GE LPS-O - 303: Z3 PCHARANG; 304: Z3 P_TIME; Z4 DISTANCE

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LPS-O Line Protection System GE Power Management
2.3 PROTECTION SETTINGS 2 CALCULATION OF SETTINGS
2
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 "Maximum Allowable Reach" method of Figure 2–2: MAXIMUM ALLOWABLE REACH on page 2–9.
304: Z3P_TIME - Zone 3 Phase Timer
Z1P_TIME
can be set over the range of 0.0 to 10.0 seconds and establishes the time delay that the Zone 3
phase functions can be picked up before tripping is initiated. It should be set to 2.0 for traditional Zone 3 appli-
cation for line protection. For the system backup application, it should be set with appropriate delay consistent
with the reach setting.
2.3.5 Z4DISTANCE
The settings to be used on the Zone 4 distance functions in the LPS-O system depend on the application. The
phase distance functions are set to look in the reverse direction relative to the Zone 1, Zone 2 and Zone 3
phase distance functions (see Figure 2–4: PHASE DISTANCE REACH below). The reverse direction is
required in certain applications and/or schemes as described below.
Figure 2–4: PHASE DISTANCE REACH
Historically, Zone 4 distance functions have been provided with offset to include the origin of the R-X diagram
within their characteristics (see Figure 2–5: R-X DIAGRAM FOR ZONE 4 DISTANCE FUNCTIONS below).
Without the offset, memory would have to be relied on to provide an output for a zero voltage fault right at the
relay location, and the output would last only as long as the memory lasted. With the offset, the function will
operate on current alone and thus provide a continuous output for a zero voltage fault right at the relay loca-
tion. A continuous output is required from the Zone 4 functions in some schemes to insure that incorrect trip-
ping does not occur for certain fault conditions.
Z4PHREACH
Zr
X
R
Forward
Reverse
NOTE: In the LPS-O system, Zone 4 phase
distance functions are reverse-
looking only.