I.L. 40-386.3
3-2 (10/94)
• One inverse overcurrent ground unit with CO characteristics (see Figures 2-32
through 2-38) for ground backup:
Pickup (0.5 - 4.0) in 0.1 A steps for 5 A (ct type).
Choice of 7 time-curve families (CO-2, 5, 6, 7, 8, 9, 11 Characteristics), 63 curves
per family.
Set for directional or non-directional operation.
(Pickup (0.1 - 2.0) in 0.1 A steps for 1 A (ct type).)
• One forward set instantaneous directional overcurrent ground unit. (REL 302 only,
Pilot-high resistance ground faults, supervised by I
CM
).)
• One reverse set instantaneous directional overcurrent ground unit. (REL 302 only,
Carrier Start, Weakfeed and Transient Block Logic, supervised by IOS.)
UNDERVOLTAGE MEASUREMENTS
• Three under-voltage units (L
VA
, L
VB
, L
VC
) for Close-Into-Fault, Loss of Potential and
Weakfeed Trip (REL 302 only) supervision with one setting (Low V).
40 to 60 Vrms in 1 - Volt steps.
OHMS PER UNIT DISTANCE (x / Dist)
• For fault locator measurement
0.300 - 1.500 in 0.001 Ohms per Distance Unit (Kilometers or Miles) in primary
ohms.
OUT-OF-STEP BLOCK (OS Block)
• OUT-OF-STEP BLOCK Override Timer
400 - 4000 ms in 16 ms steps
• OUT-OF-STEP BLOCK Inner Blinder (RT)
1.0 - 15.0 Ohms in 0.1 Ohm steps
NOTE: The inner blinder (RT) is a required setting since it is used as a load
restriction blinder even when OUT-OF-STEP BLOCK is not used.
• OUT-OF-STEP BLOCK Outer Blinder (RU)
3.0 - 15.0 Ohms in 0.1 Ohm steps
3.2. CALCULATION OF REL 301/302 SETTINGS
The following REL 301/302 setting calculations correspond to the setting categories
in the Installation Section (4). Assume that the protected line has the following data:
• 18.27 miles
• Line reactance 0.8 ohms/mile
• 69 kV, 60 cycles
• Positive and negative sequence impedances:
• ZIL (Pri) = Z2L (Pri) = 15∠77° ohms
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