ABB REL 356 Current Differential Protection
3-31
Settings and Application
Ground Overcurrent Timer (TOG)
TOG = BLK
This timer starts timing after IOM has operated. The relay system will trip when the timer has operated. It is used as
complement to the ground distance units for high resistive ground faults. This unit needs to be coordinated with down-
stream devices.
As with the distance units, the ground time overcurrent function is only enabled during channel failure or when the
differential protection is blocked, as selected by the BKUP setting.
Zone 2 and Zone 3 Settings - Versions with Distance Option only
Settings for Zone 2 and Zone 3 protective systems are similar. Application of the distance units follow the standard
application for a conventional step distance, non-pilot relaying system.
Even though they are called Zone 2 and Zone 3, functionally they can serve as one underreaching instantaneous zone
and one overreaching time delayed zone as a conventional Zone 1 and Zone 2 stepped system.
If used as an instantaneous underreaching zone, Zone 2 should be set to never overreach the remote end. Recom-
mended setting is 80% of the line impedance. Zone 3 should be set to underreach any Zone 1 covering the adjacent lines
coming out of the remote terminal. Zone 3 should also cover at least 100% of the protected line plus 20% of the shortest
adjacent line under all conditions.
Zone 3 timers, for phase and ground, should be set to coordinate with the forward and reverse adjacent high speed trips.
The timer should include the breaking time of the slowest adjacent breaker plus a tolerance of two to three cycles.
The characteristic of the distance measuring elements are determined by the settings PANG, GANG, ZR specified
above and the reach settings ZGF, ZGR, and ZP.
Ground units in both zones are self polarized and have a forward reach (ZGF) and a reverse reach (ZGR). The FDOG
(forward ground directional unit) is used to supervise the forward direction while the reverse reach is used to define the
overall size of the characteristic and thus the reach along the R-axis.
The phase to phase and three phase units in REL 356 have only a forward reach, ZP. These units are inherently
directional.
Zone 2 Phase Reach (Z2P)
Z2P = 0.78 ohms
This setting coordinates the Zone 2 reach for phase to phase faults and three phase faults. The setting is in secondary
ohms.
When using Z2 as an underreaching, instantaneous zone, set Z2P = 80% Z1L (secondary) = 0.8 x 4.855 (primary)
x 0.2 = 0.78 secondary
Þ
Z2P = 0.78 ohms
Zone 2 Phase Timer (T2P)
T2P = 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 2 Forward Ground Reach (Z2GF)
Z2GF = 0.78 ohms
This setting controls the forward reach of the Zone 2 ground unit. The setting is in secondary ohms.
When using Z2 as an underreaching, instantaneous zone, set Z2GF = 80% Z1L (secondary) = 0.8 x 4.855 (pri-
mary) x 0.2 = 0.78 secondary
Þ
Z2GF = 0.78 ohms
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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