Siemens SIPROTEC 4 7SJ61 Manual page 23

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In-rush restraint with second harmonic current quantities
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Instantaneous tripping by any overcurrent element upon switch onto fault is possible.
Dynamic Cold Load Pick-up Function 50C, 50NC, 51C, 51NC, 67C, 67NC
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Dynamic changeover of time overcurrent protection settings, e.g. when cold load conditions are recog-
nized
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Detection of cold load condition via circuit breaker position or current threshold
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Activation via automatic reclosure (AR) is possible
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Activation also possible via binary input.
Single-Phase Overcurrent Protection
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Evaluation of the measured current via the sensitive or insensitive ground current transformer
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Suitable as differential protection that includes the neutral point current on transformer side, generator
side or motor side or for a grounded reactor set
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As tank leakage protection against abnormal leakage currents between transformer tanks and ground.
Negative Sequence Protection 46
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Evaluation of the negative sequence component of the currents
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Two definite-time elements 46-1 and 46-2 and one inverse-time element 46-TOC; curves of common
standards are available for 46-TOC.
Motor Starting Protection 48
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Inverse time tripping characteristic based on an evaluation of the motor starting current
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Definite time delay for blocked rotor.
Motor Restart Inhibit 66, 86
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Approximate computation of the rotor overtemperature
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Startup is permitted only if the rotor has sufficient thermal reserves for a complete startup
•
Disabling of the start inhibit is possible if an emergency startup is required.
Load Jam Protection for Motors 51M
•
Protection of motors during sudden rotor blocking
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Evaluation of the positive sequence system of phase currents
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Evaluation of the circuit breaker switching state
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Blocking of function during motor standstill and during motor startup
Thermal Overload Protection 49
•
Thermal profile of energy losses (overload protection has full memory capability)
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True r.m.s. calculation
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Adjustable thermal warning element
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Adjustable alarm level based on current magnitude
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Additional time constant setting for motors to accommodate the motor at standstill
•
Integration of ambient temperature or coolant temperature is possible via external temperature sensors
and RTD-Box.
SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016
Introduction
1.3 Characteristics
23