Symbol Description Units
R
Resistance W
R Gnd.
A distance zone resistive reach setting: Used for ground (earth) faults.
R Ph
A distance zone resistive reach setting used for Phase-Phase faults.
Rct
Secondary winding resistance W
Rl
Resistance of single lead from relay to current transformer W
Rr
Resistance of any other protective relays sharing the current transformer W
Rrn
Resistance of relay neutral current input W
Rrp
Resistance of relay phase current input W
Rs
Value of stabilizing resistor W
Rx
Receive: typically used to indicate a communication receive line/pin.
S1
Used in IEC terminology to identify the secondary CT terminal polarity: Replace by a dot when using ANSI standards.
S2
Used in IEC terminology to identify the secondary CT terminal polarity: The non-dot terminal.
t
A time delay.
t’
Duration of first current flow during auto-reclose cycle s
T1
Primary system time constant s
tfr
Auto-reclose dead time s
tIdiff
Current differential operating time s
Ts
Secondary system time constant s
Tx
Transmit: typically used to indicate a communication transmit line/pin.
V
Voltage. V
V<
An undervoltage element. V
V<1
First stage of undervoltage protection: Could be labeled 27-1 in ANSI terminology. V
V<2
Second stage of undervoltage protection: Could be labeled 27-2 in ANSI terminology. V
V>
An overvoltage element. V
V>1
First stage of overvoltage protection: Could be labeled 59-1 in ANSI terminology. V
V>2
Second stage of overvoltage protection: Could be labeled 59-2 in ANSI terminology. V
V0
Zero sequence voltage: Equals one third of the measured neutral/residual voltage. V
V1
Positive sequence voltage. V
V2
Negative sequence voltage. V
V2pol
Negative sequence polarizing voltage. V
VA
Phase A voltage: Might be phase L1, red phase.. or other, in customer terminology. V
VB
Phase B voltage: Might be phase L2, yellow phase.. or other, in customer terminology. V
VC
Phase C voltage: Might be phase L3, blue phase.. or other, in customer terminology. V
Vf
Theoretical maximum voltage produced if CT saturation did not occur V
Vin
Input voltage e.g. to an opto-input V
Vk
Required CT knee-point voltage.
IEC knee point voltage of a current transformer.
V
VN
Neutral voltage displacement, or residual voltage. V
Vn
Nominal voltage V
Vn
The rated nominal voltage of the relay: To match the line VT input. V
VN>1
First stage of residual (neutral) overvoltage protection. V
VN>2
Second stage of residual (neutral) overvoltage protection. V
Vres.
Neutral voltage displacement, or residual voltage. V
Vs
Value of stabilizing voltage V
Appendix A - Symbols and Glossary MiCOM P747
418 P747-TM-EN-1
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