System for monitoring temperature of electrical conductor

A system for monitoring temperature of an electrical conductor (31) enclosed in at least a (semi)conductive layer (13) comprising: a passive inductive unit (20), and a transceiver unit (40) and a control unit (50). The passive inductive unit (20) includes at least one temperature sensitive component and is configured to have a resonance frequency and/or Q value that vary with temperature of the electrical conductor (31). The transceiver unit (40) is configured to be electromagnetically coupled to the passive inductive unit (20) and to send out a signal representing the resonance frequency and/or Q value of the passive inductive unit (20). The transceiver unit (40) is further configured to communicate with the control unit (50) which ascertains the signal representing one or both of the resonance frequency and Q value, and which determines a value of the temperature of the electrical conductor (31) based on the ascertained signal representing one or both of the resonance frequency and Q value.

FIELD OF THE INVENTION

The present invention generally relates to systems for monitoring temperature of an electrical conductor, and in particular, to systems for monitoring temperature of an electrical conductor enclosed in at least a (semi)conductive layer, for example, an electrical conductor of an electrical power cable in a high voltage power distribution system.

BACKGROUND OF THE INVENTION

High voltage power distribution systems play an important role in modern society. Safety and security are always considerable factors for the “health” of such high voltage power distribution system. Accordingly, there should be a technology that enables monitoring of the “health” of the high voltage power distribution system.

In a high voltage power distribution system, the temperature of conductors of electrical cables will increase as currents carried by the cables increase. Accordingly, the “health” of such system can be assessed by monitoring the temperature of the on-line electrical conductor, for example, at the cable splices or the junctions, which may be the weak points, in such a system. Usually, normal currents flowing through the cable splices or the junctions may create a temperature of up to about 90 degrees Celsius. If the temperatures of the cable splices or the junctions were to increase beyond that, it could be an indication that something may be wrong in this power distribution system. On the other hand, it is also useful to know if the existing power distribution system is at maximum current carrying capacity, to know if additional power can be reliably distributed with the existing system, or, to know if additional infrastructure expenditures are needed.

On-line power cables, as well as the cable splices and the junctions, in high voltage power distribution systems are typically insulated and protected by a number of insulative and (semi)conductive layers and are commonly buried underground or are high overhead. Therefore, it is not easy to monitor the temperature of the on-line electrical conductor, for example, directly at the cable splices or the junctions.

As used in this specification:

“(semi)conductive” indicates that the layer may be semi-conductive or conductive, depending on the particular construction.

“thermal contact” between two articles means that the articles can exchange energy with each other in the form of heat.

“direct contact” between two articles means physical contact.

FIG. 1illustrates a type of standard high voltage cable splice assembly30in which two sections of an electrical cable10are spliced. As shown inFIG. 1, the electrical cable10comprises electrical conductor31, insulation layer33, and (semi)conductive layer35. A connector12concentrically surrounds the spliced electrical conductor31. A first (semi)conductive (or electrode) layer13, in this case a metallic layer, concentrically surrounds the spliced electrical conductor31and the connector12, forming a shielding Faraday cage around the connector12and electrical conductor31. An insulating layer11(containing geometric stress control elements16) surrounds the first (semi)conductive layer13. The foregoing construction is placed inside a second (semi)conductive layer14, in this case a metallic housing, which functions as a shield and ground layer. A resin17is poured into the metallic housing14through one of the ports18to fill in the area around insulating layer11. And a shrinkable sleeve layer15serves as an outermost layer.

Therefore there is a need to develop a solution to monitor the temperature of an electrical conductor enclosed in at least a (semi)conductive layer, for example, in a high voltage power distribution system.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a system for monitoring a temperature of an electrical conductor enclosed in at least a first (semi)conductive layer is disclosed. The system includes a passive inductive unit, and a transceiver unit and a control unit. The system optionally further includes a control unit. The passive inductive unit includes at least one temperature sensitive component and is configured to have a resonance frequency and/or Q value that varies with temperature of the electrical conductor. The temperature sensitive component has a characteristic parameter that varies with temperature and adapted to be in thermal contact with the electrical conductor. The transceiver unit is configured to be electromagnetically coupled to the passive inductive unit and to send out a signal representing the resonance frequency and/or Q value of the passive inductive unit. The transceiver unit is further configured to communicate with the control unit which ascertains the signal representing one or both of the resonance frequency and Q value, and which determines a value of the temperature of the electrical conductor based on the ascertained signal representing one or both of the resonance frequency and Q value. The control unit is configured to communicate with the transceiver unit to ascertain the signal representing the resonance frequency and/or Q value, and to determine a value of the temperature of the electrical conductor based on the ascertained signal representing the resonance frequency and/or Q value.

During operation, if there is a need to monitor the temperature of the electrical conductor, the control unit may send out an instruction signal to the transceiver unit. Once the transceiver unit receives the instruction signal, it then sends out an excitation signal to the inductive unit. The inductive unit thereby will oscillate by the excitation of the excitation signal. The transceiver unit will detect an oscillation signal from the inductive unit and then send out a feedback signal to the control unit. The oscillation signal and the feedback signal contain the information representing the resonance frequency and/or Q value of the inductive unit, which is varied with the temperature of the electrical conductor. Therefore, the control unit is able to determine a value of the temperature of the electrical conductor based on the ascertained feedback signal.

In this disclosure, the temperature of the electrical conductor (e.g. adjacent a connector) is ascertained via detecting other parameters like the resonance frequency and/or Q value of the passive inductive unit, which embody the temperature information of the electrical conductor. In contrast, many existing solutions in the art use temperature sensors mounted on the exterior surface of the power cable, and estimate the temperature at the conductor. In addition, the passive inductive unit of the present invention does not need electrical power and constitutes passive electric elements having long usage lifetimes. It thereby enables the system to be more reliable with long lifecycle.

The scope of the present invention will in no way be limited to the simple schematic views of the drawings, the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as an example of an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present disclosure provides embodiments of systems for monitoring a temperature of an electrical conductor of an electrical cable, for example, at a cable splice or junction. In some embodiments, such system and method are capable of remotely monitoring the temperature at the conductor within the cable. As mentioned above, cable splices or junctions may have the weakest current carrying capacity in a high voltage power distribution system and may have a higher possibility of failing when the current is overloaded. The systems for monitoring a temperature of an electrical conductor according to embodiments of the present invention can be used to monitor the temperature of the electrical conductor located in cable splices or junctions, so that a judgment that the electrical conductor, as well as the cable splices or junctions is working well or not can be made based on the temperature.

FIG. 2is a schematic diagram of a system100for monitoring a temperature of an electrical conductor31according to one embodiment. The system100includes a passive inductive unit20, a transceiver unit40and a control unit50. The passive inductive unit20is configured to include at least one temperature sensitive component, for example, a temperature sensitive capacitor, a temperature sensitive inductor, a temperature sensitive switch, or a temperature sensitive resistor as described hereinafter. The temperature sensitive component has a characteristic parameter that varies with temperature and is configured to be in thermal contact with the electrical conductor31, for example via direct contact with the outer surface of the electrical conductor31. The passive inductive unit20is further configured to have a resonance frequency and/or Q value that varies with the temperature of the electrical conductor31. The transceiver unit40is configured to be electromagnetically coupled to the passive inductive unit20and to send out a signal representing the resonance frequency and/or Q value of the inductive unit20. The control unit50is configured to communicate with the transceiver unit40to ascertain the signal representing the resonance frequency and/or Q value, and to determine a value of the temperature of the electrical conductor31based on the ascertained signal representing the resonance frequency and/or Q value.

During operation, if there is a need to monitor the temperature of the electrical conductor31, the control unit50may send out an instruction signal S1to the transceiver unit40. Once the transceiver unit40receives the instruction signal S1, it then sends out an excitation signal S2to the inductive unit20. The excitation signal S2will induce the inductive unit20to oscillate. The transceiver unit40will detect an oscillation signal S3from the inductive unit20and then send out a feedback signal S4to the control unit50. The oscillation signal S3and the feedback signal S4contain the information representing the resonance frequency and/or Q value of the inductive unit20, which is varied with the temperature of the electrical conductor31. Therefore, the control unit50is able to determine a value of the temperature of the electrical conductor31based on the ascertained feedback signal S4.

Alternatively, as illustrated inFIG. 2, the system100may further include an energy harvesting unit60. The energy harvesting unit60is adapted to harvest electrical power from the electrical conductor31when an AC current flows through the electrical conductor31and to supply the harvested electrical power to the transceiver unit40and/or the control unit50.

According to one embodiment, the energy harvesting unit60may comprise an inductive coil61shown inFIG. 11, such as an iron-core current transformer, an air-core current transformer, or a Rogowski coil. The inductive coil61can be positioned outside the first (semi)conductive layer13, or outside the second (semi)conductive layer if one is used. Preferably, the energy harvesting unit60may be used mainly to provide the harvested electrical power to the transceiver unit40, so the energy harvesting unit60can be positioned outside the layer in which the transceiver unit40is located. Thus, the energy harvesting unit60may be electrically connected with the transceiver unit40via one or more wires.

Alternatively, the energy harvesting unit60may further include a rectifier circuit to adapt the harvested electrical power right for the transceiver unit40and/or the control unit50.

In one embodiment, the inductive unit20includes an LC loop21as shown inFIG. 3. The LC loop21includes an inductive coil21L and a capacitor21C electrically connected in series, e.g. via a wire. Alternatively, the capacitor21C can be a temperature sensitive component, that is, a temperature sensitive capacitor, and has a capacitance that varies with temperature. In this instance, during practical application, this temperature sensitive capacitor21C will be in thermal contact or in direct contact with the outer surface of the electrical conductor31. The inductive coil21L can also be the temperature sensitive component; that is, a temperature sensitive inductive coil, for which the inductance varies with temperature. In this latter instance, during practical application, this temperature sensitive inductive coil21L will be in thermal contact or in direct contact with the outer surface of the electrical conductor31. Alternatively, both of the capacitor21C and the inductive coil21L can be temperature sensitive components.

The resonance frequency fr of the L-C loop21can be calculated according to the formula given as below:

in which L denotes a value of inductance, e.g. the inductance of the inductive coil21L; C denotes a value of capacitance, e.g. the capacitance of the capacitor21C.

In actuality, LC loop21may have some resistive, dissipative, and/or absorptive loss, which can be modeled as a single small series resistance, Rs. The Q value of such an L-C loop21can be calculated according to the formula given below:

where ω0=2πfr, and where fr is the resonant frequency.

It can be seen that if either the inductance or the capacitance of the L-C loop21is changed, the resonance frequency fr and Q value will change accordingly. In the embodiments as shown inFIG. 3, as at least one of the coil21L and the capacitor21C is temperature sensitive and is configured to be in thermal contact with the outer surface of the electrical conductor31, the temperature of this temperature sensitive coil21L and/or capacitor21C will vary with the change in the temperature of the electrical conductor31, thereby causing a change in the inductance or capacitance of the L-C loop21. Consequently, the resonance frequency fr and the Q value of the L-C loop21is that varies with different temperature of the electrical conductor31.

It can be understood that the L-C loop21may include a plurality of capacitor and/or a plurality of the inductive coil. The inductive coil can be replaced by other type of inductor.

FIG. 4is a graph showing the relationship among the temperature of the electrical conductor31, the electric inductance of the temperature sensitive inductive coil21L, and the resonance frequency fr of the L-C loop21. This relationship was determined by experiments in which the temperature sensitive inductor coil21L contained temperature sensitive ferrite with a Curie temperature of 80° C., and the capacitor21C had a constant capacitance of 2.64 μF. FromFIG. 4, it can be seen that with the increase of the temperature of the electrical conductor31, the electric inductance of the inductive coil21L decreases, and the resonance frequency fr of the L-C loop21increases accordingly. There is a specific relationship between the temperature of the electrical conductor31and the resonance frequency fr of the L-C loop21. When the resonance frequency fr of the L-C loop21is measured, the temperature of the electrical conductor31can be determined using this specific relationship.

In another embodiment, the passive inductive unit20includes an L-C loop22, shown inFIG. 5, which includes a plurality of capacitive branches220in parallel with one another, and an inductive coil22L electrically connected in series with the plurality of capacitive branches220. Each of the plurality of capacitive branches220includes a capacitor22C (i.e. C1, C2, C3, C4, and so on as Cn) and a temperature-sensitive switch22S (i.e. S1, S2, S3, S4, and so on as Sn) electrically connected in series. In practice, in consideration of energy balance, there may be a separate capacitor CB electrically connected in parallel with the plurality of capacitive branches220. Alternatively, each capacitor22C has constant capacitance. Each temperature-sensitive switch22S has a unique switch-on temperature and/or a unique switch-off temperature. These switch-on or switch-off temperatures constitute continuous and non-overlapping temperature regions, such that when the electrical conductor31is in a specific temperature sub-region, at least one switch of the temperature-sensitive switches22S is in switch-on state and enables the corresponding capacitive branch220electrically connected in series with the inductive coil22L. Thus, for a specific temperature sub-region, e.g. 85° C.-90° C., the L-C loop22has a unique capacitance, and consequently the L-C loop22has a unique resonance frequency fr and/or Q value. In practice application, the plurality of temperature-sensitive switch22S will be in thermal contact or direct contact with the outer surface of the electrical conductor31so that the temperature of the switch22S is the same with that of the electrical conductor31.

In another embodiment, the passive inductive unit20includes an L-C loop23as shown inFIG. 6. The L-C loop23includes an inductive coil23L and a first capacitor23C1electrically connected in series, and a temperature sensitive resistor23R is connected in parallel with the first capacitor23C1and the inductive coil23L. The temperature sensitive resistor23R is configured to have a resistance that varies with temperature. Further, a second capacitor23C2may be connected in series with the temperature sensitive resistor23R. The temperature sensitive resistor23R is configured to be in thermal contact with the outer surface of the electrical conductor31in practical application. To be simple, preferably, the inductive coil23L, first capacitor23C1, and the second capacitor23C2can be temperature insensitive components.

FIG. 7is a graph showing the relationship among the temperature of the electrical conductor31, the electrical resistance of the temperature sensitive resistor23R in the L-C loop23, and the resonant frequency of the L-C loop23according to the embodiment shown inFIG. 6. InFIG. 7, the X axis represents the temperature of the electrical conductor31, the left Y axis represents the resistance of the temperature sensitive resistor23R, and the right Y axis represents resonant frequency of the L-C loop23. FromFIG. 7, it can be seen that with the increase of the temperature of the electrical conductor31, the resistance of the temperature sensitive resistor23R decreases, and the resonance frequency fr of the L-C loop23decreases accordingly. There is a specific relationship between the temperature of the electrical conductor31and the resonance frequency fr of the L-C loop23. When the resonance frequency fr of the L-C loop23is measured, the temperature of the electrical conductor31can be determined using this specific relationship.

In another embodiment, the passive inductive unit20includes an L-C loop24, as shown inFIG. 8. The L-C loop24is a small variation of the L-C loop23shown inFIG. 6. The L-C loop24includes a first inductive coil24L1and a capacitor24C electrically connected in series, and a temperature sensitive resistor24R is connected in parallel with the capacitor24C and the first inductive coil24L1. The temperature sensitive resistor24R is configured to have a resistance that varies with temperature. Further, a second inductor24L2is connected in series with the temperature sensitive resistor24R. The temperature sensitive resistor24R is configured to be in thermal contact with the outer surface of the electrical conductor31in practical application. To be simple, preferably, the first inductive coil24L1, the second capacitor inductive coil24L2and the capacitor24C can be temperature insensitive components.

FIG. 9is a graph showing the relationship among the temperature of the electrical conductor31, the electrical resistance of the temperature sensitive resistor24R in the L-C loop24, and the resonant frequency of the L-C loop24according to the embodiment shown inFIG. 8. InFIG. 9, the X axis represents the temperature of the electrical conductor31, the left Y axis represents the resistance of the temperature sensitive resistor23R, and the right Y axis represents resonant frequency of the L-C loop23. FromFIG. 9, it can be seen that with the increase of the temperature of the electrical conductor31, the resistance of the temperature sensitive resistor24R decreases, and the resonance frequency fr of the L-C loop24increases accordingly. There is a specific relationship between the temperature of the electrical conductor31and the resonance frequency fr of the L-C loop24. When the resonance frequency fr of the L-C loop24is measured, the temperature of the electrical conductor31can be determined using this specific relationship.

Just like the embodiments shown inFIGS. 6 and 8, the resonance frequency and/or Q value of the passive inductive unit20may be also ascertained based on the change in resistance of the temperature sensitive resistor.

In another aspect, besides the L-C loop21,22,23,24disclosed above, the passive inductive unit20may further include a signal transceiver component, which is configured to transmit signal between the L-C loop and the transceiver unit40, for example, to receive and send out signals from and to the transceiver unit40. The signal transceiver component can be in series or parallel connection with the L-C loop and can be an inductive coil electromagnetically coupled to the transceiver unit40or an antenna.

In some practical applications, the electrical conductor31may be enclosed within conductive material, for example a metallic sheet, in a way that an antenna signal may not be transmitted out through the conductive material with a satisfactory quality. Then the inductive coil used as the signal transceiver component electromagnetically coupled to the transceiver unit40will be a good choice to transmit the oscillation signal of the L-C loop out through the conductive material. Thus, an inductive coil can be used as the signal transceiver component. Even more preferably, this inductive coil can be the same one used in the L-C loop21,22,23,24. That is, the inductive coil or the temperature sensitive inductive coil21L,22L,23L,24L1respectively illustrated in the L-C loop21,22,23,24may have two functions, one is signal transmission and another one is to contribute inductance to the L-C loop. In this instance, the components in the system can be fewer and bring cost saving advantage.

In this disclosure, the temperature determination of the electrical conductor is ascertained via detecting other parameters like the resonance frequency and/or Q value of the passive inductive unit, which embody the temperature information of the electrical conductor. In contrast, existing solutions in the art often use temperature sensors mounted on the exterior surface of the power cable, and estimate the temperature at the conductor. In addition, the passive inductive unit of the present invention does not need electrical power and constitutes passive electric elements having long usage lifetimes. It thereby enables the system to be more reliable with long lifecycle.

The transceiver unit40is provided to be in communication with the passive inductive unit20and the control unit50. In practice, as the transceiver unit40and the control unit50may be both located outside the first (semi)conductive layer which encloses the electrical conductor (31) to be monitored, it may be easy to set up the communication between the transceiver unit40and the control unit50, for example, via one or more wires. However, as the passive inductive unit20is commonly located inside the first (semi)conductive layer, it may be difficult to set up the communication between the transceiver unit40and the passive inductive unit20if the first (semi)conductive layer has a strong blocking effect on the antenna signal. Some embodiments of this disclosure propose to use an electromagnetic coupling relationship between the transceiver unit40and the passive inductive unit20to enable the communication, so as to detect a signal embodying the resonance frequency and/or Q value of the passive inductive unit20.

In some embodiments, as shown inFIGS. 14(a), 14(b), and15, the transceiver unit40may include an inductive transmitting coil42and an inductive receiving coil41. The inductive transmitting coil42is configured to emit an excitation signal under the control of control unit50so as to cause the passive inductive unit20to oscillate. The inductive receiving coil41is configured to oscillate with the oscillation of the passive inductive unit20so as to generate a feedback signal (i.e. an oscillation signal) to the control unit50. In practical application, both the inductive transmitting coil42and the inductive receiving coil41are in electromagnetic coupling with the passive inductive unit20, for example, via the inductive coil or the temperature sensitive inductive coil21L,22L,23L,24L1. Alternatively, the inductive transmitting coil42and the inductive receiving coil41may be configured to have different frequencies, and in this instance, a better communication quality can be ascertained.

In another embodiment, as shown inFIG. 10, the transceiver unit40includes an inductive coil44which is configured to emit an excitation signal which induces oscillation in the passive inductive unit20and also to oscillate with the oscillation of the passive inductive unit20. That means this inductive coil44has the functions that are provided by the inductive transmitting coil42and the inductive receiving coil41together. In this instance, the system can include fewer components and thereby a simpler structure.

The foregoing description has illustrated some examples of the passive inductive unit20and the transceiver unit40.FIG. 10illustrates a schematic circuit of the system100as an example according to an embodiment of the present invention. The system100includes a passive inductive unit20formed by the inductive coil21L and the temperature sensitive capacitor21C, transceiver unit40formed by the inductive coil44as mentioned above, and control unit50. The inductive coil21L of the passive inductive unit20is electromagnetically coupled to the inductive coil44of the transceiver unit40, which is electrically connected to the control unit50.

As mentioned above, the control unit50is configured to communicate with the transceiver unit40to ascertain a signal representing the resonance frequency and/or Q value of the passive inductive unit20, and to determine a value of the temperature of the electrical conductor31based on the ascertained signal representing the resonance frequency and/or Q value. The control unit50may be remotely located outside the second (semi)conductive layer14. The control unit50may be electrically connected to the transceiver unit40, for example, via one or more wires. The control unit50may comprise an algorithmic table to show a relationship between the value of the temperature of the electrical conductor31and the value of the resonance frequency and/or Q value. The algorithmic table may be given from experiments or tests.

An example of such experiments is given based on an embodiment of a system as shown inFIG. 10. Copper conductor was used as the tested electrical conductor, the inductive coil21L of the passive inductive unit20had an electrical inductance of 1.24 mH and the temperature sensitive capacitor21C had an electrical capacitance of 17 nF at 25° C. Values of capacitance of the temperature sensitive capacitor21C varied in accordance with the change in the temperature of the copper electrical conductor, in a ratio of 100 pF per one Celsius degree.

The copper conductor was heated to different temperatures and the corresponding values of the resonance frequency and/or Q were measured. Through these experiments, various values of the temperature of the electrical conductor31and corresponding values of the resonance frequency and/or Q were ascertained as shown in Table 1.

FIGS. 11 to 17illustrate various suitable locations that the passive inductive unit20, the transceiver unit40, and the control unit50can be positioned when the system is used to monitor temperature of an electrical conductor31, for example enclosed in a high voltage cable splice assembly.

According to one embodiment of the present invention, as illustrated inFIG. 11, which shows an embodiment of the present invention applied to measure the temperature of an electrical conductor31enclosed in a cable splice assembly. In this embodiment, portions of the electrical conductor31are covered by a connector12and then are enclosed by a first (semi)conductive layer13, an insulating layer11, a second (semi)conductive layer14, and a shrinkable sleeve layer15. In this embodiment, the shrinkable sleeve layer15includes two overlapping sections151and152to leave a passage153between the overlapping portions. The passage153is from the outside of the shrinkable sleeve layer15through the port18on the second (semi)conductive layer14to the inside of the second (semi)conductive layer14.

As shown inFIG. 11, the passive inductive unit20is positioned close to the electrical conductor31and inside the first (semi)conductive layer13. Preferably, a portion of the electrical conductor31is exposed between the insulation layer33of the cable10and the connector12, and the passive inductive unit20may be positioned around the exposed portion of the electrical conductor31. More detailed description about the position of the passive inductive unit20will be given hereinafter with reference toFIG. 12.

The transceiver unit40is positioned outside the first (semi)conductive layer13and inside the second (semi)conductive layer14, i.e. between the first (semi)conductive layer13and the second (semi)conductive layer14. Preferably, the transceiver unit40and the passive inductive unit20are located in a same cross section, so as to improve the electromagnetic coupling. In the case that an inductive coil44functions as the transceiver unit40as illustrated inFIG. 10, the inductive coil44can be wound around the insulating layer11. More detailed description about embodiments of the transceiver unit40and its positioning will be provided hereinafter with reference toFIGS. 13-15.

The control unit50is configured to communicate with the transceiver unit40through wire51. The wire51can be accommodated within passage153so that the wire51can extend from transceiver unit40, through port18, to control unit50. The energy harvesting unit60including a power inductive coil61can be located outside the assembly30and around the cable10, or located between the second (semi)conductive layer14and the shrinkable sleeve layer15. The energy harvesting unit60is used to supply power to the transceiver unit40and/or the control unit50through wire52. Throughout this specification, although wire51and wire52are each referred to as a “wire,” it should be understood that either or both of wire51and wire52may comprise multiple wires as needed for the system to function.

FIG. 12is an enlarged view illustrating an exemplary location of the passive inductive unit20. As an example, the passive inductive unit20includes the inductive coil21L and the capacitor21C which is a temperature sensitive component, as shown inFIG. 3. The inductive coil21L and the temperature sensitive capacitor21C is electrically connected via a wire220. A fixture210is provided to install the inductive coil21L and the capacitor21C. For example, the fixture210may include a main body2101and a channel2102. The channel2102is adapted to accommodate the electrical conductor31to have the conductor31pass through the channel2102. The main body2101has a chamber2103to accommodate the temperature sensitive capacitor21C and the chamber2103can communicate with the channel2102in a way that the temperature sensitive capacitor21C can be in thermal contact or direct contact with the outer surface of the electrical conductor31in operation. The inductive coil21L is adapted to wind around the main body2101. The fixture210further includes a cover2104to enclose the main body2101.

In the case that the inductive coil21L is a temperature sensitive component, the inductive coil21L can be wound directly around the electrical conductor31and in direct contact with the outer surface of the electrical conductor31.

FIG. 13illustrates a closer perspective view of inductive unit20placed on the electrical conductor31adjacent to connector12. In this embodiment, shrinkable sleeve layer15is continuous and a hole has been cut in shrinkable sleeve layer15to accommodate port18and allow the egress of wire51.

FIG. 14(a)illustrates another embodiment of the present invention in which a separate receiving coil41and transmitting coil42are used as transceiver unit40. In this embodiment, both receiving coil41and transmitting coil42are located within second (semi)conductive layer14. Transmitting coil42is positioned so that the excitation signal it emits will cause the passive inductive unit20to oscillate, and the receiving coil41is positioned so that it is centered approximately radially with inductive unit20to allow receiving coil41to oscillate with the oscillation of the passive inductive unit20. Receiving coil41and transmitting coil42are separately connected to control unit50by wire51. In this embodiment, the two sections of shrinkable sleeve15do not overlap, leaving a portion of second (semi)conductive layer14exposed.

FIG. 14(b)illustrates another embodiment of the present invention in which transceiver unit40comprises a separate first receiving coil41, transmitting coil42, and second receiving coil43. In this embodiment, first receiving coil41, transmitting coil42, and second receiving coil43are located within second (semi)conductive layer14. Transmitting coil42is positioned so that the excitation signal it emits will cause the passive inductive unit20to oscillate, and the receiving coil41is positioned so that it is centered approximately radially with inductive unit20to allow receiving coil41to oscillate with the oscillation of the passive inductive unit20. First and second receiving coils41,43and transmitting coil42are separately connected to control unit50by wire51. In some embodiments, first receiving coil41and second receiving coil43are connected in series but may be wound in alternating directions. This configuration may reduce noise and improve the signal to noise ratio of the system. As inFIG. 14(a), in this embodiment, the two sections of shrinkable sleeve15do not overlap, leaving a portion of second (semi)conductive layer14exposed.

FIG. 15illustrates another embodiment of the present invention similar to the embodiment ofFIG. 14(a)except that receiving coil41is also located outside metal housing14. Similar configurations could be used in which transceiver unit40is used and comprises separate receiving coil41and transmitting coil42(as shown inFIG. 11), or in which a second receiving coil is also used (as shown inFIG. 14(b)). The coils may be inside or outside of shrinkable sleeve15. InFIG. 15, they are shown outside of shrinkable sleeve15.

FIG. 16illustrates another embodiment of the present invention used for a splice assembly30in which the second (semi)conductive layer14comprises a metal housing that includes insulative metallic shield sectionalizer19, which provides a ring of insulative material between two sections of second (semi)conductive layer (conductive metal housing)14. Metal housings of this type, for example, in which the metallic shield sectionalizer19comprises a fiberglass insert, are commercially available. When using this type of metal housing, the transceiver unit40can be placed around and outside of the insulative metallic shield sectionalizer19. In this embodiment, transceiver unit40will be able to easily read information from the inductive unit20through the insulative material. Similar configurations could be used in which transceiver40is replaced with one or two separate receiving coil(s)41,43, and transmitting coil42.

FIG. 17illustrates another embodiment of the present invention used for a different type of standard splice assembly30′ comprising a polymeric multilayer splice body39. The splice body39may comprise suitable materials such as ethylene propylene diene monomer (EPDM) rubber or silicone rubber. The splice body39may be cold shrinkable or push on and typically consists of three layers, which include first (semi)conductive layer13, insulating layer11, and second (semi)conductive layer14. An additional conductive shield (not shown) may be applied over second (semi)conductive layer14, prior to application of shrinkable sleeve layer15, which is shown as two separate pieces, to allow for egress of wires51,52. Shrinkable sleeve layer15is insulative and overlaps a portion of cable jacket37. A commercially available splice body of this type is 3M™ Cold Shrink QS-III Splice Kit, 3M Company, USA. As illustrated inFIG. 17, inductive unit20is attached to an outer surface of the electrical conductor31. Transceiver unit40is located outside of second (semi)conductive layer14and beneath shrinkable sleeve layer15. Transceiver unit40may comprise a single coil44, separate receiving coil41and transmitting coil42, or separate first receiving coil41, transmitting coil42, and second receiving coil43. In embodiments in which second (semi)conductive layer14is polymeric and/or semi-conductive, transceiver40can more easily communicate with inductive unit20than in embodiments in which (semi)conductive layer14is a metal. In embodiments in which an additional conductive layer, such as a wire mesh shield sock, is used over second (semi)conductive layer14, the additional conductive layer can be placed over or under transceiver40. Power inductive coil61of energy harvesting unit60is located on (semi)conductive layer35of cable10. In an alternate embodiment, one or more of the first (semi)conductive layer13, insulating layer11, and second (semi)conductive layer14may be formed separately. For example, second (semi)conductive layer14may be formed separately from first (semi)conductive layer13and insulating layer11. In this embodiment, transceiver coil40could be placed beneath second (semi)conductive layer14.