Protection element and current-limiting resonance eliminator

Abstract

The utility model relates to the field of resonance eliminators, and discloses a protection element and a current limiting type resonance eliminator, the protection element comprises at least two groups of protection units, the two adjacent groups of protection units are connected in series, and each protection unit comprises a protection module; the current-limiting resonance eliminator based on the current-sensitive resistor made of the current-sensitive material is connected in series between the PT neutral point and the ground. Under the normal operation condition, the current-limiting resonance eliminator is in a low-resistance state, and system parameters and PT performance are not affected; when excitation energy is generated due to a system fault, the current-limiting resonance eliminator suddenly changes into a high resistance state, quickly absorbs resonance energy, destroys resonance parameters, suppresses PT excitation current below 200mA, and ensures that a voltage transformer is unsaturated and a PT fuse is not fused; and a built-in current sensor is connected, so that the running state of the current-limiting resonance eliminator can be monitored in real time.

Description

Technical Field

[0001] This utility model relates to the field of harmonic suppressors, and in particular to a protective element and a current-limiting harmonic suppressor. Background Technology

[0002] Substation 6-35kV electromagnetic voltage transformers (PTs) frequently shut down due to resonance and surges, causing fuse blowouts and winding burnouts. This poses significant safety risks to the system and, due to the lack of corresponding protection measures, puts considerable pressure on the power supply bureau's grassroots maintenance personnel. To address these issues, projects often employ measures such as installing microprocessor-based harmonic suppression devices on the open delta windings of the PTs, and adding nonlinear resistors (SiC) or single-phase PTs between the primary neutral point and ground. However, current voltage transformer losses and branch fuse failures are not decreasing but rather showing an increasing trend. This is mainly due to the inherent physical characteristic of nonlinear resistors (SiCs) being high resistance under normal conditions and low resistance during faults. The nonlinear characteristics of silicon carbide materials are as follows: When the power grid is operating normally, the resistance of the varistor is high (for example, the resistance of 10kV is about several megohms), which has a large damping effect and suppresses inrush current, making the voltage transformer unsaturated and making it difficult for ferroresonance to develop in the initial stage; when an unbalanced fault occurs in the system (single-phase grounding of the power grid), the neutral point voltage of the voltage transformer rises, the voltage on the varistor is also high, and its resistance is low, which is not conducive to suppressing current. Utility Model Content

[0003] Therefore, the technical problem to be solved by this utility model is that the existing nonlinear resistor SiC harmonic suppressor has the inherent physical characteristic of high resistance under normal conditions and low resistance under fault conditions. This results in the inability to effectively suppress the zero-sequence loop current of the voltage transformer when the system fails, and even the SiC harmonic suppressor may thermally collapse due to the fault current flowing through it during a system fault.

[0004] The above-mentioned technical problems are solved by the following technical solution: This utility model proposes a protective element, which includes,

[0005] The protection unit is configured in at least two groups, with adjacent groups of the protection unit connected in series.

[0006] The protection unit includes a protection module.

[0007] In a preferred embodiment of the protective element of this utility model: the protective unit includes at least one set of the protective modules, and if two or more sets of the protective modules are provided, then the two adjacent sets of the protective modules are connected in parallel.

[0008] In a preferred embodiment of the protective element of this utility model: the protective module specifically includes a current-sensitive resistor and a zinc oxide varistor, wherein the current-sensitive resistor and the zinc oxide varistor are connected in parallel.

[0009] This utility model also provides a current-limiting harmonic suppressor, including the aforementioned protective element, and further comprising,

[0010] The housing includes an outer insulating sheath, quartz sand disposed on the inner wall of the outer insulating sheath, an insulating sealing cover fixedly connected to the top of the outer insulating sheath, and a terminal disposed on the top of the inner side of the insulating sealing cover.

[0011] A support base is fixedly connected to the bottom end of the housing.

[0012] In a preferred embodiment of the current-limiting harmonic suppressor of this utility model: an upper electrode and a lower electrode are respectively provided at the upper and lower ends of the inner side of the outer insulating sheath, and the protective module is stacked between the upper electrode and the lower electrode.

[0013] In a preferred embodiment of the current-limiting harmonic suppressor of this utility model: the current-sensitive resistor and the zinc oxide varistor are installed inside the outer insulating sheath, and the zinc oxide varistor is attached to one side of the current-sensitive resistor and forms the protection module with the current-sensitive resistor, and is stacked between the upper electrode and the lower electrode.

[0014] In a preferred embodiment of the current-limiting harmonic suppressor of this utility model: a current sensor is installed inside the support base, and the current sensor is installed below the lower electrode.

[0015] In a preferred embodiment of the current-limiting harmonic suppressor of this utility model: the terminal is connected in series with the uppermost protection module through the upper electrode, and the lowermost protection module is connected in series with the support base through the lower electrode;

[0016] The current sensor is connected in series between the lower electrode and the support base.

[0017] The beneficial effects of this invention are as follows: A current-limiting harmonic suppressor based on a current-sensitive material is connected in series between the neutral point of the PT and ground. Under normal operating conditions, the current-limiting harmonic suppressor is in a low-resistance state, which does not affect the system parameters and PT performance. When a system fault generates excitation energy, the current-limiting harmonic suppressor abruptly switches to a high-resistance state, rapidly absorbing the resonant energy, disrupting the resonant parameters, and suppressing the PT excitation current to below 200mA, ensuring that the voltage transformer does not saturate and the PT fuse does not blow. Furthermore, a built-in current sensor is connected to monitor the operating status of the current-limiting harmonic suppressor in real time. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings of the embodiments of this utility model will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this utility model, and are not intended to limit the utility model.

[0019] Figure 1 A schematic diagram of the current-limiting harmonic suppressor of this utility model is shown.

[0020] Figure 2 A schematic diagram of the limit protection unit structure of this utility model is shown.

[0021] Figure 3 A schematic diagram of the protective module structure of this utility model is shown.

[0022] Figure 4 The diagram shows the integrated structure of the current-limiting harmonic suppressor and the current sensor of this utility model.

[0023] Figure 5 The schematic diagram of the current-limiting harmonic suppressor of this utility model is shown.

[0024] Figure 6 A flowchart of the current-limiting harmonic suppressor of this utility model is shown.

[0025] Figure 7 The current-voltage characteristic curve of the flow-sensitive material is shown. Detailed Implementation

[0026] To enable those skilled in the art to better understand this utility model, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0027] The terminology used in this invention refers to those general terms currently widely used in the art in consideration of the functionality of this invention; however, these terms may vary according to the intent, precedent, or new technology of those skilled in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of this invention. Therefore, the terminology used in this specification should not be construed as simple names, but rather based on the meaning of the terms and the overall description of this invention.

[0028] Reference Figure 2 , Figure 3 as well as Figures 5-7 This embodiment provides a protective element, including:

[0029] Protection unit 1, at least two sets of protection unit 1 are provided, and two adjacent sets of protection unit 1 are connected in series;

[0030] The protection unit 1 includes a protection module 11.

[0031] The protection unit 1 includes at least one set of protection modules 11. If two or more sets of protection modules 11 are provided, then two adjacent sets of protection modules 11 are connected in parallel.

[0032] The protection module 11 specifically includes a current-sensitive resistor 111 and a zinc oxide varistor 112, with the current-sensitive resistor 111 and the zinc oxide varistor 112 connected in parallel.

[0033] The damping effect of the current-sensitive resistor 111 can disrupt the PT resonance condition, thus eliminating the resonance. The current-limiting harmonic suppressor is connected in series between the PT neutral point and ground. Under normal operating conditions, its resistance is in the kiloohm range, while the impedance of the PT primary winding is in the megaohm range. Therefore, it will not affect the PT's performance or significantly alter the system parameters. When the PT resonates, the core saturates, increasing the primary winding excitation current. The temperature of the current-sensitive resistor 111 inside the current-limiting harmonic suppressor rises, and its resistance increases rapidly, effectively exerting its damping effect. Furthermore, the greater the resonance energy, the shorter the harmonic suppression time of the current-limiting harmonic suppressor, which is more beneficial to the equipment insulation. Simultaneously, when the voltage transformer neutral point voltage exceeds 10kV, the zinc oxide varistor 112 connected in parallel across the current-sensitive resistor 111 quickly conducts, protecting the current-limiting harmonic suppressor and preventing the risk of voltage transformer neutral point breakdown.

[0034] A current-sensitive resistor 111, made of current-sensitive material, suppresses the neutral point current of the voltage transformer. Connected in series between the primary neutral point of the voltage transformer and ground, it utilizes the physical characteristics of nonlinear resistance to suppress inrush current; that is, the greater the current, the greater the resistance. This dissipates the current that would cause the voltage transformer to saturate, thus preventing the voltage transformer from saturating and the PT fuse from blowing.

[0035] The current-limiting harmonic suppressor 111, made of a current-sensitive material, has an automatic control function. At a certain transition temperature, a phase change occurs, and the resistivity increases rapidly, forming the automatic control function of a PTC. Conversely, when the current-sensitive material cools from a high-temperature environment to room temperature, its resistance also decreases to a low-resistance state. That is, under normal operating conditions, the three-phase voltage on the primary side of the voltage transformer is balanced, there is no displacement voltage at the neutral point, and the current-sensitive resistor 111 exhibits low resistance at low temperatures, allowing the voltage transformer to operate normally. When the excitation current of the primary winding increases, a displacement voltage appears at the neutral point, resulting in a larger current flowing through the neutral point. The temperature of the current-sensitive resistor 111 rises, and its resistance increases rapidly with temperature, effectively exerting a damping effect. Moreover, the greater the resonant energy, the shorter the harmonic suppression time of the current-sensitive resistor 111.

[0036] A matrix design using current-sensitive resistors 111, connected in parallel with zinc oxide varistor 112, ensures reliable operation of the current-limiting harmonic suppressor under high current and high voltage conditions. To improve the thermal capacity of the current-limiting harmonic suppressor under prolonged single-phase ground faults, a matrix design using current-sensitive resistors 111 is employed to guarantee reliable operation of the current-limiting harmonic suppressor under fault conditions. In the event of intermittent arcing ground faults in the system, repeated arcing ground fault oscillations will generate arcing overvoltages, resulting in overvoltages at the neutral point of the voltage transformer. When the voltage at the neutral point of the voltage transformer exceeds the insulation level of the primary N terminal of the voltage transformer, the parallel-connected zinc oxide varistor 112 quickly conducts, thereby protecting the current-limiting harmonic suppressor 111 and the neutral point of the voltage transformer.

[0037] As one embodiment provided, such as Figure 1 A current-limiting harmonic suppressor, including protective elements, also includes,

[0038] The housing 2 includes an outer insulating sleeve 21, quartz sand 22 disposed on the inner wall of the outer insulating sleeve 21, an insulating sealing cover 23 fixedly connected to the top of the outer insulating sleeve 21, and a terminal 24 disposed at the top of the inner part of the insulating sealing cover 23.

[0039] Support base 3 is fixedly connected to the bottom end of housing 2.

[0040] The upper end electrode 25 and the lower end electrode 26 are respectively provided at the upper and lower ends of the inner insulating sleeve 21, and the protective module 11 is stacked between the upper end electrode 25 and the lower end electrode 26.

[0041] The current-sensitive resistor 111 and the zinc oxide varistor 112 are installed inside the outer insulating sleeve 21, and the zinc oxide varistor 112 is attached to one side of the current-sensitive resistor 111, forming a protection module 11 with the current-sensitive resistor 111, and is stacked between the upper electrode 25 and the lower electrode 26.

[0042] Terminal 24 is connected in series with the uppermost protective module 11 via the upper electrode 25, and the lowermost protective module 11 is connected in series with the support base 3 via the lower electrode 26.

[0043] In the current-limiting harmonic suppressor, the current-sensitive resistor 111 and the zinc oxide varistor 112 are protected by the outer insulating sleeve 21 and the insulating sealing cover 23, effectively avoiding the risk of electric shock. In addition, the design of the quartz sand 22 not only further enhances the insulation effect, but also has arc-extinguishing and heat dissipation functions, thereby ensuring the reliable operation of the current-limiting harmonic suppressor.

[0044] As one embodiment provided, such as Figures 2-4 The support base 3 has a current sensor 31 installed inside, and the current sensor 31 is installed below the lower electrode 26.

[0045] The current sensor 31 is connected in series between the lower electrode 26 and the support base 3.

[0046] By embedding the current sensor 31 within the current-limiting harmonic suppressor, the suppressor's status is monitored. Since the PTC element is housed in a sealed enclosure, to prevent the system from being unable to monitor its operating status in real time during long-term use, the high-precision through-hole current sensor 31 and the current-limiting harmonic suppressor are integrated into a single design and installed inside the support base 3 of the current-limiting harmonic suppressor, thus avoiding the high-voltage requirement of the current sensor 31. This enables monitoring of the primary neutral point current of the voltage transformer and the operating status of the current-limiting harmonic suppressor.

[0047] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of this utility model.

Claims

1. A protection element, characterized in that: Including, The protection unit (1) is provided at least in two groups, and adjacent two groups of the protection unit (1) are connected in series; The protection unit (1) comprises a protection module (11); The protection unit (1) comprises at least one group of the protection module (11), and two or more groups of the protection module (11) are connected in parallel. The protection module (11) comprises a flow-sensitive resistor (111) and a zinc oxide voltage-dependent resistor (112), and the flow-sensitive resistor (111) and the zinc oxide voltage-dependent resistor (112) are connected in parallel.

2. A current limiting harmonic eliminator characterized by: The protection element of claim 1 further comprises, The shell (2) comprises an outer insulating sheath (21), quartz sand (22) arranged on the inner wall of the outer insulating sheath (21), an insulating sealing cover (23) fixedly connected to the top end of the outer insulating sheath (21), and a terminal (24) arranged at the inner top end of the insulating sealing cover (23). The support seat (3) is fixedly connected to the bottom end of the shell (2).

3. The current limited anemharmonic device of claim 2, wherein: The upper and lower ends of the inner part of the outer insulating sheath (21) are respectively provided with an upper electrode (25) and a lower electrode (26), and the protection module (11) is stacked between the upper electrode (25) and the lower electrode (26).

4. The current limited anitiharmonic device of claim 3, wherein: The flow-sensitive resistor (111) and the zinc oxide voltage-dependent resistor (112) are installed in the inner part of the outer insulating sheath (21), and the zinc oxide voltage-dependent resistor (112) is attached to one side of the flow-sensitive resistor (111) and forms the protection module (11) with the flow-sensitive resistor (111), and is stacked between the upper electrode (25) and the lower electrode (26).

5. The current limited anemharmonic device of claim 4, wherein: The current sensor (31) is installed in the inner part of the support seat (3), and the current sensor (31) is installed below the lower electrode (26).

6. The current limited anemharmonic device of claim 5, wherein: The terminal (24) is connected in series with the uppermost protection module (11) through the upper electrode (25), and the lowermost protection module (11) is connected in series with the support seat (3) through the lower electrode (26). The current sensor (31) is connected in series between the lower electrode (26) and the support seat (3).

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