AU2003257711B2 - Apparatus and method for evaluating underground electric power cables - Google Patents
Apparatus and method for evaluating underground electric power cables Download PDFInfo
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- AU2003257711B2 AU2003257711B2 AU2003257711A AU2003257711A AU2003257711B2 AU 2003257711 B2 AU2003257711 B2 AU 2003257711B2 AU 2003257711 A AU2003257711 A AU 2003257711A AU 2003257711 A AU2003257711 A AU 2003257711A AU 2003257711 B2 AU2003257711 B2 AU 2003257711B2
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
- H02H7/228—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices for covered wires or cables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/58—Testing of lines, cables or conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
- G08B29/02—Monitoring continuously signalling or alarm systems
- G08B29/06—Monitoring of the line circuits, e.g. signalling of line faults
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
- H02J13/00016—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using a wired telecommunication network or a data transmission bus
- H02J13/00017—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using a wired telecommunication network or a data transmission bus using optical fiber
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
- H02J13/00036—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers
- H02J13/0004—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers involved in a protection system
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
- Y04S40/124—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using wired telecommunication networks or data transmission busses
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Power Engineering (AREA)
- Computer Networks & Wireless Communication (AREA)
- Computer Security & Cryptography (AREA)
- Laying Of Electric Cables Or Lines Outside (AREA)
- Electric Cable Installation (AREA)
Description
WO 2004/088338 PCTiKR2003/001545 1 APPARATUS AND METHOD FOR EVALUATING UNDERGROUND ELECTRIC POWER CABLES Technical Field The present invention relates to an apparatus for evaluating underground electric power cables included in electric power transmission equipment, and more particularly to an apparatus and method for evaluating, in real time, the conductor temperature and allowable current of an underground electric power cable to efficiently calculate the transmission capacity of the electric power cable.
Background Art Generally, the transmission capacity of an electric power cable is determined based on a temperature range in which the insulating performance of an insulator surrounding the electric power cable is maintained.
In the case of some electric power cables, in particular, cross-linked polyethylene (XLPE) cables, their cable conductor temperature is limited to 90 0
C.
In the case of oil filled (OF) cables, their conductor temperature is limited to Practically, it is very difficult to measure the conductor temperature of an electric power cable because the electric power cable is in a state in which high voltage is applied.
Upon determining the conductor temperature of an electric power cable, it is important to determine heat sources. To be taken into consideration for such a determination are Joule loss caused by current flowing through the cable conductor, insulation loss caused by high voltage applied to the cable conductor, Joule loss caused by Eddy current generated at the sheath of the cable and sheath circulating current, the thermal condition around the cable, etc.
In this regard, the transmission capacity of an underground electric power cable is calculated by evaluating the conductor temperature and allowable current of the under ground electric power cable. The evaluation of the conductor temperature and allowable current is achieved using a method recommended by an WO 2004/088338 PCT/KR2003/001545 2 international Standard, for example, IEC 287 or JCS 168.
IEC 287 is an international Standard established by the International Electro-technical Commission (IEC). This IEC Standard includes standards for ships, electrical installations, electric power cables, high-frequency cables, windings, etc. On the other hand, JCS 168 is a Standard established by JCS for standardization of electric wire products.
However, conventional methods according to such international Standards cannot take into consideration a temperature variation in the conductor of a cable and a variation in the internal temperature of the cable in practical cases. That is, they utilize a static heat transfer system taking into consideration only the thermal conductivity of the core material of the cable. In such conventional methods, the heat transfer system of the cable is modeled as a static system on the assumption that when the transmission current flowing the cable varies, the internal temperature of the cable varies immediately without any time difference, for calculation of the transmission capacity of the cable.
However, a considerable time is required for the cable to vary in temperature by virtue of the specific heat of the core material of the cable in practical cases. For this reason, it is possible to transmit, through an electric power cable, a larger quantity of electric power than a calculated transmission capacity of the electric power cable, for a certain short period of time (for example, up to about 100 hours).
Furthermore, since conventional transmission capacity determining methods aim to secure an increased stability, they calculate the transmission capacity of a cable by setting the worst temperature condition without taking into consideration an actual temperature variation occurring at the cable due to a variation in the environmental condition around the cable. For this reason, the transmission capacity of the cable is calculated, based on a limited static transmission capacity and a limited emergency operation condition, so that the calculated transmission capacity provides unnecessarily high security. In other words, the conventional methods propose a transmission capacity considerably WO 2004/088338 PCT/KR2003/001545 3 lower than a practically-allowable transmission capacity. Most national key underground electric power transmission networks in, for example, Korea, are installed in electric power cable tunnels. In such a case, the temperature of each electric power cable tunnel is simply prescribed to be 40'C. However, the temperature of each electric power cable tunnel is typically maintained at a temperature of 30 to 35 0 C even in the summer season exhibiting the highest temperature. Although it is possible to achieve an increase in the transmission capacity of a cable by directly measuring the thermal condition of the cable, there is no conventional method to which such a direct measurement is applicable.
Meanwhile, emergency power transmission is typically carried out when an accident occurs. For such an emergency power transmission, allowable current is set, based on a fixed transmission time stipulated in the international Standard.
However, this method is inefficient because electric power can be transmitted only in a transmission capacity fixed based on the fixed transmission time, in spite of the fact that a higher transmission capacity can be given when the emergency power transmission time is shorter than the time stipulated in the international Standard.
On the other hand, where a new heat source such as a steam pipe is arranged around an underground electric power cable as it is embedded under the ground around the underground electric power cable due to an erroneous pipe installation work, the ambient temperature of the cable may be considerably higher than the ambient temperature applied to a standard for calculation of transmission capacity. In this case, transmission of electric power in a transmission capacity calculated in accordance with conventional methods may cause a dangerous situation. However, conventional methods cannot cope with such a dangerous situation. In severe cases, a cable accident may occur.
Where an increase in ground resistance occurs at an electric power cable due to an erroneous cable grounding work, excessive sheath circulating current may flow through the electric power cable, thereby causing Joule loss. Such Joule loss causes an abrupt increase in the internal temperature of the cable. However, conventional transmission capacity calculation methods cannot calculate the sheath P 1OPERRAB\RnpOw 25669W sa Ip. do.26AO2I2W7 -4circulating current. For this reason, there is no method of coping with the problem caused by the sheath circulating current.
Although there are conventional methods in which sheath circulating current is taken into consideration, they simply calculate the sheath circulating current as a certain ratio to the current flowing the cable conductor, without actually measuring the sheath circulating current in a state of taking into consideration the ground type of the cable.
For example, in the case of a grounding method using cross bonding of an aluminum sheath, which is frequently applied to national underground electric power cables in, for example, Korea, sheath circulating current corresponding to 2% or 5% of conductor current is applied in accordance with the JCS 168 Standard. In such a cross bonding system, however, sheath circulating current of up to 10% of the conductor current may often flow. In this case, the internal temperature of the cable may be erroneously calculated. In the worst case in which the transmission capacity calculated based on the sheath circulating current corresponding to 2% of the conductor current is applied to an actual transmission operation, there may be a great danger.
It is desired to provide an apparatus for evaluating, in real time, an underground electric power cable and a method for calculating and evaluating, in real time, a transmission capacity of an underground electric power cable that alleviate one or more of the above difficulties, or at least provide a useful alternative.
Summary Preferred embodiments of the present invention include an apparatus and method for evaluating, in real time, underground electric power cables, which can measure, in real time, the sheath circulating current and cable temperature of an underground electric power cable in order to calculate the conductor temperature of the cable to be basically used for calculation of a transmission capacity, thereby providing accurate information for calculation of a transmission capacity, not only in a general transmission operation, but also in an emergency electric power transmission operation carried out when a cable P OPER\RAB ReSp 2\l 66950 spaI daC-26102,200 accident occurs or a peak load is generated in the summer season, while being capable of reflecting, in real time, an external thermal variation, so as to cope with the external thermal variation, so that the allowable transmission capacity of the current transmission line can be accurately calculated, in order to efficiently transmit electric power.
In accordance with one aspect, the present invention provides an apparatus for evaluating, in real time, an underground electric power cable, comprising: cable current measuring means for measuring current flowing through a conductor of the cable; sheath current measuring means for measuring current circulating through a sheath of the cable, thereby acquiring actual data about the sheath circulating current; cable temperature measuring means for measuring a temperature of the cable; and a communication unit for connecting the cable current measuring means, sheath current measuring means, and cable temperature measuring means to a main computer; and the main computer connected to the communication unit, and adapted to calculate, in real time, a conductor temperature of the cable based on data received from the cable current measuring means, sheath current measuring means, and cable temperature measuring means, and to calculate a transmission capacity of the cable, based on the calculated cable conductor temperature. The main computer of this apparatus can inform the line operator of the calculated cable conductor temperature and transmission capacity, and send an alarm to the line operator when an abnormality in cable transmission occurs. Thus, this apparatus provides convenience to the line operator.
In accordance with another aspect, the present invention provides a method for calculating and evaluating, in real time, a transmission capacity of an underground electric power cable, comprising the steps of inputting an installation condition including a cable installation length and a cable installation type when current begins to flow through the cable; calculating a thermal constant, based on the inputted installation condition along with respective thermal conductivities and respective specific heats of inner and outer materials of the cable, and a structure of the cable; measuring conductor current and sheath current of the cable, calculating Joule heat generated at a conductor of the cable, based on the calculated conductor current and the electrical and thermal characteristics of the cable conductor, calculating insulation loss based on a voltage applied to the cable conductor and WO 2004/088338 PCT/KR2003/001545 6 characteristics of an insulator of the cable, and calculating sheath Joule heat caused by sheath circulating current in accordance with the inputted installation condition to calculate a heat source; measuring a temperature of the cable varying in a longitudinal direction of the cable; and calculating, in real time, a conductor temperature of the cable, based on information acquired in the calculations carried out at the above steps, and the measured cable temperature.
The method may further comprise the steps of: determining whether or not the difference between a measured temperature of a temperature-measured cable portion on a cross section of the cable and a calculated temperature of the cable portion is less than a predetermined temperature difference, after execution of the step of calculating, in real time, the conductor temperature of the cable; calculating an allowable transmission capacity, based on acquired data when the difference between the measured and calculated temperatures is less than the predetermined temperature difference; and informing a line operator of the conductor temperature of the cable and the calculated allowable transmission capacity.
The method may further comprise the step of adjusting the thermal constant and the correction coefficient of the heat source when it is determined that the difference between the measured and calculated temperatures is not less than the predetermined temperature difference.
The method may further comprise the steps of: comparing the calculated conductor temperature with a predetermined temperature, after execution of the conductor temperature calculating step; sending an alarm to a line operator when the calculated conductor temperature is not less than the predetermine temperature, thereby informing the line operator of generation of an abnormal temperature.
The calculation of the conductor temperature may be carried out using a method in which the conductor temperature is calculated using the temperature of a temperature-measured cable portion on the cross section of the electric power cable as a temperature boundary, or a method in which the conductor temperature is calculated using the temperature of the measured cable portion as a feedback value.
The feedback method comprises the steps of: calculating respective P IOPERR BRppos ,I 25M'M0 sp I doc-2&I62/2O7 tF t\q t-€3 -7temperatures of all layers of the cross section of the cable under the condition in which the surrounding temperature around the cable is set as an ambient temperature; comparing the temperature of the measured cable portion with the calculated temperature of the same layer as the temperature-measured cable portion; and determining the calculated result to be reliable when the difference between the calculated temperature and the measured temperature is less than a predetermined temperature difference.
When it is determined at the comparison step that the difference between the calculated temperature and the measured temperature is not less than the predetermined temperature difference, adjustment of the thermal constant and the correction coefficient of the heat source is carried out, and respective temperatures of all layers of the cable are calculated again, based on the adjusted thermal constant and correction coefficient. Based on the resultant calculated temperatures, the comparison step is carried out again. Thus, it is possible to increase the reliability of the conductor temperature calculation.
The method may further comprise the steps of: informing the line operator of the calculated and measured temperatures when it is determined at the comparison step that the difference between the calculated temperature and the measured temperature is less than the predetermined temperature difference; calculating an allowable transmission capacity, and informing the line operator of the calculated allowable transmission capacity.
The method may further comprise the step of generating an alarm when the calculated conductor temperature is not less than the predetermine temperature, thereby informing the line operator of generation of an abnormal temperature. Thus, convenience is provided to the line operator.
Brief Description of the Drawings Preferred embodiments of the present invention are hereinafter described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is a block diagram illustrating the configuration of an apparatus for evaluating, in real time, an underground electric power cable in accordance with a P \OPER\fABMRc pn x\l 2 M6950 splI do.26/n2/2mX)7 -8preferred embodiment of the present invention; and Fig. 2 is a flow chart illustrating a method for evaluating, in real time, an underground electric power cable in accordance with a preferred embodiment of the present invention.
Fig. 1 is a block diagram illustrating the configuration of an apparatus for evaluating, in real time, an underground electric power cable. Fig. 2 is a flow chart illustrating a method for evaluating, in real time, an underground electric power cable.
The underground electric cable evaluating apparatus shown in Fig. 1 is applied to, for example, an electric power cable 2 installed in an electric power tunnel 1. As shown in Fig. 1, the underground electric cable evaluating apparatus includes a cable current measuring means 3 for measuring current flowing through a conductor of the cable 2, a sheath current measuring means 4 for measuring current circulating through a sheath of the cable 2, a cable temperature measuring means 5 for measuring the temperature of the cable2, a cable surrounding temperature measuring means 6 for measuring the surrounding temperature around the cable 2, and a communication unit 7 for connecting the cable current measuring means 3, sheath current measuring means 4, cable temperature measuring means 5, and cable surrounding temperature measuring means 6 to a main computer 9 which is also included in the cable evaluating apparatus. The main computer 9 is connected to the communication unit 7, and adapted to calculate, in real time, the transmission capacity of the cable 2 based on data received through the communication unit 7, and to inform a line operator of the calculated transmission capacity. The main computer 8 also sends an alarm to the line operator when the temperature of the cable conductor is not less than a predetermined cable conductor temperature or when the temperature of the electric power tunnel is not less than a predetermined tunnel temperature.
The cable current measuring means 3 is installed such that it surrounds the WO 2004/088338 PCT/KR2003/001545 9 cable 2, in order to measure current flowing through the conductor of the cable 2.
For this cable current measuring means 3, current transformers may be used, each of which serves as a current measuring sensor. Preferably, each current transformer has a measuring range of 0 to 2,000A.
Since the same current flows through all transmission lines, only one current transformer for the cable current measuring means 3 is installed on each transmission line.
The sheath current measuring means 4 is installed to measure current circulating through the sheath of the cable 2. For the sheath current measuring means 4, current transformers may be used, each of which serves as a current measuring sensor, as in the cable current measuring means 3. The current transformers for the sheath current measuring means 4 are arranged at respective grounding points on the transmission lines. Preferably, each current transformer for the sheath current measuring means 4 has a measuring range of 0 to 500A.
The cable temperature measuring means 5 is installed on an insulator sheath, sheath layer, or armour layer or jacket, where the cable temperature measuring means 5 does not damage an insulator of the cable, or outside the cable, in order to measure the temperature of the cable 2.
For the cable temperature measuring means 5, resistance temperature detectors may be used, each of which serves as a point temperature sensor.
Alternatively, thermocouples may be used. The resistance temperature detectors or thermocouples may be installed on the cable 2 while being uniformly spaced apart from one another in the longitudinal direction of the cable 2 by a distance of 1 to Preferably, the resistance temperature detectors or thermocouples are arranged at intervals of 10m, taking into consideration economical purposes and cable characteristics.
In place of the point temperature sensors, fiber optic distributed temperature sensors may be used which are adapted to acquire longitudinal temperature data.
Such a fiber optic distributed temperature sensor employs a single optical fiber as its sensor medium. This sensor can utilize the temperature dependency of P OPER\RAB'Respon slI 2SM9SO sp I doc.261OO2O07 Raman scattering and Brillian scattering. Where optical fibers are used, it is possible to achieve lightness and miniaturization. It is also possible to easily measure the temperature of the entire portion of an object without any influence of electromagnetic noise.
In addition to the cable temperature measuring means 5, the cable surrounding t temperature measuring means 6 may be used in order to measure the surrounding temperature around the cable 2. For an electric power cable installed in an electric power tunnel 1, the cable surrounding temperature measuring means 6 is preferably installed in the electric power tunnel 1. On the other hand, for an electric power cable installed in a pipeline, the cable surrounding temperature measuring means 6 is preferably installed on the wall surface of the pipeline or in the earth around the pipeline. Also, for an electric power cable directly embedded in the ground, the cable surrounding temperature measuring means 6 may be installed in the earth while being spaced apart from the cable by a certain distance.
Although the cable evaluating apparatus has been described above as being applied to the case in which the underground electric power cable 2 is installed in the electric power tunnel 1, it is also applicable to other cable installation types, for example, the case in which the cable is installed in a pipeline, or the case in which the cable is directly embedded in the ground, by appropriately installing the cable surrounding temperature measuring means 6.
Meanwhile, the current measuring means 3 and 4 and temperature measuring means 5 and 6 are connected to the communication unit 7 via communication lines or in a wireless manner so that they are connected to the main computer 9.
The communication unit 7 preferably uses a programmable logic controller (PLC).
In particular, where the communication unit 7 using such a PLC is used, it is possible to transmit data without any influence of the high-voltage electric power cable, in so far as optical communication transmitting/receiving equipment and communication lines 8 made of optical cables are used.
P OPER\RABRMRspons\! 25669J5 sp I dc.2602/'Of7 -11- The main computer 9 connected to the communication unit 7 calculates, in real time, the conductor temperature of the cable, based on data received from the current measuring means 3 and 4 and temperature measuring means 5 and 6, thereby calculating the transmission capacity of the cable, based on the calculated conductor temperature. The main computer 9 subsequently informs a line operator of the calculated transmission capacity. Also, the main computer 9 sends an alarm to the line operator when an abnormality in the power transmission of the cable occurs. Thus, the main computer calculates, in real time, the transmission capacity of the underground electric power cable, so that it appropriately operates the underground electric power cable.
Now, a method for evaluating an underground electric power cable by calculating the conductor temperature of the cable will be described. This method includes: an installation condition inputting step 110 for inputting an installation condition having high influence on sheath circulating current, such as a cable installation length and a cable installation type; a thermal constant calculating step 120 for calculating a thermal constant, based on the inputted installation condition along with respective thermal conductivities and respective specific heats of the inner and outer materials of the cable, and the structure of the cable; a current measuring and heat source calculating step 130 for measuring the conductor current and sheath current of the cable, calculating Joule heat generated at the conductor of the cable, based on the calculated conductor current and the electrical and thermal characteristics of the cable conductor, calculating insulation loss based on the voltage applied to the cable conductor and the characteristics of an insulator of the cable, and calculating sheath Joule heat caused by sheath circulating current in accordance with the inputted installation condition; a longitudinal cable temperature measuring step 140 for measuring a temperature of the cable varying in a longitudinal direction of the cable; and a conductor temperature calculating step 150 for calculating, in real time, the conductor temperature of the cable, based on information acquired in the calculations carried out at the above steps, and the measured cable temperature.
The calculation of the conductor temperature based on the measured temperature may be carried out using a method in which the conductor temperature is calculated using P 'OPER\RAB~RcspOscslI 2S695 spa I dOC-26/02007 Q-12- Sthe temperature of a measured cable portion on the cross section of the electric power cable Sas a temperature boundary, or a method in which the conductor temperature is calculated using the temperature of the measured cable portion as a feedback value.
S 5 In the feedback method in which the temperature of the measured cable portion is tt used as a feedback value, respective temperatures of all layers of the cross section of the cable are calculated under the condition in which the surrounding temperature around the Scable is set as an ambient temperature. The temperature of the measured cable portion is then compared with the calculated temperature of the same layer as the measured cable portion. When the difference between the calculated temperature and the measured temperature is less than a predetermined temperature difference, it is determined that the calculated result is reliable.
On the other hand, where it is determined at the comparison step that the difference between the calculated temperature and the measured temperature is not less than the predetermined temperature difference, adjustment of the thermal constant and the correction coefficient of the heat source is carried out, and respective temperatures of all layers of the cable are calculated again, based on the adjusted thermal constant and correction coefficient. Based on the resultant calculated temperatures, the comparison step is carried out again. Thus, it is possible to increase the reliability of the conductor temperature calculation.
Meanwhile, the method can further include step 160 for determining whether or not the difference between a measured temperature of a cable portion on the cross section of the cable and a calculated temperature of the cable portion is less than a predetermined temperature difference, after execution of the step 150 of calculating, in real timrne, the conductor temperature of the cable, step 170 for calculating an allowable transmission capacity, based on the received data when the difference between the measured and calculated temperatures is less than the predetermined temperature difference, and step 180 for informing a line operator of the conductor temperature and the calculated allowable transmission capacity. In this case, it is possible to calculate, in real time, the allowable P \OPER\RAB Rcsposc\I2566950 spaI dm26f2l2007 Q)-13- Stransmission capacity, and to inform the line operator of the calculated allowable transmission capacity.
The method further includes step 210 for adjusting the thermal constant and the correction coefficient of the heat source when it is determined at step 160 that the rn difference between the measured and calculated temperatures is not less than the (,i predetermined temperature difference.
For convenience of the operation, the method may further include step 310 for comparing the calculated conductor temperature with a predetermined temperature, after execution of the step for calculating the conductor temperature, and step 320 for sending an alarm to the line operator when the calculated conductor temperature is not less than the predetermine temperature, thereby informing the line operator of generation of an abnormal temperature. Thus, it is possible to immediately inform the line operator of generation of an abnormal temperature.
It is possible to alert the line operator of an abnormality by measuring, in real time, the current and temperature of an underground electric power cable, and comparing each measured value with an associated calculated value. Also, the currently allowable transmission capacity can be accurately calculated, based on the measured values. It is also possible to output one or more allowable transmission capacities respectively calculated in association with transmission periods desired by the line operator. For example, it is possible to calculate respective transmission capacities allowable for 2 hours, 4 hours, 6 hours, 12 hours, 24 hours, 100 hours, etc., and to inform the calculated allowable transmission capacities, thereby allowing the line operator to efficiently manage the transmission capacity of the electric power cable.
Also, the currently allowable transmission capacity can be calculated and evaluated in real time, even in an emergency transmission operation caused by an accident, irrespective of the span of the restoring time.
That is, the cable sheath circulating current is not calculated, based on its WO 2004/088338 PCT/KR2003/001545 14 ratio to conductor current, but calculated in real time, and the calculated value is used for calculation of transmission capacity. Accordingly, it is possible to accurately evaluate Joule loss caused by sheath circulating current generated due to an erroneous grounding work or unbalance of cable installation distance.
Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. For example, although the present invention has been described in conjunction with an embodiment implementing a real-time evaluating apparatus and method for underground electric power cables, it is not limited to such an embodiment.
Industrial Applicability The real-time evaluating apparatus and method for underground electric power cables can measure, in real time, the temperature and current of an underground electric power cable to calculate the transmission capacity of the cable.
Accordingly, it is possible to achieve calculation of the transmission capacity within a certain tolerance, and verification of the calculated transmission capacity.
Also, it is possible to rapidly detect generation of an abnormal temperature caused by a variation in the conditions of the cable and surroundings, and to cope with the detected abnormal temperature. An actual variation in temperature occurring at the cable can be expected, taking into consideration the thermal conductivity and specific heat of the cable. Such a temperature variation is also monitored in real time, taking into consideration the influence of the surroundings.
Accordingly, stable transmission management can be achieved.
Thus, the present invention is useful and effective in that it is possible to calculate, in real time, the transmission capacity allowable for a desired period, thereby efficiently operating transmission of electric power.
P 'OPER'RA6BepOnm I \1256i95O0 pa I doc-26/112/207 14A- Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
Claims (14)
1. An apparatus for evaluating, in real time, an underground electric power cable, comprising: cable current measuring means for measuring current flowing through a conductor of the cable; sheath current measuring means for measuring current circulating through a sheath of the cable, thereby acquiring actual data about the sheath circulating current; cable temperature measuring means for measuring a temperature of the cable; and a communication unit for connecting the cable current measuring means, sheath current measuring means, and cable temperature measuring means to a main computer; and the main computer connected to the communication unit, and adapted to calculate, in real time, a conductor temperature of the cable based on data received from the cable current measuring means, sheath current measuring means, and cable temperature measuring means, and to calculate a transmission capacity of the cable, based on the calculated cable conductor temperature.
2. The apparatus according to claim 1, wherein: the cable current measuring means comprises first current transformers each serving as a current measuring sensor, the first current transformers being installed on respective transmission lines; and the sheath current measuring means comprises second current transformers each serving as a current measuring sensor, the second current transformers being installed at respective grounding points on the transmission lines.
3. The apparatus according to claim 1, wherein the cable temperature measuring means is installed in a longitudinal direction of the cable outside an WO 2004/088338 PCT/KR2003/001545 16 insulator of the cable.
4. The apparatus according to claim 1, wherein the cable temperature measuring means comprises resistance temperature detectors each serving as a point temperature sensor.
5. The apparatus according to claim 1, wherein the cable temperature measuring means comprises thermocouples.
6. The apparatus according to claim 4 or 5, wherein the resistance temperature detectors or thermocouples are installed to be spaced apart from one another by a distance of 1 to 50 m in a longitudinal direction of the cable.
7. The apparatus according to claim 1, wherein the cable temperature measuring means comprises fiber optic distributed temperature sensors.
8. The apparatus according to claim 1, wherein the main computer informs a line operator of the calculated transmission capacity, and sends an alarm to the line operator when an abnormality in cable transmission occurs.
9. A method for calculating and evaluating, in real time, a transmission capacity of an underground electric power cable, comprising the steps of: inputting an installation condition including a cable installation length and a cable installation type when current begins to flow through the cable; calculating a thermal constant, based on the inputted installation condition along with respective thermal conductivities and respective specific heats of inner and outer materials of the cable, and a structure of the cable; measuring conductor current and sheath current of the cable, calculating Joule heat generated at a conductor of the cable, based on the calculated conductor current and the electrical and thermal characteristics of the cable conductor, WO 2004/088338 PCT/KR2003/001545 17 calculating insulation loss based on a voltage applied to the cable conductor and characteristics of an insulator of the cable, and calculating sheath Joule heat caused by sheath circulating current in accordance with the inputted installation condition to calculate a heat source; measuring a temperature of the cable varying in a longitudinal direction of the cable; and calculating, in real time, a conductor temperature of the cable, based on information acquired in the calculations carried out at the above steps, and the measured cable temperature.
10. The method according to claim 9, wherein the step of calculating, in real time, the conductor temperature of the cable comprises the step of calculating the conductor temperature of the cable, using a temperature of a temperature- measured cable portion on a cross section of the cable as a temperature boundary.
11. The method according to claim 9, further comprising the steps of: determining whether or not the difference between a measured temperature of a temperature-measured cable portion on a cross section of the cable and a calculated temperature of the cable portion is less than a predetermined temperature difference, after execution of the step of calculating, in real time, the conductor temperature of the cable; calculating an allowable transmission capacity, based on acquired data when the difference between the measured and calculated temperatures is less than the predetermined temperature difference; and informing a line operator of the conductor temperature of the cable and the calculated allowable transmission capacity.
12. The method according to claim 11, further comprising the step of: adjusting the thermal constant and the correction coefficient of the heat source when it is determined that the difference between the measured and P \OPERRAB\Rcsposcs\125M950 spal doc .2602/2(07 -18- Scalculated temperatures is not less than the predetermined temperature difference. (N
13. The method according to claim 9, further comprising the steps of: comparing the calculated conductor temperature with a predetermined temperature, after execution of the conductor temperature calculating step; sending an alarm to a line operator when the calculated conductor temperature is not less than the predetermine temperature, thereby informing the line operator of Sgeneration of an abnormal temperature.
14. An apparatus for evaluating, in real time, an underground electric power cable, substantially as hereinbefore described with reference to the accompanying drawings. A method for calculating and evaluating, in real time, a transmission capacity of an underground electric power cable, substantially as hereinbefore described with reference to the accompanying drawings.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR10-2003-0021321A KR100496994B1 (en) | 2003-04-04 | 2003-04-04 | Underground Cable real time determining System and method thereof |
| KR10-2003-0021321 | 2003-04-04 | ||
| PCT/KR2003/001545 WO2004088338A1 (en) | 2003-04-04 | 2003-07-31 | Apparatus and method for evaluating underground electric power cables |
Publications (2)
| Publication Number | Publication Date |
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| AU2003257711A1 AU2003257711A1 (en) | 2004-10-25 |
| AU2003257711B2 true AU2003257711B2 (en) | 2007-03-15 |
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| AU2003257711A Ceased AU2003257711B2 (en) | 2003-04-04 | 2003-07-31 | Apparatus and method for evaluating underground electric power cables |
Country Status (5)
| Country | Link |
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| KR (1) | KR100496994B1 (en) |
| CN (1) | CN100397090C (en) |
| AU (1) | AU2003257711B2 (en) |
| NZ (1) | NZ538181A (en) |
| WO (1) | WO2004088338A1 (en) |
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| KR100691728B1 (en) * | 2004-09-30 | 2007-03-12 | 이관우 | The Measuring Method of the Unperfected Circuiting Current of Underground Cable |
| US7023217B1 (en) | 2004-12-16 | 2006-04-04 | Honeywell International Inc. | Method and apparatus for determining wear of resistive and conductive elements |
| KR101386414B1 (en) * | 2007-12-21 | 2014-04-21 | 재단법인 포항산업과학연구원 | Method for predicting maximum tolerance current using load current and the temperature of power facility |
| CN101672880B (en) * | 2009-09-21 | 2012-09-05 | 广东电网公司广州供电局 | Identification method of cable current-carrying capacity and identification device |
| US20120299603A1 (en) * | 2011-05-25 | 2012-11-29 | Electric Power Research Institute, Inc. | On-line monitoring system of insulation losses for underground power cables |
| CN102494793A (en) * | 2011-12-01 | 2012-06-13 | 国网电力科学研究院 | Temperature thermocouple for high-voltage and ultrahigh-voltage power cable |
| CN102590594B (en) * | 2012-03-07 | 2014-05-28 | 广东电网公司佛山供电局 | Transient state thermal circuit model-based method and device for determining permissible current of overhead conductor |
| CN102680135B (en) * | 2012-05-23 | 2014-07-23 | 重庆大学 | Method and system for monitoring cable tunnel environment based on cable temperature measurement |
| DE102012012401A1 (en) | 2012-06-25 | 2014-01-02 | Rwe Innogy Gmbh | METHOD FOR CURRENT CONTROL |
| CN102830314B (en) * | 2012-08-30 | 2015-04-22 | 广东电网公司佛山供电局 | Detection method for current-carrying capacity of overhead conductor |
| DE102012218067A1 (en) * | 2012-10-02 | 2014-04-03 | Wobben Properties Gmbh | Method for monitoring a plurality of electrical power lines of a wiring harness |
| CN103439609A (en) * | 2013-08-29 | 2013-12-11 | 华南理工大学 | Method for calculating power cable real-time emergency carrying capacity |
| KR102055414B1 (en) | 2013-09-25 | 2019-12-12 | 한국전력공사 | Apparatus for calculating driving capacity of distribution line |
| CN103823138A (en) * | 2014-02-25 | 2014-05-28 | 胡兴耀 | Circuit for monitoring power supply line electric parameters with auxiliary line |
| CN103995190A (en) * | 2014-04-10 | 2014-08-20 | 李�禾 | Current carrying capacity test method for overhead conductor |
| CN104330659B (en) * | 2014-10-21 | 2017-02-15 | 国网上海市电力公司 | Quasi dynamic compatibilization method based on cable heat transmission model |
| CN104459380A (en) * | 2014-11-20 | 2015-03-25 | 广州供电局有限公司 | Method and system for measuring cable load carrying capacity |
| KR20160074987A (en) | 2014-12-19 | 2016-06-29 | 주식회사 포스코 | Live line cable insulation monitoring apparatus |
| CN105932607B (en) * | 2016-07-22 | 2018-06-22 | 南京电力工程设计有限公司 | Cable laying experimental method and device based on cable support system eddy-current loss |
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| KR102027826B1 (en) * | 2019-04-17 | 2019-11-08 | 주연이엔에스 주식회사 | Automatic tracking system failure in distribution lines |
| CN110160481B (en) * | 2019-04-26 | 2021-03-02 | 云南电网有限责任公司电力科学研究院 | Method and device for measuring insulation damage area of cable |
| KR102421261B1 (en) * | 2020-09-17 | 2022-07-15 | 엘아이지넥스원 주식회사 | Apparatus and method for instpecting cable |
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- 2003-04-04 KR KR10-2003-0021321A patent/KR100496994B1/en not_active IP Right Cessation
- 2003-07-31 AU AU2003257711A patent/AU2003257711B2/en not_active Ceased
- 2003-07-31 WO PCT/KR2003/001545 patent/WO2004088338A1/en active IP Right Grant
- 2003-07-31 CN CNB038211149A patent/CN100397090C/en not_active Expired - Fee Related
- 2003-07-31 NZ NZ538181A patent/NZ538181A/en not_active IP Right Cessation
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| KR100496994B1 (en) | 2005-06-23 |
| CN1678916A (en) | 2005-10-05 |
| KR20040087077A (en) | 2004-10-13 |
| NZ538181A (en) | 2007-08-31 |
| AU2003257711A1 (en) | 2004-10-25 |
| CN100397090C (en) | 2008-06-25 |
| WO2004088338A1 (en) | 2004-10-14 |
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| PC | Assignment registered |
Owner name: LS CABLE LTD. Free format text: FORMER OWNER WAS: LG CABLE LTD. |
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| MK14 | Patent ceased section 143(a) (annual fees not paid) or expired |