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1.4
SEL-351-5, -6, -7 Relay
Instruction Manual
Date Code 20070117
Introduction and Specifications
SEL-351 Models
Firmware revisions numbered R309 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
for details on the open-delta connection.
Also in firmware revisions numbered R309 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
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 residual
voltage “3V0” exceeds the VS channel rating, an external step-down
instrumentation transformer may be required. See
for details on the input ratings. See
for an example
connection that uses a step-down transformer.
Summary of Contents for SEL-351-5
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