-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 EG 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 EG 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 IE 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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