13.34
SEL-311C Relay Instruction Manual Date Code 20060320
Testing and Troubleshooting
Test Procedures
Load-Encroachment Logic
The relay includes Load-Encroachment logic to help prevent the relay phase
distance elements from operating improperly under heavy load conditions.
Forward and reverse load regions are defined through use of impedance and
angle settings. The relay calculates the positive-sequence impedance. If the
calculated impedance falls within the set load area, the phase distance
elements are blocked from operating. This may result in a phase distance
element characteristic that appears to have a bow tie-shaped section missing
near the area of the resistive axis. Double-check the relay Load-Encroachment
logic settings if your test results appear incorrect near the resistive axis.
Out-of-Step Blocking Logic
The relay includes Out-of-Step Tripping and Blocking logic that operates
based on the Zone 5 and Zone 6 positive-sequence impedance zones and
several timers. If you suspect that the Out-of-Step logic is blocking operation
of a phase distance element under test, check the relay settings associated with
the Out-of-Step function and review the relay event report.
Phase Distance Element Test Using Three Voltage Sources and One
Current Source
Step 1. Execute the SHOWSET command and verify the following
relay settings: Z1MAG, Z1ANG, PMHOZ, Z2P, 50PP2, Z2F,
and 50QF. The example relay settings use the following
settings:
Z1MAG = 7.8
Z1ANG = 83.97°
PMHOZ = 3
Z2P = 9.36 Ω
50PP2 = 2.22
Z2F = 0.77 Ω
50QF = 0.5 amps secondary
Step 2. Execute the SET command and change the example ELOP
setting from Y to N. This prevents the relay Loss-of-Potential
logic from blocking operation of the relay distance elements.
Step 3. Select an output contact to indicate operation of the M2P
element. In this example we use the OUT106 output.
Step 4. From Access Level 2, execute the SET L n command to
configure Output 6 to close for assertion of the M2P element.
=>>SET L 1 OUT106 <Enter>
SELogic group 1
OUT106 =0
? M2P <Enter>
OUT107 =0
? END <Enter>
Step 5. After you type END <Enter> to end the set procedure, the
relay displays the current logic settings.
Step 6. Type Y <Enter> to accept those settings.
Step 7. Connect output OUT106 to the sense input of your test set, an
ohmmeter, or some other contact sensing device.
NOTE: This test refers directly to the
Zone 2 phase distance element, but it
can be applied to any other forward-
reaching phase-to-phase distance
element zone. To test reverse-
reaching zones, simply add 180° to the
calculated test current phase angle.
Verify correct operation of the 32QR
element for the test voltage and
current signals through use of
Equation in Negative-Sequence
Directional Element Based Upon
Negative-Sequence Impedance on
page 13.22.
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