Schweitzer Engineering Laboratories SEL-700G Series, Инструкция по эксплуатации

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4.134
SEL-700G Relay Instruction Manual Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
(controlled by level direction setting DIR1). The same setting principles apply
to the other levels as well. Many variations are possible.
Load-Encroachment Logic
The load-encroachment feature allows certain elements (system backup, phase
directional, etc.) to be set without regard for load levels. For example, to
obtain necessary system backup sensitivity, it may be necessary to set the
impedance element reach very long. Because of the long reach setting, the
phase distance element would pick up during heavy load. The SEL-700G
distance and phase directional elements are supervised by a load-
encroachment function that prevents element misoperation under heavy load.
You must set load impedance magnitude and angles to the necessary values to
enable load-encroachment supervision. The relay uses these settings to define
a region in the impedance plane where operation of the three-phase elements
is prevented. This allows you to make the phase protection element reach the
settings without concern for misoperation under heavy load.
Note that a positive-sequence impedance calculation (Z
1
) is made in the load-
encroachment logic in Figure 4.94 and Figure 4.95. Load is largely a balanced
condition, so apparent positive-sequence impedance is a good load measure.
The load-encroachment logic operates only if the positive-sequence current
(I
1
) is greater than the Positive-Sequence Threshold defined in Figure 4.94
and Figure 4.95. For a balanced load condition, I
1
= phase current magnitude.
Forward load (load flowing out) lies within the hatched region labeled
ZLOUT. Relay Word bit ZLOUT asserts to logical 1 when the load lies within
this hatched region.
Reverse load (load flowing in) lies within the hatched region labeled ZLIN.
Relay Word bit ZLIN asserts to logical 1 when the load lies within this
hatched region. The reverse load feature applies to Y side only, because the
generator protection applications (X side) do not require load encroachment
for the ZLIN condition.
Relay Word bit ZLOAD is the OR-combination of ZLOUT and ZLIN:
ZLOADY := ZLOUTY OR ZLINY
ZLOADX := ZLOUTX
Table 4.37 Load-Encroachment Settings
Setting Prompt Setting Range
Setting Name :=
Factory Default
FWD LD IMPEDANCE OFF, 0.10–128.00 ohm
a
a
Setting ranges and default ohm values shown are for 5 A nominal CT rating. Multiply by 5 for
1 A CTs.
ZLFX := 6.50
a
POS-FWD LD ANGLE –90.00 to 90.00 deg PLAFX := 30.00
NEG-FWD LD ANGLE –90.00 to 90.00 deg NLAFX := -30.00
LOAD ENCROACH EN Y, N ELOADY := N
FWD LD IMPEDANCE 0.10–128.00 ohm
a
ZLFY := 6.50
a
POS-FWD LD ANGLE –90.00 to 90.00 deg PLAFY := 30.00
NEG-FWD LD ANGLE –90.00 to 90.00 deg NLAFY := –30.00
REV LD IMPEDANCE 0.10–128.00 ohm
a
ZLRY := 6.50
a
POS-REV LD ANGLE 90.00–270.00 deg PLARY := 150
NEG-REV LD ANGLE 90.00–270.00 deg NLARY := 210.00