Schweitzer Engineering Laboratories SEL-421-4 - Table 5.4 Available Voltage Source Selection Setting Combinations

5.6
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Functions
Current and Voltage Source Selection
➤ Series-compensation line logic
➤ Load-encroachment logic
➤ OOS (out-of-step) logic
➤ Distance elements
➤ Instantaneous line overcurrent elements
➤ Inverse-time overcurrent elements
➤ DCUB (directional comparison unblocking) trip scheme logic
➤ Metering on page 7.1, except synchrophasors
Breaker current-source settings (BK1I and BK2I) identify the currents used in the
following elements/features described in later in this section and in other sec-
tions:
➤ Open-phase detection logic
➤ Inverse-time overcurrent elements
➤ Circuit breaker failure protection
➤ Circuit Breaker Monitor on page 7.7
➤ Metering on page 7.1
Polarizing current-source setting IPOL identifies the single current input con-
nected to a zero-sequence current source (e.g., transformer bank neutral). This
zero-sequence current is used as a reference in the zero-sequence current-polar-
ized directional element. Such a directional element is applied to ground overcur-
rent elements (see Tabl e 5 .3 1 and Table 5 .27). Setting IPOL is not used often and
thus is usually set to NA. Notice that in Table 5.1, Table 5 .2 and Tab le 5 .3 there
are relatively few scenarios where setting IPOL can be set to a current channel
selection (only those cases where three-phase current input IX is not used for any
other function). An example of using setting IPOL is found later in this subsec-
tion.
Voltage Source Switching and Uses
Refer to the global settings in Table 8.13 on page 8.5. Alternate voltage source
switching between VY and VZ in Tab le 5.1 is more straightforward (as shown in
Table 5.4) than the preceding discussion on current-source selection/switching
(compare to Table 5.1 through Tab l e 5 .3 ).
Table 5.4 Available Voltage Source Selection Setting Combinations
a
(Sheet 1 of 2)
NUMBK (number of
breakers)
ESS
(source selection)
Line Voltage Source
ALINEV (alternate
line voltage source)
1 Y VY VZ or NA
1NVY
NA
11VYVZ or NA
12VYVZ or NA
1 3 not allowed
1 4 not allowed
2 Y VY VZ or NA
2NVY
NA
2 1 not allowed
2 2 not allowed