Siemens SIPROTEC 7SJ531 - Page 86

-ETHOD OF OPERATION3*
6
#
' #

%VALUATION OF THE MEASURED VALUES OCCURS AFTER THE
FAULT HAS BEEN CLEARED &ROM THE STORED AND FILTERED
VALUES AT LEAST THREE RESULTANT PAIRS FOR 2 AND 8 ARE
DETERMINED )F LESS THAN THREE RESULTANT PAIRS ARE
AVAILABLE NO FAULT LOCATION IS GIVEN &ROM THE RESUL
TANT PAIRS AVERAGE VALUE AND STANDARD DEVIATION ARE
CALCULATED !FTER ELIMINATION OF
EXCEPTIONS  WHICH
ARE RECOGNIZED BY THEIR EXCESSIVE DIFFERENCE FROM
THE STANDARD DEVIATION ANOTHER AVERAGE IS AGAIN CAL
CULATED FOR 8 4HIS AVERAGE IS TAKEN AS FAULT REAC
TANCE
!S A RESULT OF THE FAULT LOCATION CALCULATION THE FOLLOW
ING OUTPUTS ARE GIVEN
THE SHORT CIRCUIT LOOP FROM WHICH THE FAULT REAC
TANCE IS DETERMINED
THE REACTANCE PER PHASE IN /HMS SECONDARY
THE FAULT DISTANCE IN KM OR MILES LINE LENGTH PRO
PORTIONAL TO THE REACTANCE CALCULATED ON THE BASIS
OF THE SET UNIT REACTANCE OF THE LINE
.OTE #ALCULATION OF THE DISTANCE IN KM OR MILES CAN
ONLY BE APPLICABLE TO HOMOGENEOUS LINE LENGTHS
"UT IF THE LINE IS MADE UP OF SECTIONS WITH DIFFERING
REACTANCE VALUES EG OVERHEAD LINE
CABLE COMBI
NATIONS THE DISTANCE TO FAULT CAN STILL BE CALCULATED
MANUALLY FROM THE REACTANCE DETERMINED BY THE FAULT
LOCATION IF THE LINE CHARACTERISTICS ARE KNOWN
 #IRCUIT BREAKER FAILURE PROTECTION
4HE CIRCUIT BREAKER FAILURE PROTECTION MONITORS THE
CORRECT OPENING OF THE ASSOCIATED CIRCUIT BREAKER
&OR THIS PURPOSE TWO CRITERIA ARE AVAILABLE
CHECK WHETHER THE CURRENT BECOMES ZERO AFTER A
TRIP COMMAND IS GIVEN
MONITOR THE CIRCUIT BREAKER S AUXILIARY CONTACTS
4HE CRITERIA WHICH SHALL CAUSE PICK
UP ARE SELECT
ABLE AND DEPEND ALSO ON THE PROTECTION FUNCTION
WHICH HAS GIVEN THE TRIP COMMAND 7HEN A TRIP COM
MAND IS GIVEN WITHOUT SHORT
CIRCUIT CURRENT EG BY
A VOLTAGE PROTECTION THEN THE CURRENT IS NOT A RELIABLE
CRITERION FOR THE CIRCUIT BREAKER
S REACTION 4HEREFORE
THE PICK
UP CAN BE MADE DEPENDENT ON THE AUXILIA
RY CONTACT CRITERION ALONE )F HOWEVER THE CURRENT CRI
TERION IS FULFILLED IE THE CURRENT REMAINS ABOVE A SET
TABLE THRESHOLD THEN THE TRIP COMMANDS ARE NOT DIS
TINGUISHED AS TO THEIR ORIGINATING PROTECTION FUNCTION
)N THIS CASE A CIRCUIT BREAKER FAILURE IS ALWAYS AS
SUMED
4HERE ARE THREE DIFFERENT SOURCES FOR AN INITIATION OF
THE CIRCUIT BREAKER FAILURE PROTECTION
INTERNAL PROTECTION FUNCTIONS IN THE 3*
EXTERNAL STARTING SIGNALS VIA BINARY INPUT
CONTROL COMMAND VIA OPERATING PANEL OR INTER
FACE
%ACH OF THESE SOURCES CAN BE SWITCHED ON OR OFF SEP
ARATELY AND CREATES DIFFERENT ANNUNCIATIONS
5PON DETECTION OF A CIRCUIT BREAKER FAILURE THE CORRE
SPONDING ALARM IS GIVEN AND FAULT CLEARING IS INITIATED
VIA THE SURROUNDING CIRCUIT BREAKERS AFTER A SETTABLE
TIME DELAY 4HIS CAN BE ACHIEVED BY MEANS OF ONE OF
THE MARSHALLABLE TRIP RELAYS A MARSHALLABLE ALARM
RELAY CAN BE USED AS WELL BECAUSE IN MANY CASES
AUXILIARY RELAYS WITH HIGH
DUTY CONTACTS ARE USED FOR
CONTACT MULTIPLICATION SWITCHING CAPACITY
&IGURE  SHOWS THE LOGIC DIAGRAM OF THE CIRCUIT
BREAKER FAILURE PROTECTION 4HE COMPLETE CIRCUIT
BREAKER FAILURE PROTECTION CAN BE SWITCHED ON OR OFF
VIA PARAMETERS AND BINARY INPUTS AS WELL AS DYNAMI
CALLY BLOCKED VIA BINARY INPUTS
%ACH OF THE THREE SOURCES CREATES A PICK
UP ANNUN
CIATION OF ITS OWN STARTS A TIME DELAY OF ITS OWN AND
FORMS A TRIP COMMAND OF ITS OWN 4HE PARAMETER VAL
UES FOR CURRENT THRESHOLD AND TIME DELAY ARE COM
MON
)N CASE THAT ONE OF THE CRITERIA CURRENT VALUE AUXILIA
RY CONTACT WHICH LED TO THE PICK
UP BECOMES IN
VALID DURING THE RUNNING TIME DELAY THE PICK
UP RE
SETS AND NO TRIP COMMAND IS CREATED BY THE CIRCUIT
BREAKER FAILURE PROTECTION
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