Analysis of a Smart Sensor Based Solution for Smart Grids Real-Time Dynamic Thermal Line Rating

Abstract

Dynamic thermal line rating (DTLR) allows us to take advantage of the maximum transmission capacity of power lines, which is an imperious need for future smart grids. This paper proposes a real-time method to determine the DTLR rating of aluminum conductor steel-reinforced (ACSR) conductors. The proposed approach requires a thermal model of the line to determine the real-time values of the solar radiation and the ambient temperature, which can be obtained from weather stations placed near the analyzed conductors as well as the temperature and the current of the conductor, which can be measured directly with a Smartconductor and can be transmitted wirelessly to a nearby gateway. Real-time weather and overhead line data monitoring and the calculation of DTLR ratings based on models of the power line is a practical smart grid application. Since it is known that the wind speed exhibits important fluctuations, even in nearby areas, and since it plays a key role in determining the DTLR, it is essential to accurately estimate this parameter at the conductor’s location. This paper presents a method to estimate the wind speed and the DTLR rating of the analyzed conductor. Experimental tests have been conducted to validate the accuracy of the proposed approach using ACSR conductors.

On-Line Core Losses Determination in ACSR Conductors for DLR Applications

“…According to [ 17 , 18 , 42 ], the losses due to Joule ( P J ), core ( P M ) and redistribution ( P redi s , transformer effect) effects can be expressed as follows: P J + P M + P redis = I 2 R ac …”

“…The heat balance equation, which must always be satisfied, is the basis for implementing DLR approaches for ACSR conductors [ 18 ]. It states that the sum of the ohmic ( P J + P M + P redi s ) and solar heat gain must equal the heat loss by convection and radiation [ 44 ].…”

“…According to [ 10 , 18 ], convective heat losses are calculated as: where Nu is the Nusselt number, which can be calculated as detailed in [ 18 ] once the conductor diameter, surface roughness, local wind speed, local temperature, relative density and kinematic viscosity of the air are known.…”

“…The alternating current resistance ( R ac ) of the conductor is a key parameter which allows the ampacity or maximum current capacity of power conductors to be accurately estimated. This can increase their effective capability [ 16 ], since Joule and core losses represent the main heat source of the conductor, and can be determined from the alternating current (AC) resistance R ac [ 17 , 18 ]. Line current, along with ac resistance, are used in some DLR approaches to estimate the effective wind speed [ 18 ].…”

“…This can increase their effective capability [ 16 ], since Joule and core losses represent the main heat source of the conductor, and can be determined from the alternating current (AC) resistance R ac [ 17 , 18 ]. Line current, along with ac resistance, are used in some DLR approaches to estimate the effective wind speed [ 18 ]. Therefore, DLR enables the development of more accurate power flow analysis approaches if the ac resistance, which changes with temperature, is measured in real time [ 19 ].…”