Siemens SIPROTEC 7SJ62 Manual page 27

Ground Fault Protection 50N, 51N
• Three definite time overcurrent protective elements and one inverse time overcurrent protective element for
high-resistance ground faults in grounded systems;
• Different curves of common standards are available for 51 and 51N, or a user-defined characteristic;
• In-rush restraint with second harmonic oscillation;
• Instantaneous tripping by any overcurrent element upon switch onto fault is possible.
Directional Time Overcurrent Protection 67, 67N
• Three directional time overcurrent elements for both phase protection and ground protection operate in par-
allel to the non-directional time overcurrent elements. Their pickup values and time delays can be set inde-
pendently from the non-directional time overcurrent elements.
• Fault direction with cross-polarized voltages and voltage memory. Dynamically unlimited direction sensitivi-
ty;
• Fault direction is calculated phase-selectively and separately for phase faults, ground faults and summation
current faults.
Dynamic Cold Load Pick-up Function 50C, 50NC, 51C, 51NC, 67C, 67NC
• Dynamic changeover of time overcurrent protection settings, e.g. when cold load conditions are anticipated;
• Detection of cold load condition via circuit breaker position or current threshold;
• Activation via automatic reclosure (AR) possible;
• Start also possible via binary input.
Single-Phase Overcurrent Protection
• Evaluation of the measured current via the sensitive or insensitive ground current transformer;
• Suitable as differential protection that includes the neutral point current on a transformer side, a generator
side or a motor side or for a grounded reactor set;
• As tank leakage protection against illegal leakage currents between transformer casing and ground.
Voltage Protection 27, 59
• Two-element undervoltage detection via the positive sequence system of the voltages, phase-to-phase or
phase-ground voltages;
• Choice of current supervision for 27-1 and 27-2;
• Two-element overvoltage detection via the positive sequence system voltages, negative sequence system
voltages, phase-to-phase or phase-ground voltages;
• For a single-phase connection, the connected single-phase phase-to-ground or phase-to-phase voltage is
evaluated;
• settable dropout ratio for all elements of the undervoltage and overvoltage protection.
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
Introduction
1.3 Characteristics
27