Schweitzer Engineering SEL-351P, Quick Start Manual

Page: 176 / 674

3-8 Overcurrent, Voltage, Synchronism Check, and Frequency Elements Date Code 990430
SEL-351P Manual Técnico
Setting Range
Setting range for pickup settings 50PP1P through 50PP4P:
0.20 - 34.00 A secondary (1 A nominal phase current inputs, IA, IB, IC)
Accuracy
Pickup:
±
0.01 A secondary and
±
3% of setting (1 A nominal phase current inputs, IA, IB, IC)
Pickup Operation
The pickup settings for each level (50PP1P through 50PP4P) are compared to the magnitudes of
the individual phase-to-phase difference currents I
AB
, I
BC
, and I
CA
. The logic outputs in
Figure SECTION 3: .7 are the following Relay Word bits (Level 1 example shown):
50AB1 = 1 (logical 1), if I
AB
> pickup setting 50PP1P
= 0 (logical 0), if I
AB
≤
pickup setting 50PP1P
50BC1 = 1 (logical 1), if I
BC
> pickup setting 50PP1P
= 0 (logical 0), if I
BC
≤
pickup setting 50PP1P
50CA1 = 1 (logical 1), if I
CA
> pickup setting 50PP1P
= 0 (logical 0), if I
CA
≤
pickup setting 50PP1P
Pickup and Reset Time Curves
See Figure SECTION 3: .5 and Figure SECTION 3: .6.
Neutral Ground Instantaneous/Definite-Time Overcurrent Elements
Four levels of neutral ground instantaneous/definite-time overcurrent elements are available.
Two additional levels of neutral ground instantaneous overcurrent elements (Levels 5 and 6) are
also available. The different levels are enabled with the E50N enable setting, as shown in
Figure SECTION 3: .8 and Figure SECTION 3: .9.
Level 2 element 67N2S in Figure SECTION 3: .8 is used in directional comparison blocking
schemes (see
Directional Comparison Blocking (DCB) Logic in Section 5: Trip and Target
Logic ). All the other neutral ground instantaneous/definite-time overcurrent elements are
available for use in any tripping or control scheme.
To understand the operation of Figure SECTION 3: .8 and Figure SECTION 3: .9, 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 current I
N
(channel IN current) for phase currents and substituting like settings and
Relay Word bits.