Study On Calculation Method Of Probabilistic Power Flow Considering The Electro-thermal-mechanical Correlations Of The Overhead Conductor

The thermal state(temperature)and mechanical state(tension,sag)of overhead conductors are the essential physical quantities that determine their life and safety operation status.Excessively high temperature of the conductor will cause the metal annealing effect,which will lead to loss of tensile strength of the conductor,which will affect the service life of the conductor.The magnitude of the horizontal tension directly determines the vibration frequency and sag of the overhead conductors.The greater the horizontal tension,the higher the vibration frequency of the conductors,which will accelerate the fatigue damage of the conductors.Conversely,the smaller the horizontal tension,the greater the sag.In severe cases,it will destroy the safety clearance of the conductor and endanger the safe operation of the overhead line.In this regard,DTR technology has been able to achieve online monitoring of the electrical,thermal,and mechanical conditions(current carrying,temperature,tension,and sag)and operating environment of overhead conductors,and essentially reflects the safe operating conditions of the thermal and mechanical conditions of overhead conductors.And current carrying potential.On the basis of DTR technology,the electrical,thermal,and mechanical states of overhead conductors and their correlations can be incorporated into power flow calculations to help power system operators anticipate the electrical,thermal,and mechanical states of overhead conductors in various system scenarios.The thermal and mechanical states essentially reveal the current-carrying potential and safety status of overhead conductors,and accordingly make corresponding control decisions.However,the current carrying capacity,temperature and tension of overhead conductors are closely related to their operating environment(air temperature,wind conditions and sunshine intensity,etc.)and the power flow distribution of the power grid.Under the operating environment of the power system,due to the uncertainty of the source charge of the power system and the uncertainty of the meteorological environment,there are also strong uncertainties in the electrical,thermal,and mechanical states of the overhead conductors.Therefore,the power flow calculation that takes into account the electrical,thermal,and mechanical correlations of overhead conductors needs to consider the above-mentioned uncertainties in order to provide operators with a more comprehensive range of electrical,thermal,and mechanical state changes and probability distribution information for overhead conductors.In this regard,on the basis of the electric-thermal coupled power flow,this paper further studies the probability power flow calculation method that takes into account the electrical,thermal,and mechanical correlations of overhead conductors.First,the relationship and mathematical model between the electrical,thermal,and mechanical states of overhead conductors are introduced,as well as the representative gauge method and the precise method of mechanical state for calculating the tension of continuous gears in the operating environment.Then the calculation accuracy of the two methods at different conductor temperatures are compared and analyzed.Furtherly this paper combines the heat balance equation of the overhead conductor,the mechanical state equation and the power flow equation of the power system,and considers the uncertainty of the meteorological environment.Based on the Monte Carlo simulation method,a probabilistic power flow calculation method considering the electrical,thermal,and mechanical correlations of overhead conductors is proposed.Combined with the decoupling of the relationship between electricity,thermal and mechanical in the power flow calculation and the fast algorithm of the thermal balance model of the overhead conductor,this method can effectively increase the calculation speed of the probabilistic power flow under the premise of meeting the calculation accuracy required by the project.This method can provide probabilistic safety early warning information based on the thermal and mechanical status of overhead conductors,and reveal the current carrying potential of overhead conductors from the nature of thermal and mechanics.