Siemens SIPROTEC 7SJ62 Manual page 28

Introduction
1.3 Characteristics
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
Frequency Protection 81 O/U
• Monitoring on undershooting (f<) and/or overshooting (f>) with 4 frequency limits and delay times that are
independently adjustable;
• Insensitive to harmonics and abrupt phase angle changes;
• Adjustable undervoltage threshold.
Thermal Overload Protection 49
• Thermal profile of energy losses (overload protection has total memory capability);
• True r.m.s. calculation;
• Adjustable thermal alarm level;
• Adjustable alarm level based on current magnitude;
• 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.
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SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008