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Introduction

1.3 Characteristics

SIPROTEC, 7SK80, Manual

E50417-G1140-C344-A4, Release date 08.2010

Frequency Protection 81 O/U

• Monitoring on underfrequency (f<) and/or overfrequency (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 the ambient temperature or coolant temperature is possible via internal temperature detection

or an external thermobox.

Monitoring Functions

• Reliability of the device is greatly increased because of self-monitoring of the internal measurement circuits

as well as the hardware and software.

• Fuse failure monitor with protection function blocking.

• Monitoring of the current transformer and voltage transformer secondary circuits using summation and sym-

metry monitoring with optional protection function blocking.

• Trip circuit monitoring;

• Phase rotation check.

Ground Fault Detection 50N(s), 51N(s), 67N(s), 59N/64

• Displacement voltage is measured or calculated from the three phase voltages;

• Determination of a faulty phase on ungrounded or grounded systems;

• Two-element Ground Fault Detection: High-set element 50Ns-2 and overcurrent element 50Ns-1.

• High sensitivity (as low as 1 mA);

• Overcurrent element with definite time or inverse time delay;

• For inverse time overcurrent protection, a user-defined characteristic is available.

• Direction determination with zero sequence quantities(I

, V

), wattmetric ground fault direction determina-

tion;

• A sector characteristics can be set as directional characteristic.

• Any Element can be set as directional or non-directional — forward sensing directional, or reverse sensing

directional;

• Optionally applicable as additional ground fault protection.

Siemens SIPROTEC 7SK80 User Manual

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