Overfrequency Protection Logic; Application Notes; Figure 223: Overfrequency Logic (Single Stage) - GE MiCOM P40 Technical Manual

Chapter 15 - 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
All Poles Dead All Poles Dead
Freq Not Found Freq Not Found
F>1 Timer Block F>1 Timer Block

Figure 223: 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.
404
&
890
1
1370
1153
1159
DT
1165
P446SV
F>1 Start F>1 Start
F>1 Trip F>1 Trip
V00862
P446SV-TM-EN-1