Figure 1-1 Overcurrent Characteristics - Siemens 7SG11 Manual

1.3.1.1 Phase-fault and Earth-fault Overcurrent
Phase-fault and earth-fault inputs each have four independent overcurrent elements. Each has a current setting
and timing characteristic as illustrated in Figure 1-1.
The principal overcurrent element is selectable between IDMTL (inverse definite minimum time lag) and DTL
(definite time lag) characteristics. Four IDMTL curves are available, namely normal inverse (NI), very inverse (VI),
extremely inverse (EI) and long time inverse (LTI). The IDMTL algorithms operate correctly for developing faults
where current varies with time.
Two independent highsets and an independent lowset are included with shaped instantaneous characteristics and
DTL. The instantaneous outputs are designed for transient free operation where high values of system X/R are
experienced.
Time
1.3.1.2 Sensitive Earth-fault/Restricted Earth-fault
Sensitive earth-fault and restricted earth-fault protection schemes are achieved with identical internal functionality.
They incorporate filtering for rejection of second, third and higher harmonics of the power system frequency.
Two DTL timers and a lowset characteristic are provided. The lowset does not have an independent current
setting in this case. The delayed reset function operates on the two DTL timers.
1.3.1.3 Directional Control
Argus 2 and Argus 6 only.
Directional elements are available for phase-fault and earth-fault as an ordering option. Bi-directional elements
provide independent characteristic, current and time settings for each direction of each overcurrent stage. In
models with three phase-fault directional elements, single-phase or two-out-of-three directional decisions are
available.
In most models, the phase fault characteristic angles are selectable from +30° and +45°; the earth-fault
characteristic angle is selectable from 0°, -15°, -45° and -65°.
In Argus 2 models with voltage and power measurement, the phase-fault and earth-fault characteristic angles are
selectable to any angle between -90 and + 90 in 1 steps.
©2013 Siemens Protection Devices Limited
I
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Figure 1-1 Overcurrent Characteristics
7SG11 Argus User Manual
I IDMTL current setting
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t time multiplier
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I highset 1 current setting
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t highset 1 time delay setting
HS1
I highset 2 current setting
HS2
t highset 2 time delay setting
HS2
I lowset current setting
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t lowset time delay setting
LS
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HS2
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Current
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