Conductor Ampacity Research Articles

Reliability assessment of dynamic line rating methods based on conductor temperature estimation

Dynamic line rating techniques are increasingly prevalent in the computation of ampacity for overhead transmission lines. Some of these methods, commonly employed by system operators, rely on real-time measurements to calculate conductor temperature, either directly or indirectly. Despite their widespread usage, the susceptibility of these techniques to measurement errors has been largely disregarded in prior research. In this regard, this paper includes a groundbreaking reliability analysis addressing the impact of measurement errors on various dynamic line rating techniques in overhead lines, based on conductor temperature estimation. Two case studies are presented, incorporating typical errors from simulations. The first case study adopts a standard 24-hour profile for the variables involved in the conductor ampacity calculation. In the second study, Monte Carlo simulations are conducted, in which meteorological variables are randomly assigned with five load levels to evaluate the current’s influence on measurement noise sensitivity. The resulting ampacity errors across all methods considered are remarkably high, with mean values exceeding 150% in specific scenarios. This unequivocally demonstrates that the commonly accepted levels of measurement accuracy in these widely used rating techniques yield estimations falling far below acceptable reliability standards.

Application Research on Online Power Cable Temperature Detection via Fiber Optics

Abstract Power cable conductor ampacity directly correlates with conductor temperature. Traditional thermocouple measurement fails to ensure real-time monitoring, risking cable operation. Leveraging Raman scattering principles, this study establishes a method for continuous surface temperature detection of long-distance power cables using distributed fiber optics. This approach surpasses OTDR-based measurement in speed and reliability, offering superior online monitoring for cable systems, suitable for widespread adoption.

Upaya Peningkatan Keandalan Penyulang dengan Manuver Jaringan

The Tlogosari feeder was disturbed 20 times so that the reliability of system wasn’t said to be good. The purpose of this research was to make efforts to increase reliability and reduce ENS by maneuvering the network and adding CO Branch. Hoped that after these efforts the reliability level of Tlogosari Feeder will be better and ENS will be as minimal as possible. The network maneuver is carried out by delegating part of Tlogosari Feeder load when it experiences a disturbance to the nearest feeders on the condition that the total load current after the maneuver doesn’t exceed the current setting and conductor ampacity. The addition of CO Branch is based on fault data to localize fault points to reduce transformer outages. After performing network maneuvers and adding CO Branch in the sub-networks, it was found that the SAIDI and SAIFI values were improved and the ENS was reduced. Network maneuvering and addition of CO Branch are quite effective in implementing the Tlogosari Feeder.

WITHDRAWN: Fast Assessment of Distributed Photovoltaic Hosting Capacity of Distribution Networks Based on Photovoltaic Barycenter Theory

• The concepts of moment and barycenter of PV and load distributions are given. • The PV Barycenter Theory with three metrics is proposed for the first time. • A quick PV maximum hosting capacity assessment method is established. • The rapidity, accuracy, practicability and universality of the method are verified. High penetration distributed PV deployment will lead to serious power quality problems and a significant active power return, posing a serious threat to the safe and stable operation of distribution networks. This paper proposes an innovative fast assessment method of distributed PV maximum H osting C apacity (HC) of distribution networks based on P V B arycenter T heory (PBT). The new concepts of moment and barycenter are proposed, and the global metric GM of PV barycenter is achieved. The non-iterative formulas of HC that meet the node voltage upper limit and the conductor ampacity upper limit are derived, and the local metric LM1 of voltage upper limit and the local metric LM2 of ampacity upper limit are obtained. Together with the global metric GM, a complete PV Barycenter Theory is constituted. A new quick assessment method for HC of distributed PV in distribution networks is proposed. This method is applied to four 10kV distribution feeders in Chengde, Hebei Electric Power Company. The calculation results in all scenarios show that, compared to the classical Monte Carlo method, the new method boosts the average calculation efficiency by 4856 times while maintaining a 0.83% average error. The proposed method can also take into account the real-world constraints such as the existing PV capacity of the distribution networks and the exploitable PV capacity of the deploying point, making the deployment scheme more practical and feasible. The comprehensive analysis results on load rate sensitivity and PV penetration all verify the rapidity, accuracy, practicability and universality of this method.

A Multi-Variable DTR Algorithm for the Estimation of Conductor Temperature and Ampacity on HV Overhead Lines by IoT Data Sensors

The transfer capabilities of High-Voltage Overhead Lines (HV OHLs) are often limited by the critical power line temperature that depends on the magnitude of the transferred current and the ambient conditions, i.e., ambient temperature, wind, etc. To utilize existing power lines more effectively (with a view to progressive decarbonization) and more safely with respect to the critical power line temperatures, this paper proposes a Dynamic Thermal Rating (DTR) approach using IoT sensors installed on some HV OHLs located in different Italian geographical locations. The goal is to estimate the OHL conductor temperature and ampacity, using a data-driven thermo-mechanical model with the Bayesian probability approach, in order to improve the confidence interval of the results. This work highlights that it could be possible to estimate a space-time distribution of temperature for each OHL and an increase in the actual current threshold values for optimizing OHL ampacity. The proposed model is validated using the Monte Carlo method.

Improvement and sensitivity analysis of equivalent heat transfer model for dynamic thermal rating of overhead lines

With the rapid growth of power demand, the conductor ampacity calculation method based on the dynamic thermal rating (DTR) becomes more and more important. Based on the shortcomings of the current DTR models, a new DTR model that does not need to measure the wind speed and the operating state of conductor is proposed, which is called the equivalent heat transfer (EHT) model. However, there are still shortcomings in the accuracy of the EHT model in application. In this paper, the EHT model is improved at first according to the consideration of the effect of air physical parameters and the redetermination of the experimental parameters of the EHT equipment. Then, the operation of EHT equipment is simulated through the established experimental platform. The improved EHT model is verified by the IEEE standard. Finally, the sensitivity analysis of the improved EHT model is carried out. The results show that the improved EHT model is greatly improved on application accuracy compared to the original EHT model. Moreover, the improved EHT model can choose the steady-state temperature at any position on the surface of the aluminum ball to calculate the conductor ampacity, and the relative error does not exceed 6%. The improved EHT model is reliable and can meet the safe operation requirements of the power system in practical engineering applications.

Dynamic Line Rating Solution: Deployment Opportunities for the Power Transmission Grid of Vietnam

Power system usually have standard static ratings (SLR) that determines load constraints. It refers to the maximum allowable conductor ampacity pre-determined by worst-case conditions (high ambient temperature, maximum solar radiation, and low wind speed) of their overhead transmission lines, that rises the line’s temperature without infringing ground clearance and causing loss of conductor tensile strength. Line’s dynamic capacity is created as an alternative to standard constant rating that is designed with reference to extreme weather and load conditions. Dynamic line rating allows assets the real power line’s operating capacity using available information on weather conditions. DLR is hence often more flexible than SLR, that have a chance of extending capacity of existing power lines for some periods of time with favorable weather conditions for transportation higher electrical power capacity from production site to the load. This paper investigates the possibility of using dynamic line rating (DLR) to expand the existing power transmission capacity of overhead lines which can be implemented on 220 kV transmission lines in Vietnam, especially in some line areas with high-density of renewable energy integration. This work applies a DLR caculation models to determine the power lines’ additional theoretical ampacity obtained by using this methodology for a Ninh Thuan region with distinct conditions regarding i) weather database, ii) topography and iii) wind and solar power resource. The results show that the dynamic rating is predominantly higher than the static rating, which potentially enhances the system’s reliability. This research provides a comprehensive study of literature on dynamic line rating, current constraints on the power system based on the geography of Vietnam, and analysis in Python and Matlab environment of real-time weather databases applied to dynamic rating on a proposed case study.

An Equivalent Heat Transfer Model Instead of Wind Speed Measuring for Dynamic Thermal Rating of Transmission Lines

With the increase in electricity demand, the ampacity calculation based on the dynamic thermal rating (DTR) technology is increasingly significant for assessing and improving the power transfer capacity of the existing overhead conductors. However, the DTR models now available present some inadequacies in measurement techniques related to wind speed. Therefore, it is essential to propose a new model instead of wind speed measuring in DTR technology. In this paper, the influence analysis of various weather parameters on the conductor ampacity is carried out by using the real weather data. Based on the analysis, it is confirmed that the impact of wind speed is significant, especially in the case of the low wind speed. Moreover, an equivalent heat transfer (EHT) model for DTR technology is proposed instead of wind speed measuring. For this EHT model, the calculation of conductor ampacity is realized through investigating the correlation of heat losses between the heating aluminum (Al) ball and conductor. Finally, combined with the finite element method (FEM), the EHT model proposed in this paper is verified by the Institute of Electrical and Electronic Engineers (IEEE) standard. The results indicate that the error of the EHT model is less than 6% when employing the steady thermal behavior of the Al ball to calculate the ampacity. The EHT model is useful in the real-time thermal rating of overhead conductors. It can increase the utilization of overhead conductors while also avoiding the limitation of the existing measurement techniques related to wind speed.

Investigation of Novel DC Wind Farm Layout During Continuous Operation and Lightning Strikes

This paper proposes a novel layout for a grid-connected DC wind farm (DCWF) and investigates the performance under continuous operation and direct lightning strikes particularly for high soil resistivity. The DCWF employs internal dc grid that supplies generated power to the host AC utility through high voltage direct current (HVDC) transmission link. The proposed layout ensures sustainability of power supply against potential interruptions of DCWFs either during normal conditions or lightning incidents to comply with grid codes regulations. During continuous operation, the proposed layout safeguards the entire DCWF cables against flow of return currents to avert derating of conductor ampacity. Besides, protects WT nacelle switchgear and entire interface converters against hazards of surge currents. Furthermore, an effective grounding system design is proposed to introduce a low impedance path for system return currents, minimize voltage drop across grounding impedance and thus maximize DCWF delivered power to the grid. A detailed system that sufficiently represents models of system cables, grounding network and interface converters is built to verify the proposed scheme significance. The obtained results assure the capability of proposed layout to cease return currents via cable sheath during continuous operation and provide superior mitigation of lightning-associated transient voltages and currents.

Investigations on High Temperature Low Sag (HTLS) Conductors

Electric power demand is growing at an exponential rate due to establishment of industries and economic growth in the country. Central electricity authority of India (CEA) has estimated per capita electricity consumption will increase at a rate of 6 percent per annum, this will increase the load on the transmission and distribution system. Limitations of Right of Way (ROW) has made it difficult to construct new lines, particularly in metropolitan and densely populated cities, hence high temperature low sag (HTLS) conductors are being used adopted, several projects in the country are being executed to overcome the problem of burdening of transmission/distribution system. HTLS conductors operate at 2–3 times higher ampacity and thermal rating, hence can be used for higher power transmission without upgrading the existing towers and infrastructure. The present investigation aims to understand and estimate the conductor temperature and ampacity dependent on different parameters like wind velocity, wind angle, emissivity and fault current level. The investigation highlights the dynamic thermal rating of HTLS conductor with change in wind velocity and angle, thermal performance of conductor during fault condition and thermal rating with emissivity, absorptivity and ambient temperature during flow of fault current is presented. A new experimental setup is established to investigate the performance of HTLS and Traction copper conductor in the laboratory, attempt has been made to study effect of magnetic fields and conduct EBSD analysis, some important conclusions drawn from the investigations are analyzed and presented.

Case study of the increase in capacity of transmission lines in the Chilean system through probabilistic calculation model based on dynamic thermal rating

The usual practice in operators is to specify conductor thermal limits based on worst-case weather condition scenarios. However, given that environmental conditions change constantly, so does the ampacity of the conductor. This is why line thermal limitation should not be established in a conservative, fixed or invariable way. In the case of Chile, the Independent System Operator (ISO) establishes current-carrying capacity curves. Nevertheless, these are only a function of the ambient temperature in the presence of the sun. Such methodology is insufficient since it does not consider the effect of wind as the main conductor cooling mechanism.The main contribution of this paper is the development of a new approach for a probabilistic current calculation model based on dynamic thermal rating. This approach accounts for the spatial and temporal variation of weather conditions along a line. The approach maximizes the line’s current capacity by employing an iterative process based on the span identification that limits the conductor ampacity. Furthermore, the approach includes temperature restrictions to avoid conductor mechanical problems.The model is applied in the Chilean system, particularly to the Maitencillo–Nogales 220 kV transmission path. The new current limitations established by the proposed approach are compared to those set by the Chilean ISO and show significant increases in the current-carrying capacity of the lines and hence a better use of NCRE generation to lower production costs and CO2 emissions.

Experimentally validated partial least squares model for dynamic line rating

This study presents a model based on partial least squares (PLS) regression for dynamic line rating (DLR). The model has been verified using data from field measurements, lab tests and outdoor experiments. Outdoor experimentation has been conducted both to verify the model predicted DLR and also to provide training data not available from field measurements, mainly heavily loaded conditions. The proposed model, unlike the direct measurement based DLR techniques, enables prediction of line rating for periods ahead of time whenever a reliable weather forecast is available. The PLS approach yields a very simple statistical model that accurately captures the physical performance of the conductor within a given environment without requiring a predetermination of parameters as required by many physical modelling techniques. Accuracy of the PLS model has been tested by predicting the conductor temperature for measurement sets other than those used for training. Being a linear model, it is straightforward to estimate the conductor ampacity for a set of predicted weather parameters. The PLS estimated ampacity has proven its accuracy through an outdoor experiment on a piece of the line conductor in real weather conditions.

Permormance Analysis of Distribution System with Distributed Generation, A Case Study of Nepal

This paper presents analysis of impact of synchronous machine based distributed generation (DG) in distribution networks at various penetration levels. Higher DG penetration level raises important issues about distribution system operation. Therefore, new techniques are needed to determine the maximum amount of DG that may be installed without requiring major changes in the existing electric power system. In this paper, DG is placed at the terminal points of the lateral one at a time and both real and reactive power is injected at power factor ranging from unity to zero. Limiting factor for maximum penetration primarily taken is load bus voltage at upper voltage limit of 1.05 pu. Variation in substation voltage is taken as another important constraint. System under consideration for studies is the radial distribution network originating from Chaumala Substation that is situated in Kailali district of Nepal. This paper reveals that maximum allowable voltage rise perspective is recommendable if substation voltage is regulated at 1.05 pu but if substation voltage is kept at 1.00 pu, highly utopist scenario of penetration occurs. So, conductor ampacity or line loading perspective shall be suitable. Further, if DG is injected taking substation voltage at 1.05pu, there is a chance of under voltage at bus that is situated at the end of the critical branch. On contrary, if substation voltage is taken to be 1.00pu, voltage dip is severe at the bus situated very close to substation.Lastly, if the DG is placed closer to the substation, its penetration level should be increased and vice versa.

A Holistic Method for Conductor Ampacity and Sag Computation on an OHL Structure

The rating current (ampacity) of a conductor erected on a particular overhead line (OHL) structure installed at a specified location is influenced by the conductor, the OHL structure, as well as weather and operational parameters. Many studies have been carried out regarding calculating an aerial bare conductor's ampacity at a steady-state conductor temperature, but without considering the OHL structure as part of the system. In this paper, a holistic methodology for calculating the conductor's ampacity and sag at any temperature and power frequency, erected onto a prespecified OHL structure is developed, considering together the mechanical and electrical parameters of the overall system. This methodology incorporates the conductor's basic material properties allowing the calculations to be applied to newly developed high-temperature low-sag composite conductors. In this way, it becomes possible to identify, at the system level, the potential benefits that may result from the improved performance of these conductors as well as to indicate new sizes that may better fit a prespecified system, optimizing its performance. The methodology is also validated with a real system application, resulting in correct predictions of the performance of a four-span double-line system.

Photovoltaic Generation Penetration Limits in Radial Distribution Systems

Photovoltaic generating units connected to distribution systems represent a type of distributed generation (DG) that has been experiencing increased growth in recent years. Higher DG penetration levels may be interesting from many different points of view, but raise important issues about distribution system operation. Therefore, new techniques are needed to determine the maximum amount of DG that may be installed without requiring major changes in the existing electric power system. According to the literature, voltage rises at load bus bars are a serious limiting factor when installing DG. This paper presents and discusses studies proving that conductor ampacity and voltage rises are limiting factors that manifest themselves under different conditions. The present study highlights situations in which line overloads are more restrictive than voltage rises. Variation in substation voltage, load, and its power factor were simulated in a simplified radial distribution system model, and the amount of distributed generation that may be installed was obtained. Mathematic formulae were developed to determine the amount of distributed generation for existing utility systems.

Evaluating opportunities for increasing power capacity of existing overhead line systems

Re-tensioning and/or re-conductoring are considered the most popular cost-effective ways to increase the efficiency of power capacity of an existing aerial line. The identification of the most beneficial method requires ampacity and sag calculations to consider all the system factors that influence its performance. A holistic methodology for calculating conductor ampacity and sag at any temperature and power frequency when different conductors are implemented onto a pre-specified overhead line structure is used to illustrate how the properties of the conductors allow opportunities for thermal and voltage uprating on existing overhead line systems. This is achieved through a comparative analysis of the electrical and mechanical behaviour of conductors of different technologies and sizes on a 33 kV wood pole system. The analysis focuses on normal operating temperatures for novel conductors that can operate at elevated temperatures to avoid the increase in losses, and also allow the comparison with conventional conductors in order to identify potential benefits for the investigated overhead lines (OHL) system.

A fast and exact method for real-time overhead conductor ampacity evaluation

The paper presents a new method to evaluate conductor ampacity which combines accuracy and rapidity. With the proposed model, the conductor temperature in a large number of lines can be evaluated in real-time using a computer and a centralized data acquisition system.

Wire and Cable Update-1985

Power distribution within a large modern petrochemical complex involves many thousands of feet of instrument and power cables that must be applied and installed with optimum life, reliability, and cost. Current practice and trends in evaluating, sizing, specifying, and installing the more commonly used cables and cable systems in petrochemical plants are reviewed. Current trends in industrial cable design and construction are considered. This includes low-and medium-voltage power cable, control cable, and instrument cable. The relative merits of various materials used in cable constructions are reviewed with particular emphasis on insulations, shields, jackets, and overall sheaths. Protection of cable from harsh environmental conditions is included. Methods are presented for selecting the proper cable construction for differing applications. Installation methods, including conduit, tray, and direct burial systems, are reviewed with emphasis on the additional ampacity tables for the 0-2000-V cables proposed for the 1987 National Electrical Code (NEC). These tables, as well as the existing NEC tables for the 2001-35 000-V cables, were generated using the Neher-McGrath method which permits the calculation of any conductor ampacity for a specific installation. Proper conductor sizing is presented based on short circuit rating, voltage drop, temperature rating, and actual cable installation method.

Experimental Verification of a Real-Time Program for the Determination of Temperature and SAG of Overhead Lines

An outdoor test facility was used to experimentally verify real-time overhead conductor ampacity and sag programs. The facility consists of a 213m span of 26/7 336 kcmil ACSR conductor completely instrumented ented with 13 thermocouples as well as a sag and tension device. A weather station mounted near mid-span monitors all pertinent weather conditions. The measured conductor tempetatures fluctuated significantly antly along the length of the test span. Spanwise variations in the measured instantaneous temperatures were frequently in excess of 100C for a wide variety of conductor currents and weather conditions. The conductor temperatures predicted by the real-time ampacity program ram were within°C100C of the average measured conductor temperatures for all tests. Measured conductor sags were within 5 percent of values predicted by a real-time sag program. The results of the experimental project show that accurate predictions of real-time conductor temperatures and sags can be achieved by knowing the conductor current, wind speed, wind direction and the ambient air temperature. Therefore, computer programs are capable of predicting conductor temperatures and sags with a minimum amount of weather data provided by a simple and inexpensive weather station. Instrumentation ation placed on the conductor is not necessary for execution of the ampacity and sag programs.

Determination of Transmission Line Ampacities by Probability and Numerical Methods

The determination of transmission line ampacities using a statistical approach has been studied at the University of Saskatchewan [6]. This paper describes a method of statistically representing the weather elements by the method of moments and the Pearson family of curves. A digital method of determining the permanent loss of tensile strength due to annealing is also described. These two methods are combined and used to determine the conductor ampacity for selected assumed load patterns.