Design and calculation method for Dynamic Increasing Transmission Line Capacity

The Dynamic Line Rating (DLR) system is designed to improve the transmission capacity of overhead lines, which decreases or delays to re-build transmission lines. The system is composed of sampling terminals installed on dead-end configuration of a line and one control instrument equipped in dispatch center. The data between the sampling terminals and the control instrument is transmitted through GPRS/GSM. Through Ethernet, the control instrument exchanges data with SCADA interface in order to integrate DLR and SCADA system. A solar Photovoltaic (PV) power supply system based on Perturb & Observe MPPT techniques was designed and successfully applied to outdoor on-line monitoring DLR system. The paper analyzed mechanical actions for overhead line concerned wind speeds and wind direction in a deflection plane. The force balance for overhead line in wind was analyzed in detail, which deduces the mechanical model to calculate sags from the measured tension. Overhead line’s state equation was corrected used the relation of temperature and sags, and deduced the ultimately line’s temperature. Analyzed the advantages and drawbacks of some mathematical model used to calculate transmission capacity. In order that the DLR system received the optimum dynamic capacity curve, combined the WM and TS model. The result shows that the DLR system is effective in increasing line capacity without violating the legal ground clearance, monitoring the on-line parameters of transmission lines, and insuring the safe ground clearances of transmission line at all times. Key-Words: Dynamic Line Rating (DLR); Transmission line; Transmission capacity; Data acquisition terminal; Photovoltaic Power Supply, MPPT, Conductor sag; Conductor tension