limiting device for power transformer and power transformer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN218498822U true CN218498822U (en) | 2023-02-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202222604367.7U Active CN218498822U (en) | 2022-09-29 | 2022-09-29 | Grounding current limiting device for power transformer and power transformer |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN218498822U (en) |
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2022
- 2022-09-29 CN CN202222604367.7U patent/CN218498822U/en active Active
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