Date Code 20001006
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
3-13
SEL-351 Instruction Manual
Figure 3.11: Levels 5 Through 6 Residual Ground Instantaneous Overcurrent Elements
Level 2 element 67G2S in Figure 3.10 is used in directional comparison blocking schemes (see
Directional Comparison Blocking (DCB) Logic
in
Section 5: Trip and Target Logic
). All the
other residual ground instantaneous/definite-time overcurrent elements are available for use in any
tripping or control scheme.
To understand the operation of Figure 3.10 and Figure 3.11, follow the explanation given for
Figure 3.1, Figure 3.2, and Figure 3.3 in the preceding
Phase Instantaneous/Definite-Time
Overcurrent Elements
subsection, substituting residual ground current I
G
(I
G
= 3I
0
= I
A
+ I
B
+ I
C
)
for phase currents and substituting like settings and Relay Word bits.
Settings Ranges
Setting range for pickup settings 50G1P through 50G6P:
0.25 - 100.00 A secondary
(5 A nominal phase current inputs, IA, IB, IC)
0.05 - 20.00 A secondary
(1 A nominal phase current inputs, IA, IB, IC)
Setting range for definite-time settings 67G1D through 67G4D:
0.00 - 16000.00 cycles, in 0.25-cycle steps
Setting range for definite-time setting 67G2SD (used in DCB logic):
0.00 - 60.00 cycles, in 0.25-cycle steps
Accuracy
Pickup:
±
0.05 A secondary and
±
3% of setting (5 A nominal phase current inputs, IA, IB, IC)
±
0.01 A secondary and
±
3% of setting (1 A nominal phase current inputs, IA, IB, IC)
Timer:
±
0.25 cycles and
±
0.1% of setting
Transient Overreach:
±
5% of setting
Pickup and Reset Time Curves
See Figure 3.5 and Figure 3.6.
Содержание SEL-351
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