Functions
2.26 Additional Functions
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
472
2.26.4
Measurement During Operation
2.26.4.1 Functional Description
A series of measured values and the values derived from them are available for on-site retrieval or for data
transfer.
A precondition for the correct display of primary and percentage values is the complete and correct entry of the
nominal values of the instrument transformers and the power system as well as the transformation ratio of the
current and voltage transformers in the earth paths.
Display and Transmission of Measured Values
Operational measured values and metered values are determined in the background by the processor system.
They can be called up on the front of the device, read out via the operator interface using a PC with DIGSI, or
transferred to a control centre via the system interface.
Depending on ordering code, connection of the device and configured protection functions, only some of the
operational measured values listed in Table 2-21 may be available. Of the current values
I
EE
,
I
Y
and
I
P
only the
one which is connected to current measuring input
I
4
can apply. Phase-to-earth voltages can only be measured
if the phase-to-earth voltage inputs are connected. The displacement voltage 3U
0
is e-n-voltage multiplied by
√
3 — if U
en
is connected — or calculated from the phase-to-earth voltages 3U
0
= |U
L1
+ U
L2
+ U
L3
|. All three
voltage inputs must be phase-earth connected for this.
The zero sequence voltage U
0
indicates the voltage between the centre of the voltage triangle and earth.
If multiple devices are connected via their protection data interfaces, a common frequency value is calculated
via the constellation (constellation frequency). This value is displayed as the operational measured value „Fre-
quency“. It allows to display a frequency even in devices in which local frequency measurement is not possible.
The constellation frequency is also used by the differential protection for synchronizing the measured values.
Locally operating functions such as frequency protection always use the locally measured frequency.
If the device is in „Log out device“ ON mode, in differential protection test mode or if there is no protection data
interface connection, the locally measured frequency is displayed.
For the thermal overload protection, the calculated overtemperatures are indicated in relation to the trip over-
temperature. Overload measured values can appear only if the overload protection was configured
Enabled
.
If the device features synchronism and voltage check and if, when configuring the functions (address
135
),
these functions were set as
Enabled
and the parameter
U4 transformer
(address
210
) to
Usy2 transf.
,
you can read out the characteristic values (voltages, frequencies, differences).
The power and operating values upon delivery are set such that power in line direction is positive. Active com-
ponents in line direction and inductive reactive components in line direction are also positive. The same applies
for the power factor cos
ϕ
.
It is occasionally desired to define the power drawn from the line (e.g. as seen from the consumer) positively.
Using parameter
1107
P,Q sign
the signs for these components can be inverted.
The operational measured values are also calculated in the event of a running fault in intervals of approximately
0.5 s.
