CABLE TERMINATION WITH AN INTEGRATED MONITORING DEVICE

Abstract

A cable termination including a cable terminal and a cable joint assembly. The cable terminal includes: a terminal conductor; a monitoring device including a capacitive voltage sensor around the terminal conductor; and an electrically insulating body fitted around the terminal conductor, including a bell-shaped end portion in which the voltage sensor is at least partially embedded. The cable terminal alternatively includes: a terminal conductor; a monitoring device including a capacitive voltage sensor around the terminal conductor; and an electrically insulating body fitted around the terminal conductor, including a bell-shaped end portion in which the voltage sensor is at least partially embedded and a stem end portion, the terminal conductor extending beyond the stem end portion.

Claims

1-16. (canceled)

17. A cable termination comprising: a cable terminal and a cable joint assembly; wherein the cable terminal comprises: a terminal conductor; a monitoring device comprising a capacitive voltage sensor around the terminal conductor; and an electrically insulating body fitted around the terminal conductor, comprising a bell-shaped end portion in which the voltage sensor is at least partially embedded.

18. A cable termination according to claim 17, wherein the capacitive voltage sensor includes a hollow cylinder including a first rim and a second rim, at least the first rim having a rounded shape.

19. A cable termination according to claim 18, wherein first rim has thickness greater than thickness of the second rim.

20. A cable termination according to claim 18, wherein the first rim is embedded in the bell-shaped end portion.

21. A cable termination according to claim 17, wherein the capacitive voltage sensor includes a portion protruding out of the body bell-shaped end portion.

22. A cable termination according to claim 21, wherein the protruding portion is covered by an insulating coating.

23. A cable termination according to claim 17, wherein the monitoring device comprises a current sensor.

24. A cable termination according to claim 23, wherein the current sensor is embedded in the bell-shaped end portion.

25. A cable termination according to claim 17, wherein the monitoring device comprises a processing unit.

26. A cable termination according to claim 25, wherein the monitoring device comprises a current sensor, and wherein the processing unit is positioned on a surface of the current sensor facing the voltage sensor.

27. A cable termination according to claim 17, wherein the cable joint assembly comprises a mechanical connector.

28. A cable termination according to claim 17, wherein the cable joint assembly comprises a sleeve.

29. A cable termination according to claim 28, wherein the sleeve comprises an insulating joint comprising, in turn, layers of: an internal semi-conductive layer; a high permittivity layer; an external insulating layer; and an external semi-conductive layer.

30. A cable termination according to claim 29, wherein the capacitive voltage sensor includes a portion protruding out of the body bell-shaped end portion, and wherein the layers have longitudinal extensions such that only the external semiconducting layer at least partially covers the portion of the capacitive voltage sensor protruding from the bell-shaped end portion.

31. A cable termination according to claim 28, wherein the sleeve comprises an insulating sheath.

32. A cable terminal, comprising: a terminal conductor; a monitoring device comprising a capacitive voltage sensor around the terminal conductor; and an electrically insulating body fitted around the terminal conductor, comprising a bell-shaped end portion in which the voltage sensor is at least partially embedded and a stem end portion, the terminal conductor extending beyond the stem end portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Further characteristics and advantages will be more apparent from the following description of a preferred embodiment and of its alternatives given as a way of an example with reference to the enclosed drawings in which:

[0068] FIG. 1 shows a side view of a cable termination according to the present invention in assembled condition and joined to a power cable;

[0069] FIG. 2 shows a section view along the plane II-II of FIG. 1 of the cable termination according to the present invention;

[0070] FIG. 3 shows an exploded perspective view of a cable terminal according to the present invention;

[0071] FIG. 4a shows a section view of an insulating joint for the cable termination of the present invention;

[0072] FIG. 4b shows a sketched view of a connector for the cable termination of the present invention;

[0073] FIG. 5 shows a detail of the positioning of a capacitive voltage sensor in the cable termination of the present invention;

[0074] FIG. 6 shows a section view of a sleeve for the cable termination of the present invention.

[0075] FIG. 7 shows a section view of a cable terminal according to the present invention.

DETAILED DESCRIPTION

[0076] In the following description, same alphanumeric references are used for analogous exemplary elements when they are depicted in different drawings.

[0077] FIGS. 1-2 show a particular embodiment of a cable termination 100 according to the present invention in assembled condition. In particular, the cable termination 100 comprises a cable terminal 1 and a cable joint assembly 3.

[0078] In FIGS. 1 and 2 a cable 2 is connected to the cable termination 100 of the invention. For accomplishing such connection, the outer layers 2a (comprising, for example, an outer jacket, one or more screens and outer semiconducting layer) of cable 2 are partially removed from the underlying layers 2b (comprising, for example, insulating layer and inner semiconducting layer) and an electrically conductive core 4, and the underlying layers 3 are partially removed from the electrically conductive core 4.

[0079] The cable terminal 1 comprises a terminal conductor 8 having the function of electrically connecting the terminal 1 with the cable 2 at one end and, at the opposite end, with other parts of the electric system, such as external apparatuses. To this purpose, the terminal conductor 8 comprises or forms or is connected to a terminal lug 9, protruding from the conductor 8 at the end portion opposite to that of the connection with cable 2 so to be easily accessible for a user. The terminal conductor 8 has an elongated shape, and is made of an electrically conductive material, such as a copper or aluminum or composite thereof.

[0080] The terminal conductor 8 and the cable 2 are connected, both mechanically and electrically, by means of a mechanical connector 11 comprised in the cable termination 100. The connector 11 is a range taking one, suitable to join electric conductors of different shape and/or size and/or material. For example, the connector is of the so called “shear-bolts” type. In this type of connector, an end portion of cable 2, specifically the end of the conductive core 4 bare of the any overlying layer 2a, 2b, is operatively joined to the connector 11 at a connector first end 12a and is locked in position by contact pressure controlled by bolts 10 (to be inserted in bolt seats 10a as from FIG. 4b) which may have a tapered or a weak portion and shear off at predetermined torque. Such an arrangement can allow the locking of cables having different section shapes and sizes, for example from 70 to 240 mm.sup.2.

[0081] The terminal conductor 8 is inserted into the connector 11 at a connector second end 12b opposite to the connector first end 12a and locked in position by a contact pressure controlled by bolts 10 as above. In this manner, both the cable conductive core 4 and the terminal conductor 8 are coupled to the connector 11 and, consequently, mechanically and electrically coupled each other. An enlarged view of the connector 11 according to a possible embodiment is shown in FIG. 4b.

[0082] The cable terminal 1 comprises an electrically insulating body 22 made of an electrically insulating material and located in the vicinity of the terminal lug 9. The insulating body 22 comprises a bell-shaped end portion 26 where the capacitive voltage sensor 14 is at least partially embedded, as it will be explained further on.

[0083] The bell-shaped end portion 26 has a radial width R (with reference to the longitudinal axis, lying on the plane II-II as indicated in FIG. 1) decreasing from one end to another, preferably decreasing towards the terminal lug 9. The bell-shaped end portion 26 has a base portion 23 and a top portion 24, the top portion 24 being closer to the terminal lug 9 than the base portion 23. The bell-shaped end portion 26 of the insulating body 22 is advantageously suitable for controlling the electric gradient, while conveniently at least partially embedding the sensor 14 and, possibly, the whole current sensor 17.

[0084] According to a possible embodiment, the bell-shaped end portion 26 of the insulating body 22 comprises a recess 25 into the base portion 23 suitable to embed the first rim 14a of the voltage sensor 14 (as from FIG. 5). The recess 25 has a shape, advantageously, at least partially matching the voltage sensor 14 shape.

[0085] The insulating body 22 further comprises a stem end portion 27 projecting from the base portion 23, which is preferably made in one piece (or monolithic) with and in the same material of the bell-shaped end portion 26. The bell-shaped end portion 26 and the stem end portion 27 form a substantially central through opening suitable to accommodate the insulating body 22 onto the terminal conductor 8.

[0086] The insulating body 22 is fitted around the terminal conductor 8, so to be integral with the latter. For example, the insulating body 22 can be molded directly on the terminal conductor 8.

[0087] The electrically insulating body 22 is preferably made of curable electrically insulating material. Advantageously, the electrically insulating material can be cured at room temperature and pressure in order to avoid any damage to the monitoring unit during the manufacturing process. For example, the electrically insulating material can be a silicone, an epoxy resin, or a silicone gel.

[0088] The cable terminal 1 comprises a monitoring device 13 for sensing, measuring, recording and saving or transmitting information regarding the condition or operation of the power cable such as current and voltage, so detecting possible faults in the network. The monitoring device 13 is located in the vicinity of the terminal lug 9. An enlarged exploded view of the monitoring device 13 integrated in the cable termination according to an embodiment of the invention is shown in FIG. 3, while cross section views are shown in FIGS. 2 and 7, as it will be detailed in the following.

[0089] The monitoring device 13 comprises a capacitive voltage sensor 14 located around the terminal conductor 8 and in contact with the electrically insulating body 22 surrounding the terminal conductor 8, as from FIGS. 2, 5 and 7. The voltage sensor 14 is able to perform measurements on the terminal conductor 8, which is electrically coupled with the cable 2, as discussed above. Since the size and shape, in particular the diameter, of the terminal conductor 8 are uniform, the capacitance is fixed and therefore measurements performed by voltage sensor 14 are independent from the shape and size of the cable 2, which can be therefore substituted without requiring a new field tuning of the sensor and/or a geometrical adapter.

[0090] Advantageously, capacitive voltage sensor 14 has at least one rounded shaped rim. As shown in FIGS. 3 and 5, voltage sensor 14 has a first rim 14a and a second rim 14b, the first rim 14a having a larger thickness than the second rim 14b. The first rim 14a acts as field deflector. Together with the electrically insulating body, the first rim shape and size makes the presence of further stress relief arrangements (both geometric and non-linear) redundant. Both rims 14a, 14b preferably have a rounded profile.

[0091] In the cable terminal 1, the voltage sensor 14 is preferably positioned so as the thicker first rim 14a is closer to the terminal lug 9 than the second rim 14b. The first rim 14a is preferably the portion of the voltage sensor 14 embedded in the bell-shaped end portion 26.

[0092] As from FIG. 5, an insulating coating 15 covers and is in contact with the portion of the voltage sensor 14 out of the bell-shaped end portion 26 and comprising the second rim 14b. Preferably, the insulating coating 15 is made by wrapping an insulating tape around the protruding portion of the voltage sensor 14.

[0093] The voltage sensor 14 can be made, for example, of a metal, such as tinned brass, or of a semiconducting compound, for example ethylene propylene rubber charged with carbon black.

[0094] The monitoring device 13 further comprises a current sensor 17. The current sensor 17 is in form of a plate with a coil (not shown) embedded into. In the embodiment of FIGS. 2, 3 and 7, a processing unit 18 is provided on a portion of the current sensor plate and is preferably arranged on the current sensor surface facing the voltage sensor 14. This position, besides providing a more compact design, allows minimizing the electric connection between the processing unit 18 and the voltage sensor 14, said connection being effect by, for example, a linking cable 20.

[0095] In the embodiments of FIGS. 3, 5 and 7, the monitoring device 13 further comprises a data cable 19 configured to connect the monitoring device 13, in particular the processing unit 18, to external apparatuses able to collect and analyze the measurement data. The data cable 19 comprises, advantageously, an end plug 21 configured to connect the monitoring device 13 to external apparatuses.

[0096] In the embodiments of FIGS. 3, 5 and 7, the monitoring device 13 further comprises a ground cable 16 configured to connect the monitoring device 13 in particular the current sensor 17, to earth.

[0097] In the embodiments of FIGS. 3 and 7, the monitoring device 13 further comprises a linking cable 20, configured to connect the voltage sensor 14 to the processing unit 18, to collect measurement data.

[0098] Preferably, data cable 19 and linking cable 20 are shielded cables.

[0099] The monitoring device 13 is at least partially housed in the electrically insulating body 22. In particular, the current sensor 17, advantageously bearing the processing unit 18, is preferably embedded in or coated by the electrically insulating material of the insulating body bell-shaped end portion 26. Also the linking cable 20 can be at least partially housed in the insulating body bell-shaped end portion 26. Such a positioning makes the cable terminal more compact and provides the current sensor 17, the processing unit 18 and the linking cable 20 of the monitoring device 13 with protection from the environment. However, it is to be noted that the current sensor 17 and the processing unit 18, and the linking cable 20 accordingly, are not necessarily housed in the insulating body 22, particularly in the bell-shaped end portion 26, since both of them can be at a distance from the terminal conductor 8.

[0100] In accordance with the embodiments shown in FIGS. 1, 2, 3 and 7, the current sensor 17 and the processing unit 18 are embedded in the insulating body 22, particularly at the base portion 23 of the bell-shaped end portion 26. In order to more conveniently embed the current sensor 17 and/or the processing unit 18, the base portion 23 may have an abutting portion 29 preferably substantially perpendicular to the termination longitudinal axis II-II.

[0101] The cable joint assembly 3 of the termination 100 further comprises a sleeve 39 comprising, in turn, an insulating joint 30 and, advantageously, an insulating sheath 37, as from FIGS. 2, 4a and 6.

[0102] The sleeve 39 provides electrical insulation and stress relief to the connection between cable 2 and terminal conductor 8 and to the portions of cable 2 exposed for the connecting procedure. Advantageously, the sleeve 39 also at least partially covers the stem end portion 27 of the electrically insulating body 22 and the capacitive voltage sensor 14.

[0103] An exemplary section view of the insulating joint 30 is shown in FIGS. 2, 4a and 6. The joint 30 comprises: [0104] an internal semi-conductive layer 34, for example made of EPR (ethylene-propylene rubber) or ethylene-propylene-diene rubber (EPDM) charged with a conductive filler; [0105] a high permittivity layer 35, for example made of EPDM, configured to limit the electric gradient; [0106] an external insulating layer 36, for example made of EPR; and [0107] an external semi-conductive layer 38 for example made of EPR or EPDM charged with a conductive filler.

[0108] Preferably, the insulating joint 30 is a cold-shrink joint. An example of cold-shrink joint is disclosed in WO06/046089. The insulating joint 30 and its component collapse onto the underlying portions of the kit 100 when assembled, and take the shape thereof.

[0109] Preferably, the external semiconducting layer 38 at least partially, and more preferably totally, covers the portion of the capacitive voltage sensor 14 protruding from the bell-shaped end portion 26, and it is in direct contact with the insulating coating 15 covering said portion, as shown in FIGS. 2 and 5.

[0110] Advantageously, an insulating sheath 37 envelopes the insulating joint 30 when the termination 100 is assembled (as shown in FIG. 6, where the sheath 37 is represented as fictitiously detached from the underlying insulating joint 30). The insulating sheath 37, can be made, for example, of silicone rubber.

[0111] The insulating sheath 37 can at least partially envelope the portion of the voltage sensor 14 not embedded into the bell-shaped end portion 26 of the electrically insulating body 22, as shown in FIGS. 2 and 5.

[0112] Advantageously, the ground cable 16 and the data cable 19 of the monitoring device 13 are positioned so to at least partially run in said sleeve 39. Preferably, during cable termination 100 assembling, both cables 16 and 19 are laid over the external semi-conductive layer 38 of the insulating joint 30 and the insulating sheath 37 is made to shrink around them all, such that both cables 16 and 19 run between the insulating sheath 37 and the external semi-conductive layer 38 of the insulating joint 30 in the assembled cable termination 100. In this manner, the cables 16 and 19 are mechanically protected and the overall appearance and handling of the cable termination 100 is improved.

[0113] Advantageously, the sleeve 39 comprises a metal braid (not shown) enveloping the insulating joint 30 and, at least partially, the capacitive voltage sensor 14. In turn the metal braid is covered by the insulating sheath 37.

[0114] According to an embodiment of the invention, during the cable termination assembling, the insulating joint 30 and, if present, the insulating sheath 37 and/or the metal braid are slipped—together or independently, and preferably mounted onto a tubular support—onto the cable 2 at a distance from the cable end. When the cable 2 and the terminal conductor 8 are inserted and locked in the connector 11, the insulating joint 30 is fitted onto the connector 11 as shown in FIG. 2, for example by removing the tubular support, the ground cable 16 and the data cable 19 are position along the joint surface, and the insulating sheath 37 and/or the metal braid is fitted onto the joint 30 as shown in FIG. 2, for example by removing the tubular support, and over the ground cable 16 and the data cable 19.

[0115] The cable termination of the invention is equipped with a monitoring system suitable for performing a variety of functions such as detecting polyphase and phase to ground faults with insulated or grounded by impedance neutral; alarming the circuit breaker opening and closing the circuit in case of fault; detecting voltage absence; metering voltage, current and active/reactive power on the network; interfacing with grid generators for coordinating line voltage regulation and the remote disconnecting signals.