Overfrequency Protection Logic; Application Notes; Figure 119: Overfrequency Logic (Single Stage) - GE P4A Technical Manual

Chapter 11 - Frequency Protection Functions
2.2.2

OVERFREQUENCY PROTECTION LOGIC

Averaging
Freq Freq
F>1 Setting F>1 Setting
F>1 Status F>1 Status
Enabled Enabled
890
All Poles Dead All Poles Dead
1370
Freq Not Found Freq Not Found
1153
F>1 Timer Block F>1 Timer Block

Figure 119: Overfrequency logic (single stage)

If the frequency is above the setting and not blocked, the DT timer is started and after this has timed out, the trip is
produced. If the frequency cannot be determined, the function is blocked.
2.2.3

APPLICATION NOTES

2.2.3.1 SETTING GUIDELINES
Following changes on the network caused by faults or other operational requirements, it is possible that various
subsystems will be formed within the power network. It is likely that these subsystems will suffer from a
generation/load imbalance. The "islands" where generation exceeds the existing load will be subject to
overfrequency conditions. Severe over frequency conditions may be unacceptable to many industrial loads, since
running speeds of motors will be affected. The overfrequency element can be suitably set to sense this
contingency.
240
&
1
1159
DT
1165
P54A/B/C/E
F>1 Start F>1 Start
F>1 Trip F>1 Trip
V00862
P54xMED-TM-EN-1