Overvoltage suppression circuit and voltage transformer

Abstract

The invention relates to an overvoltage suppression circuit and a voltage transformer, the overvoltage suppression circuit is applied to the voltage transformer, the overvoltage suppression circuit comprises a surge protection unit and a T-type filtering unit, the surge protection unit is connected with an acquisition unit in parallel, and when transient overvoltage flows through the acquisition unit of the voltage transformer, the T-type filtering unit is connected with the surge protection unit in parallel. The surge protection unit can limit transient overvoltage and protect normal operation of the acquisition unit, and the T-type filtering unit is connected in parallel with the surge protection unit, so that suppression of high-frequency components in the transient overvoltage flowing through the acquisition unit is realized, and normal operation of the acquisition unit is further ensured; by adopting the overvoltage suppression circuit provided by the invention, the overvoltage is limited, the high-frequency component of the overvoltage is suppressed, and the safety and stability of the operation of a system where the voltage transformer is located are improved.

Description

Technical Field

[0001] The present application relates to the technical field of electrical equipment, and in particular to an overvoltage suppression circuit and a voltage transformer. Background Art

[0002] In a system with an ungrounded neutral point, when the voltage transformer operates normally, its three phases are basically balanced, that is, the neutral point of the power grid is at ground potential; but when a disturbance occurs in the system (for example, closing the circuit breaker to connect an open busbar, the disappearance of a single-phase arc grounding fault, drastic changes in system load, etc.), the potential of the neutral point of the power grid shifts relative to the ground potential, causing an unbalanced increase in the single-phase, two-phase or three-phase voltage. At this time, a higher displacement voltage (zero-sequence voltage) will be generated at the neutral point of the power grid, which will cause overvoltage in the power grid and affect the safety and stability of the system operation. Summary of the Invention

[0003] Based on this, it is necessary to provide an overvoltage suppression circuit and a voltage transformer to improve the safety and stability of system operation in order to address the above technical problems.

[0004] In a first aspect, the present application provides an overvoltage suppression circuit, which is applied to a voltage transformer. The overvoltage suppression circuit includes:

[0005] The surge protection unit is connected in parallel with the acquisition unit in the voltage transformer, and is used to limit the voltage flowing through the acquisition unit;

[0006] The T-type filter unit is connected in parallel with the surge protection unit and is used to filter the voltage flowing through the acquisition unit.

[0007] In one embodiment, the surge protection unit includes a non-linear resistor;

[0008] The two ends of the nonlinear resistor are connected in parallel with the acquisition unit, and the two ends of the nonlinear resistor are also connected in parallel with the T-type filter unit; the nonlinear resistor is used to trigger the voltage when the voltage flowing through the acquisition unit is greater than the trigger voltage U C When , the voltage flowing through the acquisition unit is limited.

[0009] In one embodiment, the trigger voltage U C It is determined by the preset voltage and the operating voltage corresponding to the acquisition unit. The preset voltage is associated with the environment in which the voltage transformer is located.

[0010] In one embodiment, the trigger voltage U C The value range of is as follows:

[0011] U C ≥1.3*U Tmax ;

[0012] UC ≤0.9*U OVmin ;

[0013] Among them, U Tmax is the operating voltage corresponding to the acquisition unit; U OVmin is the preset voltage.

[0014] In one embodiment, the T-type filter unit includes a first inductor L1, a second inductor L2 and a first capacitor C1;

[0015] One end of the first inductor L1 is connected to one end of the surge protection unit, the other end of the first inductor L1 is connected to one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the first capacitor C1, one end of the first capacitor C1 is also connected to the other end of the surge protection unit, and the other end of the first capacitor C1 is connected between the other end of the first inductor L1 and one end of the second inductor L2.

[0016] In one embodiment, the capacitance value of the first capacitor C1 is determined by the capacity of the voltage transformer;

[0017] The inductance values of the first inductor L1 and the second inductor L2 are both determined by the rated current of the voltage transformer, and the inductance value of the second inductor L2 is smaller than the inductance value of the first inductor L1.

[0018] In one embodiment, the capacitance range of the first capacitor C1 is as follows:

[0019] C≤5%*Yn;

[0020] ;

[0021] Wherein, C is the capacitance value of the first capacitor C1; Yn is the capacity of the voltage transformer; Sn is the rated capacity of the voltage transformer; ω1 is the power supply angular frequency; Un is the rated operating voltage of the voltage transformer; the inductance value of the first inductor L1 and the inductance value of the second inductor L2 are shown as follows:

[0022] ;

[0023] ;

[0024] L'=m*L;

[0025] Wherein, L is the inductance of the first inductor L1; Un is the rated operating voltage of the voltage transformer; Δimax is the current ripple; Pn is the rated active power of the voltage transformer; L' is the inductance of the second inductor L2; and the value range of m is 0.5 to 0.8.

[0026] In a second aspect, the present application further provides a voltage transformer, which includes a collection unit and the overvoltage suppression circuit as described above;

[0027] The acquisition unit is connected in parallel with the surge protection unit of the overvoltage suppression circuit.

[0028] In one embodiment, the voltage transformer further includes a primary winding, and the acquisition unit includes a first resistor R1, a second resistor R2, a third resistor R3, a second capacitor C2, and a third capacitor C3;

[0029] One end of the second capacitor C2 is connected to the primary winding, the other end of the second capacitor C2 is connected to one end of the third capacitor C3, and the other end of the third capacitor C3 is grounded;

[0030] One end of the first resistor R1 is connected between the other end of the second capacitor C2 and one end of the third capacitor C3, the other end of the first resistor R1 is connected to one end of the second resistor R2, the other end of the second resistor R2 is respectively connected to one end of the third resistor R3 and the surge protection unit, and the other end of the third resistor R3 is respectively connected to the other end of the third capacitor C3 and the surge protection unit.

[0031] In one embodiment, the voltage transformer further comprises an iron core, a primary winding, a secondary winding, a shielding layer, and a junction box;

[0032] The primary winding and the secondary winding are evenly wound on the iron core. A shielding layer is provided on one side of the primary winding. The primary winding is connected to the acquisition unit, and the secondary winding is connected to the junction box.

[0033] The above-mentioned overvoltage suppression circuit and voltage transformer, the overvoltage suppression circuit in the voltage transformer includes a surge protection unit and a T-type filtering unit, wherein the surge protection unit is connected in parallel with the acquisition unit. When a transient overvoltage flows through the acquisition unit of the voltage transformer, the surge protection unit can limit the transient overvoltage to protect the normal operation of the acquisition unit. The T-type filtering unit is connected in parallel with the surge protection unit to suppress the high-frequency components of the transient overvoltage flowing through the acquisition unit, further ensuring the normal operation of the acquisition unit; in this application, a surge protection unit and a T-type filtering unit are provided in the overvoltage suppression circuit to achieve the limitation of overvoltage and the suppression of its high-frequency components, thereby improving the safety and stability of the operation of the system in which the voltage transformer is located. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 is a structural block diagram of an overvoltage suppression circuit in one embodiment;

[0036] Figure 2 1 is a schematic structural diagram of an overvoltage suppression circuit in one embodiment;

[0037] Figure 3 1 is a schematic structural diagram of a voltage transformer in one embodiment;

[0038] Figure 4 FIG. 1 is a schematic structural diagram of a voltage transformer in another embodiment. DETAILED DESCRIPTION

[0039] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings provide embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0041] It will be understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor without departing from the scope of this application. The first resistor and the second resistor are both resistors, but they are not the same resistor.

[0042] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if there is transmission of electrical signals or data between the connected circuits, modules, units, etc.

[0043] It is understood that “at least one” refers to one or more, “a plurality” refers to two or more, and “at least a portion of an element” refers to a portion or all of an element.

[0044] As used herein, the singular forms "a," "an," and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include," "comprising," "having," and the like specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Furthermore, the term "and / or" as used in this specification includes any and all combinations of the relevant listed items.

[0045] Currently, in ungrounded neutral point systems (referred to as "systems"), electromagnetic voltage transformers (Y0 / Y0 connection) are often connected to the busbars of power plants and substations. Therefore, the system's ground parameters include not only the ground capacitance (C0) of the power equipment and conductors but also the voltage transformer's magnetizing inductance (L0). During normal system operation, the three-phase inductive reactance of the voltage transformer is symmetrical (XL0), and the three-phase capacitive reactance of the system to ground is also symmetrical (XC0). The three-phase load to ground is balanced, meaning the grid neutral point is at ground potential. A transient disturbance in the system can cause a transient voltage increase in one or two phases. This causes magnetic saturation in the voltage transformer in the phase with the increased voltage, resulting in a decrease in magnetizing inductance and an unbalanced three-phase load to ground. Consequently, a high displacement voltage (zero-sequence voltage) is generated at the grid neutral point, causing overvoltages in the grid and impacting the safety and stability of system operation.

[0046] The overvoltage suppression circuit provided in the embodiment of the present application is applied to a voltage transformer. The overvoltage suppression circuit includes a surge protection unit and a T-type filtering unit, wherein the surge protection unit is connected in parallel with the acquisition unit. When a transient overvoltage flows through the acquisition unit of the voltage transformer, the surge protection unit can limit the transient overvoltage to protect the normal operation of the acquisition unit. The T-type filtering unit is connected in parallel with the surge protection unit to suppress the high-frequency components of the transient overvoltage flowing through the acquisition unit, further ensuring the normal operation of the acquisition unit and improving the safety and stability of the operation of the system in which the voltage transformer is located.

[0047] In an exemplary embodiment, Figure 1 As shown, an overvoltage suppression circuit 100 is provided, which is applied to a voltage transformer. The overvoltage suppression circuit 100 includes:

[0048] The surge protection unit 110 is connected in parallel with the acquisition unit in the voltage transformer, and is used to limit the voltage flowing through the acquisition unit;

[0049] The T-type filter unit 120 is connected in parallel with the surge protection unit 110 , and is used to filter the voltage flowing through the acquisition unit.

[0050] Specifically, through the analysis of the coupling path of the influence of transient overvoltage (referred to as overvoltage) on the voltage transformer, the transient overvoltage flowing through the acquisition unit is mainly due to the overvoltage generated by the operation of the isolating switch in the voltage transformer, which is directly coupled to the acquisition unit through the primary circuit of the voltage transformer. By setting a surge protection unit 110 in parallel with the acquisition unit, the nonlinear characteristics of the surge protection unit 110 are used to limit the influence of the transient overvoltage on the acquisition unit. It can be understood that at this time, the surge protection unit 110 can provide an energy discharge path in the transient process, thereby realizing the limitation processing of the transient overvoltage flowing through the acquisition unit.

[0051] When the surge protection unit 110 limits the transient overvoltage, it may cause the temperature of the components in the surge protection unit 110 to rise, reducing the surge protection unit 110's ability to suppress transient overvoltages. By setting the T-type filter unit 120 in parallel with the surge protection unit 110, the high-frequency component of the transient overvoltage is suppressed, thereby limiting the transient overvoltage from invading the acquisition unit, effectively suppressing the impact of the overvoltage generated by the isolation switch operation on the voltage transformer, ensuring the normal operation of the acquisition unit while improving the safety and stability of the system operation of the voltage transformer.

[0052] It should be noted that the T-type filtering unit 120 may also be connected in parallel with the acquisition unit.

[0053] The above-mentioned overvoltage suppression circuit includes a surge protection unit and a T-type filtering unit, wherein the surge protection unit is connected in parallel with the acquisition unit. When a transient overvoltage flows through the acquisition unit of the voltage transformer, the surge protection unit can limit the transient overvoltage to protect the normal operation of the acquisition unit. The T-type filtering unit is connected in parallel with the surge protection unit to suppress the high-frequency components of the transient overvoltage flowing through the acquisition unit, further ensuring the normal operation of the acquisition unit, limiting the overvoltage and suppressing its high-frequency components, and improving the safety and stability of the operation of the system in which the voltage transformer is located.

[0054] In one embodiment, Figure 2 As shown, the surge protection unit 110 includes a nonlinear resistor;

[0055] The two ends of the nonlinear resistor are connected in parallel with the acquisition unit, and the two ends of the nonlinear resistor are also connected in parallel with the T-type filter unit 120; the nonlinear resistor is used to trigger the voltage when the voltage flowing through the acquisition unit is greater than the trigger voltage U C When , the voltage flowing through the acquisition unit is limited.

[0056] Among them, the trigger voltage U C It can be used to represent the maximum voltage corresponding to keeping the surge protection unit 110 in a high-impedance state. It can be set according to actual conditions and is not limited in the embodiments of the present application.

[0057] Specifically, the resistance of the nonlinear resistor can change with the voltage U at both ends and the trigger voltage U C There are two resistance states: Under normal working conditions, the voltage U across the nonlinear resistor is less than or equal to the trigger voltage U C When the surge protection unit 110 is in a high-resistance state, which is equivalent to an open circuit; when the system has an abnormal overvoltage operation such as an operational overvoltage, the voltage U across the nonlinear resistor is greater than the trigger voltage U C When the surge protection unit 110 is in a low resistance state, which is equivalent to a short circuit; the characteristic of the nonlinear resistor that the resistance changes with the voltage is applied to the acquisition unit to provide an energy discharge path in the transient process, which can effectively limit the transient overvoltage to the trigger voltage U C level to protect the normal operation of the acquisition unit.

[0058] It should be noted that the nonlinear resistor may be a varistor.

[0059] In an embodiment of the present application, a nonlinear resistor is set in the surge protection unit, and both ends of the nonlinear resistor are connected in parallel with the acquisition unit, and both ends of the nonlinear resistor are also connected in parallel with the T-type filter unit. The nonlinear characteristics of the resistor are used to limit the impact of transient overvoltage on the acquisition unit, thereby protecting the normal operation of the acquisition unit and improving the safety and stability of the system operation.

[0060] In one embodiment, the trigger voltage U C It is determined by the preset voltage and the operating voltage corresponding to the acquisition unit. The preset voltage is associated with the environment in which the voltage transformer is located.

[0061] Among them, the preset voltage is associated with the transient overvoltage level corresponding to the environment in which the voltage transformer is located, and can be set according to actual conditions, and is not limited in the embodiment of this application; the operating voltage corresponding to the acquisition unit can be set according to actual conditions, and is not limited in the embodiment of this application.

[0062] Specifically, when determining the trigger voltage U C When determining the voltage, it should be based on the transient overvoltage level corresponding to the on-site installation environment and the maximum operating voltage of the protected equipment (voltage transformer); on the one hand, it should be less than the lowest overvoltage level U that the installation location may withstand. OVmin (preset voltage), on the other hand, it should be greater than the maximum operating voltage U of the protected equipment Tmax (operating voltage) to achieve the limitation of transient overvoltage.

[0063] For example, the voltage drop ΔU of the lead of the surge protection unit 110 and the withstand voltage level U of the protected device can also be used. W To set the maximum protection level U corresponding to the nonlinear resistorpmax , that is, setting the maximum transient voltage that the surge protection unit 110 can withstand, so as to better achieve the limitation processing of transient overvoltage.

[0064] In the embodiment of the present application, the trigger voltage U is reasonably set according to the preset voltage and the operating voltage corresponding to the acquisition unit. C , to achieve the limiting processing of transient overvoltage flowing through the acquisition unit, protect the normal operation of the acquisition unit, and improve the safety and stability of the system operation.

[0065] In one embodiment, the trigger voltage U C The value range of is as follows:

[0066] U C ≥1.3*U Tmax ;

[0067] U C ≤0.9*U OVmin ;

[0068] Among them, U Tmax is the operating voltage corresponding to the acquisition unit; U OVmin is the preset voltage.

[0069] Specifically, in order to avoid the maximum operating voltage U Tmax , and improve the sensitivity of the surge protection unit 110 to transient overvoltage, triggering the voltage U C The value range can be set to 1.3 times the operating voltage U Tmax To 0.9 times the preset voltage U Ovmin .

[0070] For example, at the maximum operating voltage U Tmax Take 1.145pu as an example to illustrate, the trigger voltage U C The value range can be set to 1.49pu to 2.39pu; in order to take into account the insulation withstand voltage level of the protection equipment, the maximum voltage protection level U pmax (Maximum voltage limiting performance) can be determined as follows:

[0071] (U pmax +ΔU)≤0.8U W ;

[0072] Wherein, ΔU is the lead voltage drop of the surge protection unit 110, U W The withstand voltage level of the protected equipment is U , and the withstand voltage level of the acquisition unit of the voltage transformer used in the embodiment of the present application is U W It can be 6kV, with a maximum voltage protection level of U pmax Should be less than or equal to 4.8kV.

[0073] In one embodiment, Figure 2 As shown, the T-type filter unit 120 includes a first inductor L1, a second inductor L2 and a first capacitor C1;

[0074] One end of the first inductor L1 is connected to one end of the surge protection unit, the other end of the first inductor L1 is connected to one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the first capacitor C1, one end of the first capacitor C1 is also connected to the other end of the surge protection unit, and the other end of the first capacitor C1 is connected between the other end of the first inductor L1 and one end of the second inductor L2.

[0075] Specifically, the surge protection unit 110 has a general effect in suppressing the high-frequency components of transient overvoltages, and when a high-performance varistor (non-linear resistor) overheats, an unstable leakage current will occur, reducing the suppression capability. In order to compensate for the shortcomings of the varistor-type surge protection unit 110 and reliably suppress transient overvoltages, a T-type filter unit 120 is configured at the outlet of the surge protection unit 110. At this time, the surge protection unit 110 and the T-type filter unit 120 are connected in parallel. When there is an h-order frequency component in the transient overvoltage Uov, the relationship between the outlet current I2 of the T-type filter unit 120 and the h-order frequency component Uov (jhω) can be:

[0076] ;

[0077] Wherein, X1 is the reactance value of the first inductor L1; X2 is the reactance value of the second inductor L2; Xc is the reactance value of the first capacitor C1; It can be obtained from the above formula that when the frequency of the component included in the transient overvoltage is higher, the suppression effect of the T-type filter unit 120 is better.

[0078] In the embodiment of the present application, the first inductor L1, the second inductor L2 and the first capacitor C1 are provided to suppress the high-frequency components of the transient overvoltage flowing through the acquisition unit, thereby further ensuring the normal operation of the acquisition unit and improving the safety and stability of the operation of the system in which the voltage transformer is located.

[0079] In one embodiment, the capacitance value of the first capacitor C1 is determined by the capacity of the voltage transformer;

[0080] The inductance values of the first inductor L1 and the second inductor L2 are both determined by the rated current of the voltage transformer, and the inductance value of the second inductor L2 is smaller than the inductance value of the first inductor L1.

[0081] Specifically, in order to improve the suppression effect of the T-type filtering unit 120 , the capacitance of the first capacitor C1 is set according to the capacity of the voltage transformer, and the inductances of the first inductor L1 and the second inductor L2 are set according to the rated current of the voltage transformer.

[0082] In the embodiment of the present application, by reasonably setting the capacitance value of the first capacitor C1, and the inductance values of the first inductor L1 and the second inductor L2, the T-type filter unit 120 is improved in suppressing the high-frequency components of transient overvoltage, thereby improving the safety and stability of the system operation.

[0083] In one embodiment, the capacitance range of the first capacitor C1 is as follows:

[0084] C≤5%*Yn;

[0085] ;

[0086] Wherein, C is the capacitance value of the first capacitor C1; Yn is the capacity of the voltage transformer;

[0087] Sn is the rated capacity of the voltage transformer; ω1 is the power supply angular frequency; Un is the rated operating voltage of the voltage transformer;

[0088] The inductance of the first inductor L1 and the inductance of the second inductor L2 are shown in the following formula:

[0089] ;

[0090] ;

[0091] L'=m*L;

[0092] Wherein, L is the inductance of the first inductor L1; Un is the rated operating voltage of the voltage transformer; Δimax is the current ripple; Pn is the rated active power of the voltage transformer; L' is the inductance of the second inductor L2; and the value range of m is 0.5 to 0.8.

[0093] Specifically, according to a preset design standard (set according to actual conditions), the reactive power of the capacitor of the T-type filter unit 120 is less than or equal to 5% of the voltage transformer capacity Yn, that is, the capacitance value of the first capacitor C1 is less than or equal to 5% of the voltage transformer capacity Yn; the inductance value of the first inductor L1 and the inductance value of the second inductor L2 can be determined according to the size of the current ripple Δimax, and the current ripple Δimax can be 10% of the rated current peak value, and the inductance value of the second inductor L2 is less than the inductance value of the first inductor L1.

[0094] For example, the capacitance of the first capacitor C1 may be less than or equal to 5.57 μF, the inductance of the first inductor L1 may be 5.82 mH, and the inductance of the second inductor L2 may be 3.492 mH.

[0095] In an exemplary embodiment, Figure 1As shown, the present application also provides a voltage transformer, which includes a collection unit and the overvoltage suppression circuit 100 as described above;

[0096] The acquisition unit is connected in parallel with the surge protection unit 110 of the overvoltage suppression circuit 100 .

[0097] Specifically, the voltage transformer includes an isolating switch arranged in the primary circuit. When a transient disturbance occurs in the system, the overvoltage generated by the isolating switch operation is directly coupled to the circuit of the acquisition unit through the primary circuit. At this time, the acquisition unit is connected in parallel with the surge protection unit 110, which can use its nonlinear characteristics to limit the transient overvoltage.

[0098] It should be noted that the surge protection unit 110 and the T-type filter unit 120 in the overvoltage suppression circuit 100 are connected in parallel. It can be understood that the acquisition unit is also connected in parallel with the T-type filter unit 120 to suppress the high-frequency components of the transient overvoltage flowing through the acquisition unit, further ensuring the normal operation of the acquisition unit and improving the safety and stability of the system operation of the voltage transformer.

[0099] The above-mentioned voltage transformer is provided with an acquisition unit and an overvoltage suppression circuit. When a transient overvoltage exists in the system, the overvoltage suppression circuit provides an energy discharge path, limits and filters the transient overvoltage, effectively suppresses the impact of the transient overvoltage generated by the operation of the disconnector on the voltage transformer, and improves the safety and stability of the operation of the system in which the voltage transformer is located.

[0100] In one embodiment, Figure 3 As shown, the voltage transformer further includes a primary winding, and the acquisition unit includes a first resistor R1, a second resistor R2, a third resistor R3, a second capacitor C2, and a third capacitor C3;

[0101] One end of the second capacitor C2 is connected to the primary winding, the other end of the second capacitor C2 is connected to one end of the third capacitor C3, and the other end of the third capacitor C3 is grounded;

[0102] One end of the first resistor R1 is connected between the other end of the second capacitor C2 and one end of the third capacitor C3, the other end of the first resistor R1 is connected to one end of the second resistor R2, the other end of the second resistor R2 is respectively connected to one end of the third resistor R3 and the surge protection unit, and the other end of the third resistor R3 is respectively connected to the other end of the third capacitor C3 and the surge protection unit.

[0103] Specifically, the acquisition unit is provided with a first resistor R1, a second resistor R2, a third resistor R3, a second capacitor C2 and a third capacitor C3. One end of the second capacitor C2 is connected to the primary winding for acquiring the voltage signal.

[0104] In one embodiment, Figure 4 As shown, the voltage transformer further includes an iron core 210, a primary winding 220, a secondary winding 230, a shielding layer 240 and a junction box 250;

[0105] The primary winding 220 and the secondary winding 230 are evenly wound on the iron core 210 . A shielding layer 240 is provided on one side of the primary winding 220 . The primary winding 220 is connected to the acquisition unit, and the secondary winding 230 is connected to the junction box 250 .

[0106] Specifically, if Figure 4 As shown, the voltage transformer also includes a shell 260, an iron core 210 is arranged in the shell 260, a secondary winding 230 is arranged above the iron core 210, a primary winding 220 and a shielding layer 240 are sequentially arranged on one side of the secondary winding 230, a top cover 270 is provided on the outside of the shell 260, and a surge protection unit 110 and a T-type filter unit 120 are arranged in the top cover 270; the surge protection unit 110 and the T-type filter unit 120 are connected in parallel; the surge protection unit 110 and the T-type filter unit 120 are both connected to the primary winding 220 through a first lead. It can be understood that the acquisition unit is also connected to the primary winding 220 through the first lead; by arranging the surge protection unit 110 in parallel with the acquisition unit, an energy discharge path is provided in the transient process, and by configuring the T-type filter unit 120, high-frequency components are suppressed, thereby limiting the transient overvoltage from intruding into the acquisition unit.

[0107] A junction box 250 is provided on one side of the housing 260. The bottom ends of the junction box 250 and the housing 260 are both mounted on the bottom plate 280. The primary winding 220 and the secondary winding 230 are evenly wound around the core 210. The second lead of the secondary winding 230 extends from the bottom of the housing 260 and is connected to the junction box 250.

[0108] It should be noted that the junction box 250 is integrally cast with epoxy resin to form an outer insulator, and the housing 260 is made of insulating material.

[0109] In the description of this specification, reference to the terms "some embodiments" or "other embodiments" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0110] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. An overvoltage suppression circuit, characterized in that: Applied to a voltage transformer, the overvoltage suppression circuit includes: a surge protection unit connected in parallel with the acquisition unit in the voltage transformer, the surge protection unit being used to limit the voltage flowing through the acquisition unit; A T-type filtering unit is connected in parallel with the surge protection unit, and the T-type filtering unit is used to filter the voltage flowing through the acquisition unit.

2. The overvoltage suppression circuit according to claim 1, wherein: The surge protection unit includes a nonlinear resistor; The two ends of the nonlinear resistor are connected in parallel with the acquisition unit, and the two ends of the nonlinear resistor are also connected in parallel with the T-type filter unit; the nonlinear resistor is used to trigger the voltage when the voltage flowing through the acquisition unit is greater than the trigger voltage U C When the voltage flowing through the acquisition unit is limited.

3. The overvoltage suppression circuit according to claim 2, wherein: The trigger voltage U C It is determined by a preset voltage and an operating voltage corresponding to the acquisition unit, and the preset voltage is associated with the environment in which the voltage transformer is located.

4. The overvoltage suppression circuit according to claim 3, characterized in that: The trigger voltage U C The value range of is as follows: IN C ≥ 1.3*U Tmax ; IN C ≤ 0.9* U OVmin ; Among them, the U Tmax is the operating voltage corresponding to the acquisition unit; the U OVmin is the preset voltage.

5. The overvoltage suppression circuit according to claim 1, wherein: The T-type filter unit includes a first inductor L1, a second inductor L2 and a first capacitor C1; One end of the first inductor L1 is connected to one end of the surge protection unit, the other end of the first inductor L1 is connected to one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the first capacitor C1, one end of the first capacitor C1 is also connected to the other end of the surge protection unit, and the other end of the first capacitor C1 is connected between the other end of the first inductor L1 and one end of the second inductor L2.

6. The overvoltage suppression circuit according to claim 5, characterized in that: The capacitance value of the first capacitor C1 is determined by the capacity of the voltage transformer; The inductance values of the first inductor L1 and the second inductor L2 are both determined by the rated current of the voltage transformer, and the inductance value of the second inductor L2 is smaller than the inductance value of the first inductor L1.

7. The overvoltage suppression circuit according to claim 6, characterized in that: The capacitance range of the first capacitor C1 is shown in the following formula: C≤ 5%*Yn; ； Wherein, C is the capacitance value of the first capacitor C1; Yn is the capacity of the voltage transformer; Sn is the rated capacity of the voltage transformer; ω1 is the power supply angular frequency; Un is the rated operating voltage of the voltage transformer; The inductance value of the first inductor L1 and the inductance value of the second inductor L2 are shown in the following formula: ； ； L' = m*L; Wherein, L is the inductance value of the first inductor L1; Un is the rated operating voltage of the voltage transformer; Δimax is the current ripple; Pn is the rated active power of the voltage transformer; L' is the inductance value of the second inductor L2; and the value range of m is 0.5 to 0.

8.

8. A voltage transformer, characterized in that: The voltage transformer comprises a collection unit and an overvoltage suppression circuit according to any one of claims 1 to 7; Wherein, the acquisition unit is connected in parallel with the surge protection unit of the overvoltage suppression circuit.

9. The voltage transformer according to claim 8, characterized in that: The voltage transformer further includes a primary winding, and the acquisition unit includes a first resistor R1, a second resistor R2, a third resistor R3, a second capacitor C2, and a third capacitor C3; One end of the second capacitor C2 is connected to the primary winding, the other end of the second capacitor C2 is connected to one end of the third capacitor C3, and the other end of the third capacitor C3 is grounded; One end of the first resistor R1 is connected between the other end of the second capacitor C2 and one end of the third capacitor C3, the other end of the first resistor R1 is connected to one end of the second resistor R2, the other end of the second resistor R2 is respectively connected to one end of the third resistor R3 and the surge protection unit, and the other end of the third resistor R3 is respectively connected to the other end of the third capacitor C3 and the surge protection unit.

10. The voltage transformer according to claim 8, characterized in that: The voltage transformer also includes an iron core, a primary winding, a secondary winding, a shielding layer and a junction box; The primary winding and the secondary winding are evenly wound on the iron core. The shielding layer is provided on one side of the primary winding. The primary winding is connected to the acquisition unit, and the secondary winding is connected to the junction box.

Images