Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 393 / 706

9.37
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Setting the Relay
Settings Explanations
Settings Explanations
Note that most of the settings in the settings sheets that follow include
references for additional information. The following explanations are for
settings that do not have reference information anywhere else in the
instruction manual.
Identifier Labels
Refer to Identifier Labels (See Settings Explanations on page 9.37) on
page SET.1 .
The SEL-351 Relay has two identifier labels:
➤
the Relay Identifier (RID)
➤
the Terminal Identifier (TID)
The Relay Identifier is typically used to identify the relay or the type of
protection scheme. Typical Terminal Identifiers include an abbreviation of the
substation name and line terminal.
The relay tags each report (event report, meter report, etc.) with the Relay
Identifier and Terminal Identifier. This allows you to distinguish the report as
one generated for a specific breaker and substation.
RID and TID settings may include the following characters:
➤
0–9
➤
A–Z
➤
-
➤
/
➤
.
➤
space
These two settings cannot be made via the front-panel interface.
Current Transformer
Ratios
Refer to Current and Potential Transformer Ratios (See Settings Explanations
on page 9.37) on page SET.1 .
Phase and neutral current transformer ratios are set independently. If neutral
channel
IN
is connected residually with
IA
,
IB
, and
IC
, then set CTR and CTRN
the same. Relay settings CTR and CTRN are used in relay event reports and
metering functions to scale secondary current quantities into primary values.
For directional control on low-impedance grounded, Petersen Coil-grounded,
and ungrounded/ high-impedance grounded systems, neutral channel
IN
is
usually connected to a core-balance current transformer that encompasses the
three phases (see
Figure 2.18 – Figure 2.21 ). This type of current transformer
typically has a lower ratio than the phase current transformers, which allows
for more sensitivity in ground fault detection. Core-balance current
transformers are also used for nondirectional sensitive earth fault (SEF)
protection (see
Figure 2.16 ).