Siemens SIPROTEC 4 7UT6 Series Manual page 23

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High stability against external earth faults using the magnitude and phase relationship of through-
flowing earth current
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2 restricted earth fault protection functions possible (only 7UT613/63x)
Time Overcurrent Protection for Earth Current
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Two definite time delayed overcurrent stages for the earth current, e.g. current between starpoint and
earth
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Additionally, one inverse time delayed overcurrent stage for the earth current
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Selection of various inverse time characteristics of different standards is possible, alternatively a user
defined characteristic can be specified
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The 3 stages can be combined as desired
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External blocking facility for any desired stage (e.g. for reverse interlocking)
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Instantaneous trip when switching on a dead fault with any desired stage
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Inrush restraint function with 2nd harmonic
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Dynamic switchover of the time overcurrent parameters, e.g. during cold-loaded start-up of the power
plant
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2 time overcurrent protection functions for earth current possible (only 7UT613/63x)
1-phase Overcurrent Protection
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Two definite time delayed overcurrent stages which can be combined as desired
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For any 1-phase overcurrent detection
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Can be assigned to the "normal" 1-phase current input or to the highly sensitive current input
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Suitable for detection of very small current (e.g. for high-impedance unit protection or tank leakage
protection)
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Suitable for detection of any desired AC voltage using an external series resistor (e.g. for high-impedance
unit protection)
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External blocking facility for any stage
Unbalanced Load Protection
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Evaluation of the negative sequence system of the three phase currents of any desired side of the
protected object or any three-phase measuring point
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Two definite time delayed negative sequence current stages and one additional inverse time delayed
negative sequence current stage
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Selection of various inverse time characteristics of different standards is possible, alternatively a user
defined characteristic can be specified
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The stages can be combined as desired
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Trip blocking on detection of broken wire
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Thermal characteristic with adjustable negative sequence factor and adjustable cooldown time
Thermal Overload Protection
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Thermal replica of current-initiated heat losses
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True RMS current calculation
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Can be assigned to any desired side of the protective object
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Adjustable thermal warning stage
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Adjustable current warning stage
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
Introduction
1.3 Characteristics
23