High-resistance and high-impedance neutral point grounding device capable of switching grounding modes

Abstract

The utility model discloses a high-resistance and high-impedance neutral point grounding device capable of switching grounding modes, and relates to the technical field of motor maintenance. Comprising a grounding cabinet body, a high-voltage isolation switch K1, a grounding transformer B, a current transformer CT1 and a grounding end G which are connected in sequence. According to the utility model, a high-resistance and high-impedance switchable mode is adopted, the current amplitude of a ground fault is effectively controlled, and the stator core of the generator is protected, so that the effects of preventing the insulation of the stator winding from being damaged and avoiding the inter-phase or turn-to-turn short circuit are achieved.

Description

Technical Field

[0001] This utility model relates to the field of motor maintenance technology, and in particular to a neutral point grounding device with switchable grounding modes of high resistance and high impedance. Background Technology

[0002] Transformer-type neutral grounding devices are used for neutral grounding protection of large and medium-sized synchronous generators. Because many grounding capacitance parameters of the unit have certain errors between the design stage and the actual operating parameters, the selected grounding method may not be optimal, and grounding fault currents may sometimes exceed the allowable range.

[0003] To better protect the generator, a reasonable grounding method should be adopted according to the actual situation during unit operation to limit the ground fault current within the allowable range. When a single-phase ground fault occurs in the generator, the generator stator core should be protected, thereby preventing the stator winding insulation from being damaged and avoiding phase-to-phase or turn-to-turn short circuits. Ultimately, this will provide more ways to protect the unit.

[0004] Therefore, proposing a neutral point grounding device with switchable high resistance and high impedance grounding modes to solve the problem that the existing technology cannot stabilize the ground fault current within the allowable range is an urgent problem to be solved by those skilled in the art. Utility Model Content

[0005] In view of this, the present invention provides a neutral point grounding device with switchable high resistance and high impedance grounding modes. By adopting a switchable high resistance and high impedance mode, the amplitude of the ground fault current is effectively controlled, thereby protecting the generator stator core and preventing the stator winding insulation from being damaged, thus avoiding phase-to-phase or turn-to-turn short circuits.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A neutral point grounding device with switchable grounding modes for high resistance and high impedance includes a grounding cabinet, a high-voltage disconnect switch K1, a grounding transformer B, a current transformer CT1, and a grounding terminal G connected in sequence.

[0008] Optionally, the high-voltage disconnector K1 in the aforementioned device includes multiple normally open and normally closed contacts connected in parallel.

[0009] Optionally, the above-mentioned device may also include a grounding resistor R and a grounding reactor L, which are connected in parallel to the secondary side of the grounding transformer B.

[0010] Optionally, the aforementioned device may also include a low-voltage disconnector K2 connected in series with a grounding reactor L.

[0011] Optionally, the above-mentioned device may also include a current transformer CT2, a grounding resistor R and a grounding reactor connected in parallel and then connected in series with the current transformer CT2.

[0012] As can be seen from the above technical solution, compared with the prior art, this utility model provides a neutral point grounding device with switchable grounding modes of high resistance and high impedance, which has the following beneficial effects: 1) This utility model adopts a switchable mode of high resistance and high impedance, and the grounding mode can be switched as needed during shutdown maintenance according to the actual operation of the unit; 2) This utility model can effectively control the amplitude of ground fault current, and when a single-phase ground fault occurs in the generator, it can protect the generator stator core, thereby preventing the stator winding insulation from being damaged, avoiding phase-to-phase or turn-to-turn short circuits, and providing more options for unit protection. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 This is a diagram of a neutral point grounding device with switchable grounding modes for high resistance and high impedance disclosed in this utility model. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0016] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0017] Reference Figure 1 As shown, this utility model discloses a neutral point grounding device with switchable grounding modes of high resistance and high impedance, including a grounding cabinet, a high-voltage disconnecting switch K1, a grounding transformer B, a current transformer CT1, and a grounding terminal G connected in sequence.

[0018] Furthermore, a generator neutral point is installed inside the grounding cabinet.

[0019] Furthermore, the high-voltage disconnector K1 includes multiple normally open and normally closed contacts connected in parallel.

[0020] Specifically, a normally open contact and a normally closed contact are used as a group of contacts, and four groups of contacts are connected in parallel inside the high-voltage disconnector K1.

[0021] Furthermore, it also includes a grounding resistor R and a grounding reactor L, which are connected in parallel to the secondary side of the grounding transformer B.

[0022] Furthermore, it also includes a low-voltage disconnector K2, connected in series with a grounding reactor L.

[0023] Furthermore, it also includes a current transformer CT2, a grounding resistor R and a grounding reactor L connected in parallel and then in series with the current transformer CT2.

[0024] In one specific embodiment, the primary side of grounding transformer B is connected to the generator neutral point via a high-voltage disconnector K1. The secondary side of the grounding transformer is connected in parallel with a grounding resistor R and a grounding reactor L. A low-voltage disconnector K2 is installed on the current branch of the grounding reactor L. When disconnector K2 is closed, it operates in high-impedance mode; when open, it operates in high-resistance mode. The actual operating value of the system capacitance may differ from the calculated value. To ensure that the ground fault current in both high-impedance and high-resistance grounding modes is ≤15A, the secondary side resistor and reactor of the grounding transformer have ±2×10% taps based on their rated resistance, providing a certain degree of adjustability and improving protection efficiency.

[0025] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0026] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A neutral point grounding device with switchable grounding modes for high resistance and high impedance, characterized in that, It includes a grounding cabinet, a high-voltage disconnect switch K1, a grounding transformer B, a current transformer CT1, and a grounding terminal G connected in sequence.

2. A neutral point grounding device with switchable high resistance and high impedance grounding modes according to claim 1, characterized in that, The high-voltage disconnector K1 includes multiple normally open and normally closed contacts connected in parallel.

3. A neutral point grounding device with switchable high resistance and high impedance grounding modes according to claim 1, characterized in that, It also includes a grounding resistor R and a grounding reactor L, which are connected in parallel to the secondary side of the grounding transformer B.

4. A neutral point grounding device with switchable high resistance and high impedance grounding modes according to claim 3, characterized in that, It also includes a low-voltage disconnector K2, which is connected in series with the grounding reactor L.

5. A neutral point grounding device with switchable grounding modes for high resistance and high impedance according to claim 3, characterized in that, It also includes a current transformer CT2, a grounding resistor R and a grounding reactor L connected in parallel and then in series with the current transformer CT2.

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