ABB Relion RES670, Technical Manual

Page: 327 / 934

10.4.6 Monitored data
PID-6515-MONITOREDDATA v4
Table 181: FTAQFVR (81A) Monitored data
Name Type Values (Range) Unit Description
FREQ REAL - Hz Measured frequency value
ACCTIME REAL - s Accumulated time for
frequency band limits
10.4.7 Operation principle
GUID-DB8A3411-2FA6-47B1-BC75-9892BD224DC0 v4
Frequency time accumulation protection function FTAQFVR (81A) is used to protect
the turbine against an abnormal frequency operation. During the startup and shutdown
of the turbine-generator set, FTAQFVR (81A) is blocked to avoid unnecessary
accumulation of time or tripping of generator. FTAQFVR (81A) is also blocked when
the system positive-sequence voltage magnitude deviates from the given voltage band
limit, which can be enabled with the
EnaVoltCheck setting. The overall logic of
FTAQFVR (81A) is explained in Figure 112 .
The frequency of the measured input voltage is monitored continuously and compared
to the set frequency band limits
FreqHighLimit and FreqLowLimit . When the measured
system frequency is above the FreqLowLimit setting and below the FreqHighLimit
setting, the
FREQOK
and
PICKUP
signals are activated. The
BFI_3P
signal is
controlled by the measured current and voltage input magnitude and the status of the
circuit breaker position.
FTAQFVR (81A) function will block
BFI_3P
signal activation and Accumulation of
time under two following conditions even if the system frequency falls within set band
limits.
• When the generator is not synchronized as indicated by the
CBOPEN
signal input:
Generator currents are considered to detect whether the generator is supplying its
unit auxiliary supply transformers or not. FTAQFVR (81A) function will be
blocked when the measured current magnitude drops below the setting
PickupCurrentLevel and
CBOPEN
input is high. FTAQFVR (81A) remains
blocked until the generator returns to the operation condition. It can be verified by
using the
CBCLOSE
signal. Generator's start and stop detection logics for the
BFI_3P
output can be ignored by disabling the CBCheck setting.
• When the positive-sequence voltage of the measured input voltage is outside the
band limit.
The
BFI_3P
output will be blocked if the EnaVoltCheck setting is enabled and the
system positive sequence voltage is not within the voltage band limits.
1MRK 511 408-UUS A
Section 10
Frequency protection
Phasor measurement unit RES670 2.2 ANSI 321
Technical manual