Schweitzer Engineering SEL-351P, Quick Start Manual

Page: 181 / 674

Date Code 990430 Overcurrent, Voltage, Synchronism Check, and Frequency Elements 3-13
SEL-351P Manual Técnico
Figure SECTION 3: .11: Levels 5 through 6 Residual Ground Instantaneous
Overcurrent Elements
Level 2 element 67G2S in Figure SECTION 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 SECTION 3: .10 and Figure SECTION 3: .11, follow the
explanation given for Figure SECTION 3: .1, Figure SECTION 3: .2, and Figure SECTION 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:
0.05 - 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:
±
0.01 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 SECTION 3: .5 and Figure SECTION 3: .6.