SE1100923A1 - Simplified and more robust method for determining process parameters suitable for flexible jointing of high voltage power cables - Google Patents

Abstract

A heating system for heating power lines and a method for heating power lines are shown. A first power line is provided with a temperature sensor on a portion of a conductor of the first power line. The temperature sensor is connected to a control unit which is connected to an electromagnetic induction element which is arranged in relation to the portion of the conductor of the first power line in such a way that it is capable of heating the portion of the conductor of the first power line by means of induction heating. The control unit is capable of outputting control signals to a power source which controls the supply of electric current to the electromagnetic induction element from the power source. The control unit is arranged for regulating the temperature of the portion of the conductor of the first power line by varying the electric current supplied to the electromagnetic induction element via the control signals output from the control unit. The control signals are registered continuously while the heating of the first power line is in progress. A portion of a conductor of a second power line can then be heated by means of induction heating by repeating or reproducing the recorded control signals and feeding them to the power source, which recorded control signals then control the supply of electric current to an electromagnetic induction element arranged in relation to the portion of the conductor of the second power line in such a way that it is able to heat the portion of the conductor of the other power line by means of induction heating.Fig 1

Description

2 access to the conductor, which may entail damaging or even destroying the insulation layer of the HV power cable.

For ible exible jointing, such as factory jointing, of HV power cables, usually tape or extrusion molded joints are used. These joints are used to restore the HV power cable properties, mechanical and electrical, to as great an extent as possible. Each joint may be crosslinked using a process involving applying heat and pressure to the joint. Such a process may be individually adapted to the particular design or construction of the HV power cables to be jointed.

Simulation tools, e.g. based on finite element method, may be unreliable due to a great number of unpredictable environmental conditions involved. instead, for each individual cable design and / or constuction, an individually tailored process has to be produced by means of experiments.

Repetitive measurements may have to be performed, with analysis and parameter improvements made between each measurement. Hence, an iterative process may have to be performed. lt may be difficult or even impossible to measure the temperature within the power cables during a crosslinking process of the jointing process in case the power cables to be jointed are subsequently to be used in e.g. a power distribution system, since measuring the temperature in the conductors of the power cables may entail damaging or even destroying the insulation layer of the power cables, thereby possibly compromising the functionality of the subsequently jointed power cable in the power distribution system.

The production of crosslinking processes adapted to individual cable designs and / or constructions by means of repetitive measurements may be time consuming since time is required for power cables to be prepared, measurements to be done and evaluated, etc.

The production of crosslinking processes adapted to individual cable designs and / or constructions by means of repetitive measurements may require qualified and / or experienced staff to for achieving reliable results.

Moreover, it may be practically infeasible or even impossible to verify or change a certain process in case of e.g. changed environmental conditions on site within a reasonable timeframe.

Summary ln view of the above discussion, a concern of the present invention is to provide a method for heating power cables that has a decreased complexity. 10 15 20 25 30 35 3 A further concern of the present invention is to provide a method for heating power cables that can be performed relatively quickly.

A further concern of the present invention is to provide a method for heating power cables that can be performed relatively simply.

To address at least one of these concerns and other concerns, a heating system and a method for heating power cables in accordance with the independent claims are provided. Preferred embodiments are defined by the dependent claims.

According to a first aspect of the present invention, there is provided a heating system for heating power cables.

The heating system comprises a first power cable, a second power cable, a first electromagnetic induction element, a second electromagnetic induction element, at least one temperature sensor, an electrical current source, and a control signal generator.

The first power cable comprises a conductor. A portion of the conductor of the first power cable is exposed.

The second power cable comprises a conductor.

The first electromagnetic induction element is arranged relative to the portion of the conductor of the first power cable such that the portion of the conductor of the first power cable is heated by means of induction heating, on a condition that an electrical current is supplied to the first electromagnetic induction element.

The electrical current source is coupled to the first electromagnetic induction element.

The control signal generator adapted to transmit control signals to the electrical current source, which control signals cause the electrical current source to supply an electrical current, dependent on the control signals, to the first electromagnetic induction element, whereby the portion of the conductor of the first power cable is induction heated by means of the first electro-magnetic induction element.

The at least one temperature sensor is arranged on the portion of the conductor of the first power cable. The at least one temperature sensor is coupled to the control signal generator.

The at least one temperature sensor is adapted to sense temperature of the portion of the conductor of the second power cable.

The control signal generator is adapted to determine a difference between the sensed temperature and a predefined temperature. 10 15 20 25 30 35 4 On a condition that there is a difference between the sensed temperature and the predefined temperature, the control signal generator is adapted to adjust the control signals transmitted to the electrical current source on the basis of the difference, whereby the electrical current supplied to the first electromagnetic induction element is adjusted.

The control signal generator, and / or a signal recorder separately arranged with respect to the control signal generator, is adapted to record the control signals transmitted to the electrical current source as a function of time.

The second electromagnetic induction element is arranged relative to the portion of the conductor of the second power cable such that the portion of the conductor of the second power cable is heated by means of induction heating, on a condition that an electrical current is supplied to the second electromagnetic induction element.

The control signal generator is adapted to transmit the recorded control signals to the electrical current source, which recorded control signals cause the electrical current source to supply an electrical current, dependent on the recorded control signals, to the second electromagnetic induction element, whereby the portion of the conductor of the second power cable is induction heated by means of the second electromagnetic induction element.

According to a second aspect of the present invention, there is provided a method for heating power cables.

The method comprises exposing a portion of a conductor of a first power cable. At least one temperature sensor is arranged on the portion of the conductor of the first power cable. A first electromagnetic induction element is arranged relative to the portion of the conductor of the first power cable such that the portion of the conductor of the first power cable is heated by means of induction heating on a condition that an electrical current is supplied to the first electromagnetic induction element. Control signals are transmitted to an electrical current source, which control signals cause the electrical current source to supply an electrical current, dependent on the control signals, to the first electromagnetic induction element, whereby the portion of the conductor of the first power cable is induction heated by means of the first electromagnetic induction element. A temperature of the portion of the conductor of the first power cable is sensed by means of the at least one temperature sensor. A difference between the sensed temperature and a predefined temperature is determined. On a condition that there is a 10 15 20 25 30 35 5 difference between the sensed temperature and the predefined temperature, the control signals transmitted to the electrical current source are adjusted on the basis of the difference, whereby the electrical current supplied to the first electromagnetic induction element is adjusted. The control signals transmitted to the electrical current source as a function of time are recorded.

The method comprises arranging a second electromagnetic induction element relative to a portion of a conductor of a second power cable such that the portion of the conductor of the second power cable is heated by means of induction heating on a condition that an electrical current is supplied to the second electromagnetic induction element. The recorded control signals are transmitted to the electrical current source, which recorded control signals cause the electrical current source to supply an electrical current, dependent on the recorded control signals, to the second electromagnetic induction element, whereby the portion of the conductor of the second power cable is induction heated by means of the second electromagnetic induction element.

An exemplifying embodiment of the present invention is described in the following.

First, a “dummy 'power cable is prepared with a temperature sensor such as a thermocouple mounted on a portion of a conductor of the dummy power cable, and an electromagnetic induction element such as a solenoid or coil arranged around the dummy power cable so as to be able to heat the portion of the conductor of the dummy power cable by means of induction hea fi ng.

The temperature sensor, e.g. a thermocouple, is coupled to a control unit. The control unit is arranged to receive signals and / or temperature readings from the temperature sensor and output control signals, e.g. constituted by voltage signals. The control signals output by the control unit are adapted to control or maneuver a power source or electrical current source coupled to the electromagnetic induction element, at least so as to influence or determine the electrical current supplied from the power source to the electromagnetic induction element. Thereby, by means of transmitting control signals to the power source, the control unit can control the electrical current supplied to the electromagnetic induction element, and thereby the induction heating capability of the electromagnetic induction element.

The control unit is adapted to vary the electrical current supplied from the power source to the electromagnetic induction element by transmitting 10 15 20 25 30 35 6 control signals to the power source for achieving a desired or required heating session of the dummy power cable, for example so as to regulate the heat provided such that a desired or required temperature, eg about 160 ° C, of the portion of the conductor of the dummy power cable is attained and maintained during the remainder of the heating session. The heating session may alternatively or optionally be indicated or described by a function of temperature of the portion of the conductor of the dummy power cable versus time to be adhered to or 'followedï During the heating session, a signal recorder repeatedly or continuously records the control signals output by the control unit. The signal recorder may be integrated in the control unit.

After this initial heating session performed on the dummy power cable has been performed, heating of another power cable or other power cables may be performed by means of the control signals previously recorded during the initial heating session. To this end, the control unit uses the previously recorded control signals to control or maneuver the power source, whereby the initial heating session is reproduced, repeated, or 'replayed' on another power cable or other power cables. Thereby, it is possible to heat a portion of a conductor of the other power cable, e.g. so as to attain a desired temperature in the portion of the conductor of the other power cable, without requiring any temperature measurements to be performed on the conductor of the other power cable. Thereby, need for gaining 'physical' access to the conductor of the other power cable, which may entail damaging or even destroying the insulation layer of the power cable, may be mitigated or even eliminated.

For example when jointing two power cable ends, heating of the power cables may be required so as to at least momentarily attain a particular temperature in a cable component or components. Jointing of two power cables may be desired or required for example for effecting repairs or during installation and / or maintenance of a power distribution system operating over relatively long distances. However, when ends of two power cables that are to be used in e.g. a power distribution system are to be jointed, it may be difficult or even impossible to measure the temperature in the conductors, since this may entail damaging or even destroying the insulation layer of the power cables, thereby possibly compromising the functionality of the subsequently jointed power cable in the power distribution system.

Embodiments of the present invention may enable producing a cross-linking process for factory joints relatively quickly and / or easily, that may be 10 15 20 25 30 35 7 compatible with current practice and training of staff performing jointing of power cables on site.

Further objects and advantages of the present invention are described in the following by means of exemplifying embodiments. lt is noted that the present invention relates to all possible combinations of features recited in the claims. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. Those skilled in the art realize that different features of the present invention may be combined to create embodiments other than those described in the following.

Brief description of the drawings Exemplifying embodiments of the invention will be described below with reference to the accompanying drawings, in which: Figs. 1-4 are schematic views of parts of a heating system according to respective embodiments of the present invention. In the accompanying drawings, the same reference numerals denote the same or similar elements throughout the views.

Detailed description The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying embodiments of the present invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will convey the scope of the invention to those skilled in the art. Furthermore, like numbers refer to like or similar elements or components throughout.

Referring to Fig. 1, there is shown a schematic view of a part of a heating system 100 according to an embodiment of the present invention.

A first power cable or 'dummy' power cable 101 has been equipped with a temperature sensor 102 such as a thermocouple mounted on a portion 103 of a conductor 104 of the dummy power cable 101. An electromagnetic induction element, schematically indicated by 105, for example comprising a solenoid or coil, is arranged around or about the dummy power cable 101 so as to be able to heat the portion 103 of the conductor 104 of the dummy power cable 101 by means of induction heating. 10 15 20 25 30 35 8 The temperature sensor 102 is coupled to a control signal generator and / or control unit 106. The contro | unit 106 is arranged to receive signals and / or temperature readings from the temperature sensor 102 and output control signals, e.g. constituted by voltage signals. The control signals output by the contro | unit 106 are adapted to control a power source or electrical current source 108 coupled to the electromagnetic induction element 105 so as to in fl uence or determine the electrical current supplied from the power source 108 to the electromagnetic induction element 105. Thereby, by means of transmitting control signals to the power source 108, the contro | unit 106 controls the electrical current supplied to the electromagnetic induction element 105, and thereby the induction heating capability of the electro-magnetic induction element 105.

Controlling the electrical current may include controlling the electrical current with regards to phase, frequency and / or amplitude.

The control unit 106 is adapted to vary or contro | the electrical current supplied from the power source 108 to the electromagnetic induction element 105 by transmitting control signals to the power source 108 for achieving a desired or required heating session of the dummy power cable 101, for example so as to regulate the heat provided to the portion 103 of the conductor 104 of the dummy power cable 101 such that a desired or required temperature, eg about 160 ° C, of the portion 103 of the conductor 104 of the dummy power cable 101 is attained and maintained during the remainder of the heating session. During the heating session, a signal recorder repeatedly or continuously records the control signals output by the control unit 106.

According to the embodiment in Fig. 1, the signal recorder is integrated in the contro | unit 106.

Alternatively or optionally, as can be seen in Fig. 2, the signal recorder can be arranged as a component 110 seperately arranged with respect to the contro | unit 106.

After the initial heating session performed on the dummy power cable 101 as described above with reference to Fig. 1 or 2 has been performed, heating of another power cable or other power cables may be performed by means of the control signals previously recorded during the initial heating session.

Reference is made to Fig. 3, which shows a schematic view of a part of a heating system 100 according to an embodiment of the present invention.

A second power cable 112 includes a conductor 113. 10 15 20 25 30 35 9 An electromagnetic induction element, schematically indicated by 105, for example comprising a solenoid or coil, is arranged around or about the second power cable 112 so as to be able to heat a portion 114 of the conductor 113 of the second power cable 112 by means of induction heating.

A control unit 106 is arranged to output control signals, e.g. constituted by voltage signals, adapted to control a power source or electrical current source 108 coupled to the electromagnetic induction element 105 so as to in fl uence or determine the electrical current supplied from the power source 108 to the electromagnetic induction element 105. Thereby, by means of transmitting control signals to the power source 108, the control unit 106 controls the electrical current supplied to the electromagnetic induction element 105, and thereby the induction heating capability of the electro-magnetic induction element 105.

The control unit 106 uses the control signals previously recorded by the control unit 106 or by a signal recorder of the control unit 106 during the initial heating session to control the power source 108, whereby the initial heating session is 'rep | ayed' on the second power cable 113 for heating the portion 114 of the conductor 113 of the second power cable 112 by means of induction heating.

Alternatively or optionally, as depicted in Fig. 4, the control unit 106 may retrieve the previously recorded control signals from a signal recorder 110 separately arranged with respect to the control unit 106 such as described above with reference to Fig. 2.

Each of Figs. 1 and 2 shows cross-sectional views of portions of the dummy power cable 101 along a direction perpendicular to longitudinal direction of the dummy power cable 101.

Each of Figs. 3 and 4 shows cross-sectional views of portions of the second power cable 113 along a direction perpendicular to longitudinal direction of the second power cable 113. In conclusion, a heating system for heating power cables and a method for heating power cables are disclosed. A first power cable is arranged with a temperature sensor on a portion of a conductor of the first power cable. The temperature sensor is connected to a control unit coupled to an electro-magnetic induction element arranged relative to the portion of the conductor of the first power cable so as to be capable of heating the portion of the conductor of the first power cable by means of induction heating. The control unit is capable of outputting control signals to a power source that controls 10 15 20 25 10 supply of electrical current to the electromagnetic induction element from the power source. The control unit is adapted to regulate the temperature of the portion of the conductor of the first power cable by varying the electrical current supplied to the electromagnetic induction element via the control signals output from the control unit. The controls signals are continuously recorded during the heating session performed on the first power cable. A portion of a conductor of a second power cable can then be heated by means of induction heating, by repeating or reproducing the recorded control signals and supplying them to the power source, which recorded control signals then controls supply of electrical current to an electromagnetic induction element arranged relative to the portion of the conductor of the second power cable so as to be capable of heating the portion of the conductor of the second power cable by means of induction heating.

While the present invention has been illustrated and described in detail in the appended drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplifying and not restrictive; the present invention is not limited to the disclosed embodiments. Other Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims (2)

10 15 20 25 30 35 11 Claims 1. A heating system for heating power cables, the heating system comprising: a first power cable comprising a conductor, wherein a portion of the conductor is exposed; a second power cable comprising a conductor; a first electromagnetic induction element arranged relative to the portion of the conductor of the fi rst power cable such that the portion of the conductor of the first power cable is heated by means of induction heating on a condition that an electrical current is supplied to the first electromagnetic induction element; an electrical current source coupled to the first electromagnetic induction element; a control signal generator adapted to transmit control signals to the electrical current source, which control signals cause the electrical current source to supply an electrical current, dependent on the control signals, to the first electromagnetic induction element, whereby the portion of the conductor of the first power cable is induction heated by means of the first electro-magnetic induction element; at least one temperature sensor arranged on the portion of the conductor of the first power cable, the at least one temperature sensor being adapted to sense temperature of the portion of the conductor of the first power cable, the at least one temperature sensor being coupled to the control signal generator; the control signal generator being adapted to determine a difference between the sensed temperature and a predefined temperature, and, on a condition that there is a difference between the sensed temperature and the predefined temperature, adjust the control signals transmitted to the electrical current source on basis of the difference, whereby the electrical current supplied to the first electromagnetic induction element is adjusted; the control signal generator being adapted to record the control signals transmitted to the electrical current source as a function of time; a second electromagnetic induction element arranged relatively to a portion of the conductor of the second power cable such that the portion of the conductor of the second power cable is heated by means of induction 10 15 20 25 30 35 12 heating on a condition that an electrical current is supplied to the second electromagnetic induction element; the control signal generator being adapted to transmit the recorded control signals to the electrical current source, which recorded control signals cause the electrical current source to supply an electrical current, dependent on the recorded control signals, to the second electromagnetic induction element, whereby the portion of the conductor of the second power cable is induction heated by means of the second electromagnetic induction element. 2. A method for heating power cables, the method comprising: exposing a portion of a conductor of a first power cable; arranging at least one temperature sensor on the portion of the conductor of the first power cable; arranging a first electromagnetic induction element relative to the portion of the conductor of the first power cable such that the portion of the conductor of the first power cable is heated by means of induction heating on a condition that an electrical current is supplied to the fi rst electromagnetic induction element; transmitting control signals to an electrical current source, which control signals cause the electrical current source to supply an electrical current, dependent on the control signals, to the first electromagnetic induction element, whereby the portion of the conductor of the first power cable is induction heated by means of the first electromagnetic induction element; sensing a temperature of the portion of the conductor of the first power cable by means of the at least one temperature sensor; determining a difference between the sensed temperature and a predefined temperature; on a condition that there is a difference between the sensed temperature and the predefined temperature, adjusting the control signals transmitted to the electrical current source on the basis of the difference, whereby the electrical current supplied to the first electromagnetic induction element is adjusted; recording the control signals transmitted to the electrical current source as a function of time; arranging a second electromagnetic induction element relative to a portion of a conductor of a second power cable such that the portion of the 10 13 conductor of the second power cable is heated by means of induction heating on a condition that an electrical current is supplied to the second electro-magnetic induction element; and transmitting the recorded control signals to the electrical current source, which recorded control signals cause the electrical current source to supply an electrical current, dependent on the recorded control signals, to the second electromagnetic induction element, whereby the portion of the conductor of the second power cable is induction heated by means of the second electromagnetic induction element.