Siemens SIPROTEC 7SJ61 - Page 24

Introduction
1.3 Characteristics
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
24
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.
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.
Negative Sequence Protection 46
• Evaluation of negative sequence component of the currents;
• Two definite-time elements 46-1 and 46-2 and one inverse-time element 46-TOC; curves of common stan-
dards are available for 46-TOC.
Motor Starting Protection 48
• Inverse time tripping characteristic based on an evaluation of the motor starting current;
• Definite time delay for blocked rotor.
Motor Restart Inhibit 66, 86
• Approximate replica of excessive rotor temperature;
• 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
• Evaluation of the positive sequence system of phase currents
• Evaluation of the circuit breaker switching state
• Blocking of function during motor standstill and during motor startup