R.1.6
SEL-421 Relay Reference Manual Date Code 20111215
Protection Functions
Current and Voltage Source Selection
Current Source Uses
Refer to the global settings in Table 10.14 on page R.10.9. Line current source
setting LINEI and alternate line current source settings ALINE1 and ALTI, if
used, identify the currents used in the following elements/features described
later in this section and in other sections:
➤ Fault location
➤ Open-phase detection logic
➤ LOP (loss-of-potential) logic
➤ FIDS (fault-type identification selection) logic
➤ Directional elements
➤ CVT (capacitor voltage transformer) transient detection logic
➤ 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 A.2.26, except synchrophasors
NOTE: Starting in firmware version
R112, synchrophasor measurements
are no longer affected by the line
current source settings ALINEI and
LINEI. See Synchrophasors on
page R.7.1.
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
sections:
➤ Open-phase detection logic
➤ Inverse-time overcurrent elements
➤ Circuit breaker failure protection
➤ Circuit Breaker Monitor on page A.2.1
➤ Metering on page A.2.26
Polarizing current-source setting IPOL identifies the single current input
connected 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-
polarized directional element. Such a directional element is applied to ground
overcurrent elements (see Table 1.26 and Figure 1.23). Setting IPOL is not
used often and thus is usually set to NA. Notice that in Table 1.1, Tab le 1.2
and Table 1.3 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 subsection.
Voltage Source
Switching and Uses
Refer to the global settings in Table 10.14 on page R.10.9. Alternate voltage
source switching between VY and VZ in Figure 1.1 is more straightforward
(as shown in Table 1.4) than the preceding discussion on current-source
selection/switching (compare to Tabl e 1 .1 through Table 1.3).
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