Toshiba GRD140 Instruction Manual

⎯ 13 ⎯6 F 2 S 0 7 5 8Definite time resetThe definite time resetting characteristic is applied to the IEC/IEEE/US operating characteristics.If definite time resetting is selected, and the delay period is set to instantaneous, then nointentional delay is added. As soon as the energising current falls below the reset threshold, theelement returns to its reset condition.If the delay period is set to some value in seconds, then an intentional delay is added to the resetperiod. If the energising current exceeds the setting for a transient period without causing tripping,then resetting is delayed for a user-definable period. When the energising current falls below thereset threshold, the integral state (the point towards operation that it has travelled) of the timingfunction (IDMT) is held for that period.This does not apply following a trip operation, in which case resetting is always instantaneous.Dependent time resetThe dependent time resetting characteristic is applied only to the IEEE/US operate characteristics,and is defined by the following equation:⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡⎟⎠⎞⎜⎝⎛−×= bSIIkrRTMSt1(2)where:t = time required for the element to reset fully after complete operation (seconds),I = energising current (amps),Is = overcurrent setting (amps),kr = time required to reset fully after complete operation when the energising current is zero(see Table 2.1.1),RTMS = reset time multiplier setting.b = constants defining curve.Figure 2.1.4 illustrates the dependent time reset characteristics.