4.123
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
Frequency Protection
The SEL-751 provides six trip over- or underfrequency elements with inde-
pendent level and time-delay settings. Table 4.48 lists the ranges and settings.
When an element level setting is less than the nominal frequency setting, the
element operates as an underfrequency element. When the level setting is greater
than the nominal frequency setting, the element operates as an overfrequency ele-
ment. Figure 4.75 shows the logic diagram for the frequency elements.
Table 4.47 Vector Shift Element Settings
Setting Prompt Setting Range
Setting Name :=
Factory De fault
EN VECTOR SHIFT Y, N E78VS := N
VS ANGLE PU THR 2.0–30.0 deg 78VSAPU := 10.0
VS VOLT SUPV THR 20.0–100.0% 78VS59 := 80
VS BLOCK SEL
OGIC 78VSBL := 0
Table 4.48 Frequency Settings
Setting Prompt Setting Range
Setting Name :=
Fac to ry Defa ult
FREQ1 TRIP LEVEL OFF, 15.00–70.00 Hz 81D1TP := OFF
FREQ1 TRIP DELAY
a
a
Frequency element time delays are best set no less than five cycles. The relay requires at
least three cycles to measure frequency.
0.00–240.00 sec 81D1TD := 1.00
81D1 TRQCTRL SEL
OGIC 81D1TC := 1
FREQ2 TRIP LEVEL OFF, 15.00–70.00 Hz 81D2TP := OFF
FREQ2 TRIP DELAY
a
0.00–240.00 sec 81D2TD := 1.00
81D2 TRQCTRL SEL
OGIC 81D2TC := 1
FREQ3 TRIP LEVEL OFF, 15.00–70.00 Hz 81D3TP := OFF
FREQ3 TRIP DELAY
a
0.00–240.00 sec 81D3TD := 1.00
81D3 TRQCTRL SEL
OGIC 81D3TC := 1
FREQ4 TRIP LEVEL OFF, 15.00–70.00 Hz 81D4TP := OFF
FREQ4 TRIP DELAY
a
0.00–240.00 sec 81D4TD := 1.00
81D4 TRQCTRL SEL
OGIC 81D4TC := 1
FREQ5 TRIP LEVEL OFF, 15.00–70.00 Hz 81D5TP := OFF
FREQ5 TRIP DELAY
a
0.00–240.00 sec 81D5TD := 1.00
81D5 TRQCTRL SEL
OGIC 81D5TC := 1
FREQ6 TRIP LEVEL OFF, 15.00–70.00 Hz 81D6TP := OFF
FREQ6 TRIP DELAY
a
0.00–240.00 sec 81D6TD := 1.00
81D6 TRQCTRL SEL
OGIC 81D6TC := 1
NOTE: The relay measures system
frequency for these elements with the
positive-sequence voltage if the
voltage input is present and the
applied positive-sequence voltage is
greater than 10 volts. Otherwise, the
relay uses positive-sequence current
as long as the minimum magnitude is
0.1 • (Nominal CT Rating). The
measured frequency is set to nominal
frequency setting (FNOM) if the signal
is below the minimum level.
NOTE: Additionally, the Relay Word
bit ORED81T := 81D1T OR 81D2T OR …
81D6T.
To Next Page
Loading...
