General - Siemens SIMEAS R-PMU Manual

8

8.1 General

8.1 General
To ensure that the records of several SIMEAS R-PMU in different locations are comparable in
correct phase sequence, the devices must be synchronized using appropriate timers.
The time stamp and the measurement system synchronization of an unsynchronized SIMEAS
R-PMU are derived from the internal real-time clock (RTC). This clock has a maximum error of
30 ppm at 25 °C. After 24 hours, the time-base error is max. ±2.6 s at a constant temperature.
The time-base error may be larger with deviating temperatures.
An external timer must be connected to the SIMEAS R-PMU to compensate for the real-time
clock drift. A minute pulse or a signal according to the DCF77 protocol can be used as a
synchronizing signal. When using the recording function Phasor Measurement Unit only the
DCF77 signal of a GPS clock is allowed.
Note
The automatic time setting of the SIMEAS R-PMU by OSCOP P running in the automatic mode
is not a synchronization! The RTC of the SIMEAS R-PMU is set cyclically in steps and the
synchronization error is considerably larger than the error obtained by external synchronization.
To prevent the measuring system from being impaired by too frequent time setting procedures,
the minimum cycle time for automatic time setting is 4 hours.
Note
Additional and more detailed information on time synchronization in the Application Description
„Time Synchronization SIMEAS R/SIMEAS R-PMU", order number E50417-X1074-C403, can
be found under www.simeas.com.
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Digital Fault Recorder, SIMEAS R-PMU, Manual
E50417-H1076-C360-A5, Release 10.2012