Schweitzer Engineering Laboratories SEL-421-4 - Page 1512

GL.20
SEL-400 Series Relays Instruction Manual Date Code 20171006
Glossary
Residual Current—Self-Description
Residual Current
The sum of the measured phase currents. In normal, balanced operation, this
current is very small or zero.
Residual Directional
Overcurrent Element
A residual overcurrent element allowed to operate in only the forward or reverse
direction.
Residual
Overcurrent Protection
Overcurrent protection that operates at conditions exceeding a threshold of
system unbalance (3I
0
= I
A
+ I
B
+ I
C
).
Resistance Blinder
An operate boundary in the resistive direction of a ground quadrilateral distance
element.
Resistive Reach
The reach of a distance element in the resistive (R) direction in the R-X plane.
Restraint Current
Sum of the absolute values of current(s) entering a point, and leaving that point.
Used as basis to calculate the reference (setting) value for differential elements.
Restricted Earth Fault
Differential element that augments the phase differential element by providing
sensitive protection against ground faults close to the neutral of a grounded-wye
transformer. The element compares the phase angle of zero-sequence quantities
from the transformer neutral with zero-sequence quantities from as many as five
line CTs.
Retrip
A subsequent act of attempting to open the contacts of a circuit breaker after the
failure of an initial attempt to open these contacts.
Reverse Fault
A fault operation behind a relay terminal.
Rising Edge
Transition from logical 0 to logical 1, or the beginning of an operation.
RMS
Root-mean-square. This is the effective value of the current and voltage
measured by the relay, accounting for the fundamental frequency and higher-
order harmonics in the signal.
Rolling Demand
A sliding time-window arithmetic average in demand metering.
RTC
Real Time Control. A method for exchanging synchrophasor control data.
RTD
Resistance Temperature Detector.
RTU
Remote Terminal Unit.
RXD
Received data.
SCADA
Supervisory control and data acquisition.
SCD File
IEC 61850 Substation Configuration Description file. XML file that contains
information on all IEDs within a substation, communications configuration data,
and a substation description.
SCL
IEC 61850 Substation Configuration Language. An XML-based configuration
language that supports the exchange of database configuration data among
different software tools that can be from different manufacturers. There are four
types of SCL files used within IEC 61850: CID, ICD, SCD, and SSD.
SDN
Software-defined networking.
Self-Description
A feature of GOMSFE in the UCA2 protocol. A master device can request a
description of all of the GOMSFE models and data within the IED.