CN110085475B

CN110085475B - Double-coil contact structure of vacuum arc extinguish chamber in mechanical high-voltage direct-current circuit breaker

Info

Publication number: CN110085475B
Application number: CN201910398018.4A
Authority: CN
Inventors: 淡淑恒; 李如春
Original assignee: Shanghai University of Electric Power
Current assignee: Shanghai University of Electric Power
Priority date: 2019-05-14
Filing date: 2019-05-14
Publication date: 2021-04-09
Anticipated expiration: 2039-05-14
Also published as: CN110085475A

Abstract

The invention relates to a double-coil type contact structure of a vacuum arc extinguish chamber in a mechanical high-voltage direct-current circuit breaker, which consists of two completely same contact structures, wherein a conductive rod is a T-shaped cylindrical rod, the diameter of the large-head circular surface of the conductive rod is the same as the outer diameters of an annular coil and an annular contact, the large-head circular surface of the conductive rod, the annular coil and the annular contact are sequentially overlapped and connected, the rest parts of the two connecting surfaces except a convex part are all supported by an insulating annular gasket plane made of polytetrafluoroethylene or insulating materials with higher strength, when the contacts are separated, electric arcs are generated between the two contacts and distributed on the whole annular surface of the annular contact, so that current flows into the annular contact along a connecting conductor after flowing for a circle along the annular coil, when the current flows along the annular coil, a very large longitudinal magnetic field is generated between the contacts, and the structure is ensured not to be extruded, simple structure, the contact electricity life is longer, has just elongated electric arc when drawing electric arc to coil inside, makes electric arc extinguish more easily.

Description

Double-coil contact structure of vacuum arc extinguish chamber in mechanical high-voltage direct-current circuit breaker

Technical Field

The invention relates to a high-voltage direct-current circuit breaker, in particular to a double-coil type contact structure of a vacuum arc extinguish chamber in a mechanical high-voltage direct-current circuit breaker.

Background

The working principle of the mechanical high-voltage direct-current circuit breaker is shown in figure 1. It includes three branches: the first branch circuit is composed of a high-voltage vacuum circuit breaker, and the second branch circuit is a current transfer branch circuit and is a branch circuit for forming high-frequency current by connecting a charging capacitor and an inductor in series; and the third branch is a lightning arrester branch. After the first branch is opened, the high-voltage vacuum circuit breaker starts arcing, an IGCT switch of the second branch is closed quickly (the time difference is in millisecond level generally), and high-frequency current is flushed into the first branch, so that direct current superposed with high-frequency oscillating current flows in the high-voltage vacuum circuit breaker, the current amplitude of the high-frequency oscillating current is larger than that of the direct current, the current zero crossing point exists in the first branch, and the electric arc of the mechanical circuit breaker of the first branch is extinguished when the current crosses zero. The first branch circuit is a rapid vacuum circuit breaker, which adopts an electromagnetic repulsion mechanism to realize high-speed breaking and adopts a vacuum arc extinguish chamber to break high-frequency current.

The vacuum arc-extinguishing chamber is the vacuum arc-extinguishing chamber which is always used when power frequency current is cut off at present. The commonly used vacuum arc-extinguishing chamber adopts longitudinal magnetic or transverse magnetic contacts to improve the breaking capacity of the vacuum arc-extinguishing chamber. Fig. 2a \2b shows a coil type longitudinal magnetic contact structure, which can generate a strong longitudinal magnetic field to restrict the diffusion of electrons when the power frequency current is cut off, so as to generate a magnetic mirror effect, thereby reducing the arc voltage, reducing the energy of the arc during arcing, and enabling the arc to be extinguished more easily when the arc current passes through zero. Fig. 3 shows the magnetic field distribution along the axis of such a coil-type longitudinal magnetic contact at various frequencies. Therefore, the magnetic field generated by the coil type longitudinal magnetic contact which can generate a very strong magnetic field originally under high frequency is very small and almost zero. However, the frequency of the high-frequency current to be cut off of the high-voltage vacuum arc-extinguishing chamber of the mechanical high-voltage direct-current circuit breaker is 1kHz-10kHz, 3.8kHz is commonly used, and in order to solve the problem that the contact structure of the vacuum arc-extinguishing chamber can also generate a longitudinal magnetic field under the frequency, the conventional method for improving the magnetic field is as follows: ferromagnetic materials are added into a cavity of the contact to strengthen a magnetic field, a coil is additionally wound on the vacuum gap to generate the magnetic field, and the contact piece is provided with a groove to reduce eddy current and reduce the eddy current influence. These particular methods have been calculated to be ineffective at high frequencies, which are 3.8kHz, and which produce substantially zero magnetic field in the gap of the coiled longitudinal magnetic contact structure shown in figure 2.

Disclosure of Invention

The invention provides a double-coil type contact structure of a vacuum arc-extinguishing chamber in a mechanical high-voltage direct-current circuit breaker, aiming at the problem that the magnetic field of the vacuum arc-extinguishing chamber is difficult to improve under high frequency in the prior art, so that the contact structure can generate a large magnetic field under the high-frequency condition, and the magnetic field can well help to extinguish vacuum electric arc generated by high-frequency current.

The technical scheme of the invention is as follows: a double-coil contact structure of a vacuum arc extinguish chamber in a mechanical high-voltage direct-current circuit breaker is composed of two identical contact structures, wherein each contact structure comprises an unsealed annular coil, an insulating annular gasket and a slotted annular contact, a conducting rod is a T-shaped cylindrical rod, the diameter of the large-head circular surface of the conducting rod is equal to the outer diameters of the annular coil and the annular contact, metal bulges are arranged on the large-head circular surface of the conducting rod and the annular coil respectively, the large-head circular surface of the conducting rod, the annular coil and the annular contact are sequentially overlapped and connected, except for the bulge parts, the rest parts of the two connecting surfaces are all supported by insulating annular gaskets made of polytetrafluoroethylene or insulating materials with higher strength, the metal bulges enable the conducting rod, the annular coil and the annular contact to be electrically connected, electric arcs are generated between the two contacts when the contacts are separated, and the electric arcs are distributed on the whole annular surface of the annular contact, after flowing for a circle along the annular coil, the current flows into the annular contact along the connecting conductor, and a longitudinal magnetic field is generated between the contacts when the current flows along the annular coil.

The invention has the beneficial effects that: the double-coil type contact structure of the vacuum arc extinguish chamber in the mechanical high-voltage direct current circuit breaker has the advantages that the contact structure directly generates a large longitudinal magnetic field and is not easy to be extruded and deformed, the structure is simple, raw materials are saved, the electrical service life of the contact is longer, electric arcs are lengthened when the electric arcs are pulled into the coil, and the electric arcs are easier to extinguish.

Drawings

Fig. 1 is a working schematic diagram of a mechanical high voltage dc circuit breaker;

FIG. 2a is an exploded view of the coil type longitudinal magnetic contact structure;

FIG. 2b is a schematic view of a coil-type longitudinal magnetic contact;

FIG. 3 is a comparison of magnetic fields in the vacuum interrupter of the fast vacuum circuit breaker at high frequency and at power frequency;

fig. 4 is a perspective view of a structure of a double-coil contact of a vacuum arc-extinguishing chamber in the mechanical high-voltage direct-current circuit breaker of the present invention;

fig. 5 is a structural front view of a double-coil type contact of a vacuum arc extinguish chamber in the mechanical high-voltage direct current circuit breaker;

fig. 6 is a longitudinal magnetic field diagram generated in the contact gap under different opening distances when the same current is switched on and off in the vacuum arc-extinguishing chamber.

Detailed Description

The structure of the double-coil type contact of the vacuum arc-extinguishing chamber in the mechanical high-voltage direct-current circuit breaker is shown in fig. 4 and 5. Consists of two identical contacts, each of which comprises a non-closed annular coil, an insulating annular gasket and a slotted annular contact. The conducting rod is a T-shaped cylindrical rod, the diameter of the big-end circular surface of the conducting rod is the same as the outer diameters of the annular coil and the annular contact, metal protrusions are arranged on the big-end circular surface of the conducting rod and on the annular coil, the big-end circular surface of the conducting rod, the annular coil and the annular contact are sequentially overlapped and connected, the other parts except the protruding part of the connecting surface are supported by insulating annular gaskets made of polytetrafluoroethylene or insulating materials with higher strength, the conducting rod, the annular coil and the annular contact are electrically connected through the metal protrusions, and the optimal positions of the metal protrusions are shown in figures 4 and 5.

The annular coil plane is connected with the annular contact through a conductor, the annular coil is connected with the large-head circular surface of the conducting rod through the conductor, and the rest part of the annular coil is supported by a high-strength insulating gasket plane. The ring contact is made of the CuCr contact material with good breaking performance at present, and the surface of the ring contact and the inner and outer surfaces of the cylinder are made of the CuCr material. The other parts except the metal connection at the connection part of the annular coil and the conducting rod are all supported by a high-strength insulating material plane. When the contacts are separated, an arc is generated between them, and the arc is distributed on the whole annular surface of the annular contact, so that the current flows into the annular contact along the connecting conductor after flowing along the annular coil for one circle. The eddy current effect is small due to the function of the slot on the circular contact, and the area of the coil covered by the circular contact is small, so that a longitudinal magnetic field is generated between the contacts when current flows along the circular coil, the longitudinal magnetic field is beneficial to extinguishing electric arcs, and the current breaking capacity of the contact structure is enhanced.

The contact structure of the invention is used in a vacuum arc-extinguishing chamber, and longitudinal magnetic fields generated in contact gaps under different opening distances when the same current is cut off are calculated, as shown in figure 6. It can be seen from fig. 6 that the magnetic field decreases with increasing distance. But the magnetic field is very large at the coil. This has a great advantage in extinguishing the arc. The contact is simple in structure. And because the insulating material with high strength is added as a gasket, the impact force generated by the contact in the closing process can not reduce or deform the gap between the coil and the enlarged movable conducting rod, the shape of the coil is easy to keep unchanged, the coil of the previously used coil type longitudinal magnetic field contact is not provided with the gasket, and the front of the coil is also provided with an integral contact blade. In addition, at high frequencies, such a configuration with a contact blade in front of the coil does not yet produce a longitudinal magnetic field. The contact structure of the invention directly generates a large longitudinal magnetic field and is not easy to be extruded and deformed, the structure is simple, raw materials are saved, and the electrical life of the contact is longer. Therefore, the double-coil contact structure has the advantages of few components and the effect that more components cannot be used.

Claims

1. A double-coil contact structure of a vacuum arc extinguish chamber in a mechanical high-voltage direct-current circuit breaker is characterized by comprising two completely same contact structures, wherein each contact structure comprises an unsealed annular coil, an insulating annular gasket and a circular contact with a gap, a conducting rod is a T-shaped cylindrical rod, the diameter of a large-head circular surface of the conducting rod is equal to the outer diameters of the annular coil and the circular contact, metal bulges are arranged on the large-head circular surface of the conducting rod and the annular coil, the large-head circular surface of the conducting rod, the annular coil and the circular contact are sequentially overlapped and connected, the rest parts of the two connecting surfaces except the bulge parts are all supported by insulating annular gaskets made of polytetrafluoroethylene or insulating materials with higher strength, the metal bulges enable the conducting rod, the annular coil and the circular contact to be electrically connected, and electric arcs are generated between the two contacts when the contacts are separated, the arc is distributed on the whole annular surface of the annular contact, so that current flows into the annular contact along the connecting conductor after flowing for a circle along the annular coil, and a longitudinal magnetic field is generated between the contacts when the current flows along the annular coil.