Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 100 / 734

3-46 Line Current Differential, Distance, Out-of-Step, Overcurrent, Date Code 20011112
Voltage, Synchronism Check, and Frequency Elements
SEL-311L Instruction Manual
and enables A-phase ground distance elements and BC-phase distance elements. Distance
elements BG, CG, AB, and CA are blocked.
Zone 1 Extension
See Figure 3.38. When enabled, this logic modifies the reach of all Zone 1 distance elements by
multiplier setting Z1EXTM once all three poles are closed for Z1EXTD time. All Zone 1 reaches
retreat to their set reach when 3PO asserts (breaker open).
The Zone 1 reaches cannot be extended if any of the following elements are asserted: M1P–M2P,
Z1G–Z2G, 51G, or 51Q.
Settings
Enable Zone 1 Extension EZ1EXT
Zone 1 Extension Delay Z1EXTD Sets the minimum time the breaker must be closed
before extending the Zone 1 reach.
Zone 1 Extension Multiplier Z1EXTM Sets the scalar by which all Zone 1 reaches are
multiplied. Z1EXTM times the Zone 1 distance
setting is never set less than the Zone 1 distance
setting or greater than 90 percent of Zone 2 reach.
Z1P < (Z1EXTM • Z1P) < (0.9 • Z2P) and
Z1MG < (Z1EXTM • ZMG) < (0.9 • Z2MG) and
X1G < (Z1EXTM • X1G ) < (0.9 • X2G )
must all be true or the SEL-311L Relay will not
allow the Z1EXTM setting.
EZ1EXT = N
(Setting)
From Figure 3.49 51Q
0
Z1EXTD
S
R
Q Z1X
M311L125
From Figure 3.48 51G
From Figure 3.29 M1P
From Figure 3.32 Z1G
From Figure 3.30 M2P
From Figure 3.33 Z2G
From Figure 5.5 3PO
Z1X
0
1
X1
(See Figures 3.29, 3.32, and 3.35)
1.0
Z1EXTM
Figure 3.38: Zone 1 Extension Logic
Zone Time Delay Elements
The SEL-311L Relay supports two philosophies of zone timing: independent or common timing
(see Figure 3.39). For the independent timing mode, the phase and ground distance elements
drive separate timers for each zone. For the common mode, the phase and ground distance
elements both drive a common timer.