An improved neutral point grounding device for a tubular hydrogenerator

Abstract

The present invention relates to an improved neutral point grounding device for a tubular hydrogenerator, belonging to the technical field of hydrogenerator manufacturing. It includes a stator frame, a water frame ring, a three-phase neutral point lead device, a current mutual inductance device, a short-circuit copper bar, and a zinc oxide arrester. The current mutual inductance device is arranged on the water frame ring, and the three-phase neutral point lead device is electrically connected to the current mutual inductance device. One end of the current mutual inductance device is connected to one end of the zinc oxide arrester through the short-circuit copper bar, and the other end of the zinc oxide arrester is grounded. The output end of the current mutual inductance device is connected to an external monitoring device through a secondary lead of the mutual inductor. In the present invention, grounding is achieved through the zinc oxide arrester to form a "high-resistance grounding" mode. When a single-phase grounding fault occurs in the generator, the generator is quickly tripped to avoid damage to the generator and primary and secondary electrical equipment, and improve the reliability of the generator voltage system. The neutral point grounding device is installed inside the bulb tubular hydrogenerator unit, which is convenient for installation and saves costs.

Description

Technical Field

[0001] The invention belongs to the technical field of manufacturing of Francis hydro-generators, and particularly relates to an improved neutral point grounding device for a tubular hydro-generator. Background Art

[0002] When a single-phase grounding fault occurs in the stator winding of a generator, the current flowing through the grounding point is the three-phase capacitance current to the ground of the motor body and its outgoing circuits (main busbar, auxiliary branch line, low-voltage side of main transformer, etc.). When this current value exceeds the allowable value, it will burn out the stator core and winding insulation, and then cause inter-turn and phase-to-phase short circuits. Therefore, large-scale generator sets in China adopt measures of grounding through arc suppression coils or through high resistance of distribution transformers at the neutral point of the generator to protect the motor from damage.

[0003] However, for small and medium-sized Francis hydro-generators, the three-phase capacitance current to the ground value is very small, and according to relevant standards in China (DL / T620-1997), the ungrounded method can be completely adopted. But in recent years, the owners of most small and medium-sized hydropower plants in China require the manufacturer to set up a neutral point grounding device to further improve the operation reliability of the unit.

[0004] In this regard, the manufacturer needs to purchase neutral point complete sets of equipment externally. This equipment is generally designed and manufactured by professional manufacturers and generally includes dry single-phase distribution transformers, small resistors, zero-sequence current transformers, disconnecting switches, and temperature and humidity control devices, etc. The complete set of equipment is integrated in a cabinet. This not only increases the investment of Party A but also raises the unnecessary manufacturing cost of the product. Therefore, for small and medium-sized hydropower projects in China, especially for tubular hydropower stations, there is an urgent need for a generator neutral point grounding device with reliable structure and low cost. Summary of the Invention

[0005] The purpose of the invention is to provide an improved neutral point grounding device for a tubular hydro-generator to solve the technical problem of the structural reliability of the neutral point grounding device in the prior art.

[0006] To achieve the above purpose, the specific technical solution of an improved neutral point grounding device for a tubular hydro-generator of the invention is as follows:

[0007] An improved neutral point grounding device for a tubular hydro-generator includes a stator frame, a water frame ring, a three-phase neutral point lead device, a current mutual inductance device, a short-circuit copper bar, and a zinc oxide arrester. One end of the stator frame is provided with a water frame ring, a three-phase neutral point lead device is arranged on the stator frame, a current mutual inductance device is arranged on the water frame ring, the three-phase neutral point lead device is electrically connected to the current mutual inductance device, the current mutual inductance device end is connected to one end of the zinc oxide arrester through a short-circuit copper bar, the other end of the zinc oxide arrester is grounded, and the output end of the current mutual inductance device is connected to an external monitoring device through a secondary lead of the transformer.

[0008] Furthermore, the three-phase neutral point lead device includes a U2 lead-out device, a V2 lead-out device, and a W2 lead-out device. The U2 lead-out device, V2 lead-out device, and W2 lead-out device have the same structure and are electrically connected to the current mutual inductance device.

[0009] Furthermore, the current mutual inductance device includes a U2 current mutual inductance device, a V2 current mutual inductance device, and a W2 current mutual inductance device. The U2 lead-out device, V2 lead-out device, and W2 lead-out device are respectively connected to the U2 current mutual inductance device, V2 current mutual inductance device, and W2 current mutual inductance device through copper bars.

[0010] Furthermore, the U2 lead-out device includes a copper ring support frame and a stator copper ring. The stator copper ring is fixedly installed on the stator frame through a plurality of copper ring support frames. The stator copper ring is connected to the U2 current mutual inductance device through a copper bar.

[0011] Furthermore, the U2 current mutual inductance device includes a current transformer and a support. The support is installed on the water machine base ring, the current transformer is installed on the support. The stator copper ring is connected to the P1 end of the current transformer through a copper bar. The P2 end of the current transformer is connected to one end of the zinc oxide arrester through a short-circuit copper bar. The output end of the current transformer is connected to an external monitoring device through a transformer secondary lead.

[0012] Furthermore, the grounding end of the zinc oxide arrester is grounded through a grounding cable. The transformer secondary lead is connected to the output end of the current transformer. The grounding cable and the transformer secondary lead pass through a through-hole provided on the water machine base ring and are connected to the outside.

[0013] Furthermore, a sealing rubber ring is provided inside the through-hole for sealing the wire passing pore.

[0014] The advantages of the present invention are as follows: In the present invention, the neutral point of the generator is grounded through a zinc oxide arrester, forming a "high-resistance grounding" method, which can achieve the same protection effect as the purchased neutral point grounding complete set of equipment, that is, when a single-phase grounding fault occurs in the generator, the generator is quickly tripped to avoid damage to the generator and primary and secondary electrical equipment, and improve the reliability of the generator voltage system; the neutral point grounding device improves the relay protection system and ensures the safe operation of the unit; the neutral point grounding device is installed inside the bulb tubular hydro-generator unit equipment, without occupying the space of the power station, the overall structure is reliable, easy to install, and cost-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0016] Figure 2 is a schematic diagram of the position of the support of the present invention;

[0017] Figure 3 Schematic diagram of the circuit principle of the present invention;

[0018] Description of the markings in the figure: 1. Stator frame, 2. Water frame ring, 3. Three-phase neutral point lead device, 31. U2 lead-out device, 32. V2 lead-out device, 33. W2 lead-out device, 34. Copper busbar, 311. Copper ring support frame, 312. Stator copper ring, 4. Current mutual inductance device, 41. U2 current mutual inductance device, 42. V2 current mutual inductance device, 43. W2 current mutual inductance device, 411. Current transformer, 412. Support, 5. Shorting copper busbar, 6. Zinc oxide arrester, 61. Grounding cable, 7. Secondary lead of the transformer, 8. Through hole, 9. Rotor. Specific embodiments

[0019] In order to better understand the purpose, structure and function of the present invention, the following further describes in detail an improved neutral point grounding device for a tubular hydrogenerator of the present invention with reference to the accompanying drawings.

[0020] As Figure 1-2 shown, an improved neutral point grounding device for a tubular hydrogenerator of the present invention provides a neutral point grounding device that can be directly installed on a tubular hydrogenerator. The device is provided with a double protection structure of a zinc oxide arrester and a secondary lead of the transformer, improving the reliability.

[0021] An improved neutral point grounding device for a tubular hydrogenerator includes a stator frame 1, a water frame ring 2, a three-phase neutral point lead device 3, a current mutual inductance device 4, a shorting copper busbar 5 and a zinc oxide arrester 6. A water frame ring 2 is provided at one end of the stator frame 1, a three-phase neutral point lead device 3 is provided on the stator frame 1, a current mutual inductance device 4 is provided on the water frame ring 2, the three-phase neutral point lead device 3 is electrically connected to the current mutual inductance device 4, one end of the current mutual inductance device 4 is connected to one end of the zinc oxide arrester 6 through the shorting copper busbar 5, the other end of the zinc oxide arrester 6 is grounded, and the output end of the current mutual inductance device 4 is connected to an external monitoring device through the secondary lead 7 of the transformer, which can monitor the current change of the device and prevent excessive current when a fault occurs, causing irreversible damage to the equipment. The three-phase neutral point lead device 3 includes a U2 lead-out device 31, a V2 lead-out device 32 and a W2 lead-out device 33. The U2 lead-out device 31, the V2 lead-out device 32 and the W2 lead-out device 33 have the same structure and are electrically connected to the current mutual inductance device 4. The three-phase neutral point lead device 3 leads out the neutral point leads of the three phases U2, V2 and W2 through the U2 lead-out device 31, the V2 lead-out device 32 and the W2 lead-out device 33 respectively.

[0022] The current mutual inductance device 4 includes a U2 current mutual inductance device 41, a V2 current mutual inductance device 42, and a W2 current mutual inductance device 43. The U2 lead-out device 31, the V2 lead-out device 32, and the W2 lead-out device 33 are respectively connected to the U2 current mutual inductance device 41, the V2 current mutual inductance device 42, and the W2 current mutual inductance device 43 through copper bars 34. The currents of the neutral point leads of the U2, V2, and W2 three phases are measured through the U2 current mutual inductance device 41, the V2 current mutual inductance device 42, and the W2 current mutual inductance device 43 respectively.

[0023] The U2 lead-out device 31 includes a copper ring support frame 311 and a stator copper ring 312. The stator copper ring 312 is fixedly installed on the stator frame 1 through a plurality of copper ring support frames 311. The stator copper ring 312 is connected to the U2 current mutual inductance device 41 through a copper bar 34. The U2 current mutual inductance device 41 includes a current transformer 411 and a support 412. The support 412 is installed on the water machine base ring 2, and the current transformer 411 is installed on the support 412. The stator copper ring 312 is connected to the P1 end of the current transformer 411 through a copper bar 34. The P2 end of the current transformer 411 is connected to one end of a zinc oxide arrester 6 through a short-circuit copper bar 5. The output end of the current transformer 411 is connected to an external monitoring device through a transformer secondary lead 7. The zinc oxide arrester 6 is grounded by a high-resistance grounding method to reduce the secondary damage to the equipment caused by short-circuit faults. The transformer secondary lead 7 is connected to an external current monitoring device to monitor the current. The external monitoring device is a prior art and can be used to monitor the current changes of the equipment.

[0024] The grounding end of the zinc oxide arrester 6 is grounded through a grounding cable 61, forming a "high-resistance grounding" method. When a single-phase grounding fault occurs in the generator, the generator is quickly tripped to avoid damage to the generator and primary and secondary electrical equipment, and improve the reliability of the generator voltage system. The transformer secondary lead 7 is connected to the output end of the current transformer 411. The grounding cable 61 and the transformer secondary lead 7 pass through a through-hole 8 provided on the water machine base ring 2 and are connected to the outside. A sealing rubber ring is provided inside the through-hole 8 for sealing the wire passing pore. The transformer secondary lead 41 can monitor the current changes during the operation of the generator through a remote controller. A sealing rubber ring is provided inside the through-hole 10 for sealing the wire passing pore.

[0025] Working principle:

[0026] Such as Figure 3As shown in the figure, the circuit diagram of a neutral point grounding device for an improved tubular hydrogenerator of the present invention. After the three-phase circuit passes through the current transformer 411 via the three-phase neutral point lead-out wire of the stator copper ring, it is short-circuited together by the short-circuit copper bar 5, connected in series with the zinc oxide arrester 6, and grounded through the grounding cable 61. At the same time, the current transformer 411 realizes the monitoring of current through the secondary lead wire 7 of the transformer. In the prior art, a three-phase generator has three sets of coils. One end of the generator stator winding is the outgoing side, connected to the power grid, and the other end is short-circuited in three phases, and the output voltage and current are zero, which is the neutral point. Connecting the ends of the three-phase windings of the generator together is the neutral point side of the generator.

[0027] The neutral point of the generator of the present invention is grounded through a zinc oxide arrester, forming a "high-resistance grounding" method, which can achieve the same protection effect as the purchased neutral point grounding complete set of equipment, that is: when a single-phase grounding fault occurs in the generator, the generator is quickly tripped to avoid damage to the generator and primary and secondary electrical equipment, and improve the reliability of the generator voltage system; the neutral point grounding device improves the relay protection system and ensures the safe operation of the unit; the neutral point grounding device is installed inside the bulb tubular hydrogenerator unit, without occupying the space of the power station, with a reliable overall structure, easy to install, and cost-saving.

[0028] It can be understood that the present invention is described through some embodiments. Those skilled in the art know that without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and embodiments. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. An improved neutral point grounding device for a tubular turbine generator, characterized in that, it includes a stator frame (1), a water frame ring (2), a three-phase neutral point lead device (3), a current mutual inductance device (4), a short-circuit copper bar (5) and a zinc oxide arrester (6). One end of the stator frame (1) is provided with a water frame ring (2), the stator frame (1) is provided with a three-phase neutral point lead device (3), the water frame ring (2) is provided with a current mutual inductance device (4), the three-phase neutral point lead device (3) is electrically connected to the current mutual inductance device (4), the current mutual inductance device (4) is connected to one end of the zinc oxide arrester (6) through a short-circuit copper bar (5), the other end of the zinc oxide arrester (6) is grounded, and the output end of the current mutual inductance device (4) is connected to an external monitoring device through a secondary lead of the mutual inductor (7); The three-phase neutral point lead device (3) includes a U2 lead-out device (31), a V2 lead-out device (32) and a W2 lead-out device (33). The U2 lead-out device (31), the V2 lead-out device (32) and the W2 lead-out device (33) have the same structure and are electrically connected to the current mutual inductance device (4); The current mutual inductance device (4) includes a U2 current mutual inductance device (41), a V2 current mutual inductance device (42) and a W2 current mutual inductance device (43). The U2 lead-out device (31), the V2 lead-out device (32) and the W2 lead-out device (33) are respectively connected to the U2 current mutual inductance device (41), the V2 current mutual inductance device (42) and the W2 current mutual inductance device (43) through copper bars (34); The U2 lead-out device (31) includes a copper ring support frame (311) and a stator copper ring (312). The stator copper ring (312) is fixedly installed on the stator frame (1) through a plurality of copper ring support frames (311), and the stator copper ring (312) is connected to the U2 current mutual inductance device (41) through a copper bar (34); The U2 current mutual inductance device (41) includes a current transformer (411) and a support (412). The support (412) is installed on the water frame ring (2), the current transformer (411) is installed on the support (412), the stator copper ring (312) is connected to the P1 end of the current transformer (411) through a copper bar (34), the P2 end of the current transformer (411) is connected to one end of the zinc oxide arrester (6) through a short-circuit copper bar (5), and the output end of the current transformer (411) is connected to an external monitoring device through a secondary lead of the mutual inductor (7); The grounding end of the zinc oxide arrester (6) is grounded through a grounding cable (61). The secondary lead of the mutual inductor (7) is connected to the output end of the current transformer (411). The grounding cable (61) and the secondary lead of the mutual inductor (7) pass through a through hole (8) provided on the water frame ring (2) and are connected to the outside.

2. The improved neutral point grounding device for a tubular turbine generator according to claim 1, characterized in that, a sealing rubber ring is arranged inside the through hole (8) for sealing the wire passing pore.

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