METHOD FOR DETERMINING VALUE AND TIME OF THERMAL EFFECT OF SHORT CIRCUIT CURRENT

摘要

FIELD: electrical engineering.;SUBSTANCE: invention relates to electrical engineering, particularly to electric equipment installed on power plants and substations in systems for production, transmission and power consumption, and can be used in all electrical installations using digital data processing. Method includes measuring, recording and digitising N times during period T and in every current moment in time t_j current instantaneous value of short-circuit current x_sc(t_i) in each phase. Method includes determining value of thermal effect B_ter in each phase using following expression: where B_ter is value of thermal effect of short circuit current in one phase, A²s; Δt = T/N is time-sampling step of signal, s, summation is carried out on j from j = 1, which corresponds to moment t₁ is time of occurrence of short-circuit current, to moment of time t_apv - time completion of automatic repeated turning on, when j = f(t_apv+1)N; x_sc(t_i) is instantaneous value of short-circuit current in given phase at current time t_j, A; x_sc(t_i+1) is instantaneous value of short-circuit current in given phase in next time t_j+1, A; f is industrial frequency, Hz; N is number of sampling intervals. Thermal exposure time t_sc at each j-th measurement of cumulative monotonously increases with value t_sc = 0 for value of time sampling pitch Δt, provided that x_sc(t_j) is current instantaneous value of short-circuit current in this phase is not equal to zero and is determined in accordance with following expression: .;EFFECT: technical result is fast and accurate determination of magnitude and time of thermal effect on conductors and electric devices of short circuit current by fixation of instantaneous values and calculating using mathematical expressions given in claim.;1 cl