EP3182436A1

EP3182436A1 - Medium voltage circuit breaker for subsea applications

Info

Publication number: EP3182436A1
Application number: EP15201360.3A
Authority: EP
Inventors: Maik Hyrenbach; Christian Reuber
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2015-12-18
Filing date: 2015-12-18
Publication date: 2017-06-21

Abstract

The invention relates to a medium voltage circuit breaker for subsea applications, with a vacuum interrupter arranged inside a pressure housing, which is tight against environmental high pressure, and with a drive, in order to move a movable contact of the vacuum interrupter, relatively to a fixed contact of the vacuum interrupter, according to the preamble of claim 1.

In order to enhance the design of the vacuum circuit breaker arrangement in that way, that the arrangement is functionally safe under the aforesaid environment conditions, the invention is, that the magnetic drive is separated in two parts,wherein the first part with a mechanical link to the moved contact is arranged inside of the pole housing and a second part, consisting the coil or the coils is, or are arranged outside of the pole housing, and that the coil or the coils to control the magnetic drive, are as well arranged outside of the housing.

Description

The invention relates to a medium voltage circuit breaker for subsea applications, with a vacuum interrupter arranged inside a pressure housing, which is tight against environmental high pressure, and with a drive, in order to move a movable contact of the vacuum interrupter, relatively to a fixed contact of the vacuum interrupter, according to the preamble of claim 1.
One aspect of this invention relates to MV circuit breaker poles with vacuum interrupters operated directly by magnetic actuators operating in line with said vacuum interrupter.
Such constructions are known from EP 1843375 B1 and EP 2312606 B1 . Another aspect of this invention relates to dedicated switching poles for subsea application that can be used in oil at a pressure of up to 300 bar. A further know voltage circuit breaker arrangement is known from EP 1942514 A1 .
The disadvantage of the this design is, that a secondary connector through the insulating pole housing is required to control the magnetic actuator. These connectors are a technical risk for the pressure tightness of the housing and furthermore they are expensive. Inside of the housing, the pressure will be about 1 bar; this is also required for a reasonable operation of the vacuum interrupter.
Outside of the housing, there will be an insulating fluid, probably oil, at a pressure, that corresponds to the pressure of the surrounding water, e.g. at a depth of 3000 m the pressure will be about 300 bar. Oil and water will be separated by a tank with a pressure compensation device.
So it is the object of this invention, to enhance the design of the vacuum circuit breaker arrangement in that way, that the arrangement is functionally safe under the aforesaid environment conditions.
The main point of the invention is, that the magnetic drive is separated in two parts, wherein the first part with a mechanical link to the moved contact is arranged inside of the pole housing and a second part, consisting the coil or the coils is, or are arranged outside of the pole housing, and that the coil or the coils to control the magnetic drive, are as well arranged outside of the housing.
The one or more coils that are needed to control the magnetic drive are outside of the housing and therefore it would not be required to use a secondary connector to guide the coil wires through the housing.
In a further advantageous embodiment, that the coils and concerning magnetic yoke parts are positioned under a bottom lid of the housing.
In a further advantageous embodiment, the coils and concerning magnetic yoke parts are positioned sidely near to the bottom lid of the housing.
Furthermore, the yoke parts, arranged outside the housing, are fixed in a magnetic flux guiding connection to yoke parts inside the housing and that the flux guidance elements are pressuretightly sealed versus the housing.
In a further advantageous embodiment the yoke parts inside the housing consist of a pungler plate, coupled to a movable stem of the movable contact of the vacuum interrupter, and that the plunger plate is attracted by poles of the yoke parts inside the housing.
In a final advantageous embodiment, a ferromagnetic plate is arranged on the movable stem, in order to define the stroke of the drive and to lock the position with a relatively small force to avoid that the pressure inside the housing can close the vacuum interrupter, for an end stop.
Embodiments of the invention are shown in the drawing.

Figure 1:: cross section to a medium voltage circuit breaker with closed contacts.
Figure 2:: cross section to a medium voltage circuit breaker with opened contacts
Figure 3:: perspective view of a first positioning of the external coils
Figure 4:: perspective view of a second positioning of the external coils
Figure 5:: perspective view of a third positioning of the external coils
Figure 6:: Further details
Figure 7:: Further details
Figure 8:: Further details
Figure 9:: Further details

A possible embodiment is shown in figures 1, with status "pole is closed", and figure 2, with status "pole is open", as a cross-section.
The magnetic flux that is generated by the permanent magnet 15 is guided through the fixed ferromagnetic parts 14, 13 and 12 to the movable plunger 11. In the closed position, as shown in figure 1, the plunger 11 is strongly attracted by the magnetic flux and plunger 11 holds the movable contact 4 of the vacuum interrupter firmly pressed onto the fixed contact 3. Thereby, both the contact spring 8 and the opening spring 10 are compressed. No current in the coil(s) 16 is required to maintain this closed position.
In the position shown in Figure 1 the pole is closed, i.e. electrical current can flow through the terminals 5, 6, the flexible connector 7 and the vacuum interrupter 2, 3, 4.
When a current flows in the coil(s) 16 in the direction where its magnetic field is opposing, i.e. weakening, the magnetic field of the permanent magnet 15, the magnetic force that holds plunger 11 in its position will decrease until the forces of the compressed contact spring 8 and opening spring 10 are higher than the remaining magnetic force. Then the pole will open. Figure 2 shows this position. The movable parts 4, 8, 9, 11 and partly 10, will have an end stop 17 to define the stroke of the drive and to lock the position with a relatively small force to avoid that the pressure inside the pole housing can close the vacuum interrupter. Here, the end stop 17 is a thin ferromagnetic plate, that magnetically saturates to a certain degree, when it rests onto the poles 12.
The closing operation is initiated by an electrical current in the coil(s) 16 in the direction where its magnetic field is supporting, i.e. increasing, the magnetic field of the permanent magnet 15. As the OFF-plate 17 is already magnetically saturated to a certain degree, it will practically not obstruct the increase of the magnetic field between the poles 12 and the plunger 11. This magnetic field will attract the plunger 11 to the poles 12, the other movable parts 9, 8 and 4 will be pushed upwards until the movable contact 4 of the vacuum interrupter will hit the fixed contact 3, the closing spring 8 is compressed and the plunger 11 is attached at the poles 12. Now the pole is closed, and the current in the coil 12 can be switched off without changing the closed position of the pole.
The magnetic cross section of 14 and 15 can be different from the cross section of 12 and 13 to increase the flux density from the permanent magnet, which is in the region of 1 T, so that a higher holding force of plunger 11 to the poles 12 is obtained, as this force depends on the square of the magnetic flux density. This is certainly limited by the magnetic saturation of the iron, which is in the region of 2 T. For the same reason, the faces of pole 12 that are directed to the plunger 11 have a local reduction of the magnetic cross section, here realized by chamfers.
Figure 3 shows a perspective view of this first embodiment.
In a first step of manufacturing, the pole can be made with the ferromagnetic poles 12, but without the other external parts 13, 14, 15, 16 of the magnetic drive. These can be added later on, e.g. by screw connection with holes in 13 and internal threads in 12.
Terminals 5, 6 and the ferromagnetic poles 12 can have collars as shown in Figure 1 to enable the transfer of the outside pressure from 5, 6 and 12 to the pole housing 1 and to improve the sealing between 5, 6, 12 and 1. An alternative to these collars is a conical shape of 5, 6 and 12, in a way that the higher diameter is at the outside of the pole housing, according to the higher pressure there.
Other embodiments are shown in Fig. 4 to 9.
Fig. 4, 6 and 7 show a pole that is internally equivalent to the pole of the first embodiment. The external parts of the magnetic drive are however arranged not below but aside of the pole housing. In this embodiment, one coil 16 and two permanent magnets 15 are being used. For concentrating of the flux of the permanent magnets, in other words for being able to collect more flux from the permanent magnets, the magnetic cross section is increased in the region of the permanent magnets.
An arrangement like this can be advantageous depending on space constraints. For dielectric reasons it can be advantageous to arrange the lower electrical terminal 6 and the external parts of the magnetic drive at opposing sites of the pole housing (not shown).
Fig, 5, 8 and 9 show a switching pole where the magnetic poles are extending through the pole housing at the same side. Also here, the magnetic cross section in the area of the permanent magnet 15 is increased.
An arrangement like this can be advantageous depending on space constraints.

Numbering

1: Pole housing, electrically insulating and pressure tight, consisting e.g. of a cylinder and end caps
2: Vacuum interrupter housing
3: Upper contact of the vacuum interrupter (fixed)
4: Lower contact of the vacuum interrupter (movable)
5: Upper electrical terminal, goes through the pole housing 1 and connects the vacuum interrupter
6: Lower electrical terminal, goes through the pole housing 1 and connects 7
7: Flexible connector or sliding contact for electrical connection of vacuum interrupter and 6
8: Contact spring as well known in vacuum interrupter operation
9: Insulating pushrod
10: Opening spring; at its upper end it is fixed to the pole housing (fixation not shown)
11: Plunger of the magnetic drive, is magnetically attracted by the poles 12
12: Ferromagnetic pole that goes through the pole housing
13: Ferromagnetic yoke
14: Ferromagnetic yoke
15: Permanent magnet
16: Coil
17: Ferromagnetic OFF-plate

Claims

Medium voltage circuit breaker for subsea applications, with a vacuum interrupter arranged inside a pressure housing, which is tight against environmental high pressure, and with a drive, in order to move a movable contact of the vacuum interrupter, relatively to a fixed contact of the vacuum interrupter,
characterized in,
that the magnetic drive is separated in two parts,wherein the first part with a mechanical link to the moved contact is arranged inside of the pole housing and a second part, consisting the coil or the coils is, or are arranged outside of the pole housing, and that the coil or the coils to control the magnetic drive, are as well arranged outside of the housing.
Medium voltage circuit breaker, according to claim 1,
characterized in
that the coils and concerning magnetic yoke parts are positioned under a bottom lid of the housing.
Medium voltage circuit breaker, according to claim 1,
characterized in
that the coils and concerning magnetic yoke parts are positioned sidely near to the bottom lid of the housing.
Medium voltage circuit breaker, according to claim 1,
characterized in
that yoke parts, arranged outside the housing, are fixed in a magnetic flux guiding connection to yoke parts inside the housing and that the flux guidance elements are pressuretightly sealed versus the housing.
Medium voltage circuit breaker, according to claim 4,
characterized in
that the yoke parts inside the housing consist of a pungler plate, coupled to a movable stem of the movable contact of the vacuum interrupter, and that the plunger plate is attracted by poles of the yoke parts inside the housing.
Medium voltage circuit breaker, according to one of the aforesaid claims,
characterized in
that a a ferromagnetic plate (17) is arranged on the movable stem, in order to define the stroke of the drive and to lock the position with a relatively small force to avoid that the pressure inside the housing can close the vacuum interrupter, for an end stop.