Sel SEL-351S - Figure 3.11 Levels 5-6 Residual Ground Instantaneous Overcurrent Elements

3.14
SEL-351S Relay Instruction Manual Date Code 20080103
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Instantaneous/Definite-Time Overcurrent Elements
Figure 3.11 Levels 5–6 Residual Ground Instantaneous Overcurrent Elements
Negative-Sequence
Instantaneous/
Definite-Time
Overcurrent
Elements
IMPORTANT: See Appendix F: Setting Negative-Sequence
Overcurrent Elements for information on setting negative-sequence
overcurrent elements.
Four levels of negative-sequence instantaneous/definite-time overcurrent
elements are available. Two additional levels of negative-sequence
instantaneous overcurrent elements (Levels 5 and 6) are also available. The
different levels are enabled with the E50Q enable setting, as shown in
Figure 3.12 and Figure 3.13.
Level 2 element 67Q2S in Figure 3.12 is used in directional comparison
blocking schemes (see Directional Comparison Blocking (DCB) Logic on
page 5.27). All the other negative-sequence instantaneous/definite-time
overcurrent elements are available for use in any tripping or control scheme.
To understand the operation of Figure 3.12 and Figure 3.13, follow the
explanation given for Figure 3.1, Figure 3.2, and Figure 3.3 in the preceding
subsection Phase Instantaneous/Definite-Time Overcurrent Elements on
page 3.1, substituting negative-sequence current 3I
2
[3I
2
=I
A
+a
2
·I
B
+a·I
C
(ABC rotation), 3I
2
=I
A
+a
2
·I
C
+a·I
B
(ACB rotation), where a = 1 ∠ 120º
and a
2
=1∠ –120º] for phase currents and substituting like settings and Relay
Word bits.
Settings Ranges
Setting range for pickup settings 50Q1P–50Q6P:
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 67Q1D–67Q4D:
0.00–16000.00 cycles, in 0.25-cycle steps
Setting range for definite-time setting 67Q2SD (used in DCB logic):
0.00–60.00 cycles, in 0.25-cycle steps
5OG5
5OG6
Relay
Word
Bits
50G5P
50G6P
I
G
Settings
Enabled
Levels
(Residual)
Level 5
Setting
E5OG ≥ 5)
Level 6
Setting
E5OG = 6)