3-58
Differential, Restricted Earth Fault,
Date Code 20020129
Overcurrent, Voltage, and Frequency Elements
SEL-387E Instruction Manual
Definite-Time Characteristic
None of the elements is equipped with a definite-time delay. If you want a definite-time
characteristic, use a SEL
OGIC
control equation variable and corresponding built-in time-delay
pickup and dropout timers.
F
REQUENCY
E
LEMENT
Application Description
The SEL-387E Relay provides six levels of over-/underfrequency elements. Each element can
operate as an overfrequency or as an underfrequency element, depending on its pickup setting. If
the element pickup setting is less than the nominal system frequency setting, NFREQ, the
element operates as an underfrequency element, picking up if measured frequency is less than the
set point. If the pickup setting is greater than NFREQ, the element operates as an overfrequency
element, picking up if measured frequency is greater than the set point.
Operating Characteristic
The SEL-387E Relay determines system frequency using the A-phase voltage.
Note
: All frequency elements are disabled if any phase voltage is less than a settable voltage,
27B81P. Use the relay frequency elements for simple abnormal frequency protection.
Six frequency elements are available. The desired number of frequency elements are enabled
with the E81 enable setting:
E81 = N (none), 1 through 6
as shown in Figure 3.36. Frequency is determined from the voltage connected to voltage
terminals VA-N.
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Figure 3.36: Undervoltage Block for Frequency Elements
Содержание SEL-387E
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