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Introduction

1.3 Characteristics

SIPROTEC, 7SJ61, Manual

C53000-G1140-C210-1, Release date 02.2008

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

Siemens SIPROTEC 7SJ61 User Manual

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