P12x/EN T/Eb6 - Schneider - error

Application GuideP12x/EN AP/Eb6MiCOM P120/P121/P122/P123 Page 31/78Mathematical formula applicable to the MiCOM Relays:The calculation of the Time to Trip is given by:Ttrip = Te InWith:⎛⎜⎜⎝2K −θ⎞⎟2K −θtrip⎟⎠Ttrip =Time to trip (in seconds)Te = Thermal time constant of the protected element (in seconds)K = Thermal overload equal to Ieq/k Iθ >Ieq = Equivalent current corresponding to the RMS value of the largest phasecurrent.Iθ > = Full load current rating given by the national standard or by the supplier.k = Factor associated to the thermal state formula.θ = Initial thermal state. If the initial thermal state = 30% then θ = 0.3θtrip = Trip thermal state. If the trip thermal state is set at 100%,then θ trip = 1The settings of these parameters are available in the menus:PROTECTION G1/ [49] Therm OLPROTECTION G2/ [49] Therm OLThe calculation of the thermal state is given by the following formula:Θθ being calculated every 20ms.⎡2 ⎛ −t⎞ ⎛ −t⎞⎜⎟⎜⎟⎛ Ieq⎞ ⎢ ⎝ Te⎠ ⎥ ⎝ Te⎠τ+1 = ⎜ ⎟ 1−e + Θτe⎜ ⎟ ⎢⎝ k × IΘ > ⎠ ⎢⎣⎤⎥⎥⎦