CHAPTER 5: SETTINGS GROUPED ELEMENTSL30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 5-2155A time dial multiplier setting allows selection of a multiple of the base curve shape (where the time dial multiplier = 1) withthe curve shape (CURVE) setting. Unlike the electromechanical time dial equivalent, operate times are directly proportionalto the time multiplier (TD MULTIPLIER) setting value. For example, all times for a multiplier of 10 are 10 times the multiplier 1or base curve values. Setting the multiplier to zero results in an instantaneous response to all current levels above pickup.Time overcurrent time calculations are made with an internal energy capacity memory variable. When this variableindicates that the energy capacity has reached 100%, a time overcurrent element operates. If less than 100% energycapacity is accumulated in this variable and the current falls below the dropout threshold of 97 to 98% of the pickup value,the variable must be reduced. Two methods of this resetting operation are available: “Instantaneous” and “Timed.” The“Instantaneous” selection is intended for applications with other relays, such as most static relays, which set the energycapacity directly to zero when the current falls below the reset threshold. The “Timed” selection can be used where therelay must coordinate with electromechanical relays.IEEE curvesThe IEEE time overcurrent curve shapes conform to industry standards and the IEEE C37.112-1996 curve classifications forextremely, very, and moderately inverse curves. The IEEE curves are derived from the operate and reset time equations.Eq. 5-14whereT = operate time (in seconds)TDM = Multiplier settingI = input currentIpickup = Pickup Current settingA, B, p = constants defined in the tableTRESET = reset time in seconds (assuming energy capacity is 100% and RESET is “Timed”)tr = characteristic constant defined in the tableTable 5-29: IEEE inverse time curve constantsTable 5-30: IEEE curve trip times (in seconds)IEEE curve shape A B p t rIEEE Extremely Inverse 28.2 0.1217 2.0000 29.1IEEE Very Inverse 19.61 0.491 2.0000 21.6IEEE Moderately Inverse 0.0515 0.1140 0.02000 4.85Multiplier(TDM)Current ( I / I pickup)1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0IEEE Extremely Inverse0.5 11.341 4.761 1.823 1.001 0.648 0.464 0.355 0.285 0.237 0.2031.0 22.682 9.522 3.647 2.002 1.297 0.927 0.709 0.569 0.474 0.4072.0 45.363 19.043 7.293 4.003 2.593 1.855 1.418 1.139 0.948 0.8134.0 90.727 38.087 14.587 8.007 5.187 3.710 2.837 2.277 1.897 1.6266.0 136.090 57.130 21.880 12.010 7.780 5.564 4.255 3.416 2.845 2.4398.0 181.454 76.174 29.174 16.014 10.374 7.419 5.674 4.555 3.794 3.25210.0 226.817 95.217 36.467 20.017 12.967 9.274 7.092 5.693 4.742 4.065IEEE Very Inverse0.5 8.090 3.514 1.471 0.899 0.654 0.526 0.450 0.401 0.368 0.3451.0 16.179 7.028 2.942 1.798 1.308 1.051 0.900 0.802 0.736 0.6892.0 32.358 14.055 5.885 3.597 2.616 2.103 1.799 1.605 1.472 1.378
