Sel 421 - Figure 2.2 Rear 3 U Template, Fixed Terminal Block Analog Inputs; Figure 2.3 Rear 3 U Template, Connectorized Analog Inputs

U.2.4
SEL-421 Relay User’s Guide Date Code 20090715
Installation
Shared Configuration Attributes
Figure 2.2 Rear 3U Template, Fixed Terminal Block Analog Inputs
(In a vertical-mount relay, the right rear side is at the top.)
Figure 2.3 Rear 3U Template, Connectorized Analog Inputs
(In a vertical-mount relay, the right rear side is at the top.)
Secondary Circuits
The SEL-421 is a very low burden load on the CT secondaries and PT
secondaries. For both the CT and PT inputs, the frequency range is 40–65 Hz.
The relay accepts two sets of three-phase currents from power system CT
inputs:
➤ IAW, IBW, and ICW
➤ IAX, IBX, and ICX
For 5 A relays, the rated nominal input current, I
nom
, is 5 A. For 1 A relays,
the rated nominal input current, I
nom
, is 1 A.
Input current for both relay types can range to 20 • I
nom
. The CT burden for
each relay is the following:
➤ 5 A relay: 0.27 VA @ 5A and 2.51 VA @ 15 A
➤ 1 A relay: 0.13 VA @ 1 A and 1.31 VA @ 3A
See the AC Current Inputs (Secondary Circuits) on page U.1.13 for complete
CT input specifications.
i3359c
i3372d
Courtesy of NationalSwitchgear.com