Siemens 7VK512

-ETHOD OF OPERATION6+
6

#
' #
5 THE VOLTAGE MAGNITUDE DIFFERENCE
F THE FREQUENCY DIFFERENCE
 THE PHASE ANGLE DIFFERENCE
 -ONITORING FUNCTIONS
4HE DEVICE INCORPORATES COMPREHENSIVE MONITORING
FUNCTIONS WHICH COVER BOTH HARDWARE AND SOFTWARE
 (ARDWARE MONITORING
4HE COMPLETE HARDWARE IS MONITORED FOR FAULTS AND
INADMISSIBLE FUNCTIONS FROM THE MEASURED VALUE IN
PUTS TO THE OUTPUT RELAYS )N DETAIL THIS IS ACCOM
PLISHED BY MONITORING
!UXILIARY AND REFERENCE VOLTAGES
4HE PROCESSOR MONITORS THE OFFSET AND REFERENCE
VOLTAGE OF THE !$# ANALOGDIGITAL CONVERTER 4HE
PROTECTION IS BLOCKED AS SOON AS IMPERMISSIBLE
DEVIATIONS OCCUR 0ERMANENT FAULTS ARE ANNUN
CIATED
&AILURE OR SWITCH
OFF OF THE AUXILIARY VOLTAGE AUTO
MATICALLY PUTS THE SYSTEM OUT OF OPERATION THIS
STATUS IS INDICATED BY A FAIL
SAFE CONTACT 4RAN
SIENT DIPS IN SUPPLY VOLTAGE OF LESS THAN  MS WILL
NOT DISTURB THE FUNCTION OF THE RELAY
#OMMAND OUTPUT CHANNELS
4HE COMMAND RELAYS FOR CLOSING ARE CONTROLLED BY
TWO COMMAND AND ONE ADDITIONAL RELEASE CHAN
NELS !S LONG AS NO PICK
UP CONDITION EXISTS THE
CENTRAL PROCESSOR MAKES A CYCLIC CHECK OF THESE
COMMAND OUTPUT CHANNEL FOR AVAILABILITY BY EXCIT
ING EACH CHANNELS ONE AFTER THE OTHER AND CHECK
ING FOR CHANGE IN THE OUTPUT SIGNAL LEVEL #HANGE
OF THE FEED
BACK SIGNAL TO LOW LEVEL INDICATES A
FAULT IN ONE OF THE CONTROL CHANNELS OR IN THE RELAY
COIL 3UCH A CONDITION LEADS AUTOMATICALLY TO
ALARM AND BLOCKING OF THE COMMAND OUTPUT
-EMORY MODULES
4HE MEMORY MODULES ARE PERIODICALLY CHECKED
FOR FAULT BY
C 7RITING A DATA BIT PATTERN FOR THE WORKING
MEMORY 2!- AND READING IT
C &ORMATION OF THE MODULUS FOR THE PROGRAM
MEMORY %02/- AND COMPARISON OF IT WITH A
REFERENCE PROGRAM MODULUS STORED THERE
C &ORMATION OF THE MODULUS OF THE VALUES STORED
IN THE PARAMETER STORE %%02/- THEN COM
PARING IT WITH THE NEWLY DETERMINED MODULUS AF
TER EACH PARAMETER ASSIGNMENT PROCESS
 3OFTWARE MONITORING
&OR CONTINUOUS MONITORING OF THE PROGRAM SE
QUENCES A WATCHDOG TIMER IS PROVIDED WHICH WILL RE
SET THE PROCESSOR IN THE EVENT OF PROCESSOR FAILURE OR
IF A PROGRAM FALLS OUT OF STEP &URTHER INTERNAL PLAUSI
BILITY CHECKS ENSURE THAT ANY FAULT IN PROCESSING OF
THE PROGRAMS CAUSED BY INTERFERENCE WILL BE RECOG
NIZED 3UCH FAULTS LEAD TO RESET AND RESTART OF THE PRO
CESSOR
)F SUCH A FAULT IS NOT ELIMINATED BY RESTARTING FURTHER
RESTARTS ARE INITIATED )F THE FAULT IS STILL PRESENT AFTER
THREE RESTART ATTEMPTS THE PROTECTIVE SYSTEM WILL
SWITCH ITSELF OUT OF SERVICE AND INDICATE THIS CONDITION
BY DROP
OFF OF THE AVAILABILITY RELAY THUS INDICATING
EQUIPMENT FAULT AND SIMULTANEOUSLY THE ,%$
"LOCKED COMES ON