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Introduction

1.3 Characteristics

SIPROTEC, 7SJ61, Manual

C53000-G1140-C210-1, Release date 02.2008

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.

Monitoring Functions

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

power supply, hardware, and software;

• Supervision of the current transformer secondary circuits by means of sum and symmetry checks.

• Trip circuit monitoring;

• Phase rotation check.

Ground Fault Detection 50N(s), 51N(s)

• Two-element ground fault detection: High-current element 50Ns-1 and 50Ns-2;

• High sensitivity (as low as 1 mA);

• The overcurrent protection element may be operated with either a definite time or an inverse time delay;

• One user-defined and two logarithmic-inverse current/time curves are available for inverse time O/C protec-

tion;

• Optionally applicable as additional ground fault protection.

Intermittent Ground Fault Protection

• Detects and accumulates intermittent ground faults;

• Tripping after configurable total time.

Automatic Reclosing System 79

• Single-shot or multi-shot;

• With separate dead times for the first and all succeeding shots;

• Protective elements that initiate automatic reclosing are selectable. The choices can be different for phase

faults and ground faults;

• Different programs for phase and ground faults;

• Interaction to time overcurrent protection element and ground fault elements. They can be blocked in de-

pendence of the reclosing cycle or released instantaneously;

Breaker Failure Protection 50 BF

• Checking current flow and/or evaluation of the circuit breaker auxiliary contacts;

• Initiated by the tripping of any integrated protective element that trips the circuit breaker;

• Initiation possible via a binary input from an external protective device.

Siemens SIPROTEC 7SJ61 User Manual

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