CT secondary side overvoltage protection device

Abstract

The utility model discloses a CT secondary side overvoltage protection device which comprises a sealing device, and a box body device is arranged at the bottom of the sealing device. The box body device comprises a protection box; according to the CT secondary side overvoltage protection device provided by the utility model, the MOS tube in the X-Y-FKL open circuit protection device which is connected in parallel enters a conducting state instantly, and a CT secondary winding can be short-circuited quickly and reliably within ms generated by overvoltage, so that the damage of secondary overvoltage of a mutual inductor to a meter and the harm to personal safety of operators are effectively avoided. And after the fault is eliminated, the device is automatically reset, the internal MOS tube is cut off, a high-resistance state occurs, and the device enters a normal working state again. The device is reasonable in circuit design, reliable in performance, small in size and low in power consumption, the TVS is used, the action time is short, and the conduction time is shorter than ms; the absorption energy is large, the instantaneous power can reach W, and the break-over voltage is about V and is lower than the safety voltage V.

Description

Technical Field

[0001] The utility model belongs to the technical field of CT secondary side overvoltage protection device design, in particular to a CT secondary side overvoltage protection device. Background Art

[0002] CT secondary overvoltage protection device is a device used to protect the secondary side of the current transformer (CT) from overvoltage damage. The current transformer is an important device for measurement and protection in the power system. It converts high current into low current for measurement and relay protection equipment.

[0003] The existing CT secondary side overvoltage protection device is large in size, consumes high power during operation, and has a slow action time during operation. Utility Model Content

[0004] The purpose of the utility model is to provide a CT secondary side overvoltage protection device to solve the problems existing in the above-mentioned background technology.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] A CT secondary side overvoltage protection device comprises a closing device, wherein a box device is arranged at the bottom of the closing device; the box device comprises a protection box, wherein a fixing seat is fixedly arranged at the bottom of the protection box, and four fixing holes are evenly arranged at the four corners of the fixing seat, an XY-FKL open circuit protection device is installed at the bottom of the protection box, a MOS tube is arranged at one side of the XY-FKL open circuit protection device, a TVS transient suppression diode is installed at the top of the XY-FKL open circuit protection device, two interfaces are symmetrically arranged at one side of the protection box, a plurality of signal lights are evenly arranged in the middle of the interfaces, and four first fixing cylinders are evenly fixed at the four corners inside the protection box.

[0007] Furthermore: the closing device comprises a cover plate, four second fixing tubes are evenly and fixedly arranged on one side of the cover plate, and a fixing bolt is arranged in the middle of the second fixing tube.

[0008] Furthermore: the fixing seat and the protection box are integrally formed, and the fixing seat is square.

[0009] Furthermore: the interface passes through the protection box.

[0010] Furthermore: the XY-FKL open circuit protection device is bolted to the protection box.

[0011] Furthermore: the second fixing tube and the cover plate are integrally formed, and the fixing bolt is threadedly connected to the first fixing tube.

[0012] Compared with the prior art, the beneficial effects of the utility model are:

[0013] 1. During the use of the device, when the CT secondary works normally, the secondary side is approximately short-circuited, and the output voltage is very low. However, when the secondary circuit is open or the primary winding has an abnormal overcurrent, the voltage generated in the secondary winding is much higher than the normal operating voltage (the value depends on the CT's own parameters and operating conditions). This is mainly because the primary current of the CT is determined by the number of primary turns. After the secondary circuit is open, the current becomes zero. To maintain the same power, the voltage can only be increased infinitely until the core is saturated. At this time, the internal MOS tube of the parallel-connected XY-FKL open circuit protection device instantly enters the on state, and can quickly and reliably short-circuit the CT secondary winding within ms of the overvoltage, thereby effectively avoiding the damage of the transformer secondary overvoltage to the meter and the personal safety of the operator. After the fault is eliminated, it automatically resets, the internal MOS tube is cut off, and a high-resistance state appears, and the device re-enters the normal working state. The device has a reasonable circuit design, reliable performance, small size, and low power consumption. By using TVS transient suppression diodes, the action time is fast and the conduction time is less than ms; the absorbed energy is large, the instantaneous power can reach W, and the conduction voltage is about V, which is lower than the safety voltage V. The switch cabinets of different customers have different transformation ratios of current transformers in the measurement circuit, protection circuit, and zero-sequence circuit, and the conduction voltage of the protection device is also different. The device can adjust the conduction voltage value according to customer requirements;

[0014] 2. After being turned on, the voltage at the secondary terminals of the transformer can be limited to within V, which can not only ensure the personal safety of the inspection personnel, but also reliably protect the safe operation of the circuit instruments. When the device is turned on, the leakage current is less than mA, and the influence on the measuring instrument and the accuracy of the transformer can be ignored. By adopting high-sensitivity components as the voltage-limiting components and matching them with reasonable internal control circuits, the problem of overtemperature of the protection device is effectively solved. After being turned on, it can work for a long time, and the protection device is maintenance-free and easy to operate and install. When the secondary transformer is connected (fault elimination), the device automatically disconnects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 It is a structural schematic diagram of a CT secondary side overvoltage protection device described in the utility model;

[0017] Figure 2It is a structural schematic diagram of a box device of a CT secondary side overvoltage protection device described in the utility model;

[0018] Figure 3 It is a structural schematic diagram of a closing device of a CT secondary side overvoltage protection device described in the utility model.

[0019] In the accompanying drawings: 1. Box device; 101. Protection box; 102. Fixing seat; 103. Fixing hole; 104. XY-FKL7 open circuit protection device; 105. MOS tube; 106. TVS transient suppression diode; 107. Interface; 108. Signal light; 109. First fixing tube; 2. Closing device; 201. Cover plate; 202. Second fixing tube; 203. Fixing bolt. DETAILED DESCRIPTION

[0020] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0022] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0023] See also Figure 1-Figure 3 A CT secondary side overvoltage protection device comprises a closing device 2, and a box device 1 is arranged at the bottom of the closing device 2.

[0024] In this embodiment: the box device 1 includes a protection box 101, a fixing seat 102 is fixedly arranged at the bottom of the protection box 101, four fixing holes 103 are evenly arranged at the four corners of the fixing seat 102, an XY-FKL7 open circuit protection device 104 is installed at the bottom of the protection box 101, a MOS tube 105 is arranged on one side of the XY-FKL7 open circuit protection device 104, a TVS transient suppression diode 106 is installed on the top of the XY-FKL7 open circuit protection device 104, two interfaces 107 are symmetrically installed on one side of the protection box 101, a number of signal lights 108 are evenly arranged in the middle of the interface 107, and four first fixing cylinders 109 are evenly fixed at the four corners of the protection box 101. During installation, the fixing seat 102 is fixed to the area to be installed through the fixing holes 103, and the CT cables are respectively connected to the two interfaces 107. During the use of the device, when the CT secondary works normally, the secondary side is approximately short-circuited, and the output voltage is very low at this time. However, when the secondary circuit is open or the primary winding has an abnormal overcurrent, the voltage generated in the secondary winding is much higher than the normal operating voltage. The value depends on the CT's own parameters and operating conditions. This is mainly because the primary current of the CT is determined by the number of primary turns. After the secondary circuit is open, the current becomes zero. To maintain the same power, the voltage can only be increased infinitely until the core is saturated. At this time, the internal MOS tube 105 of the parallel-connected XY-FKL7 open circuit protection device 104 instantly enters the on state, and can quickly and reliably short-circuit the CT secondary winding within 10ms of the overvoltage, thereby effectively avoiding the damage of the transformer secondary overvoltage to the meter and the personal safety of the operator. After the fault is eliminated, it automatically resets, the internal MOS tube 105 is cut off, and a high-resistance state appears, and the device re-enters the normal working state. The device has a reasonable circuit design, reliable performance, small size, and low power consumption. By using TVS transient suppression diode 106, the action time is fast and the conduction time is less than 10ms; the energy absorption is large, the instantaneous power can reach 600W, and the conduction voltage is about 30V, which is lower than the safety voltage of 36V. The switch cabinets of different customers have different ratios of current transformers in the measurement circuit, protection circuit, and zero-sequence circuit, and the conduction voltage of the protection device is also different. The device can adjust the conduction voltage value according to customer requirements. After conduction, the voltage of the secondary terminal of the transformer can be limited to less than 2V, which can not only ensure the personal safety of the inspection personnel, but also reliably protect the safe operation of the circuit instruments. The leakage current of the device is less than 1mA when it is turned on, and the influence on the accuracy of the measuring instrument and the transformer can be ignored. By adopting a high-sensitivity element as a voltage-limiting element and matching it with a reasonable internal control circuit, the phenomenon of over-temperature of the protection device is effectively solved. It can work for a long time after conduction, and the protection device is maintenance-free and easy to operate and install. When the fault of the secondary connection of the transformer is eliminated, the device automatically disconnects;

[0025] In this embodiment: the closing device 2 includes a cover plate 201, and four second fixed cylinders 202 are evenly fixedly arranged on one side of the cover plate 201. A fixing bolt 203 is arranged in the middle of the second fixed cylinder 202. When it is necessary to repair the internal parts of the protection box 101, the fixing bolt 203 is removed to separate the first fixed cylinder 109 from the second fixed cylinder 202, and then the cover plate 201 is removed. At this time, the parts in the protection box 101 can be replaced and repaired.

[0026] Working principle: During installation, fix the fixing seat 102 in the area to be installed through the fixing hole 103, and the CT cable is connected to the two interfaces 107 respectively. When the internal parts of the protection box 101 need to be repaired, remove the fixing bolts 203 to separate the first fixing tube 109 from the second fixing tube 202, and then take off the cover 201. At this time, the parts in the protection box 101 can be replaced and repaired. During the use of the device, when the CT secondary works normally, the secondary side is approximately short-circuited, and the output voltage is very low. However, when the secondary circuit is open or the primary winding has an abnormal overcurrent, the voltage generated in the secondary winding is much higher than the normal operating voltage. The value depends on the CT's own parameters and operating conditions. This is mainly because the primary current of the CT is determined by the number of primary turns. After the secondary circuit is open, the current becomes zero. If the same power is to be maintained, the voltage can only be increased infinitely until the core is saturated. At this time, the MOS tube 105 inside the parallel-connected XY-FKL7 open circuit protection device 104 instantly enters the on state, and can quickly and reliably short-circuit the CT secondary winding within 10ms of the overvoltage, thereby effectively avoiding the damage to the meter caused by the secondary overvoltage of the transformer and the personal safety hazard to the operator. After the fault is eliminated, it automatically resets, the internal MOS tube 105 is cut off, and a high-resistance state appears, and the device re-enters the normal working state. The device has reasonable circuit design, reliable performance, small size and low power consumption. By using TVS transient suppression diode 106, the action time is fast and the conduction time is less than 10ms; the energy absorption is large, the instantaneous power can reach 600W, and the conduction voltage is about 30V, which is lower than the safety voltage of 36V. The switch cabinets of different customers have different ratios of current transformers in the measuring circuit, protection circuit and zero-sequence circuit, and the conduction voltage of the protection device is also different. The device can adjust the conduction voltage value according to customer requirements. After conduction, the voltage of the secondary terminal of the transformer can be limited to less than 2V, which can ensure the personal safety of the inspection personnel and the safe operation of the circuit instruments. The leakage current of the device is less than 1mA when it is turned on, and the influence on the accuracy of the measuring instrument and the transformer can be ignored. By adopting high-sensitivity components as the voltage-limiting components and matching them with reasonable internal control circuits, the phenomenon of over-temperature of the protection device is effectively solved. It can work for a long time after conduction, and the protection device is maintenance-free and easy to operate and install. When the fault of the secondary connection of the transformer is eliminated, the device automatically disconnects.

[0027] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A CT secondary side overvoltage protection device, comprising a sealing device (2), characterized in that: A box device (1) is arranged at the bottom of the closing device (2); The box device (1) comprises a protection box (101), a fixing seat (102) is fixedly arranged at the bottom of the protection box (101), four fixing holes (103) are evenly arranged at the four corners of the fixing seat (102), an XY-FKL7 open circuit protection device (104) is installed at the bottom of the protection box (101), a MOS tube (105) is arranged at one side of the XY-FKL7 open circuit protection device (104), a TVS transient suppression diode (106) is installed at the top of the XY-FKL7 open circuit protection device (104), two interfaces (107) are symmetrically arranged at one side of the protection box (101), a plurality of signal lights (108) are evenly arranged in the middle of the interfaces (107), and four first fixing cylinders (109) are evenly fixedly arranged at the four corners inside the protection box (101).

2. A CT secondary side overvoltage protection device according to claim 1, characterized in that: The sealing device (2) comprises a cover plate (201), four second fixing cylinders (202) are evenly fixedly arranged on one side of the cover plate (201), and a fixing bolt (203) is arranged in the middle of the second fixing cylinder (202).

3. The CT secondary side overvoltage protection device according to claim 1, characterized in that: The fixing seat (102) and the protection box (101) are integrally formed, and the fixing seat (102) is square.

4. The CT secondary side overvoltage protection device according to claim 1, characterized in that: The interface (107) passes through the protection box (101).

5. The CT secondary side overvoltage protection device according to claim 1, characterized in that: The XY-FKL7 open circuit protection device (104) is bolted to the protection box (101).

6. A CT secondary side overvoltage protection device according to claim 2, characterized in that: The second fixing tube (202) and the cover plate (201) are integrally formed, and the fixing bolt (203) is threadedly connected to the first fixing tube (109).

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