Sepam - HV/MV Protection and control units (ENG) - Trinet

Checking of IDMT set point and time delayThe set point and time delay are interrelated. They correspond to curve coordinates(see appendices).ttT1,2Is i 10Isa time t corresponds to an injected value i.I/Isc protection parameter setting: O/C Xv select the standard inverse (SIT), very inverse (VIT), extremely inverse (EIT)or ultra inverse (UIT) curvev set Is (asymptote: for an injection i = Is, so t = infinity)v set T (corresponding to 10 Is: for an injection i = 10 Is, so t = T)v identify on the curve the different coordinates of the points that you will be testing(i and t)c test the different points on the curvev preset the injection i (to a value > 1.2 Is) and make a note of the valuev stop the injection and reset the chronometer to zerov press reset if required (1)v start up injection and the chronometer at the same timev check the injection value on the ammeter (stability)v Sepam's 2000 output relay stops the chronometerv read the t value measured by the chronometerv compare with the value given in the curvev check the meter and the I TRIP (1) values on the display unit or pocket terminalv stop the injectionv press reset (1) on Sepam 2000 to erase the messages and reset the output relayExampleStatus In = 400 Asettings very inverse curveIs = 200 AT = 0.5 sinjection i = 300 A (0.75 or 3.75 A)In the very inverse column of the chart which gives Kfor I/Is, read the value K = 18 which corresponds to I/Is = 1.5 (= 300/200)for an injection i = 300 A, the relay will pick up after a time periodt = 18 x 0.5 s = 9 s (t = K x T) (Ib is not used in the O/C protections)(1)this function may only be activated if your program logichas been customized.X = number of the protective relay.Sepam 2000 - Testing1/5