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2 Functions
190
7ST6 Manual
E50417-G1176-C251-A3
2.19.2 Measurement
2.19.2.1 Functional Description
Display of Mea-
sured Values
For local retrieval, or for data transmission via system interface, measured values and
resulting computed values are continuously available. The operational measured
values can be read out as secondary, primary or percent values. The measured values
can only be correctly displayed if the transformer ratings are entered completely and
correctly.
Calculation of Mea-
sured Values
In auto-transformer systems, the active and reactive power is calculated from the cur-
rents and voltages of the overhead contact line and the negative feeder. The operating
impedance and the load angle are calculated using the overhead contact line voltage
and the summation current.
Depending on the ordering code, connection type to the device and the configured
protection function, only some of the listed operational measured values in Table 2-9
may be available.
Table 2-9
Operational measured values of the local device
Measured values
Primary
Second-
ary
% referred to
I
Operating current
R
R
Rated operational current
U
Operational voltage
kV
V
Rated operational voltage
IF
Negative feeder current (in auto-trans-
former systems)
R
R
Rated operational current
CL
Feeder voltage (in auto-transformer
systems)
kV
V
Rated operational voltage
IX
Defrosting current
R
R
Rated operational current
f
Frequency
Hz
Hz
Rated system frequency
P, Q
Active and reactive power
kW, kVAr —
U
N
· I
N
Operational ratings
Uref
Reference voltage
kV
V
Operational rated voltage
ϕ
dif
Differential angle between operational
voltage and reference voltage
°
°
—
Z
Operational impedance
Ω
Ω
—
R
Operational resistance
Ω
Ω
—
X
Operational reactance
Ω
Ω
—
ϕ
Load angle
°
°
—
Zsec
Calculated fault impedance (fault loca-
tion)
—
Ω
—
Tline
Catenary temperature
°
C
—
—
Tamb
Ambient temperature
°
C
—
—
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