Application Possibilities; Inadvertent Generator Energization - Hitachi Relion 670 Series Applications Manual

1MRK511407-UUS Rev. N
11.1.3.3

Application possibilities

Due to its flexibility the general current and voltage protection (CVGAPC) function can be used, with
appropriate settings and configuration in many different applications. Some of possible examples are
given below:
1. Transformer and line applications:
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2. Generator protection
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11.1.3.4

Inadvertent generator energization

When the generator is taken out of service, and stand-still, there is a risk that the generator circuit
breaker is closed by mistake.
Three-phase energizing of a generator, which is at standstill or on turning gear, causes it to behave and
accelerate similarly to an induction motor. The machine, at this point, essentially represents the
subtransient reactance to the system and it can be expected to draw from one to four per unit current,
depending on the equivalent system impedance. Machine terminal voltage can range from 20% to 70%
of rated voltage, again, depending on the system equivalent impedance (including the block transformer).
Higher quantities of machine current and voltage (3 to 4 per unit current and 50% to 70% rated voltage)
can be expected if the generator is connected to a strong system. Lower current and voltage values (1 to
2 per unit current and 20% to 40% rated voltage) are representative of weaker systems.
Since a generator behaves similarly to an induction motor, high currents will develop in the rotor during
the period it is accelerating. Although the rotor may be thermally damaged from excessive high currents,
Phasor measurement unit RES670
Application manual
Underimpedance protection (circular, non-directional characteristic) (21)
Underimpedance protection (circular mho characteristic) (21)
Voltage Controlled/Restrained Overcurrent protection (51C, 51V)
Phase or Negative/Positive/Zero Sequence (Non-Directional or Directional) Overcurrent
protection (50, 51, 46, 67, 67N, 67Q)
Phase or phase-to-phase or Negative/Positive/Zero Sequence over/under voltage protection
(27, 59, 47)
Thermal overload protection (49)
Open Phase protection
Unbalance protection
80-95% Stator earth fault protection (measured or calculated 3Vo) (59GN)
Rotor earth fault protection (with external COMBIFLEX RXTTE4 injection unit) (64F)
Underimpedance protection (21)
Voltage Controlled/Restrained Overcurrent protection (51C, 51V)
Turn-to-Turn & Differential Backup protection (directional Negative Sequence. Overcurrent
protection connected to generator HV terminal CTs looking into generator) (67Q)
Stator Overload protection (49S)
Rotor Overload protection (49R)
Loss of Excitation protection (directional positive sequence OC protection) (40)
Reverse power/Low forward power protection (directional positive sequence OC protection,
2% sensitivity) (32)
Dead-Machine/Inadvertent-Energizing protection (51/27)
Breaker head flashover protection
Improper synchronizing detection
Sensitive negative sequence generator over current protection and alarm (46)
Phase or phase-to-phase or Negative/Positive/Zero Sequence over/under voltage protection
(27x, 59x, 47)
Generator out-of-step detection (based on directional positive sequence OC) (78)
Inadvertent generator energizing
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Section 11
Multipurpose protection
SEMOD53443-136 v3
SEMOD151947-4 v2
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