ABB REL 356 Current Differential Protection
3-32
Settings and Application
Zone 2 Reverse Ground Reach (Z2GR)
Z2GR = 0.20 ohms
This setting controls the reverse reach of the Zone 2 ground unit. The setting is in secondary ohms. The Z2GR setting
is determined by the desired reach along the R-axis.
Assume 25% of the forward reach gives desired fault resistance coverage
Þ
Z2GR = 0.25 x 0.78 = 0.20 ohms
Zone 2 Ground Timer (T2G)
T2G = 0.00 sec
Selects the time delay for Zone 2 phase fault detection. When set to zero, Zone 2 should be set underreaching. The
setting is in seconds.
Zone 3 Phase Reach (Z3P)
Z3P = 1.17 ohms
This setting coordinates the Zone 3 reach for phase to phase faults and three phase faults. The setting is in secondary
ohms.
Z3 is used overreaching. Minimum recommended setting is 1.2 x ZL1
Þ
Z3P = 1.2 x 4.885 x 0.2 = 1.17 ohms
secondary
Zone 3 Phase Timer (T3P)
T3P = 0.30 sec
Selects the time delay for Zone 3 phase fault detection. The setting is in seconds.
Zone 3 Forward Ground Reach (Z3GF)
Z3GF = 1.17 ohms
This setting controls the forward reach of the Zone 3 ground unit. The setting is in secondary ohms.
Z3 is used overreaching. Minimum recommended setting is 1.2 x ZL1
Þ
Z3GF = 1.2 x 4.885 x 0.2 = 1.17 ohms
secondary
Zone 3 Reverse Ground Reach (Z3GR)
Z3GR = 0.29 ohms
This setting controls the reverse reach of the Zone 3 ground unit. The setting is in secondary ohms.
Using the same relation as for Z2
Þ
Z3GR = 0.25 x Z3GF = 0.25 x 1.17 = 0.29 secondary ohms
Zone 3 Ground Timer (T3G)
T3G = 0.30 sec
Selects the time delay for Zone 3 phase fault detection. The setting is in seconds.
Out of Step Settings - Versions with Distance Option only
Current differential protection is immune to power swings. When voltage inputs are part of the REL 356, blinders are
provided for power swing detection. The out of step trip and block logic is provided as part of the distance option. Out of
step block is only enabled when the distance backup protection is switched due to channel trouble or differential block
as determined by the setting BKUP. Out of step trip, when selected, is always active regardless of the BKUP setting.
Out of Step Trip (OST)
OST = NO
This setting enables the out of step trip logic. The setting options are:
NO
No OST trip
WAYI
Trip on the way into the operating characteristic of the relay
WAYO
Trip on the way out of the operating characteristic of the relay
Summary of Contents for REL 356
Page 23: ...ABB REL 356 Current Differential Protection 1 10 Product Overview and Specifications ...
Page 83: ...ABB REL 356 Current Differential Protection 3 36 Settings and Application ...
Page 127: ...ABB REL 356 Current Differential Protection 5 28 Testing ...
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