CYG PRS-7367 - Over frequency protection 81 O

Protection Functions
PRS-7367 103
3.17.4 CUB_27 Settings
Table 3.17-3 capacitor 27 settings
No.
Name
Values（Range）
Unit
Step
Default
Description
1
CUB_27_Cu
r_Blk
0.04-20.00In
A
0.01In
1
The current blocking value
2
CUB_27_Vol
_Str
1.00 -120.00
V
0.01
50.00
The voltage start value
3
CUB_27_Op
_T
0.04 –120.00
s
0.01
120.0
The time delay of definite time
4
CUB_27_En
a
0~1
-
1
0
Relay Enable/Disable
5
CUB_27_Vol
_Select
1
-
1
1
Phase voltage
6
2
Phase to phase voltage
3.18 Over frequency protection 81O
3.18.1 81O Overview
The feeder relay provides a two-stage over frequency protection with independent definite time
delay characteristics, and each stage has the same protection logics.
An increase in system frequency occurs, e.g. when large blocks of load (island network) are
removed from the system, or again when a malfunction occurs with a generator governor. This
entails risk of self-excitation for generators feeding long lines under no-load conditions.
The calculation of the frequency is based on the voltage sampled values.
3.18.1.1 Function Block
The function block of the protection is as below.
U3P
81O
Blk
Str
Op
Figure 3.18-1 Function block
3.18.1.2 Signals