A SAG monitoring device based on a cluster of code-based GPS receivers.

摘要

In an interconnected high voltage electrical power transmission system, there is a need to define the maximum amount of power that may be transferred without violating the system safety, reliability, and security criteria that are in place. Hence, real-time ratings of transmission line circuits are critical to system capacity utilization. In most cases, the ultimate measure of reaching maximum thermal rating is 'conductor sag'. Therefore, real-time measurement of conductor sag can help in achieving optimal operation of a transmission system.;A relatively new method of measuring physical sag of an overhead conductor involves differential global positioning technique (DGPS). The method relies on the information received from the GPS satellites. It was recently demonstrated at Tennessee Technological University that the DGPS system was capable of measuring sag to an accuracy of approximately 2 cm using a carrier frequency-based technique. However, the overall cost of the system was found to be extremely high. This thesis mainly focused on the development of a cost-effective 'code-based' GPS system for sag measurement which could be a viable alternative to the relatively expensive carrier frequency-based GPS system.;A single code-based GPS receiver is considerably inaccurate to the extent that it is almost unusable for a vertical measurement such as sag. This thesis described three different approaches to improve the accuracy of altitude data from a cluster of cheap GPS receivers so that they could be used for sag measurement. Kalman filter, bad data rejection, and artificial neural network techniques were adapted to reduce vertical error in the measurement of sag. An error of +/- 2 m in the raw data were reduced to +/-0.95 m after using the bad data rejection, to +/-0.45 m after using the Kalman filter technique, and to +/- 0.1 meters after using neural network technique. Also, a high voltage test on a cluster of GPS receivers indicate that electric fields associated with power lines may not interfere with the GPS satellite signals. Field tests indicated that a cluster of GPS receivers could be a cost-effective alternative system for the measurement of sag in an overhead transmission line conductor.