4.75
Date Code 20170814
Instruction Manual
SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
81ACCTC := NOT 3POX blocks the element until the generator is
synchronized and on-line. Relay Word bit FREQTRKX inherently blocks the
element if the relay cannot accurately measure the frequency (see
Figure 4.45).
Abnormal Frequency Protection Setting Calculation
Consult the turbine manufacturer’s abnormal operating frequency protection
information before calculating the setting.
Recommendations
Steam turbine manufacturers can provide documentation showing turbine
operating time limitations during abnormal frequency. This documentation
should show continuous operation at nominal frequency, an area of restricted
time of operation, and an area of prohibited time of operation. Define
accumulator frequency bands and assign times to those bands that prevent the
generator from operating in the restricted area. Figure 4.44 shows an example,
with settings shown.
Abnormal Frequency Tripping
Consult the generator and prime mover manufacturers to determine the need
to trip the generator when it reaches the set time accumulation.
Figure 4.44
Example Turbine Operating Limitations During Abnormal Frequency
Continuous Operation
Restricted
Operation
Prohibited
Operation
Summary of Contents for SEL-700G Series
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