Regulation 3. AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (ORIGINAL) Name of Applicant: Noja Power Switchgear Pty Ltd Actual Inventors: Dr Brett Watson Address for Service: DAVIES COLLISON CAVE, Patent Attorneys, Level 3, 303 Coronation Drive, Milton 4064, Queensland. Invention Title: "Electrical insulating system" Details of Associated Provisional Application(s) No(s): Australian Provisional Patent Application No. 2008901445, filed on 26 March 2008 The following statement is a full description of this invention, including the best method of performing it known to us: Q:\oper\nS\2009\nmrch\4032242 noja AU It PO lodging complete 11032009.doc - 10/3/09 -2 ELECTRICAL INSULATING SYSTEM Background of the Invention The present invention relates to an electrical switching apparatus, and in particular to an electrical switching apparatus including an insulating system. Description of the Prior Art The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. Reclosers have been in use world wide for more than 30 years. Reclosers are medium voltage circuit breakers used in medium voltage applications, such as on overhead power lines and substation applications, which typically operate at between 10-38kV. Reclosers operate to detect over current faults on a line, and then break the current path, to thereby interrupt power supplies. After the over current has passed, the recloser closes again automatically, thereby restoring the current path. This operation is typically performed up to four times, to allow transient faults such as lightning strikes, to be interrupted, thereby preventing damage to the power lines and equipment coupled thereto. Typically the fault is interrupted within 200 milliseconds and 0 supply is restored within 500 milliseconds to several seconds. The protection characteristics can be programmed by the user and today are all based on microprocessor based electronic controls. EP-A-1,017,142 describes a vacuum switch having its contacts in the shape of current inputs as well as transmission-type transformers connected to said current inputs. The components 5 are all coated with a polymeric isolation material which is covered by a metallic protection casing attached to the isolation of the current inputs. All conductive parts are isolated so that a loss in the casing tightness has no incidence on the operation capacity of the apparatus. The -- - - - -3 current inputs are connected to isolated conductors by collet clamps and protected by an atmosphere-resistant resin-based isolation. The lower part of the casing is made of an atmosphere-resistant semi-unbreakable glass of the Lexan type so that the position indicator of the switch remains clearly visible and that the operation of the vacuum switch can be visually monitored. One issue with such vacuum switches is that a high potential difference exists within the equipment, meaning it is generally necessary for grounded elements, such as actuators or the like, to be insulated from the high voltage elements, such as the terminals. However, any breakdown of insulation can cause a short circuit, leading to vacuum switch failure. A number of different mechanisms have been used in an attempt to provide suitable insulation. The most basic mechanism is to provide a sufficiently long distance between the high voltage elements and any portions of the vacuum switch at ground potential. However, this leads to a large increase in volume for the vacuum switch which is not practical in many situations. The use of solid insulating dielectrics has been proposed but this in turn leads to difficulties in providing a suitable actuation system. Summary of the Present Invention It is an object of the present invention to substantially overcome, or at least ameliorate, one or more disadvantages of existing arrangements. In a first broad form the present invention provides an electrical switching apparatus o including: a) a housing; b) a switch provided in the housing for selectively switching electrical connections; c) an actuator for actuating the switch; d) an insulating movable member for coupling the actuator to the switch; and, 5 e) at least one flexible insulating element coupled to the moveable member and the housing. Typically the flexible insulating element is for electrically isolating the actuator from at least one of: -4 a) terminals; and, b) the switch. Typically the switch includes: a) a first arm electrically coupled to a first terminal; and, b) a second arm electrically coupled to a second terminal, the first and second arms being relatively movable between a closed position in which the first and second arms are in contact, and an open position in which the first and second arms are not in contact. Typically the switch includes a resilient member for biasing the first and second arms into the open position. Typically the resilient member is a spring. Typically the actuator urges the arms into the closed position against the biasing of the resilient member. Typically the movable member is a push rod. Typically apparatus includes at least two flexible insulating elements. Typically each flexible insulating element is formed from rubber. Typically each flexible insulating element has a substantially annular shape. Typically the housing has a substantially cylindrical shaped portion defining a housing axis, the movable member being positioned substantially on the axis, with each flexible insulating 0 element extending from the movable member to the housing. Typically each flexible insulating element is configured to allow movement of the movable member. Typically the housing is a polymer housing. Typically the switch is a vacuum interrupter.
-5 Typically the actuator is a magnetic actuator. Typically the actuator is electrically connected to ground. Typically the housing is mounted to a support in use. Typically the support is a support pole for supporting the housing above ground level. Typically the apparatus includes at least two terminals extending from the housing for connecting to electrical power lines, the switch being for selectively interconnecting the terminals. Typically the electrical switching apparatus is used in medium voltage applications. Brief Description of the Drawings An example of the present invention will now be described with reference to the accompanying drawings, in which: Figure IA shows a schematic perspective view of an example of a switching apparatus; Figure 1 B shows a schematic plan view of the switching apparatus of Figure IA; Figure 2 shows a schematic cross sectional view of the switching apparatus of Figure IA; Figure 3A shows a schematic cross sectional view of the insulating members of the switching apparatus of Figure IA; and, Figures 3B and 3C shows schematic cross sectional views of the insulating members with the push rod in different positions. Detailed Description of the Preferred Embodiments 0 An example of a switching apparatus, such as a recloser, will now be described with reference to Figures IA and lB. In this example, the switching apparatus 100 is coupled to a support pole 101 via a bracket 102. The support pole 101 is used to support electrical distribution lines shown generally at 110, 111 which are electrically isolated from the support pole 101 by insulating elements 112.
-6 The switching apparatus 100 includes terminals 120, 121 which are connected to the power lines 110, 111 via respective connections 122, 123. In use the switching apparatus 100 can selectively interconnect the terminals 120, 121, which in turn interconnect the distribution lines 110, 111 to allow transmission of electricity. In use, the switching apparatus may be coupled to a controller 130 via a connection 131 allowing operation of the switching apparatus to be controlled and/or to allow information regarding the operation of the switching apparatus 100 to be displayed. Control of the switching apparatus may be performed automatically, and/or in accordance with input commands from an operator. For example, under normal operation the switching apparatus will operate automatically to disconnect the distribution lines 110, 111 should a fault arise, and acting to reconnect the distribution lines 110, 111 once the fault has been corrected. However, additionally or alternatively, an operator may provide input commands via the controller 130, allowing operation of the switching apparatus 100 to be manually controlled. The switching apparatus 100 and the controller 130 are typically connected to ground via connection 132 as shown. One example of the switching apparatus is shown in more detail in Figure 2. In this example, the switching apparatus is formed from a tank 200, containing a housing 210, which is typically formed from an insulating material such as a polymer. The housing includes bushings 211, 212 having terminals 220, 221 mounted therein, and a switch 222, 0 which in one example is a vacuum interrupter, for selectively interconnecting the terminals 220, 221. In one example, the switch 222 includes a first arm 223 electrically coupled to the terminal 220 and a second arm 224 electrically coupled to the terminal 221, via an electrical connector 227. The arm 224 is biased in the direction of arrow 230 via a resilient member, such as a 5 biasing spring 225. The arm 224 is also physically coupled via a push connector 226 to an insulating movable member, such as a push rod 228, which is in turn coupled to an actuator 229, such as a magnetic actuator.
-7 In use, the actuator 229 selectively urges the push rod 228 in a direction opposite to the arrow 230, which in turn urges the arms 223, 224 into a closed position against the biasing action of the spring 225. In the closed position the arms 223, 224 are in contact, and as a result, the terminals 220, 221 are electrically interconnected. If the actuator 229 is opened, the spring 225 urges the arm 224 in the direction of arrow 230, thereby moving the arms 223, 224 to an open position in which the arms 223, 224 are not in contact, which in turn disconnects the terminals 220, 221. Operation of the actuator can be controlled using suitable control electronics, provided for example, in the controller 130. It will be appreciated that the controller 130 can be connected to suitable sensors, such as current and/or voltage sensors (not shown), which allow faults to be detected, and hence the switch 222 to be controlled. An example of an insulating system for isolating the actuator from high voltage components will now be described with reference to Figures 3A to 3C. In this example, the insulating system includes at least one flexible insulating element 300 coupled to the polymer housing 210 and the push rod 228. It is possible to provide multiple flexible insulating elements, and a second flexible element is shown at 310, for the purpose of illustration. The flexible insulating elements are typically formed from an electrically non-conductive material that provides a high degree of insulation between the high voltage elements such as o the terminal 221 and the grounded elements, such as the actuator 229. This can include any suitable material such as rubber or the like. In this regard, the term rubber is understood to encompass natural rubber as well as artificial rubber like compounds such as silicone rubber, or the like. By using a flexible insulating element, this allows the push rod 228 to move, with the 5 movement being accommodated by suitable flexure and/or deformation of the insulating element, as shown in Figures 3B and 3C. This allows the flexible insulating element 300 to be sealed to both the housing 210 and the push rod 228, which in turn vastly increases the -8 reliability of the insulating properties and ensures that the required degree of insulation is maintained as the push rod 220 moves. In one example, the flexible insulating members 300, 310 have a generally annular shape. This allows the flexible insulating members 300, 310 to be positioned on the push rod using a stretch fit that maintains the electrical insulating properties at the interface between the push rod 228 and the respective member 300, 310. Similarly, the flexible insulating members 300 can be coupled to the housing 210 using a compression fit, which again maintains the electrical insulating properties at the interface between the housing 210 and the members 300, 310. Additionally, by using flexible insulating members, this allows pressure variations between different portions of the system and in particular different pressures within the polymer housing 210 to be accommodated through movement or deformation of the flexible insulating elements. It will be appreciated by the use of multiple flexible insulating elements has a number of advantages. For example, the use of multiple members vastly increases the insulating properties between the low potential and high potential areas within the recloser. The reason for this is that the breakdown mechanism must now ionize gas in each of the regions between the flexible insulating members, as well as breaching the flexible insulating members themselves. In one 0 example, the use of two insulating elements increases the insulating ability to allow peak impulse voltages of up to 210 kV to be used instead of 150 kV, as would be provided by a single flexible insulating member. It will be appreciated that the use of more than two insulating elements can also further increase the insulating ability. A further benefit of these multiple insulating elements is that if one of the elements fails for 5 example due to mechanical fatigue, then the other element will still operate to provide a degree of insulation thereby allowing the recloser to continue to function in many circumstances.
-9 The thickness and other properties of the flexible insulating members, such as the material used, can also be adjusted to allow different degrees of insulation to be provided. The above described arrangement provides greater electrical withstand performance than other insulating methods, such as using a convoluted air path, or the like. This allows a compact design whilst maintaining electrical surface stress requirements. The above described examples have focussed on a recloser. However, this is not essential, and it will be appreciated that the insulating system can be used in any medium voltage application, which typically operates at up to 38 kV, and more typically between 10 kV and 38 kV. Suitable applications include any switch gear, such as vacuum switches, vacuum circuit breakers, load break switches, sectionalisers, reclosers or the like. Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art should be considered to fall within the spirit and scope that the invention broadly appearing before described.