Calculation Of Rel301/302 Settings - ABB REL 301 Instruction Leaflet

I.L. 40-386.4
• 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
with instantaneous or time delay reset. 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
• One reverse set instantaneous directional overcurrent ground unit. (REL 302 only, Carrier
Start, Weakfeed and Transient Block Logic, supervised by I
UNDERVOLTAGE MEASUREMENTS ("Low V")
• Three under-voltage units (L
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 ("OSOT")
400 - 4000 ms in 16 ms steps
• OUT-OF-STEP BLOCK Inner Blinder ("OS Inner")
1.0 - 15.0 Ohms in 0.1 Ohm steps
NOTE:
• OUT-OF-STEP BLOCK Outer Blinder ("OS Outer")
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 In-
stallation Section (4). Assume that the protected line has the following data:
• 18.27 miles
• Line reactance 0.8 ohms/mile (primary ohms)
• 69 kV, 60 cycles
• Positive and negative sequence impedances:
ZIL (Pri) = Z2L (Pri) = 15∠77
• Zero sequence impedance:
ZIL (Pri) = Z2L (Pri) = 50∠73
3-2
, L
VA
The inner blinder (RT) is a required setting since it is used as a load re-
striction blinder even when OUT-OF-STEP BLOCK is not used.
o
ohms
o
ohms
).)
OM
, L ) for Close-Into-Fault and Weakfeed Trip (REL 302
VB VC
.)
OS