Siemens SIPROTEC 4 Manual page 26

Introduction
1.3 Characteristics
Undervoltage-controlled reactive power protection (27/Q)
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Detection of critical power system situations
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Disconnection of power supply facilities from the grid
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Reconnection under stable power system conditions
Thermal Overload Protection 49
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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
Monitoring Functions
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Increased reliability due to monitoring of the internal measurement circuits as well as the hardware and
software
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Fuse failure monitor with protection function blocking
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Monitoring of the current transformer and voltage transformer secondary circuits using sum and
symmetry supervision with optional protection function blocking
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Trip circuit monitoring possible
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Phase rotation check.
Ground Fault Detection 50N(s), 51N(s), 67N(s), 59N/64
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Displacement voltage is measured or calculated from the three phase voltages
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Determination of a faulty phase on ungrounded or grounded systems
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Two-element Ground Fault Detection: 50Ns-1 and 50Ns-2
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High sensitivity (as low as 1 mA)
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Overcurrent element with definite time or inverse time delay
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For inverse-time overcurrent protection, a user-defined characteristic is available
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Direction determination with zero sequence quantities(Ι
nation
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Any element can be set as directional or non-directional — forward sensing directional, or reverse
sensing directional
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Optionally applicable as additional ground fault protection.
Intermittent Ground Fault Protection
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Detects and accumulates intermittent ground faults
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Tripping after configurable total time.
Directional intermittent ground fault protection
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Detects intermittent ground faults
•
Direction determination
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Tripping after settable number of intermittent re-ignitions
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, V ), wattmetric ground fault direction determi-
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SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017