Prototype of real-time monitoring system for dynamic line rating

Abstract

The load of the electric grid in increased by the connection of more renewable energy sources and less controlled power stations. The transmission operator has to decide where and when new overhead lines are required. However the operator can also chose to utilize existing lines more by increasing the transport capacity. This can be accomplished by applying dynamic line rating. In this case the conductor temperature and sag will increase but should not not violate the safety limits. Therefore a device can be installed on over-head lines to monitor the temperature and sag in real-time. Several devices are already manufactured and tested. However these devices require a reliable communication. In this thesis the feasibility and reliability of communication with Low Power Wide area Network (LoRaWAN) protocol in an overhead line environment is studied. The first objective is to determine the consequences of DLR on overhead lines. Second shielding of the electric and magnetic field in an overhead line is evaluated. Finally an antenna is chosen and a prototype is designed to evaluated its thermal behavior, low frequency magnetic shielding capabilities and communication feasibility and reliability. The first objective is to understand how the conductor temperature, the sag and magnetic field increases in respect to the transport capacity. The change in conductor temperature is examine by considering several heating gains and losses mechanisms. The sag is approached by a sagging and parabola curve to evaluate the decrease of distance to the ground. The maximum magnetic field is determined for close distances from the conductor.Two methods are examine to shield form the electric and magnetic field from the overhead lines. There-fore the materials copper, aluminum, steel and mu-metal are evaluated on their conductivity and permeability. The antenna is determined by comparing a dipole, loop and slot antenna on their complexity and expected radio noise interference. The prototype is exposed to a test setup in which the surface temperature, and magnetic field, is measured. The reliability of communication is evaluated by analyzing the amount of send and received packages.In case of an increased transport capacity the conductor temperature of an overhead line mostly increase by Joule heating. For a conductor temperature increase and concentrated weight the sag increases with negligible tents of centimeters. The maximum magnetic field was calculated and resulted in a required shielding effectiveness. The thickness of shield was determined for each material to reduce the magnetic field inside an enclosure. A slot antenna was designed and made in the prototype and compared with simulations in respect to the reflection coefficient. The surface temperature of the prototype did barely gain heat by the generated induced currents. However the prototype does reduce the magnetic field inside and confirms the theory of low frequency magnetic shielding. Furthermore the communication is tested and resulted in reliable data transfer in the case of a 0.5 cm distant from the conductor through which a current of 800 A flow. Furthermore corona discharges were generated up to 130 kV in which data still was transferred successfully