Siemens SIPROTEC 7SJ61 Manual page 25

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.
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
Introduction
1.3 Characteristics
25