Comparator
If
f <= FreqHighLimit
AND
f > FreqLowLimit
Then
START
Comparator
I < CurrStartLevel
START
Signal Routing
Based on
Generator
Start or Stop
Detection Logic
and
Voltage Band Limit
Check Logic
U3P
I3P
CBOPEN
CBCLOSE
Comparator
If
FreqHighLimit <=
FreqLowLimit
Then
ERROR
BLOCK
LOADINIT
RESETACC
HOLDTIME
START
ERROR
TRIPACC
TRIPCONT
STRORHLD
ACCTIME
ACCALARM
FREQOK FREQOK
Comparator
U
01
<= UHighLimit
AND
U
01
>= ULowLimit
VOLTOK
VOLTOK
TRIP
FREQ
Accumulation time
counter
Continuous time
counter
AND
Start & Trip
Output Logic
FREQ
START
LASTEVTD
IEC12000609-2-en.vsd
IEC12000609 V2 EN
Figure 270: Logical diagram
To achieve a proper operation, the set frequency high limit should be more than the set
frequency low limit. To avoid malfunction, a check is performed that FreqHighLimit
is greater than FreqLowLimit. If not, the ERROR signal is activated.
FTAQFVR can be instantiated with one or more frequency ranges according to the
turbine manufacturer's specification. When the frequency falls in to the common zone
when two frequency ranges overlap it is necessary to block one instance and keep only
one instance of FTAQFVR active. The STRORHLD output is activated when either the
START output is active or when the HOLDACC input signal is on. The STRORHLD
output is connected to the input HOLDACC of the other instance of FTAQFVR.
Section 10 1MRK502052-UEN B
Frequency protection
562
Technical manual
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