Method for monitoring imbalance state of two paths of current
By connecting the two currents to specific terminals of the current transformer and using the output current of the secondary winding to determine the current balance state, the problem that the existing technology cannot monitor the current imbalance between the two channels is solved, and the accurate judgment of the fault position is achieved and provide timely protective measures.
Patent Information
- Application Number
- CN202411553805.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-04
- Publication Date
- 2025-02-07
AI Technical Summary
The existing current transformers cannot monitor the imbalance of the two currents and cannot assist in determining the fault location, which makes it difficult to take timely protective measures when a series of lines in the thermal power plant fail.
By connecting the first current and the second current to the P1 and P2 terminals of the current transformer, and sharing the output to the P3 terminal, the output current of the S1 and S2 terminals in the secondary winding is used to determine the equilibrium state of the two currents by using the output current of the S1 and S2 terminals in the secondary winding to determine the equilibrium state of the two currents . When the current value is unbalanced, the output current is positive or negative, thereby identifying and indicating the current path where the fault lies.
The synchronous monitoring and comparison of the two currents is realized, the monitoring process of unbalanced current is simplified, and the current can be accurately judged whether the current is balanced, and when it is unbalanced, it indicates which current is too large, providing timely fault indication information.
Smart Images
Figure CN119395349A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of power systems, and in particular to a method for monitoring the unbalanced state of two currents. Background Art
[0002] When using series compensation technology, thermal power plants face the risk of machine-grid composite resonance divergence. Once a phase-to-phase short circuit, two-phase grounding fault or three-phase fault occurs in the series compensation line, the system will produce significant transient torque amplification, which may even cause damage to the generator set in extreme cases.
[0003] In order to effectively suppress the occurrence of subsynchronous resonance of the generator, a blocking filter is usually installed on the neutral point side of the high-voltage winding of the main transformer of each generator set. The core function of this filter is to block the subsynchronous current generated by the system from entering the stator winding of the generator to ensure the stable operation of the generator. However, when building the supporting equipment of the blocking filter, it is necessary to introduce a current transformer, but the existing current transformer cannot monitor the imbalance state of the two currents, nor can it help determine the fault location. Summary of the invention
[0004] The purpose of the present invention is to provide a method for monitoring the unbalanced state of two currents. When one of the currents is unbalanced due to a fault, the current transformer can identify and indicate the current path where the fault is located, providing information for taking protective measures in a timely manner.
[0005] To achieve the above objectives, the present application proposes a method for monitoring the unbalanced state of two currents, which is implemented based on a current transformer and specifically includes:
[0006] The input end of the first current is connected to the P1 terminal of the current transformer, and the output end of the current is connected to the P3 terminal of the current transformer; then, the input end of the second current is connected to the P2 terminal of the current transformer, and the output end of the second current is also connected to the P3 terminal of the current transformer;
[0007] When current flows through the first copper strip and the second copper strip of the current transformer, the two strips independently generate a specific electric field, and the current flows in the first copper strip and the second copper strip in opposite directions;
[0008] When the first current value is equal to the second current value, the electric fields cancel each other out to form a neutralization effect; under this condition, the output current between the S1 terminal and the S2 terminal of the secondary winding of the current transformer will be zero;
[0009] When the value of the first current is greater than the value of the second current, the electric field of the first current will be partially offset by the electric field of the second current, and the weakened electric field will appear as the electric field of the first current; under this condition, the output current between the S1 terminal and the S2 terminal of the secondary winding of the current transformer will be positive;
[0010] When the first current value is smaller than the second current value, the electric field of the second current will be partially offset by the electric field of the first current, and the weakened electric field will appear as the electric field of the second current; under this condition, the output current between the S1 terminal and the S2 terminal of the secondary winding of the current transformer will be negative.
[0011] In a preferred embodiment, the current transformer includes a transformer body, in which at least one secondary coil and a first primary winding and a second primary winding are arranged, and the two primary windings pass through the secondary coil with the same number of turns but in opposite directions; the head end of the first primary winding is the P1 terminal, and the tail end is the C2 terminal; the head end of the second primary winding is the P2 terminal, and the tail end is the C1 terminal, wherein the C1 terminal and the C2 terminal are combined to form a P3 common terminal.
[0012] In a preferred manner, the secondary coil includes an iron core, an inner buffer insulation layer, a secondary winding, an outer buffer insulation layer and a shielding layer. The inner buffer insulation layer is wrapped around the surface of the iron core, the enameled wire of the secondary winding is evenly wound around the inner buffer insulation layer and the two ends of the enameled wire extend out of the secondary coil as S1 terminals and S2 terminals respectively, the outer buffer insulation layer is wrapped around the outside of the secondary winding, and the shielding layer is arranged outside the outer buffer insulation layer, which is the outermost layer of the secondary coil, and an insulating gap is left when the shielding layer is close to the roots of the S1 terminals and S2 terminals of the secondary winding.
[0013] Preferably, the iron core is a ring-shaped structure, made of silicon steel sheet or ultra-fine crystal amorphous high magnetic permeability material, and the shielding layer is made of semi-conductive material, and is grounded by copper wire to shield the secondary coil.
[0014] In a preferred embodiment, the first primary winding includes a first copper strip, a first connecting plate, a P1 terminal, and a C2 terminal, and the second primary winding includes a second copper strip, a second connecting plate, a P2 terminal, and a C1 terminal;
[0015] The first copper strip and the second copper strip pass through the inner diameter of the secondary coil with a specific number of turns to form a square frame shape; the first connecting plate connects the P1 terminal to the beginning of the first copper strip, and the second connecting plate connects the P2 terminal to the beginning of the second copper strip; the C2 terminal is welded to the end of the first copper strip, and the C1 terminal is welded to the end of the second copper strip. It should be noted that the P1 terminal of the first primary winding and the S1 terminal of the secondary winding are the same-named terminals, and the C1 terminal of the primary winding of the second primary winding and the S1 terminal of the secondary winding are the same-named terminals.
[0016] In a preferred embodiment, the first copper strip of the first primary winding and the second copper strip of the second primary winding have the same number of turns and opposite directions of penetration; and each turn of the first copper strip and the second copper strip are separated by insulating material, and the first copper strip and the second copper strip are also separated by insulating material.
[0017] In a preferred embodiment, the P3 common terminal is an L-shaped copper bar, and the C2 terminal of the first primary winding and the C1 terminal of the second primary winding are combined into one wiring terminal by countersunk screws.
[0018] In a preferred embodiment, the transformer body is cast by epoxy resin, and the gap between the secondary coil and the two primary windings is filled and fixed by the epoxy resin.
[0019] In a preferred embodiment, the transformer body and the outer periphery of the P3 common terminal are provided with a silicone rubber shed. In order to improve the outdoor performance of the current transformer, the silicone rubber shed is bonded with epoxy resin as a whole; the silicone rubber shed includes convex rings that are evenly spaced and parallel from top to bottom. The silicone rubber shed does not affect the realization of the unbalanced current monitoring function, so technicians can choose whether to use the silicone rubber shed externally according to actual needs on site.
[0020] In a preferred embodiment, the through holes at the tops of the P1 terminal, the P2 terminal and the P3 common terminal expose the silicone rubber sheds, which serve as the connection terminals of the current transformer.
[0021] Compared with the prior art, the above technical solution adopted by the present invention has the following advantages:
[0022] 1. The current monitoring process is simplified: two currents are simultaneously introduced into one current transformer, which realizes the synchronous monitoring and comparison of the two current values, greatly simplifying the monitoring process of primary unbalanced current.
[0023] 2. Assist in judging unbalanced current: By accurately identifying the size and direction of the secondary current, it is possible to accurately judge whether the two primary currents are in a balanced state, and point out which current is larger when unbalanced.
[0024] 3. The current transformer has stable performance and high measurement accuracy: The design of the inner insulation buffer layer outside the iron core and the outer insulation buffer layer outside the secondary winding effectively reduces the impact of external forces on the performance of the iron core and the secondary winding, thereby improving the measurement accuracy of the secondary winding, thereby comprehensively improving the product performance of the current transformer.
[0025] 4. The anti-interference ability of the current transformer is significantly enhanced: by wrapping the semi-conductive material on the secondary winding to form a shielding layer and grounding the shielding layer, the anti-interference ability of the current transformer is significantly improved.
[0026] 5. The outdoor performance of the current transformer is greatly improved: the composite insulation design of epoxy resin and silicone rubber is adopted, so that the current transformer can fully adapt to the use requirements of complex outdoor environments. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 It is a schematic diagram of the secondary coil structure of the current transformer;
[0028] Figure 2 Assemble only the first primary winding structure diagram for the secondary coil;
[0029] Figure 3 Assemble only the second primary winding structure diagram for the secondary coil;
[0030] Figure 4 Schematic diagram of assembling two primary windings for the secondary coil at the same time;
[0031] Figure 5 This is the front view of the epoxy resin casting body of the current transformer;
[0032] Figure 6 This is a top view of the epoxy resin casting body of the current transformer;
[0033] Figure 7 It is the P3 common terminal of the current transformer;
[0034] Figure 8 This is a schematic diagram of the overall assembly of the current transformer structure;
[0035] Fig. 9 This is the appearance diagram of the current transformer;
[0036] Wherein: 100 is the secondary coil, 101 is the iron core, 102 is the inner buffer insulation layer, 103 is the secondary winding, 104 is the outer buffer insulation layer, 105 is the shielding layer, 106 is the S1 terminal, 107 is the S2 terminal, 201 is the first copper strip, 202 is the first connecting plate, 203 is the P1 terminal, 204 is the C2 terminal, 301 is the second copper strip, 302 is the second connecting plate, 303 is the P2 terminal, 304 is the C1 terminal, 400 is the P3 common terminal, 401 is the countersunk screw, 500 is the epoxy resin, and 501 is the silicone rubber umbrella skirt. DETAILED DESCRIPTION
[0037] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0038] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.
[0039] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" means two or more, unless otherwise clearly and specifically defined. "Several" means one or more, unless otherwise clearly and specifically defined.
[0040] In the description of the present application, it should be understood that the terms "center", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.
[0041] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0042] like Figure 1 As shown, the secondary coil 100 is the secondary core of the current transformer, which includes an iron core 101, an inner buffer insulation layer 102, a secondary winding 103, an outer buffer insulation layer 104, and a shielding layer 105; wherein the iron core 101 is a ring structure, made of high magnetic permeability materials such as silicon steel sheets or ultra-fine crystal amorphous materials, and an inner buffer insulation layer 102 is wrapped on its surface to increase the buffer thickness, reduce the impact of external forces on the performance of the iron core 101, and insulate the iron core 101. Enameled wire is evenly wound outside the inner buffer insulation layer 102, and this layer of enameled wire constitutes the secondary winding 103. The surface of the enameled wire has an insulating paint layer to form insulation between each turn. Each layer of the enameled wire is separated by an insulating material. The uniform winding can make the magnetic field of the secondary coil 100 evenly distributed.
[0043] The two ends of the enameled wire of the secondary winding 103 extend out of the secondary coil 100, one end is used as the S1 terminal 106, and the other end is used as the S2 terminal 107. An outer buffer insulation layer 104 is wrapped on the surface of the secondary winding 103, which can further reduce the impact of external forces on the performance of the iron core 101 and the secondary winding 103, thereby improving the measurement accuracy of the secondary coil 100. The outermost layer of the entire secondary coil 100 is a shielding layer 105, which is made of a semi-conductive material. When it is grounded, the secondary coil 100 can be completely shielded, thereby improving the anti-interference ability of the secondary coil 100.
[0044] It should be noted that a gap should be left when the shielding layer 105 is close to the roots of the S1 terminal 106 and the S2 terminal 107 , and the shielding layer 105 should not touch the roots of the S1 terminal 106 and the S2 terminal 107 , so as to avoid a short circuit between the shielding layer 105 and the S1 terminal 106 and the S2 terminal 107 .
[0045] In addition, it should be noted that only one secondary coil 100 is described in the embodiment of the present invention. In actual application, two, three or more secondary coils 100 may be used, which all fall within the scope of the description of the present invention.
[0046] like Figure 2 As shown, the first primary winding includes a first copper strip 201, a first connecting plate 202, a P1 terminal 203, and a C2 terminal 204; the P1 terminal 203 is a copper bar, with a through hole processed on the top to be used as a terminal block of the transformer, and the bottom is welded to the first connecting plate 202. The first connecting plate 202 is a C-shaped bent copper bar, with the top welded to the P1 terminal 203, and the bottom welded to the beginning of the first copper strip 201.
[0047] The first copper strip 201 is a whole copper strip. The end surface of the secondary coil 100 close to the S1 terminal 106 is used as a reference surface. The first copper strip 201 is inserted into the inner diameter of the secondary coil 100 from this reference surface, and then is inserted into the inner diameter of the secondary coil 100 again from the outer diameter in a square shape. Each time the first copper strip 201 passes through the inner diameter of the secondary coil 100 is a turn. The end of the first copper strip 201 is welded to the C2 terminal 204. The C2 terminal 204 is a copper busbar with a threaded hole processed on the top plane and the bottom is welded to the end of the first copper strip 201.
[0048] It should be noted that each turn of the first copper tape 201 needs to be separated by insulating material and cannot touch each other. For example, the first turn is insulated from the second turn, and the second turn is insulated from the third turn. In addition, except for the starting end of the first copper tape 201 being welded together with the first connecting plate 202, the remaining second and third turns of the first copper tape 201 and the first connecting plate 202 also need to be separated by insulating material to avoid short circuits between each other.
[0049] In addition, it should be noted that the number of turns of the first copper strip 201 in the above description and drawings is three turns, which is only a number set for demonstration and explanation. In actual application, it can be other numbers of turns, and other numbers of turns also fall within the scope of the description of the present invention.
[0050] like Figure 2 As shown, if the P1 terminal 203 is used as the input terminal of the primary current and the C2 terminal 204 is used as the output terminal of the primary current, the secondary coil 100 will induce and output the secondary current, and at this time, the S1 terminal 106 and the P1 terminal 203 are the same terminals.
[0051] like Figure 3 As shown, the second primary winding includes a second copper strip 301, a second connecting plate 302, a P2 terminal 303, and a C1 terminal 304; the P2 terminal 303 is a copper bar, with a through hole processed on the top to be used as a terminal block of the transformer, and the bottom is welded to the second connecting plate 302. The second connecting plate 302 is a C-shaped bent copper bar, with the top welded to the P2 terminal 303, and the bottom welded to the beginning of the second copper strip 301.
[0052] The second copper strip 301 is a whole copper strip. The end surface of the secondary coil 100 close to the S1 terminal 106 is used as a reference surface. The second copper strip 301 is inserted into the inner diameter of the secondary coil 100 from the opposite direction of the reference surface, and then inserted into the inner diameter of the secondary coil 100 again from the outer diameter in a square shape. Each time the second copper strip 301 passes through the inner diameter of the secondary coil 100 is a turn, and the end of the second copper strip 301 is welded to the C1 terminal 304. The C1 terminal 304 is a copper bar with a threaded hole processed on the top plane and the bottom is welded to the end of the second copper strip 301.
[0053] It should be noted that each turn of the second copper tape 301 needs to be separated by insulating material and cannot touch each other. For example, the first turn is insulated from the second turn, and the second turn is insulated from the third turn. In addition, except for the starting end of the second copper tape 301 being welded together with the second connecting plate 302, the remaining second and third turns of the second copper tape 301 and the second connecting plate 302 also need to be separated by insulating material to avoid short circuits between each other.
[0054] In addition, it should be noted that the number of turns of the second copper tape 301 in the above description and drawings is three turns, which is only a number set for demonstration and explanation. In actual application, it can be other numbers of turns, and other numbers of turns also fall within the scope of the description of the present invention.
[0055] like Figure 3 As shown, if the P2 terminal 303 is used as the input terminal of the primary current and the C1 terminal 304 is used as the output terminal of the primary current, the secondary coil 100 will induce and output the secondary current, and at this time, the S2 terminal 107 and the P2 terminal 303 are the same-name terminals.
[0056] It should be noted that the number of turns of the first copper strip 201 of the first primary winding and the second copper strip 301 of the second primary winding are the same, and the directions in which they pass through the secondary winding 100 are opposite.
[0057] like Figure 4 As shown, the first primary winding and the second primary winding are assembled on the secondary coil 100 at the same time, the two windings are placed in parallel, and a distance is maintained between the first primary winding and the second primary winding.
[0058] It should be noted that Figure 4 After the middle structure is assembled, it needs to be installed in the casting mold and poured with epoxy resin 500. After the epoxy resin 500 is cured, it can be Figure 4 Each structure in the middle is fixed.
[0059] like Figure 5 , Figure 6 As shown, the gap between the first primary winding and the second primary winding is filled with epoxy resin 500, and the gap between the secondary coil 100 and the first copper strip 201 and the second copper strip 301 is filled with epoxy resin 500. The epoxy resin serves to insulate and fix the various structures.
[0060] like Figure 7 As shown, the P3 common terminal 400 is an L-shaped copper bar, a through hole is processed on the top of the P3 common terminal 400 and used as a terminal block of the transformer, and the bottom is a plane, and a countersunk screw hole is processed above the plane.
[0061] like Figure 8 As shown, in Figure 5 , Figure 6 Install P3 common terminal 400 on the basis of. To make the structure clear, Figure 8 The epoxy resin 500 is hidden in the P3 common terminal 400. The P3 common terminal 400 is placed on top of the C2 terminal 204 and the C1 terminal 304, the bottom plane of the P3 common terminal 400 contacts the top plane of the C2 terminal 204 and the C1 terminal 304, and the countersunk screw 401 passes through the countersunk screw hole on the P3 common terminal 400 and is screwed into the threaded hole on the top of the C2 terminal 204 and the C1 terminal 304. The C2 terminal 204 and the C1 terminal 304 are combined into one terminal through the P3 common terminal 400.
[0062] At this time, the current transformer of the present invention is connected to the power grid, and the input end of the first current is first connected to the P1 terminal 203, and the output end of the current is connected to the P3 terminal 400; then, the input end of the second current is connected to the P2 terminal 303, and its output end is also connected to the P3 terminal 400. When current flows through the copper strip 201 and the second copper strip 301, they each independently generate a specific electric field. What is particularly important is that since the currents in the first copper strip 201 and the second copper strip 301 flow in opposite directions, the electric fields generated by them in the secondary coil 100 will cancel each other out.
[0063] When the first current value is equal to the second current value, the electric fields cancel each other out to form a neutralization effect. Under this condition, the output current between the S1 terminal 106 and the S2 terminal 107 of the secondary winding 103 will be zero.
[0064] When the first current value is greater than the second current value, the electric field of the first current will be partially offset by the electric field of the second current, and the weakened electric field will appear as the electric field of the first current. Under this condition, the output current between the S1 terminal 106 and the S2 terminal 107 of the secondary winding 103 will be positive.
[0065] When the first current value is less than the second current value, the electric field of the second current will be partially offset by the electric field of the first current, and the weakened electric field will appear as the electric field of the second current. Under this condition, the output current between the S1 terminal 106 and the S2 terminal 107 of the secondary winding 103 will be negative.
[0066] With such a configuration, by detecting the output currents of the secondary end S1 terminal 106 and the S2 terminal 107 , it is possible to determine whether the first current and the second current of the primary end are balanced. If they are unbalanced, which current is larger, the first current or the second current.
[0067] like Fig. 9 As shown, in Figure 8 On the basis of the epoxy resin 500 of the entire current transformer and the P3 common terminal 400, a silicone rubber shed 501 is coated, and the silicone rubber shed 501 is bonded to the epoxy resin 500 as a whole by applying a silicone rubber adhesive on the surface of the epoxy resin 500. The silicone rubber shed 501 serves as the external insulation of the current transformer. The silicone rubber shed 501 includes convex rings that are evenly spaced and parallel from top to bottom, which effectively increases the surface creepage distance of the product, improves the product's anti-pollution flashover capability under outdoor conditions, and can work at higher altitudes.
[0068] It should be noted that the through holes at the top of the P1 terminal 203, the P2 terminal 303, and the P3 common terminal 400 all expose the outer silicone rubber shed 501 to serve as the connection terminals of the current transformer.
[0069] In addition, it should be noted that the silicone rubber shed 501 is a special design for the current transformer to be used outdoors. Whether or not the silicone rubber shed 501 is provided will not affect the current transformer's function of monitoring unbalanced current. Therefore, the current transformer without the silicone rubber shed 501 is also within the protection scope of this invention.
[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A method for monitoring the unbalanced state of two currents, characterized in that: Based on current transformer implementation, it includes: The input end of the first current is connected to the P1 terminal of the current transformer, and the output end of the current is connected to the P3 terminal of the current transformer; then, the input end of the second current is connected to the P2 terminal of the current transformer, and the output end of the second current is also connected to the P3 terminal of the current transformer; When current flows through the first copper strip and the second copper strip of the current transformer, the two strips independently generate a specific electric field, and the current flows in the first copper strip and the second copper strip in opposite directions; When the first current value is equal to the second current value, the electric fields cancel each other out to form a neutralization effect; under this condition, the output current between the S1 terminal and the S2 terminal of the secondary winding of the current transformer will be zero; When the value of the first current is greater than the value of the second current, the electric field of the first current will be partially offset by the electric field of the second current, and the weakened electric field will appear as the electric field of the first current; under this condition, the output current between the S1 terminal and the S2 terminal of the secondary winding of the current transformer will be positive; When the first current value is smaller than the second current value, the electric field of the second current will be partially offset by the electric field of the first current, and the weakened electric field will appear as the electric field of the second current; under this condition, the output current between the S1 terminal and the S2 terminal of the secondary winding of the current transformer will be negative.
2. The method for monitoring the unbalanced state of two currents according to claim 1, characterized in that: The current transformer includes a transformer body, in which at least one secondary coil and a first primary winding and a second primary winding are arranged, and the two primary windings pass through the secondary coil with the same number of turns but in opposite directions; the head end of the first primary winding is a P1 terminal, and the tail end is a C2 terminal; the head end of the second primary winding is a P2 terminal, and the tail end is a C1 terminal, wherein the C1 terminal and the C2 terminal are combined to form a P3 common terminal.
3. The method for monitoring the unbalanced state of two currents according to claim 2, characterized in that: The secondary coil includes an iron core, an inner buffer insulation layer, a secondary winding, an outer buffer insulation layer and a shielding layer. The inner buffer insulation layer is wrapped around the surface of the iron core. The enameled wire of the secondary winding is evenly wound around the inner buffer insulation layer, and both ends of the enameled wire extend out of the secondary coil as S1 terminals and S2 terminals, respectively. The outer buffer insulation layer is wrapped around the outside of the secondary winding. The shielding layer is arranged outside the outer buffer insulation layer, i.e., the outermost layer of the secondary coil, and an insulating gap is left when the shielding layer is close to the roots of the S1 terminals and S2 terminals of the secondary winding.
4. The method for monitoring the unbalanced state of two currents according to claim 3, characterized in that: The iron core is a ring-shaped structure, and is made of silicon steel sheets or ultra-fine crystal amorphous high magnetic permeability materials. The shielding layer is made of semi-conductive materials and is grounded to shield the secondary coil.
5. The method for monitoring the unbalanced state of two currents according to claim 2, characterized in that: The first primary winding includes a first copper strip, a first connecting plate, a P1 terminal, and a C2 terminal, and the second primary winding includes a second copper strip, a second connecting plate, a P2 terminal, and a C1 terminal; The first copper strip and the second copper strip pass through the inner diameter of the secondary coil with a specific number of turns to form a square shape; the first connecting plate connects the P1 terminal to the starting end of the first copper strip, and the second connecting plate connects the P2 terminal to the starting end of the second copper strip; the C2 terminal is welded to the end of the first copper strip, and the C1 terminal is welded to the end of the second copper strip.
6. The method for monitoring the unbalanced state of two currents according to claim 5, characterized in that: The first copper belt of the first primary winding and the second copper belt of the second primary winding have the same number of turns and opposite directions of penetration; and each turn of the first copper belt and the second copper belt is separated by insulating material, and the first copper belt and the second copper belt are also separated by insulating material.
7. The method for monitoring the unbalanced state of two currents according to claim 1, characterized in that: The P3 common terminal is an L-shaped copper bar, and the C2 terminal of the first primary winding and the C1 terminal of the second primary winding are combined into one wiring terminal by countersunk screws.
8. The method for monitoring the unbalanced state of two currents according to claim 1, characterized in that: The transformer body is cast by epoxy resin, and the gap between the secondary coil and the two primary windings is filled and fixed by the epoxy resin.
9. The method for monitoring the unbalanced state of two currents according to claim 1, characterized in that: The transformer body and the outer periphery of the P3 common terminal are provided with a silicone rubber shed, and the silicone rubber shed includes convex rings which are distributed in parallel and at equal intervals from top to bottom.
10. The method for monitoring the unbalanced state of two currents according to claim 1, characterized in that: The through holes at the top of the P1 terminal, the P2 terminal and the P3 common terminal expose the silicone rubber sheds, which serve as the connection terminals of the current transformer.