1.5
Date Code 20080213 Instruction Manual SEL-351A Relay
Introduction and Specifications
SEL-351A Models
revisions, the auxiliary voltage channel “VS” can only be used for
synchronism check or as a general-purpose voltage input. See Access Level 2
Commands on page 10.36 for details on the VER command.
Firmware revisions numbered R105 or higher can be configured via global
setting PTCONN to accept either wye (line-to-neutral) or delta (line-to-line)
voltages using the open-delta connection. The VER command identifies these
relays as “wye or delta connected.” See Potential Transformer Inputs on
page 2.13 for details on the open-delta connection.
NOTE: The VS channel is not
supported in the SEL-351A-1.
Also in firmware revisions numbered R105 or higher, the auxiliary voltage
channel “VS” can be configured via global setting VSCONN = VS to accept a
synchronism check or general-purpose voltage input or via VSCONN = 3V0
to accept a broken-delta residual voltage connection to be used in the zero-
sequence voltage polarized ground directional elements. See Potential
Transformer Inputs for details on the broken-delta connection and other relay
elements that are affected by setting VSCONN = 3V0.
The connection type setting (wye or delta) does not affect the voltage input
rating of the relay voltage terminals. For example, a relay with 300 Vac
voltage inputs can accept up to 300 Vac line-to-neutral in the wye
configuration and up to 300 Vac line-to-line in the delta configuration. The
auxiliary voltage channel “VS” is similarly rated.
When using a broken-delta connection, if the maximum possible zero-
sequence voltage 3V
0
exceeds the VS channel rating, an external step-down
instrumentation transformer may be required. See AC Voltage Inputs on
page 1.10 for details on the input ratings. See Figure 2.23 for an example
connection that uses a step-down transformer.
Courtesy of NationalSwitchgear.com
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