Introduction
1.3 Characteristics
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
31
Restricted earth fault protection
• Earth fault protection for earthed transformer windings
• Short tripping time
• High sensitivity for earth faults
• High stability against external earth faults using the magnitude and phase relationship of through-flowing
earth current
Tripping at Line Ends with no or Weak Infeed (optional)
• Possible in conjunction with teleprotection schemes
• Allows fast tripping at both line ends, even if there is no or only weak infeed available at one line end
• Phase segregated tripping and single-pole automatic reclosure is possible (version with single-phase trip-
ping)
External Direct and Remote Tripping
• Tripping at the local line end from an external device via a binary input
• Tripping of the remote line end by internal protection functions or an external device via a binary input (with
teleprotection)
Transmission of information
• Transmission of the measured values from all ends of the protected object with the magnitude and phase
• Transmission of up to 4 fast commands to all remote ends (order option)
• Transmission of up to 24 additional binary signals to all remote ends (order option)
Time Overcurrent Protection
• Selectable as emergency function during a failure of the main protection function(s) due to a failure of the
data communication and/or the measuring voltages, or as backup function
• Maximally three definite time stages (DT) and one inverse time stage (IDMT), each for phase currents and
for earth currents
• For inverse-time overcurrent protection a selection from various characteristics based on several standards
is possible
• Blocking capability e.g. for reverse interlocking with any stage;
• Instantaneous tripping by any stage when switching onto a fault
• End fault protection: fast tripping on faults between the current transformer and line isolator (when the iso-
lator switching status feed back is available); particularly well suited to substations with
1
/
2
circuit breaker
arrangements
High Current Switch-onto-Fault Protection
• Fast tripping for all faults on 100 % line length
• Selectable for manual closure or following each closure of the circuit breaker
• With integrated line energization detection.
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