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10 Abbreviations and symbols
Technical description
VM55.EN005
VAMP 24h support phone +358 (0)20 753 3264
176
10.
Abbreviations and symbols
ANSI
American National Standards Institute. A standardization
organisation.
CB
Circuit breaker
CBFP
Circuit breaker failure protection
Dead band
See hysteresis.
DI
Digital input
DO
Digital output, output relay
DSR
Data set ready. An RS232 signal. Input in front panel port of
VAMP relays to disable rear panel local port.
DST
Daylight saving time. Adjusting the official local time
forward by one hour for summer time.
DTR
Data terminal ready. An RS232 signal. Output and always
true (+8 Vdc) in front panel port of VAMP relays.
FFT
Fast Fourier transform. Algorithm to convert time domain
signals to frequency domain or to phasors.
Hysteresis
I.e. dead band. Used to avoid oscillation when comparing
two near by values.
IEC
International Electrotechnical Commission. An
international standardization organisation.
IEEE
Institute of Electrical and Electronics Engineers
IEC-101
Abbreviation for communication protocol defined in
standard IEC 60870-5-101
IEC-103
Abbreviation for communication protocol defined in
standard IEC 60870-5-103
LAN
Local area network. Ethernet based network for computers
and relays.
Latching
Output relays and indication LEDs can be latched, which
means that they are not released when the control signal is
releasing. Releasing of lathed devices is done with a
separate action.
NTP
Network time protocol for LAN and WWW
PT
See VT
pu
Per unit. Depending of the context the per unit refers to any
nominal value. For example for overcurrent setting 1 pu =
1xI
mode
.
SNTP
Simple Network Time Protocol for LAN and WWW
TCS
Trip circuit supervision
THD
Total harmonic distortion
U
0sec
Voltage at input U
c
at zero ohm earth fault. (Used in voltage
measurement mode “2LL+Uo”)
U
a
Voltage input for U
12
or U
L1
depending of the voltage
measurement mode
U
b
Voltage input for U
23
or U
L2
depending of the voltage
measurement mode
U
c
Voltage input for U
31
or U
0
depending of the voltage
measurement mode
U
n
Nominal voltage. Rating of VT primary or secondary
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