Operational Measurement And Energy Metering - Siemens siprotec 7SA522 User Manual

Information to a
Control Centre

6.18.2 Operational Measurement and Energy Metering

Display of
Measured Values
7SA522 Manual
C53000-G1176-C119-2
The device in addition has several event buffers for operational messages, switching
statistics, etc., which are saved against loss of auxiliary supply by means of a battery
buffer. These messages can be displayed on the LCD at any time by selection via the
keypad or transferred to a personal computer via the serial service or PC interface.
The retrieval of events/alarms during operation is extensively described in Sub-section
7.1.1.
Following a system fault, it is possible to for example retrieve important information re-
garding its progress, such as pick-up and trip. The start of the fault is time stamped
with the absolute time of the internal system clock. The progress of the disturbance is
output with a relative time referred to the instant of fault detection, so that the duration
of the fault until tripping and up to reset of the trip command can be ascertained. The
resolution of the time information is 1 ms.
With a PC and the protection data processing program DIGSI
retrieve and display the events with the convenience of visualisation on a monitor and
a menu-guided dialogue. The data may be printed or stored for evaluation at a later
time and place.
The protection device stores the messages of the last eight system faults; in the event
of a ninth fault, the oldest is erased.
A system fault starts with the recognition of the fault by the fault detection of any pro-
tection function and ends with the reset of the fault detection of the last protection func-
tion or after the expiry of the auto-reclose reclaim time, so that several unsuccessful
auto-reclose cycles are also stored cohesively. Accordingly a system fault may con-
tain several individual fault events (from fault detection up to reset of fault detection).
If the device has a serial system interface, stored information may additionally be
transferred via this interface to a centralised control and storage device. Several com-
munication protocols are available for the transfer of this information.
A range of measured values and values derived from these are available continuously
for local display or data transfer (refer to Table 6-9).
A precondition for the correct display of primary and percentage values is the com-
plete and correct entry of the instrument transformer and plant rated values, as well
as the transformation ratios of the current and voltage transformers in the earth con-
nections according to Sub-section 6.1.1.
Powers P and Q are positive if the active real power or the lagging reactive power flow
into the object to be protected. Provided that this direction is configured as
"forward". The same goes for the power factor cos ϕ.
Depending on the ordering code and the manner of connection to the device, only a
portion of the listed operational measured values in Table 6-9 may be available. Of the
current values I , I und I
EE Y
input I can apply. The displacement voltage 3U
4
tiplied by √3 (setting address 211, 8SK  8GHOWD) — if U
from the phase–earth voltages 3U
inputs must be connected for this.
only the one which is connected to the current measuring
P
0
= U + U + U
0 L1 L2
®
4 it is also possible to
is the e–n voltage U , usually mul-
en
is connected — or derived
en
. The three phase–earth voltage
L3
Functions
6-247