1 Introduction
24
7UM61 Manual
C53000-G1176-C127-3
Negative Sequence
Protection
• Precise evaluation of negative sequence component of the three phase currents.
• Alarm stage when a set unbalanced load is exceeded.
• Thermal characteristic with adjustable negative sequence factor and adjustable
cooldown time.
• High-speed trip stage for large unbalanced loads (can be used for short-circuit pro-
tection).
Underexcitation
protection
• Conductance measurement from positive sequence components.
• Multi-step characteristic for steady-state and dynamic stability limits;
• Consideration of excitation voltage (only via binary input).
Reverse Power Pro-
tection
• Calculation of power from positive sequence components.
• Highly sensitive and precise active power measurement (detection of small motor-
ing powers even with low power factor cos Ï• , angle error compensation).
• Insensitive to power fluctuations.
• Long-time stage and short-time stage (active with closed emergency tripping valve).
Forward Power Su-
pervision
• Calculation of power from positive sequence components.
• Supervision of over-power (P>) and/or under-power (P<) of active power output
with individually adjustable power limits.
• Optionally high-speed or high-accuracy measurement.
Impedance protec-
tion
• Overcurrent pickup with undervoltage seal-in (for synchronous machines which
take their excitation voltage from the terminals).
• 2 impedance zones, 1 overreach zone (switchable via binary input), 4 time stages.
• Polygonal tripping characteristics;
Undervoltage Pro-
tection
• Two-stage undervoltage measurement of positive sequence component of voltag-
es.
Overvoltage Pro-
tection
• Two-stage overvoltage measurement of the highest of the three voltages.
• Optionally with phase-to-phase voltages or phase-to-earth voltages.
Frequency Protec-
tion
• Monitoring on undershooting (f<) and/or overshooting (f>) with 4 frequency limits
and delay times that are independently adjustable.
• Insensitive to harmonics and abrupt phase angle changes.
• Settable undervoltage threshold.
Overexcitation Pro-
tection
• Calculation of the ratio U/f.
• Adjustable warning and tripping stage.
• Standard characteristic or arbitrary trip characteristic for calculation of the thermal
stress, selectable.
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