AU2003292439A1 - Power line communication capacitor filter - Google Patents

Description

WO 2004/057772 PCT/GB2003/005551 Power Line Communication Capacitor Filter BACKGROUND This application relates to devices and techniques for power line communication. Power lines for delivering electrical power may be used to transmit information for communication applications. Such power line communications may provide 5 telecommunications services to consumers efficiently and cheaply. Since almost all homes and businesses are already connected to a power grid, power line communications provide a ready-made infrastructure for various communications services. However, in order to take advantage of the existing power line infrastructure, some modifications may be needed. For example, a filter is generally required, where the 10 filter acts as a short-circuit path for the power line signal along the power cables, while blocking other undesired signals. Power line communications filters are generally installed at the point of entry of the power line into the home or business. Some power line communications filters require that power be turned off for the installation process. This requirement may cause disruptions for the power line customer. Further, varying is configurations of power lines may complicate installation. It is therefore an object of the present invention to provide an improved filter. SUMMARY According to one implementation, a filter assembly includes a first connector configured to receive a first power cable, and to electrically couple a conductive region of 20 the first power cable to one or more filter elements. The filter assembly may further include a second connector configured to receive a second power cable, and to electrically couple a conductive region of the second power cable to the filter elements. The first and second connectors may be connected with a flexible coupler, which may also electrically couple the conductive regions of the two power cables. The flexible 25 coupler may be, for example, an insulated cable. The conductive regions of the power cables may be coupled to the filter elements by making a piercing connection. For example, piercing screws may be used. The 1 WO 2004/057772 PCT/GB2003/005551 piercing screws may pierce the insulation of the power cables in order to electrically couple the conductive regions to the filter elements. The filter elements may comprise a power line communication filter. For example, the filter elements may include one or more capacitors and may filter 5 frequencies in order to provide usable signal for power line communications. For example, the filter elements may pass signal frequencies from about two to about thirty MHz. A filter assembly such as that described above may be installed on first and second power cables. The first power cable may be secured in a first connector. The 10 second power cable may be secured in a second connector. The conductive region of the first power cable may be electrically coupled to one or more filter elements; for example, by making a piercing connection. The conductive region of the second power cable may be electrically coupled to one or more filter elements; for example, by making a piercing connection. The filter assembly may be installed when the power cables are energized, or 15 when they are not energized. In an implementation, a connector for a filter assembly comprises a cable securing element such as one or more cable clamps for securing a first power cable to the connector. The first power cable may be secured between a clamp portion and a corresponding abutment portion. The clamp portion and corresponding abutment portion 20 may have complementary recesses, which may be v-shaped. The clamp portion and corresponding abutment portion may allow different cable sizes to be clamped securely. The connector may also be configured to provide an electrical coupling between a conductive region of the first power cable to one or more filter elements. The electrical coupling may include a piercing connection to the conductive region of the first power 25 cable. For example, the connector may be configured to receive a piercing screw for making a piercing connection to the conductive region of the first power cable by piercing through an insulative layer of the first power cable. The connector may also be configured to be connected to a second connector with a flexible coupler. The flexible coupler may couple the conductive region of the first power cable to a conductive region 30 of a second power cable. The flexible coupler may be an insulated cable. 2 WO 2004/057772 PCT/GB2003/005551 A filter assembly as described herein may provide a number of benefits not found in previous filter assemblies for power line communications. For example, the filter assembly may be coupled to power lines while they are energized, which may improve the cost-effectiveness of power line communications, and which may reduce or eliminate 5 disruption in service for power line customers. The filter assembly is adaptable, since it may be installed in a wide variety of power line configurations using different power line sizes. Further, the flexible coupler provides flexibility that also increases the ease of installation. The details of one or more implementations are set forth in the accompanying 10 drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. DESCRIPTION OF DRAWINGS FIG. 1A is a top view of a filter assembly according to one embodiment of the present invention. 15 FIG. lB is a side view of the filter assembly according to the same embodiment as shown in FIG. 1A. FIG. IC is a bottom view of the filter assembly according to the same embodiment as shown in FIG. lA. FIG. ID is an isometric view of the filter assembly according to the same 20 embodiment as shown in FIG. 1A. FIG. 2 is a schematic of a capacitive filter according to the same embodiment as shown in FIG. 1A. FIG. 3 is an exploded view of a connector according to the same embodiment as shown in FIG 1A. 25 FIG. 4 is a exploded view of a filter body according to the same embodiment as shown in FIG 1A. FIG. 5 shows process steps that may be used to install a filter assembly according to the same embodiment as shown in FIG. IA. FIG. 6 shows another set of process steps that may be used for installing the filter 30 assembly according to another embodiment. 3 WO 2004/057772 PCT/GB2003/005551 Like reference symbols in the various drawings indicate like elements. DETAILED DESCRIPTION A capacitive filter assembly for power line communications may be installed while the power line is energized, and may be installed on a wide variety of power line 5 configurations. FIGS. lA, IB, IC and ID show different views of a capacitive filter assembly 100 according to an implementation. A capacitive filter (not shown in these figures but shown in FIG. 4) is housed within a filter housing 110. The filter may be attached to first and second power cables 130a and 130b (e.g., neutral and live cables) via connectors o10 120a and 120b and a flexible coupler including a first cable 140a and a second cable 140b. The two parts of the filter connected by two flexible coupling cables 140a and 140b allow flexible and easy installation of the filter even with a small separation between the neutral and live cables. When connectors 120a and 120b are installed on the first and second power cables, the capacitive filter is operational to filter unwanted 15 signals. The length of flexible coupling cables 140b and 140b is chosen so that connectors 120a and 120b may be coupled to a desired power line configuration. FIG. 2 shows a capacitive filter 200 that may be used in a filter assembly such as filter assembly 100 of FIG 1, according to an implementation. Note that a number of filter configurations for power line communications are known, and the shown filter is 20 exemplary. Capacitive filter 200 may pass signal at frequencies in the range of about 2MHz to about 30MHz. In other implementations, other frequencies may be passed. Connector 210 is configured to couple capacitive filter 200 to a first power cable. A first capacitor 220 and a second capacitor 230 may be used, or a single capacitor may be used. A fuse 240 may be provided. Fewer, different, or additional filter elements may 25 be used. A connector 250 is configured to couple capacitive filter 200 to a second power cable. Insulation resistance between connectors 210 and 250 may need to be greater than 100 MQ at 500 VDC for safety compliance and practice. In one implementation, first capacitor 220 is a 33 nF, 400V, X1 or X2 type capacitor, and capacitor 230 is omitted (e.g., a short circuit is provided rather than a 30 capacitor). In another implementation, capacitor 220 and capacitor 230 are both 68 nF, 4 WO 2004/057772 PCT/GB2003/005551 275V, Xl or X2 type capacitors. Note that these capacitance values, as well as the configuration of filter used, are exemplary. The 33 nF, 400V, X1 or X2 type capacitor may be chosen from the following: Philips 2222 338 14333, Vishay F1772 333 4200, Epcos B81141-C1333-M000. The 68 5 nF, 275V, Xl or X2 type capacitor may be chosen from the following: ETR MPX683K275V, Carli PX683K31C304, EVOX RIFA PME271M568M. FIG. 3 shows an exploded view of one of the connectors 120a or 120b that may be used to couple the first and second power cables to one or more filter elements provided in the filter housing 110 of the present device. In the implementation lo illustrated, the two connectors 120a and 120b are identical. Therefore, only one of the connectors will be described in detail and is referred to as 120 hereafter for ease of description. In the specific embodiment shown in FIG. 3, there are actually two separate covers for the connector. Top cover 310 is used to secure the entire housing with an insulating material to prevent any person from removing it therefrom by providing screw 15 315 as a securing means. A second main cover 330, also made of electrically insulating material, provides the attachment means for all the securing screws that are required to secure the various moving parts to the main body 320. The holes 325a and 360a have a raised housing to prevent inadvertent human contact. Describing the main body 320 in detail first, the coupling cable 140 may be made 20 of a normal electrical wire with external insulation. The metallic wire in coupling cable 140 is secured into the main body 320 by screw 340 such that the exposed metal wire (not shown) is in direct contact with metal plate 335. Screws 345a and 345b are used to connect the cable clamps 350a and 350b to the main body 320. A piercing screw 360 is also provided and is accessible through the main cover 330 via hole 360a. A power cable 25 in which connection is desired for filtering purposes is shown (part of which is shown in dotted form 130 for ease of description). Referring to FIGS. 3 and 5, during installation a technician opens top cover 310 and securely fastens cable clamps 350a and 350b to the main body 320 with the power cable 130 running therebetween (510) by tightening screws 345a and 345b. Once the 30 power cable 130 is securely fastened to the main body, the technician may screw down the piercing screw 360 until it pierces the insulation of the power cable 130 and 5 WO 2004/057772 PCT/GB2003/005551 penetrates therethrough to obtain direct contact with the metallic wires therein (520). Once direct electrical contact with the power cable 130 is obtained, the electricity from the power cable 130 will pass directly through the wire within the coupling cable 140 via the metal plate 335. By using the piercing screw 360, it is thus not necessary to cut off 5 the power supply to install the filter. The cable clamps 350a and 350b are provided with a recess that allow the secure grasping of a cable aligned across the bottom surface of the main body 320. In the embodiment shown in FIGS. IB and 3, the recess is V-shaped to allow variable diameters of cables to be securely fastened with the same device. The bottom surface of the main 10 body 320 is also provided with a V-shaped abutment means 336 with the V-shaped in the opposite direction as compared with the cable clamps 350a and 350b. The cable clamps 350a and 350b and the abutment means work complementary to each other to allow a cable to be securely fastened thereacross. This is an additional safety feature that prevents the piercing screw from any slippage in the course of insulation or thereafter. 15 FIG. 4 shows a power line communication filter body 400 inside the filter housing 110 for providing filtering elements between the first power cable 130a and the second power cable 130b as shown in FIG. la. As shown in FIG. 4, the filter elements may include one or more capacitors such as capacitors 430a and 430b, as well as other filter elements. In detail, the filter body 400 includes an assembly box 405 that is provided 20 with a fuse housing 485 for the fuse 480 and is covered by the fuse box cover 490. The fuse box cover 490 is provided with a window such that it allows the users to view the fuse 480 fitted in the fuse housing 485. Two metallic fasteners 460 and 470 connect the fuse 480 with the interior of the assembly box 405. The assembly box 405 is also provided with a space that is used as the capacitor housing 435. In this embodiment, two 25 capacitors 430a and 430b are provided therein. During assembly, the connecting wire inside coupling cable 140b is electrically connected to fastener 460 by soldering at point 460b. The electric wire inside coupling cable 140a is connected to connecting plate 341 by soldering or other means. Fasteners 460 and 470 are inserted into windows 461 and 471 respectively such that clips 460a and 30 470a are connected to the two ends of the fuse 480. Metallic connecting plate 341 is secured near one end of the capacitor housing 435 such that one end is connected to the 6 WO 2004/057772 PCT/GB2003/005551 first connecting part 430a of the first capacitor. The two capacitors 430a and 430b and the fuse 480 are connected electrically to each other in series. The same process is applied to the second connector. Upon proper assembly and connection to the power cable, electricity provided from one of the flexible cables runs through the filter assembly s 400 via the fuse 480 and the capacitors 430a and 430b in series. Appropriate signals running therebetween would be filtered appropriately. Referring to FIG. 6, as a further non-limiting example, process steps 600 for the installation of a filter include the following. The cable clamps of both of the connectors 120a and 120b are released by turning the screws 345a and 345b, respectively (610). 10 The live and neutral cables are placed in the clamp and tightened with the clamps by turning the relevant screws in opposite direction (620). Then a screw-driver with voltage test indicator is used to drive the piercing screw into the energized live cable continuously until the test indicator is lit up (630). When the test indicator is lit up, the screw-driver may be rotated one more turn to ensure that the driving screw is in good 15 contact the live cable. The same piercing screw of the corresponding second connector is used to penetrate the neutral cable in the same way until the indicator light switches off (640). Once the indicator light goes off in the second connector, the screw-driver may be turned one more turn to ensure the piercing screw is in good contact with the neutral cable. The entire installation can be dismantled in a reverse sequence. 20 In another implementation, the filter may be installed between two live cables such as a red phase cable and a blue phase cable. Fuse 480 of FIG. 4 may be removed prior to installation. After the filter assembly is installed (e.g., as described above), fuse 480 may be replaced. The V-shaped cable clamps such as the ones 350a and 350b described in FIG. 3 25 ensure a tight grasp of the power cable before piercing is performed to improve safety of the installation process. Furthermore, the cable clamps also ensure that the filter assembly such as the one 100 shown in FIG. 1 is securely fastened to the power lines even after prolonged use. The suspending filter assembly may further be fixed by fastening the filter assembly with a cable tie around the power cables. 30 The flexible coupling cables described herein provide tremendous flexibility in connecting wires in some distance apart from each other. Using this embodiment, even a 7 WO 2004/057772 PCT/GB2003/005551 big bundle of wires may be neatly and conveniently connected when using multiple filter assemblies. Furthermore, the two raised screw housing means 325a and 360a of the main cover 330 are designed to serve as safety features. When the capacitor filter 200 is in 5 function, the two screw housing means 325a and 360a raised above the main cover 330 prevent users from inadvertently touching the live screws. Other means may be used to prevent human contact with energized portions of the filter assembly 100 (e.g., insulating screw covers). As a further non-limiting example, portions of the capacitive filter assembly (e.g., 10 some or all of the housings) may be made of PVC (polyvinyl chloride). It is also suggested that the piercing screw may be any screw made of copper or stainless steel or other conducting materials with a sharp end. A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and 15 scope of the claims. For example, a variety of filter configurations may be used. Further, the structure of the connectors and other components may be changed. Additionally, process steps need not be performed in the order stated. For example, a first power cable may be clamped and electrically coupled to a first connector prior to clamping and coupling a second power cable to a second connector. Accordingly, other 20 implementations are within the scope of the following claims. 8

Claims (26)

WHAT IS CLAIMED IS:

1. A filter assembly, comprising: one or more filter elements; a first connector configured to receive a first power cable, further configured to electrically couple a conductive region of the first power cable to the one or more filter elements; a second connector configured to receive a second power cable, further configured to electrically couple a conductive region of the second power cable to the one or more filter elements; and a flexible coupler configured to flexibly connect the first connector to the second connector, further configured to electrically couple the conductive region of the first power cable to the conductive region of the second power cable.

2. The filter assembly of claim 1, wherein the first connector is configured to electrically couple the conductive region of the first power cable to the one or more filter elements by piercing an insulative region of the first power cable with a first piercing conductive element.

3. The filter assembly of claim 2, wherein said first piercing conductive element is a piercing screw.

4. The filter assembly of claim 3, wherein the second connector is configured to electrically couple the conductive region of the second power cable to the one or more filter elements by piercing an insulative region of the second power cable with a second piercing conductive element.

5. The filter assembly of claim 4, wherein the second piercing conductive element is a piercing screw.

6. The filter assembly of claim 1, further comprising a first piercing conductive element, the first piercing conductive element configured to electrically couple the conductive region of the first power cable to the one or more filter elements.

7. The filter assembly of claim 6, further comprising a second piercing conductive element, said second piercing conductive element configured to electrically couple the conductive region of the second power cable to the one or more filter elements.

8. The filter assembly of claim 1, wherein the filter elements comprise a power line communication filter.

9. The filter assembly of claim 1, wherein the filter elements include at least one capacitor.

10. The filter assembly of claim 1, wherein the flexible coupler includes a first portion connected to the first connector and further connected to a filter housing, and wherein the flexible coupler further includes a second portion connected to the filter housing and further connected to the second connector.

11. The filter assembly of claim 10, wherein at least one of the one or more filter elements is at least partially within the filter housing.

12. The filter assembly of claim 1, wherein the flexible coupler includes an insulated cable.

13. The filter assembly of claim 1 , wherein the first connector includes a cable holder for securing the first power cable to the first connector.

14. The filter assembly of claim 13, wherein the cable holder includes a clamp portion and a corresponding abutment portion.

15. The filter assembly of claim 14, wherein the clamp portion includes a v- shaped recess, and wherein the corresponding abutment portion includes a complementary v-shaped recess.

16. A method for installing a filter, comprising: securing a first power cable in a first connector; securing a second power cable in a second connector, the second connector flexibly coupled to the first connector; electrically coupling a conductive region of the first power cable to one or more filter elements by making a piercing connection to the first power cable; and electrically coupling a conductive region of a second power cable to the one or more filter elements by making a piercing connection to the second power cable.

17. The method of claim 16, wherein the first connector comprises a first piercing screw, and wherein the making a piercing connection to the first power cable comprises turning the first piercing screw.

18. The method of claim 17, wherein the turning the first piercing screw comprises turning the first piercing screw until an indicator indicates that the piercing screw is electrically coupled to the conductive region of the first power cable.

19. The method of claim 16, wherein the electrically coupling the conductive region of the first power cable to the one or more filter elements by making the piercing connection to the first power cable is performed when the first power cable is energized.

20. The method of claim 16, wherein the electrically coupling the conductive region of the first power cable to the one or more filter elements by making the piercing connection to the first power cable is performed when the first power cable is not energized.

21. A connector, comprising: a cable holder for removably securing a power cable to the connector; a conductive portion for electrically coupling the power cable to a flexible coupler using a piercing conductive element; and attachment means for attaching the flexible coupler to the connector.

22. The connector of claim 21, further including the piercing conductive element for electrically coupling the first power cable to the flexible coupler.

23. The connector of claim 21 , further including a housing.

24. The connector of claim 23, wherein the housing includes a top cover and a second main cover.

25. The connector of claim 21, wherein the cable holder includes a clamp portion and a corresponding abutment portion.

26. The connector of claim 25, wherein the clamp portion includes a v-shaped recess, and wherein the corresponding abutment portion includes a complementary v- shaped recess.