EP3155627A1

EP3155627A1 - Interrupter driven resistor switch assembly

Info

Publication number: EP3155627A1
Application number: EP15736598.2A
Authority: EP
Inventors: Walter Holaus; Kalpesh Chauhan; Rosy RAYSAHA; Bhavesh ACHARYA
Original assignee: ABB Schweiz AG
Current assignee: Hitachi Energy Switzerland AG
Priority date: 2014-06-13
Filing date: 2015-04-27
Publication date: 2017-04-19
Anticipated expiration: 2035-04-27
Also published as: KR20160140977A; WO2015189719A1; CN106575584A; CN106575584B; KR101911611B1; EP3155627B1

Abstract

The present invention relates to an interrupter driven resistor switch assembly comprising an interrupter, a slider, a lever and link arrangement, a switch and a closing resistor. The slider is connected with the interrupter such that an interrupter rod is arranged to drive the slider along a first axis and the slider is arranged to drive an interrupter arcing contact along a second axis parallel to the first axis. The lever and link arrangement comprises at least one lever mechanically coupled with the movement of the slider and at least one link mechanically coupled with the movement of the at least one lever. The switch comprises a movable contact and a fixed contact, wherein the movable contact is arranged to move proportionally in response to movement of the slider to engage with the fixed contact for one of electrically connecting and disconnecting the closing resistor.

Description

INTERRUPTER DRIVEN RESISTOR SWITCH ASSEMBLY

FIELD OF THE INVENTION

The invention relates to the field of electrical power distribution. More specifically, the invention relates to a metallic circuit breaker housing a series resistor switch driven by a driving mechanism of the interrupter inside the metallic circuit breaker.

BACKGROUND OF THE INVENTION

High voltage circuit breakers are commonly provided with a closing resistor to suppress overvoltages on operation of the high voltage circuit breaker. A closing resistor and switch can be arranged electrically in parallel with the main contacts of the circuit breaker - or the closing resistor is connected in series with the main contacts of the circuit breaker but parallel to the switch. In the former configuration, the closing resistor is connected into the circuit shortly before the closing/opening of the contact arrangement of the interrupter unit in the circuit breaker such that the current flows through the closing resistor shortly before the main current path is closed. In the latter configuration, the closing resistor can be provided in parallel to a switch and the switch is arranged in series to the interrupter unit. In such series configuration, the interrupter unit will close/open before the resistor switch of the circuit breaker. The switch for insertion of the closing resistor is being referred herein as Pre- Insertion Resistor (PIR) switch. The use of closing resistor with suitable mechanisms to drive the closing resistors during operation of the circuit breaker is well known in the art. Exemplary disclosures are made in the US patent no. 4499350 and US patent no. 8426760. These patents describe the need of a closing resistor and also the mechanisms to insert them during operation of the circuit breaker.

In view of demand for more compact circuit breakers which also includes PIR, there is a need to develop new interrupters and PIR switches, which are compact having efficient operating mechanisms for closing resistors also. This supports having gas insulated substations (GIS) without any change in the GIS bay layout. Therefore, the assembly of PIR switch within the circuit breaker and its operation is being improved upon in the present invention. SUMMARY OF THE INVENTION

Various aspects of the invention provide one or more of the following features:

• Special design technique adopted from both mechanical and electrical point of view, which provides a significant increment in the physical clearance between the tank and the end shield, reducing dielectric stresses.

• The exhaust volume inside the mechanism is significantly increased for better cooling of the arc.

• The shield around the mechanism housing is split for ensuring better shielding to the mechanism housing with ease of assembly of the interrupter sub-assembly to the resistor switch sub-assembly.

• The input for the resistor switch mechanism is taken directly from the main interrupter (via an interrupter rod) leading to a complete linear motion (does not involve any rotational to linear motion conversion) with opening operation being governed by the spring compression force which got stored during the closing operation.

• Special design technique adopted for mechanism housing to provide support and shielding to PIR retaining plate and spacer plate, as well as, significantly increasing the dielectric gap between end shield and tank making the PIR more compact.

• Arcing pin has been made moving contact to reduce moving mass in the PIR.

A circuit breaker is provided. The circuit breaker can be a gas insulated high voltage circuit breaker. However, the invention need not be limited to gas insulated high voltage circuit breakers.

In accordance with an aspect of the invention, an interrupter driven resistor switch assembly is provided. The interrupter driven resistor switch assembly comprises an interrupter, a slider, a lever and link arrangement, a switch and a closing resistor. The slider can be a substantially hollow cylindrical member that can slide over a fixed subtantially cylindrical member. In accordance with the aspect, the slider is connected with the interrupter such that an interrupter rod is arranged to drive the slider along a first axis. This connection enables the slider to operate during opening and closing of the interrupter as per the movement of the interrupter rod.

The slider is connected with an interrupter arcing contact. The interrupter arcing contact can be an interrupter arcing pin. The connection between the slider and the interrupter arcing contact can be made using one or more links. In one embodiment, the slider is connected with the interrupter arcing contact using three links. The connection between the slider and the interrupter arcing contact is such that the slider can drive the interrupter arcing contact in a second axis, which is parallel to the first axis. Further, the connection can be such that the direction of movement of the interrupter arcing contact is opposite to the direction of movement of the slider.

In addition, the slider is connected with the lever and link arrangement. The lever and link arrangement comprises at least one lever (e.g. 1, 2, 3 etc.) and at least one link (e.g. 1 , 2, 3 etc.). The at least one lever is mechanically coupled with the movement of the slider. In an embodiment, the at least one lever is mechanically coupled with the slider using a pair of rollers, wherein the pair of rollers is arranged symmetrically about the slider such that a translational motion of the slider along the first axis causes the pair of rollers to come in contact with and move the at least one lever.

In one embodiment, the lever and link arrangement comprises two lever arms, wherein each lever arm comprises a lever and a link. Further, the lever is pivoted at one end, thereby enabling the lever to rotate about the end when the slider moves it. The at least one link is mechanically coupled with the movement of the at least one lever. In one embodiment, the at least one link is attached to a portion of the at least one lever. This enables the translational motion of the slider to be transmitted to the at least one link with a desired delay.

The switch comprises a movable contact connected at an end of the at least one link . The switch also comprises a fixed contact arranged to engage with the movable contact for one of electrically connecting and disconnecting the closing resistor. The movable contact is arranged to move proportionally in response to movement of the slider as a result of the connection between the movable contact and the at least one link. In one embodiment, the movable contact is connected with a guide tube using a spring such that the spring assists in one of electrically disconnecting the closing resistor. In an embodiment, the movable contact comprises an arcing pin and is connected such that the ratio of movement of the interrupter : movement of the movable contact is about 1 : 1.36.

In an embodiment, the closing resistor comprises two adjacent resistor stacks, wherein the resistors of the two resistor stacks are connected electrically in series. In accordance with the embodiment, the interrupter driven resistor switch assembly also comprises at least two electric shields, wherein each of the two electric shields is arranged to shield a corresponding end of the closing resistor. In an aspect of the invention, a method of operating the interrupter driven resistor switch assembly is provided. The method comprises causing the interrupter rod to drive the slider along the first axis in response to occurrence of an interrupter operating condition. The method further comprises driving the interrupter arcing contact in a direction opposite to slider movement along the second axis that is parallel to the first axis. In addition, the method comprises driving at least one lever of the lever and link arrangement that is mechanically coupled with the movement of the slider. Moreover, the method comprises proportionally moving the movable contact of the switch to engage the movable contact with the fixed contact for one of electrically connecting and disconnecting the closing resistor.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings, in which:

Fig. 1 illustrates a sectional view of a circuit breaker and a circuit diagram thereof;

Fig. 2 illustrates a sectional front view and a sectional top view of the circuit breaker; Fig. 3 illustrates a closed state of a switch of the circuit breaker;

Fig. 4 illustrates an arrangement of resistors of a closing resistor of the circuit breaker; and

Fig. 5 illustrates a front view of the circuit breaker.

The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures. DETAILED DESCRIPTION

Figure 1 shows a resistor switch 11 (hereafter referred to interchangeably as PIR switch, resistor switch 11, series switch, series resistor switch or simply the switch) which is connected in parallel to a closing resistor 12 that needs to be housed inside a highly compact circuit breaker tank 13. The resistor switch arrangement is provided in series with an interrupter 14 (hereafter referred to interchangeably as main interrupter or interrupter 14). In the series PIR configuration, the breaker (interrupter 14) always operates before resistor switch 11 i.e. during the closing operation, the breaker will close before the closing of resistor switch 11 and in the opening operation, the breaker will open before the opening of resistor switch 11. One of the objectives of the invention is to efficiently operate the mechanism for closing and opening of the breaker and resistor switch 1 1. It will be apparent that the resistor switch arrangement can also be provided in parallel with interrupter 14. Exemplary prior-art methods for operating breaker and resistor switch include providing separate additional mechanisms, and providing mechanical linkage between the breaker and the resistor switch with insulating rods. Such mechanical linkages can be electrically unstable due to small space availability and also mechanically more complicated adding to the cost since it involves more components. As mentioned earlier, introduction of a series switch in a circuit breaker can be complicated because of space consideration as it involves efficient mechanical arrangements to operate the breaker and resistor switch mechanisms in a particular order within a specified time and also be efficient electrically with good insulation margins. Often, such designs require a bigger tank diameter and length, which in turn led to a change in GIS bay layout and footprint adding to the cost.

In this invention, the input for the PIR mechanism is taken from an interrupter rod (not shown in figures) of the main interrupter 14 (breaker) and hence, the motion is linear i.e., does not involve any rotational to linear motion conversion. This eliminated the need of any separate PIR mechanism leading to significant reduction in cost and space.

The interrupter rod is connected with a slider 143 such that the interrupter rod can drive slider 143. Accordingly, slider 143 moves along a first axis 25 as per the movement of the interrupter rod during opening/closing of the interrupter. Slider 143 can be in the shape of a substantially hollow cylinder such that it can slide over a substantially cylindrical member 146.

Slider 143 is connected with an interrupter arcing contact 141 via at least two links such that slider 143 can drive interrupter arcing contact 141 along a second axis 26, wherein second axis 26 is parallel to first axis 25. Interrupter arcing contact 141 can be an interrupter arcing pin. The connection between slider 143 and interrupter arcing contact 141 can be established using two or more links such that the direction of movement of interrupter arcing contact 141 is opposite to the direction of movement of slider 143. For example, when slider 143 moves towards right along first axis 25, then it drives interrupter arcing contact 141 in the left direction aloing second axis 26. In an embodiment, the connection between slider 143 and interrupter arcing contact 141 is established using three links as shown in Fig. 2 and Fig. 3. It will be apparent that there may be desired delays while transferring motion from slider 143 to interrupter arcing contact 141.

Slider 143 is also connected with a lever and link arrangement. Referring to Figure 2, in an embodiment of the new PIR mechanism, the lever and link arrangement comprises two levers (19, 19'), symmetrically arranged, which are used as cam to provide the required delay in operation. Each lever is connected to its respective links (20, 20') at a point (21) to transfer motion from the lever to moving contact 144 of resistor switch 11 , which in this case is arcing pin 15.

At the other end, the levers are connected to slider 143 through a pair of rollers (22, 22'), which are symmetrically arranged about slider 143. The pair of rollers are arranged such that when slider 143 is driven by the interrupter rod of the interrupter (14), the pair of rollers come in contact with and push the lever (19, 19'). In other words, the rollers are physically separated from the lever in the begining and push the levers later as a result of the transaltional motion of slider 143. The levers are held in their position with the help of a sleeve (not shown in Fig. 2), which slides over a pin (not shown in Fig. 2). Each pair of lever, link and the corresponding connections forms a levering arm of the lever arrangement.

The lever and link arrangement enables movable contact 144 of the switch to move propotionally in response to movement of the interrupter. The ratio of interrupter to movable contact movement is about 1 : 1.36. This is achieved by appropriately connecting the lever and links. It is possible to introduce a different delay by appropriately designing lever and link and their connection.

A part of the new PIR mechanism concept is adopted from the "Offset center slider crank mechanism" wherein the slider crank mechanism crank has 360° of rotation for a single stroke. In the new PIR mechanism, the lever considered as a crank, pivoted at one end (23) rotates by only 120° both back and forth. The pivoting center of the lever is provided with an offset from the axis of moving contact.

In order to reduce moving mass in the PIR mechanism, an arcing pin 15 is made as part of a moving contact 144 of resistor switch 11 and a tulip contact 16 is made part of a fixed contact 145 of resistor switch 11. It would be apparent that this arrangement is helpful for reducing the input energy, as well as, the reaction force on slider 143. Alternatively, the tulip contact can be made as part of the moving contact while the arcing pin is made part of the fixed contact. A guide tube 147 of the PIR mechanism is designed to have multiple cross-sectional areas such that the specified nominal current can flow through it and can also provide mechanical support to an adapter and a contact ring 18. Contact ring 18 is threaded to guide tube 147 and is provided with two tightening holes for the same. The adapter provides support to the main nozzle and also to arcing pin 15, which is bolted to it.

Figure 3 illustrates the closing position of resistor switch 11. The closing operation is achieved by combination of levers and linkages of the PIR mechanism, which helps to achieve a mechanical insertion time of about 5 millisecond (ms). While closing, the initial velocity of moving contact 144 of resistor switch 11 is very slow up to its 40 % of travel and then it gradually increases when the lever moves towards its pivoting point. Slider 143 will push the roller (22, 22') on the straight profile of lever (19, 19'), which will push the link (20, 20') attached to guide tube 147 and this in turn will move arcing pin 15 towards a part of fixed contact 145, which is arcing tulip contact 16 in this case.

Spring (24) comes into play during opening and has been designed in such a way that it can open the contact in a time between about 67 to 100 ms. For this, the spring constant has been accordingly calculated.

A damping ring (attenuation disc) is provided at the other end of the guide tube to provide damping during opening operation. While opening, the lever is disconnected from slider 143 and due to the energy stored in compression spring during closing, spring will push guide tube 147, which in turn will move arcing pin 15 away from tulip contact 16. In complete open position, there will be some physical distance between the lever and slider 143 since the damping ring will stop guide tube 147 thus preventing impact force on slider 143.

Thus the motion from the main interrupter (14) is transferred to the switch (11) using offset center slider crank mechanism. It is not necessary that the slider and switch are coaxial. The lever and link arrangement is designed to appropriately move the movable contact of the switch along its axis (whether coaxial or not).

The new PIR design comprises of the series resistor switch (11) housed inside the compact circuit breaker chamber (13) and driven by the interrupter rod of the main interrupter (14). In one implementation, closing resistor 12 comprises of total 50 resistor discs (27) with 25 discs per stack wherein the stacks are electrically connected in series and mechanically arranged in parallel. A starting point of the new PIR design was to significantly reduce the number of resistor discs without comprising on its performance, which was very crucial for the series resistor switch to be completely housed inside the compact circuit breaker tank, as well as, to provide sufficient dielectric gap. The total number of discs has been arrived from the energy calculation that is governed by two most important factors, which are energy rating of the disc and the electrical insertion time. More the energy rating of the disc and lower the electrical insertion time, lesser will be the number of discs required. The mechanical insertion time is an important parameter for the PIR mechanism design and it is determined from electrical insertion time, which has been accordingly calculated using interrupter switch and PIR switch design.

The series resistor switch has been designed to withstand both phase opposition condition during complete open position and also Basic Impulse level (BIL) case during close condition. From the phase opposition case calculations, it was found the optimum contact gap between arcing pin 15 and tulip contact 16 can be set to about 80 mm with PIR stroke set accordingly, leading to compactness of the PIR mechanism.

Also, the resistors discs (27) have been arranged in a zig-zag fashion, as shown in Figure

4, with series connection achieved by copper contact jumpers (28), to get approximately zero voltage at the central discs of both the stacks. This arrangement was very crucial for the compactness of the PIR. Also, it was important to achieve low dielectric stress on the shield of moving contact support and the shield of fixed contact support, as well as, on contact ring during phase opposition condition through an iterative process of varying the horizontal inter-axial distance between the resistor stacks and the vertical inter-axial distance between the resistor stack and switch and also the component design. As shown in Figure 4, the space between two resistor discs in a stack is filled by one PTFE spacer (29) for electrical insulation and two contact jumpers (28), each for electrical connectivity to the previous and ahead resistor disc respectively. Each resistor stack contains a retaining plate (30), which distributes the spring force evenly and a spacer plate (31) for distance adjustment. The horizontal inter-axial distance between the resistor stacks and the vertical inter-axial distance between the resistor stack and switch was determined for the optimum design.

As the resistor switch assembly is generally not concentric with the tank, special design techniques had to be adopted from both mechanical and electrical point of view. Refer Figure

5, the base (32) of the exhaust or mechanism housing has been designed to provide support and shielding to the resistor stack. This has led to an additional significant increase in the physical clearance between tank (not shown in the figure) and end shield (33), which has drastically reduced the dielectric stress on the end shield for the BIL test case. The exhaust volume inside the new mechanism housing is also increased leading to a better cooling of the arc. The mechanism housing is connected to the moving contact support through bolts, which are provided at the base of the mechanism housing. This is advantageous to reduce the dielectric stress on the top portion of the mechanism housing.

The split shield (35) not only provides shielding to the mechanism housing but also provides ease of assembly of the complete breaker sub-assembly to the resistor switch subassembly. Also, the design of mechanism housing shield (36) provides sufficient path for exhaust gas flow.

In operation, the interrupter operates according to an interrupter operating condition. The method of operating the circuit breaker can include various interrupter operating conditions such as, but not limited to, manual interruption and automatic interruption as a response to a faulty current. The method comprises causing the interrupter rod of the interrupter to drive slider 143 along first axis 25 in response to occurrence of an interrupter operating condition. The method further comprises moving interrupter arcing contact 141 along second axis 26 by slider 143. Further, the direction of movement of interrupter arcing contact 141 is opposite to the direction of movement of slider 143. Furthermore, the method comprises moving the lever and link arrangement in response to movement of slider 143. In addition, the method comprises proportionally moving movable contact 144 of swtich 11 in response to movement of slider 143 to engage movable contact 144 with fixed contact 145 for one of electrically connecting and disconnecting closing resistor 12.

Claims

We claim:

An interrupter driven resistor switch assembly comprising:

an interrupter (14);

a slider (143) connected with the interrupter such that an interrupter rod is arranged to drive the slider over a substantially cylindrical member (146) along a first axis (25);

a lever and link arrangement comprising at least one lever (19) and at least one link (20), wherein the at least one lever is mechanically coupled with the movement of the slider and the at least one link is mechanically coupled with the movement of the at least one lever;

a closing resistor (12); and

a switch (11) comprising:

a movable contact (144) connected at an end of the at least one link such that the movable contact is arranged to move proportionally in response to movement of the slider; and

a fixed contact (145) arranged to engage with the movable contact for one of electrically connecting and disconnecting the closing resistor.

The interrupter driven resistor switch assembly as claimed in claim 1, wherein slider is connected with an interrupter arcing contact (141) using at least one link (142) such that the slider is arranged to drive the interrupter arcing contact along a second axis (26) parallel to the first axis, wherein the direction of movement of the interrupter arcing contact is opposite to the direction of movement of the slider.

The interrupter driven resistor switch assembly as claimed in claim 1 , wherein the at least one lever is mechanically coupled with the slider using a pair of rollers (22,

22'), wherein the pair of rollers is arranged symmetrically about the slider such that a translational motion of the slider along the first axis causes the pair of rollers to come in contact with and move the at least one lever.

4. The interrupter driven resistor assembly as claimed in claim 1 , wherein the at least one lever is pivoted at one end (23) and the at least one link is attached to a portion (21) of the at least one lever.

5. The interrupter driven resistor switch assembly as claimed in claim 1 , wherein the lever and link arrangement comprises two identical lever arms, wherein each of the two identical lever arms comprises a lever (19, 19') and a link (20, 20'). 6. The interrupter driven resistor switch assembly as claimed in claim 1 , wherein the movable contact is connected with a guide tube (147) using a spring (24) such that the spring assists in electrically disconnecting the closing resistor.

The interrupter driven resistor switch assembly as claimed in claim 1 , wherein the movable contact comprises an arcing pin (15) and is connected such that the ratio of movement of the interrupter : movement of the movable contact is about 1 : 1.36.

The interrupter driven resistor switch assembly as claimed in claim 1 , wherein the closing resistor comprises two adjacent resistor stacks, wherein the resistors of the two resistor stacks are connected electrically in series.

The interrupter driven resistor switch assembly as claimed in claim 8 further comprising at least two electric shields, wherein each of the two electric shields arranged to shield corresponding end of the closing resistor.

10. A method of operating an interrupter driven resistor switch assembly comprising causing an interrupter rod of an interrupter (14) to drive a slider (143) connected with the interrupter rod along a first axis (25) upon occurrence of an interrupter operating condition;

driving an interrupter arcing contact (141) connected with the slider in a second axis (26) parallel to the first axis; driving at least one lever (19) of a lever and link arrangement mechanically coupled with the movement of the slider; and

proportionally moving a movable contact (144) connected at an end of the link and lever arrangement to engage the movable contact with a fixed contact (145) for one of electrically connecting and disconnecting a closing resistor, wherein the movable contact and the fixed contact are components of a switch of the interrupter driven resistor switch assembly.