Schweitzer Engineering Laboratories SEL-351-5 Instruction Manual page 100

Pickup and Reset Time Curves
See Figure 3.5 and Figure 3.6.
Negative-Sequence Instantaneous/Definite-Time Overcurrent Elements
IMPORTANT: See Appendix F 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 in Section 5: Trip and Target Logic). 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 Phase Instantaneous/Definite-Time
Overcurrent Elements subsection, substituting negative-sequence current
2
3I [3I = I + a
2 2 A
a = 1 ∠ 120° and a
bits.
Settings Ranges
Setting range for pickup settings 50Q1P through 50Q6P:
0.25–100.00 A secondary
0.05–20.00 A secondary
Setting range for definite-time settings 67Q1D through 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
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:
3-14 Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
· I + a · I (ABC rotation), 3I
B C
= 1 ∠ -120°] for phase currents and substituting like settings and Relay Word
2
(5 A nominal phase current inputs, IA, IB, IC)
(1 A nominal phase current inputs, IA, IB, IC)
±5% of setting
SEL-351-5, -6, -7 Instruction Manual
2
= I + a · I + a · I (ACB rotation), where
2 A C B
Date Code 20020426