Operational Measurement - Siemens siprotec 7SA6 User Manual

Functions
Information to a
Control Centre

6.21.2 Operational Measurement

Display of
Measured Values
6-284
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 Subsection
7.1.1.
Following a system fault, it is possible to for example retrieve important information
regarding 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
protection function and ends with the reset of the fault detection of the last protection
function 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 contain 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
communication 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 6-15).
A precondition for the correct display of primary and percentage values is the
complete 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
connections according to Sub-section 6.1.1.
Depending on the ordering code and the manner of connection to the device, only a
portion of the listed operational measured values in Table 6-15 may be available. Of
the current values I , I
EE
measuring input I can apply. The phase-earth voltages can be measured if the
4
voltage inputs phase-earth are connected. The displacement voltage 3U
, usually multiplied by √3 (setting address , 8SK  8GHOWD) — if
voltage U
en
U is connected — or derived from the phase–earth voltages 3U
en
The three phase–earth voltage inputs must be connected for this.
For the thermal overload protection the calculated overtemperatures are indicated in
relation to the trip overtemperature.
und I only the one which is connected to the current
Y P
®
4 it is also possible to
is the e–n
0
= |U + U + U |.
0 L1 L2 L3
7SA6 Manual
C53000-G1176-C133-1