SST 2016, Osijek, Croatia: PREVENTING TRANSMISSION LINE DAMAGE CAUSED BY ICE WITH SMART ON-LINE CONDUCTOR MONITORING
OTLM (Overhead Transmission Line Monitoring) is a system solution for monitoring and rating of existing and new overhead lines (OHL) based on real-time monitoring of conductor temperature, sag, load, and weather conditions in order to ensure save maximum utilization of transmission line ampacity. Successful development and more than 10 years' of experience in using the OTLM system on transmission networks in several countries all over the world has initiated some system upgrades to ensure even more crucial information on OHL behaviour. The existing functionality of conductor temperature measurements (used for static rating–STR) was initially combined with a weather station measurement that enables the determination of dynamic rating (DTR). With additional inclination (sag/tension) measurements, we developed the OTLM-SAG application. With this additional feature we are able to determine the sag on critical spans. This additional information is especially useful in case of OHL crossings over roads, railroads, other overhead lines, etc. Additionally, measured data like angle (sag) is implemented to the software application to detect ice overloads or fallen trees. The mathematical relationship between the conductor’s tensile force and sag is crucial for the calculation of the conductor’s expansion (tension) and final length over a constant span distance. The reliability of ice thickness calculations mainly depends on the accuracy of conductor temperature and angle/sag measurements. The OTLM-ICE application enables the operator of the transmission network to monitor sag and clearance changes on a conductor, subjected to ice overloads. The operator can optimize and determine the suitable ampacity of transmission lines in order to prevent the damage in early phases of ice-rain.
SEERC, Portoroz, Slovenia, 2016: OVERHEAD TRANSMISSION LINE MONITORING SYSTEM IN CROATIAN POWER GRID
Putting the transmission network in the service of the electricity market causes a large energy flow in certain transmission directions. The key technical question is how much time will transmission network tolerate this situation without damage. In this case, for the system operator, very helpful information is the actual thermal loading of the conductor in normal and emergency state for re-dispatching energy. This can be achieved through thermal monitoring system installed on overhead power lines (OHLs). In this paper 110 kV OHL Crikvenica – Vrataruša in the Croatian power system was analyzed. The line was created after interpolation of a wind farm (WF) Vrataruša of 42 MW in the existing OHL Crikvenica – Senj at the beginning of 2010. The operation of WF Vrataruša at full power, in some cases, may require a change in network topology. This is done by sectioning of busbars in substations or by redispatching production of hydro power plants (HPPs) in neighboring area. Given that this situation is not present throughout the year but occurs only in certain periods, the problem of safe energy evacuation was attempted to be solved by using the Overhead Transmission Line Monitoring (OTLM) system. This paper describes the experience with OTLM devices within the pilot project on the 110 kV OHL Crikvenica - Vrataruša, along with viewpoints from grid dispatcher and relay protection specialist.
SEERC, Portoroz, Slovenia, 2016: APPLICATION OF AN ICE-ALARM IN THE OTLM SYSTEM
The developed system for Overhead Transmission Line Monitoring (OTLM) monitors the temperature and the conductor angle of inclination in order to maximise the utilization of the transmission line. Additionally, the measured temperature and the angle can be used by software application to detect conductor elongation by ice overload or a fallen tree. The mathematical relationship between the tensile force in the conductor and the sag is crucial for the calculation of the conductor elongation and the final length of the conductor over the constant span distance. The conductor elongation increases the deflection and the angle of inclination at the position of OTLM device. The reliability of ice thickness calculation depends on the reliability of temperature and angle measurements. The ice thickness on the conductor depends also on weather conditions and the temperature of the conductor. The difference between environment temperature and temperature of the conductor depends mainly on transmission current. In the framework of the OTLM-ICE application the operator of the transmission network can monitor the change in the sag and clearance of the conductor subjected to ice overloading. The operator can optimize and determine the suitable current of the transmission line in order to prevent damage in the early phase of freezing rain.
DEMSEE, 24-25 September 2015: THE CONTRIBUTION OF CONDUCTOR TEMPERATURE AND SAG MONITORING TO INCREASED AMPACITIES OF OVERHEAD LINES (OHLs)
With the measurements captured and processed by OTLM, the operator of the transmission network can optimize and determine the operation mode of OHLs. Software solutions also provide the means for a short-term prediction of conductor temperature. Temperature data along with data gained by laser scanning or similar measurements and diagnostics of the OHLs is necessary to up-rate OHL projects. This paper is supported with case studies, which prove that temperature and sag monitoring is an essential part of the transmission smart-grid.
Romania CIGRE 2011: DYNAMIC THERMAL LINE RATING IN SLOVENIA
Due to the growth of consumption and difficulties with the erection of new overhead transmission lines, loading of majority of the power lines is gradually increasing and pushing some lines into violation of the current margin at which the line is designed to operate. This in turn means that the probability of high line loading, high temperature and low wind speeds which tailor the phase conductor temperature.As a result, power utilities and system operators are looking for solutions to increase ampacity of the existing OHL without increasing the risk of equipment or system failure due to higher loading. One approach to manage the reliable operation of these systems is to utilize modern monitoring techniques, which help to safely drive overhead line over the static thermal limit. The results obtained from a pilot project 110kV OHL (Idrija – Ajdovščina) where several monitoring devices and systems were used are presented and discussed. The measurements were obtained from the following measuring devices and systems: OTLM – overhead transmission monitoring system for conductor temperature, DAMOS station – for outside temperature, wind speed and direction, and sun radiation,and ODIN – VIS – dynamic thermal rating module and Line load module). Measurements and events where transferred to the control centre (SCADA) via standard IEC protocols and presented in 3D (4D). The results show that with the utilization of conductor temperature measurements, ambient measurements and with the help of thermal rating algorithms increase in power loading is possible.
CIGRE Romania, September 2010: TEMPERATURE MONITORING OF OVERHEAD LINES (OHL) IS SMART GRID SOLUTION FOR POWER GRID
The electric utility industry is restructuring itself from regulated environment to operation under competitive wholesale. However transmission system remains regulated entity that connects deregulated generation to the end costumer. The pace of investment in overhead lines has lagged behind the rate of load growth and generating capacity additions in many countries due to public,regulatory, environmental and financial obstacles to the construction of new transmission facilities. This results in saturation of many OHL reaching critical values of capacity and sag. Besides that renewables, especially wind farms require dynamic operation of power grid. OTLM – overhead transmission line monitoring system is adding new dimensions to operation of overhead lines and enables more efficient operation while at the same time enhances the safety of system operation. With data captured and processed by OTLM the operator of the transmission network may optimize and determine the operation mode of transmission lines. Software solution also provides means for short term prediction of line temperature. Temperature data along with data gained by lidar scanning and diagnostics of the overhead line is necessary for up rating OHL projects where with relatively low investments high capacity increase can be achieved. Article is supported with case studies which prove that temperature monitoring is necessary part of transmission smart grid.
CIGRE – CIRED Slovenia 2017: COMPARISON OF SYSTEMS FOR CONDUCTOR TEMPERATURE MONITORING ON OVERHEAD LINES IN SLOVENIA, CROATIA AND SERBIA
This paper describes and compares the results of pilot projects for thermal rating of the overhead lines in the transmission network in Slovenia (Elektro-Slovenija – ELES), Croatia (Hrvatski operator prijenosnog sustava – HOPS) and Serbia (A.D. Elektromreža Srbije – EMS A.D.). Systems consist of OTLM (Overhead Transmission Line Monitoring) devices, which allow measurements of conductor temperature, current and inclination angle, and weather stations that provide weather data. The basic objectives of the project are: to increase the reliability of grid operation in normal conditions and the possible use of dynamic reserves in case of defects, the possibility of short-term and long-term predictions of ampacity, possible gains from an increase in the capabilities of the transmission line and to eliminate network congestion as well as detect the use of Dynamic Line Rating (DLR) systems in the transmission network. Based on months of monitoring and analysis of the functionality of systems that are mounted on transmission lines of different voltage levels (110 kV and 220 kV) in the form of a collection of results of measurements from OTLM devices as well as the ampacity calculation, the projects enable the estimation of real possibilities of transmission capacities of OHLs.
CIGRE – CIRED Slovenia 2017: APPLICATION FOR DETERMINING THE GEOMETRIC SHAPE OF A HIGH-VOLTAGE CONDUCTOR CATENARY TO ENSURE SAFE CLEARANCES
To ensure safe operation of a high-voltage conductor for the transmission of electrical energy, a safe clearance distance regarding to conductor temperature must also be observed. A mathematical model in the form of a computer application was developed, in order to determine the geometric catenary shape of conductor’s sag. This article demonstrates the geometry calculation on high-voltage (HV) overhead line (OHL) 2x110 kV with an installed OTLM system for continued conductor monitoring based on spot measurement of temperature and the angle on the installation point of the OTLM device. The calculated results show that an integrated mathematical model via a computer application makes possible to determine the current safe clearance on any point of the conductor span distance. The OTLM device takes account the actual geometry of the catenary (recorded by measurements on different temperature of conductor) and the measurements of weather conditions, measurements and conductor angle. The application takes account the minimum safe clearance above objects bellow the OHL. The application sends an alarm when the safe OHL operation and its surroundings are under threat due to the load of the prescribed safe clearance. With the application upgrade for sag calculation under additional mechanical conductor loads it is possible to estimate the effect of additional load caused by ice and send the data to the control centre.
CIGRE – CIRED Slovenia 2015: ANALYSIS OF ANGLE’S CHANGE AND SAG’S CHANGE REGADING TO TEMPERATURE
The analysis in this paper based on method for on-line monitoring of sag supported by horizontal tensile force calculation by using developed mathematical model. Model based on assembly conditions, mechanical and physical properties of conductor. The result of model is relationship between sag, horizontal forces and temperature. The angle of conductor at the OTLM fixed point is using as control parameter which can be recorded by operator in distribution center. In order to provide the comparison between angles calculated by model and measuring angles, it is necessary to consider geometrical facts of conductor in transmission field. Only very high quality information can provide information about unusual additional mechanical loading of conductor. The developing and adopting of calibration function in mathematical is necessary for ensuring on-line monitoring of conductor with different level of alarms condition. In this paper the effect of both temperatures is going to be analyzed.
CIGRE – CIRED Slovenia 2015: UNDERSTANDING CATENARY GEOMETRY IS A GOOD BASIS FOR BETTER FORECASTING THE SAFETY MARGINS OF OHL LOAD
The Slovenian distribution network operator has been actively monitoring and responding to world trends of determining static and dynamic limits of overhead line loads for the last decade. The erection of a testing ground with different technologies for determining the thermal current of a conductor on OHL 2x 110kV Dravograd–Slovenj Gradec has given the researchers and experts excellent conditions to analyse and determine uncertainty margins of DTR algorithms. An elaborate analysis of the gained data has shown the necessity for controlling the catenary geometry on span SM23–SM24. Ensuring the prescribed safety height especially at points of object crossing is a warranty for safe operation of the distribution network and safeguarding lives and property. Numerous measurements of the catenary geometry and sags have been carried out on the testing ground with various measurement methods. The analysis of sag data was carried out on a concrete OHL from the project start, the conductor installation to real-time measurements, using different measuring devices and methods. The purpose of this article is to illustrate the OHL geometry from the engineering phase to the installation phase and the quality control of the conductor installation, as well as the operational phase. We were mainly focused on the methods for determining or setting sags and the subsequent sag control on the filed and the meaning of monitoring actual safety heights on the field during a certain periodical cycle, since this is the only way we can carry out DTR within a certain confidence limit.
CIGRE – CIRED Slovenia 2013: STATIC AND DYNAMIC THERMAL RATING OF OHL 2X110 KV SLOVENJ GRADEC – DRAVOGRAD ON THE BASIS OF SURFACE (LOCAL) AND CORE (ALONG THE WHOLE LONE) TEMPERATURE MEASUREMENTS
Transmission capacity of an overhead line is determined by its maximum temperature at which the overhead line (OHL) reaches maximum sag. While considering the safety margins it is obvious that the key information is the conductor temperature, because it takes into account momentarily influences (Joule losses, wind, and sun radiation) that impacts the line temperature. For monitoring of conductor temperature on the OHL line 2x110 kV Slovenj Gradec – Dravograd two technologies are used: local (spot) measurement (OTLM) and whole line measurement with the optical fibers (Raman spectroscopy) in the conductor (OPPC). OTLM system enables measurements of the conductor surface while OPPC measures temperature at OHL core. The implementation of mentioned measurement system on either local (spot) or along the whole line in connection with the weather station and SCADA enables static (STR) and dynamic (DTR) thermal rating.
CIGRE Croatia 2017: APPLICATION FOR DETERMINING THE GEOMETRY OF CATENARY FOR SAFETY CLEARANCE OF TRANSMISSION LINE
The paper presents the calculation of the sprocket geometry on two 110 kV and 220 kV high voltage power lines, to which an OTLM (Overhead Transmission Line Monitoring) system is installed. This system allows continuous monitoring of the status of the guides based on accurate temperature measurement and guide bends at the OTLM mounting location. The input data uses the material and physical properties of the guide, as well as the actual shape of the sprocket, measured at three different conductor temperatures. Changing the temperature of the conductor has an appreciable influence on the charge but also on the tension of the conductor. The calculation results show that in a computer application, using an integrated mathematical model, it is possible to determine the current security height of the guides at an arbitrary location below the guiding range. The mentioned computer application can be upgraded by calculating the execution under the additional mechanical loads of the guide, which allows the evaluation of the influence of ice on the run or on the safety height
CIGRE Croatia 2016: EXTENSION OF APPLICATION OTLM-SAG TO ICE ON CONDUCTOR IN DLR SYSTEM
High voltage transmission lines are very sensitive to weather conditions and temperature loading. At some part of It is reason for on-line monitoring of geometry of catenary in all weather conditions, e.g. during hot summer and high ampacity loading or during cold winter when ice (or wet snow) can caused additional mechanical load of conductor. Behind monitoring of catenary’s geometry, it is necessary to know tensile load of conductor, especially at low temperature. Development of “Overhead Transmission Line Monitoring - OTLM” provides monitoring of catenary’s geometry by thermometer and inclinometer, for calculating tensile load and sag of conductor. The aim of this paper is present of new OTLM system based on temperature and angle measurement for calculation of catenary's geometry, tensile loads, clearance distances/sag, which is sensitive to ice or mechanical loading of conductor.
CIGRE Croatia 2015: DEVELOPMENT OF APPLICATION FOR ON-LINE MONITORING AND ALARM OF ICE ON HIGH VOLTAGE TRANSMISSION SYSTEM
The change of temperature of conductor as consequence of current and climatic conditions (temperature of air, wind velocity and direction, sunning zone, etc…) have direct influence on conductor length, sag and tensile force at the pillar connection. Paper is dealing with boundary conditions regarding sag and tensile force. One possibility is that the existing OTLM system static and dynamic temperature monitoring added inclinometer and weather station. OTLM device is used for temperature measurement on conductor and slope at the end of conductor, while the weather conditions (wind velocity and direction, temperature of air) are measured independently by weather station. The new computer software application is developed for calculation of tensile force and sag of conductor. It is possible to estimate icing condition on transmission system on the comparison between calculated and measured angle on site of OTLM device installation.
CIGRE Croatia 2014: ON-LINE MONITORING FOR INDIRECT DETERMINATION OF HORIZONTAL FORCES VS. TEMPERATURE AND INCLINE ANGLE OF TRANSSMISION CONDUCTER
Slovenian transmission grid operator ELES is trying in last decade to design and develp sofisticated electric tansmission system. ELES introduces relaible system for controling and maintance of transmission system with modern solutions and inovative approaches. The new pilot projects are running on facilities for testing and real high voltage transmission grid network as results of collaboration between academic institutions, industrial companies and ELES. One project is aimed to analysis of efficiency system for on-line thermal rating, weather conditions and calculation of allowed thermal current. Since last winter had significant impact on failure of 110, 220 and 400 kV electricity transmissions grid, the Slovenian ELES company looking for possibility of on-line monitoring including ice alarm. Proposed computer added software in OTLM system can provide horizontal forces change vs. Temperature and incline of line in frame of regular operating conditions and in case of ice as well. Final goal of presented project is on-time worrying of distribution centre about ice on the transmission network system.
CIGRE Croatia 2013: SPOT AND LONGITUDINAL TEMPERATURE MEASUREMENTS BASE FOR STATIC AND DYNAMIC THERMAL RATING OF OHL 2×110 kV SLOVENJ GRADEC – DRAVOGRAD
Transmission capacity of an overhead line is determined by its maximum temperature at which the overhead line (OHL) reaches maximum sag. While considering the safety margins it is obvious that the key information is the conductor temperature, because it takes into account momentarily influences (Joule losses, wind and sun radiation) that impacts the line temperature. For monitoring of conductor temperature on the OHL line 2x110 kV Slovenj Gradec – Dravograd two technologies are used: local (spot) measurement (OTLM) and longitudinal temperature measurement with the optical fibers (Raman spectroscopy) in the conductor (OPPC). OTLM system enables measurements of the conductor surface while OPPC measures temperature at OHL core. The implementation of mentioned measurement system on either spot or longitudinal in connection with the weather station and SCADA enables static (STR) and dynamic (DTR) thermal rating.
CIGRE Croatia 2012: DYNAMIC THERMAL MONITORING OF OVERHEAD LINES OF TRANSMISSION SYSTEM
Implementing new technologies - solutions with systematic approach - is becoming common practice for highly skilled engineers in Slovenian transmission grid operator - ELES. One of new approaches of using new technologies is utilization of modern monitoring techniques for dynamic thermal rating (DTR) of overhead lines (OHL) that is one of the solutions for future smart transmission grid. Increasing ampacity of the existing OHL without increasing the risk of equipment or system failure due to higher load can be conducted only if you can measure OHL temperature and ambient conditions (outside temperature, wind speed and direction, and sun radiation) that have direct influence on sag. If we take into account that OHL are operating in deregulated environment, than reliability and ampacity of OHL is the most important objective of all power utilities. Existing temperature monitoring systems (spot or along the line) is now being upgraded with system that enables setting grid operations limits.
CIGRE Croatia 2010: MODERN MONITORING AND DIAGNOSTICS TECHNOLOGIES AS „SMARTGRIDS“ ELEMENTS IN SLOVENIAN TRANSMISSION SYSTEM
The Slovenian transmission system is actively involved in building electricity transmission networks of the future, smart grids with a vision. These are based on market liberalisation and production technology modification to fulfil environmental demands and future use of electrical energy. The basic idea of smart grids is effective use (production, transmission, distribution and consumption) of electrical energy, while at the same time lowering costs and electrical energy loss and improving supply quality and reliability. New technologies are implemented alongside standard and verified transmission network management and maintenance technologies. Modern technological solutions and innovations in the Slovenian transmission network are a result of systematic several years’ work of the organisation and experts. The goal of presented modern technologies is to confirm innovation as the economical power for electrical network renewal that assures secure supply and self-recovery.
CIGRE BiH 2015: INCREASING AMPACITY OF OVERHEAD LINES BY USING THE SYSTEM FOR CONDUCTOR’S TEMPERATURE AND SAG MONITORING
Nowadays the need for electric power is increasing in giant steps. Its generation is trying to satisfy it, either by using more classical (hydro, thermo and nuclear) sources or the new ones (solar and wind farms). Transmission and distribution systems are hardly following this trends. This is the reason why existing capacities should be used to its maximum limits but not jeopardizing its reliability and safety. So, we are witnesses of Smart Grid expansion and automation systems. An important step in this direction is efficient monitoring system on Over Head Lines (OHLs). A good example of this is OTLM (Overhead Transmission Line Monitoring) system which can control OHL operation and ampacities by measuring temperatures and sag of the conductors.
CIGRE Serbia 2017: DYNAMIC LINE RATING SYSTEM IMPLEMENTATION ON THE OVERHEAD TRANSMISSION LINE 220kV SS VALJEVO 3 – SS OBRENOVAC
This paper presents the results of the pilot project for dynamically monitoring the temperature of the overhead line conductor (DLR – Dynamic Line Rating) in the transmission network of EMS. The main objective of the project is that based on the several months of monitoring and analysis of the DLR system, installed on the 220kV power line 227/2 SS Valjevo 3 –SS Obrenovac, through the collection of the results of the temperature, current and inclination angle measurements, as well as the ampacity calculation, assess the real possibility of its load. The paper gives a brief review of the installed equipment namely OTLM (Overhead Transmission Line Monitoring) sensor, three weather stations, and DLR server for the collection and data processing. On the overhead transmission line three spans were choosed for the eqipment installation. Data from the sensors, and weather stations, are transmitted via GPRS network, to the DLR server installed in the National Dispatch Center. Server’s software collects and stores the data in the database, as well as does the ampacity calculation, considering the current meteorological conditions. On the basis of the measured and calculated data, it is possible to analyze the difference between dynamic line rated ampacity and static (seasonal) rated value during the monitoring period. This paper presents the analysis of the measured data for the monitored transmission line.