ABB LVS Digital FC610 - Page 9

TERM INOLOGY GEN ERA L
1TNC9 2825 0M0201 4
Abbreviation
Term
Description
PF
V
Power factor Vector
Under periodic conditions, ratio of the vector of
the active power to the apparent power
U
dip
Voltage dip
Temporary reduction of the voltage magnitude at
a point in the electrical system below a threshold
U
swl
Voltage swell
Temporary increase of the voltage magnitude at a
point in the electrical system above a threshold
U
int
Voltage interruption
Voltage Interruption including Upg int (phase to
ground) and Vp int (Phase to N)
U
nb
Unbalanced voltage
Voltage unbalance is a condition in which the
three-phase voltages differ in amplitude or are
displaced from their normal 120° phase relation-
ship, or both.
Uh
Amplitude of har-
monic voltage
The amplitude of harmonic voltage applied by
Fourier analysis
THD
u
Total harmonic dis-
tortion related to
voltage
Total harmonic distortion voltage of all harmonic
frequencies over the voltage of fundamental fre-
quency
I
h
Amplitude of har-
monic current
The amplitude of harmonic current applied by
Fourier analysis
THD
i
Total harmonic dis-
tortion related to
current
Total harmonic distortion current of all harmonic
frequencies over the current of fundamental fre-
quency
TN
One of the points in the generator or transformer
is connected with earth, usually the star point in a
three-phase system. The body of the electrical de-
vice is connected to earth via this earth connec-
tion at the transformer.
TT
The protective earth connection for the consumer
is provided by a local earth electrode, and there is
another independently installed at the generator.
There is no 'earth wire' between the two.
IT
The electrical distribution system has no connec-
tion to earth at all, or it has only a high impedance
connection.
TN-S
PE and N are separate conductors that are con-
nected only near the power source.