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2 CALCULATION OF SETTINGS
303: Z3PCHARANG - Zone 3 Phase Characteristic Angle
This setting determines the characteristic shape and, consequently, the area of resistance coverage provided
by the Zone 3 phase-distance functions. Z3PCHARANG can be set to 90° to 120° in 5° steps. A 90° setting is
recommended. If the desired reach, Z3PHREACH, with a 90° characteristic and with maximum load flow does
not allow the maximum allowable reach criteria to be met, then a "lens-shaped" characteristic must be used.
The settings of both Z3PHREACH and Z3PCHARANG may be evaluated by using the formula associated with
the method of Figure 2–4: MAXIMUM ALLOWABLE REACH on page 2–13.
304: Z3GROUND - Select Zone 3 Ground
Z3GROUND can be set to either YES or NO. When Zone 3 is used as part of a Step Distance scheme, and
Zone 3 ground distance functions are required then set Z3GROUND = YES. If Zone 3 is not required, set
Z3GROUND = NO.
305: Z3GRDREACH - Zone 3 Ground Reach
In a Step Distance scheme, Zone 3 provides backup protection for adjoining line sections out of the remote
bus. Z3GRDREACH should be set to see a multi-phase fault at the end of the longest adjoining line section out
of the remote bus, considering such factors as arc resistance and underreach caused by intermediate fault cur-
rent sources. Z3GRDREACH should never be set so large as to:
1. Exceed the maximum allowable reach ( MR ), or,
2. To cause the Zone 3 functions to lose selectivity with the third zone ground distance functions on the short-
est adjoining line section. If this requirement cannot be met by limiting the reach, then it may be necessary
to get this selectivity by setting timer Z3G_TIME with additional time delay.
306: Z3GCHARANG - Zone 3 Ground Characteristic Angle
This setting determines the characteristic shape and, consequently, the area of resistance coverage provided
by the Zone 3 phase distance functions. Z3GCHARANG can be set to 90° to 120° in 5° steps. A 90° setting is
recommended. If the desired reach, Z3GRDREACH, with a 90° characteristic and with maximum load flow
does not allow the maximum allowable reach criteria to be met, then a "lens-shaped" characteristic must be
used. The settings of both Z3GRDREACH and Z3GCHARANG may be evaluated by using the formula associ-
ated with the method of Figure 2–4: MAXIMUM ALLOWABLE REACH on page 2–13.
307: Z3P_TIME - Z3 Phase Timer
Z3P_TIME can be set from 0.10 to 10.00 seconds. If the Zone 3 phase distance functions are applied to pro-
vide traditional third zone protection, then the Z3P_TIME time delay should be set long enough to coordinate
with the second zone timers in adjoining line sections. If the Zone 3 phase distance functions are used to pro-
vide traditional second zone protection (described earlier), set Z3P_TIME with the appropriate time delay.
308: Z3G_TIME - Z3 Phase Timer
Z3G_TIME can be set over the range of 0.10 to 10.00 seconds. If the Zone 3 ground-distance functions are
applied to provide traditional third zone protection, then the Z3G_TIME time delay should be set long enough
to coordinate with the second zone timers in adjoining line sections. If the Zone 3 ground-distance functions
are used to provide traditional second zone protection (described earlier), set Z3G_TIME with the appropriate
time delay.
GE Power Management
LPS-D Line Protection System
2.3 PROTECTION SETTINGS
2
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