Sel 421 - Page 335

Date Code 20090715 SEL-421 Relay
Glossary
“a” Contact
A breaker auxiliary contact (ANSI Standard Device Number 52A) that closes
when the breaker is closed and opens when the breaker is open.
“a” Output
A relay control output that closes when the output relay asserts.
“b” Contact
A breaker auxiliary contact (ANSI Standard Device Number 52B) that opens
when the breaker is closed and closes when the breaker is open.
“b” Output
A relay control output that opens when the output relay asserts.
“c” Contact
A breaker auxiliary contact that can be set to serve either as an “a” contact or
as a “b” contact.
“c” Output
An output with both an “a” output and “b” output sharing a common post.
3U, 4U, 5U
The designation of the vertical height of a device in rack units. One rack unit,
U, is approximately 1.75 inches or 44.45 mm.
A
Abbreviation for amps or amperes; unit of electrical current flow.
ABS Operator
An operator in math SELOGIC
®
control equations that provides absolute
value.
AC Ripple
The peak-to-peak ac component of a signal or waveform. In the station dc
battery system, monitoring ac ripple provides an indication of whether the
substation battery charger has failed.
Acceptance Testing
Testing that confirms that the relay meets published critical performance
specifications and requirements of the intended application. Such testing
involves testing protection elements and logic functions when qualifying a
relay model for use on the utility system.
Access Level
A relay command level with a specified set of relay information and
commands. Except for Access Level 0, you must have the correct password to
enter an access level.
Access Level 0
The least secure and most limited access level. No password protects this
level. From this level, you must enter a password to go to a higher level.
Access Level 1
A relay command level you use to monitor (view) relay information. The
default access level for the relay front panel.
Access Level 2
The most secure access level where you have total relay functionality and
control of all settings types.
Access Level A
A relay command level you use to access all Access Level 1 and Access Level
B (Breaker) functions plus Automation, Alias, Global, Front Panel, Report,
Port, and DNP settings.
Courtesy of NationalSwitchgear.com