Instrumentation and measurement of overhead conductor sag using the differential global positioning satellite system.

摘要

This dissertation work deals with the design, construction, instrumentation and testing of a differential global positioning satellite (DGPS) system based instrument for the measurement of overhead high voltage (HV) conductor sag. Inherent and intentional errors in GPS technologies are discussed, and the DGPS method is described for accuracy enhancement. A DGPS based overhead conductor sag measuring instrument has been designed, constructed and subjected to selected laboratory bench and power substation testing. A method to directly measure the physical sag of overhead HV conductors is described. The main advantage of the concept is the real time direct measurement of a parameter (i.e., conductor sag) needed for the operation of the transmission system without intermediate measurement of conductor tension, temperature, and ambient weather conditions. A further potential advantage is cheaper cost. The main objectives of the experimental tests conducted were to evaluate the proper functioning of the radio communication links, assess the DGPS receiver capability in terms of GPS signal reception, and to also attest the behavior of the conductor sag measuring instrument under HV environment.; A digital signal processing (DSP) methodology to further improve the DGPS based altitude measurements for overhead conductor sag is described in detail in a four-level configuration. This involves data processing that is needed to attenuate noise levels and to enhance the measurement accuracy. The methods of bad data identification and modification, least squares parameter estimation, artificial neural network, and Haar wavelet transform analysis have been utilized to further reduce the error of raw DGPS measurements significantly. Typical accuracy, response time, strengths and weaknesses of the instrument and method are also described. An outline of a methodology to integrate the resulting real time direct overhead conductor sag measurement data with dynamic thermal line rating (DTLR) is also described.; Experience in many electric utility industries shows that the clearance of an overhead (HV) conductor above ground is a key factor limiting the available transfer capacity (ATC) of the conductor, especially in regions of high interconnection. Hence, the pertinence of conductor sag measurement to circuit operation relates to the calculation of DTLR. Thus, power systems operation and reliability could be improved by continuously monitoring the physical overhead HV conductor sag. To be able to rapidly and accurately determine the DTLR of a circuit has obvious pecuniary value in the open access same time information system (OASIS). Ultimately, the results obtained in this respect for a given operating condition could be used for anticipatory system loading purposes.