Siemens SIPROTEC 7UT613 series User Manual

2 Functions
280
7UT613/63x Manual
C53000-G1176-C160-2
2.19.1.2 Software Monitoring
Watchdog For the continuous monitoring of the program execution, a time monitoring is incorpo-
rated in the hardware (hardware watchdog). The watchdog expires and resets the pro-
cessor system causing a complete reboot if the processor fails or when a program
loses synchronism.
A further software watchdog ensures that any error in the processing of the programs
will be recognised. Such errors also lead to a reset of the processor.
If such an error is not eliminated by restarting, another restart attempt is initiated. If the
fault is still present after three restart attempts within 30 s, the protection system will
take itself out of service, and the red LED „Blocked“ lights up. The readiness relay („life
contact“) drops off and signals the malfunction by its healthy status contact (alterna-
tively as NO or NC contact).
2.19.1.3 Monitoring of Measured Quantities
The device detects and signals most of the interruptions, short-circuits, or wrong con-
nections in the secondary circuits of current or voltage transformers (an important
commissioning aid!). The measured quantities are periodically checked in the back-
ground for this purpose, as long as no system fault is present.
Current Symmetry In a healthy three-phase system, symmetry amongst the currents is assumed. The
monitoring of the measured values in the device checks this balance for each 3-phase
measuring location. The lowest phase current is thus set in relation to the highest. An
asymmetry is detected, if (e.g. for side 1)
|I
min
|/|I
max
| < BAL. FACT. I M1 as long as I
max
/I
N
> BAL. I LIMIT M1/I
N
I
max
is the highest of the three phase currents and I
min
the lowest. The symmetry factor
BAL. FACT. I M1 represents the allowable asymmetry of the phase currents while
the limit value BAL. I LIMIT M1 is the lower limit of the operating range of this mon-
itoring (see Figure Current Symmetry Monitoring). Both parameters can be set. The
dropout ratio is about 95%.
Current balance monitoring is available separately for each 3-phase measuring loca-
tion. For single-phase differential busbar protection this function would not be of any
use and is thus disabled. Unsymmetrical condition is indicated for the corresponding
measuring location e.g. with the alarm „Fail balan. IM1“ (No 30110). At the
same time, the common annunciation appears: „Fail I balance“ (No 163).

Siemens SIPROTEC 7UT613 series Specifications

General

Brand	Siemens
Model	SIPROTEC 7UT613 series
Category	Protection Device
Language	English