Schweitzer Engineering Laboratories SEL-421-4, Instruction Manual

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GL.22
SEL-400 Series Relays Instruction Manual Date Code 20171006
Glossary
SOTF (Switch-Onto-Fault Protection Logic) — TAP
SOTF
(Switch-Onto-Fault
Protection Logic)
Logic that provides tripping if a circuit breaker closes into a zero voltage bolted
fault, such as would happen if protective grounds remained on the line following
maintenance.
Source Impedance The impedance of an energy source at the input terminals of a device or network.
SQRT Operator Math SEL
OGIC
control equation operator that provides square root.
SSD File IEC 61850 System Specification Description file. XML file that describes the
single-line diagram of the substation and the required logical nodes.
Stable Power Swing A change in the electrical angle between power systems. A control action can
return the angular separation between systems to less than the critical angle.
Station Bus Network bus for IED communication between the bay and station levels.
Status Failure A severe out-of-tolerance internal operating condition. The relay issues a status
failure message and enters a protection-disabled state.
Status Warning
Out-of-tolerance internal operating conditions that do not compromise relay
protection, yet are beyond expected limits. The relay issues a status warning
message and continues to operate.
Strong Password A mix of valid password characters in a six-character combination that does not
spell common words in any portion of the password. Valid password characters
are numbers, upper- and lowercase alphabetic characters, “.” (period), and “-”
(hyphen).
Subnet Mask The subnet mask divides the local node IP address into two parts, a network
number and a node address on that network. A subnet mask is four bytes of
information and is expressed in the same format as an IP address.
Subsidence Current
See CT subsidence current.
SV Sampled Values, as defined in Part 9-2 of IEC 61850.
SV Channel A single-phase voltage or current transmitted as an integer value containing its
magnitude and phase angle.
SV Stream Multicast packets containing a fixed dataset transmitted periodically. In the case
of 9-2LE, SV streams contain four currents and four voltages and are transmitted
at a rate of 80 samples per cycle.
Synch Reference A phasor the relay uses as a polarizing quantity for synchronism-check
calculations.
Synchronism-Check Verification by the relay that system components operate within a preset
frequency difference and within a preset phase angle displacement between
voltages.
Synchronized Phasor A phasor calculated from data samples using an absolute time signal as the
reference for the sampling process. The phasors from remote sites have a defined
common phase relationship. Also known as Synchrophasor.
TAP Full-load secondary current that the relay uses to convert Ampere values to
dimensionless per-unit values.