The drastic consequences of emergencies force us to look for ways to increase the stability of the device operation at overhead power transmission lines (OHPTL). It can be achieved by developing new algorithms for determining the protection operation setpoints and detecting the damage location. Fault detection at OHPTL of 10 kV and above is mainly carried out by the devices based on the measurement of emergency mode parameters. For fault detecting one should analyze the parameters of not only current and voltage at the accident time, but also of the overhead power line. Specific active resistance, specific reactance, specific active conductivity and specific reactive conductivity are used to characterize the overhead power transmission lines. As a rule, these parameters are normalized to the unit of length of the overhead line (OHL) and linear values are used in the calculations. When analyzing power lines, tabular approximate values of longitudinal and transversal parameters in equivalent circuits are used, although solving problems in an unsimplified form leads to significant refinements of the known solutions, since OHLs are influenced by external atmospheric factors (ambient temperature, soil moisture, wind force, ice formation, etc.). The paper analyzes these characteristics and evaluates the influence of the listed factors on the linear longitudinal and transversal parameters of overhead lines. A functional dependence of external factors on the distance protection actuation setpoint was obtained. A method for automatic correction of the setpoint of the intelligent protection complex and an adaptive relay protection algorithm was developed, taking into account changes in climatic factors, enabling to reduce the “dead zone” length and increase the protection sensitivity. The use of line parameters obtained from the sensors in the calculations give rise to a more accurate fault detection based on the use of remote sensing methods.
The problem of preventing icing accidents in electric networks of power systems is relevant in many regions of Russia. Disruptions of overhead lines, caused by intensive icing and icing and wind loads are most severe in their effects. However, the devastating effect of icing is not fatal. This is confirmed by the experience of power systems, systematically carrying on a struggle against ice. Prevention of icing accidents is based on the use of an integrated system of activities in a systematic manner.
Various manufacturers of relay protection devices only offer two options of setpoints, which should be changed manually by the operating staff at the place of protection installation. This means that these devices do not have the ability to adapt the protection response current to changing environmental parameters, which have a significant impact on overhead power lines parameters. As a result, the setpoint set on a microprocessor relay device is not always correct and can lead to failure of the relay protection or to a false positive.
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