ABB REL 356, Instruction Booklet

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ABB REL 356 Current Differential Protection
3-19 Settings and Application
Setting Example – General Case
Line Data
For current differential measurement
CT ratio = 1200/5 = 240
Line charging current 120 A primary, 0.5 A secondary
From local terminal, L:
Minimum fault current for internal three phase fault 3600 A primary, 15 A secondary
Minimum fault current for internal phase to ground fault 2400 A primary = 67% of three phase fault current
From remote terminal, R:
Minimum fault current for internal three phase fault 2160 A primary, 9 A secondary
Minimum fault current for internal phase to ground fault 1440 A primary = 67% of three phase fault current
Maximum through current for an external three phase and ground fault 12000 A primary, 50 A secondary
Maximum through current for an external ground fault 12000 A primary, 50 A secondary
Communication media : dedicated fiber, 1.3 msec total channel delay
For fault locating and fault recording
VT ratio = 138000/115 = 1200
Line length = 20 miles
Line impedance per mile 0.971 ohms/mile, primary
For distance backup protection
Zsec = Zprim x CTratio/VTratio = Zprim x 0.2
Z1L = 4.855@79
°
= 0.952 + j 4.761 ohms primary = 0.190 + j 4.761 ohms secondary
Z0L = 9.710@79
°
= 1.904 + j 9.522 ohms primary = 0.381 + j 1.904 ohms secondary
Z1SLmin = 2.56@88
°
ohms primary (local terminal)
Z1SRmin = 4.22@87
°
ohms primary (remote terminal)
Minimum load impedance (0.8 x 138000)/(1200x
Ö
3) primary = 10.6 ohms secondary
Relay System Setup
Firmware Version (VERS) VERS = 1.21
Indicates the firmware version in the REL 356. This instruction book is for v 1.21 and earlier.
System Frequency (FREQ) FREQ = 60 Hz
Select either 50 or 60 Hz.
Readout in Primary Values (RP) RP = YES
A YES setting enables the REL 356 system to display all the monitored voltages and currents in primary kA and kV,
based on the current transformer ratio (CTR) and voltage transformer ratio (VTR) entered.
Current Transformer Type (CTYP) CTYP = 5 A
Select either 1 or 5 A, depending on the secondary current rating of the line ct.