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Introduction

1.3 Characteristics

SIPROTEC, 7SK80, Manual

E50417-G1140-C344-A4, Release date 08.2010

Ground Fault Protection 50N, 51N

• Three definite time overcurrent protective Elements and one inverse time overcurrent protective element ap-

plicable for grounded or high-resistance grounded systems;

• For inverse time overcurrent protection, selection from various characteristics of different standards.

• In-rush restraint with second harmonic current quantities;

• Instantaneous tripping by any overcurrent Element during 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 recognized;

• Detection of cold load condition via circuit breaker position or current threshold;

• Activation also possible via binary input.

Voltage Protection 27, 59

• Two-element undervoltage detection via system positive sequence voltages, phase-to-phase or phase-

ground voltages;

• Choice of current supervision for 27-1 and 27-2;

• Separate two-element overvoltage detection of the largest voltages applied or detection of the positive or

negative sequence component of the voltages.

• settable dropout ratio for all elements of the undervoltage and overvoltage protection.

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 Curve 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 Step Function

• Detection of mechanical or thermal overload of the rotor.

Siemens SIPROTEC 7SK80 User Manual

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