ABB REL 356

ABB REL 356 Current Differential Protection
3-34
Settings and Application
Out of Step Trip Override Timer (OSOT) OSOT = 100 cycles
This timer is started once an out of step condition is identified (output of OST1). A trip signal is generated if OSOT times
out and the apparent impedance seen by the relay is inside Zone 2 or Zone 3 reach and inside the RT blinder. The
recommended setting is 100 cycles.
Remote Setting and Time Settings
Remote Setting (SETR) SETR = YES
Set SETR = YES if remote setting via RCP is allowed.
Time Settings (TIME, YEAR, MONTH, DAY, WDAY, HOUR, MIN)
To set the clock in the relay, set TIME = YES and enter correct values as appropriate.
Setting Example - Tapped Load Application
Figure 3-3. Setting Example-Tapped Load Application
Line and Transformer Data
Line data as for the general case:
CT ratio = 1200/5 = 240
VT ratio = 138000/115 = 1200
Z = 4.08 ohms, primary
ZT = 7% on a 20 MVA base
65.66
20
138
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22
=⋅=⋅=
M
VA
kV
puZTohmsZT