3
Date Code 20151102
SEL Application Guide 2015-33
Step 4
From the drop-down menu on the left-hand side of the page, select
Settings
>
Protection
>
Basic
Settings
. The rated frequency and phase rotation should be set based on the power system. In this
example, the SEL-849 is applied on a 60 Hz power system with ABC phase rotations.
Application (APP)
should be set to
FEEDER
. See Figure 4 for an example of basic settings for a
feeder application.
Figure 4 Basic Settings
Step 5
In this example, the nominal feeder current is 1,200 A, which exceeds the 128 A limit of the
integrated Rogowski coil current transformers (CTs). External CTs must be used, where the
external CT leads are passed through the CT inputs of the SEL-849. When using external CTs,
divide the CT primary by the CT secondary. Enter this value into
Phase CT Ratio 1 (CTR1)
. If a
core balance CT is used for ground fault sensing,
Core Balance CT Ratio (CTRN)
should be set
equal to the core balance CT ratio, and modifications to the factory logic will be required. Set
Full Load Amps (FLA1)
equal to the current rating of the feeder to be protected divided by the
Phase CT Ratio 1 (CTR1) value
(see Figure 4). In this example, 1200/5 external CTs are used
and the current rating of the feeder is 1,200 A.
Note that the SEL-849 includes optional voltage, power, and arc-flash protection and control
elements that are not discussed in this application guide. Refer to the SEL-849 Instruction Manual
for additional details.
