Z3Distance - GE LPS-O Instruction Manual

2 CALCULATION OF SETTINGS
203: Z2PCHARANG - Zone 2 Phase Characteristic Angle
This setting determines the characteristic shape and, consequently, the area of resistance coverage provided
by the Zone 2 phase distance functions. Z2PCHARANG can be set to 90° to 120° in 5° steps. A 90° setting is
recommended. If the desired reach, Z2PHREACH, with a 90° characteristic causes the Zone 2 functions to
pick up on the maximum load flow, then a "lens-shaped" characteristic must be used to prevent operation on
load without having to reduce the reach. The settings of both Z2PHREACH and Z2PCHARANG may be eval-
uated by using the formula associated with the Maximum Allowable Reach method of Figure 2–2: MAXIMUM
ALLOWABLE REACH on page 2–9.
204: Z2TIMER - Zone 2 Timer
The choice of settings is YES or NO. Set Z2TIMER = YES if the Zone 2 phase distance time delay is to be
used, otherwise set Z2TIMER = NO.
205: Z2P_TIME - Zone 2 Phase Timer
Z2P_TIME can be set over the range of 0.0 to 10.0 seconds and establishes the time delay that the Zone 2
phase functions can be picked up before tripping is initiated. It should be set to 1.0 for traditional Zone 2 appli-
cation for line protection. For the system backup application, it should be set with appropriate delay consistent
with the reach setting.
301: Z3PHASE - Select Zone 3 Phase
Z3PHASE can be set to either YES or NO. When Zone 3 is used as part of a Step Distance scheme and Zone
3 phase distance functions are required, then set Z3PHASE = YES. If Zone 3 is not used required, set
Z3PHASE = NO.
302: Z3PHREACH - Zone 3 Phase Reach
In a Step Distance scheme, Zone 3 provides backup protection for adjoining line sections out of the remote
bus. Z3PHREACH 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. Z3PHREACH should never be set so large as to:
1. Exceed the maximum allowable reach ( MR ), or,
2. Cause the Zone 3 functions to lose selectivity with the third zone phase distance functions on the shortest
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 Z3P_TIME with additional time delay.
GE Power Management
REACH (IN PERCENT)
Figure 2–3: OPERATING TIME CHARACTERISTIC
LPS-O Line Protection System
2.3 PROTECTION SETTINGS
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2.3.4 Z3DISTANCE

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