!PPENDIX
3*
6
# ' #
4HE THEORETICAL RELATIVE END TEMPERATURE RISE CAUSED BY THE START UP CURRENT IS
4HE RELATIVE TEMPERATURE RISE DURING NORMAL OPERATION UNDER RATED CONDITIONS IS
%
)
!
K
,
)
"
!
!
ROTOR .
K
,
)N ORDER TO ENSURE THE LAST START UP WHEN N
C
START UPS HAVE ALREADY OCCURRED THE THERMAL ROTOR REPLICA
HAS A SMALL NEGATIVE TOLERANCE OPERATIONAL MEASURED VALUE
,
,4RIP
)F THE COOLING DOWN TIME CONSTANT IS DIFFERENT FROM THE HEATING UP TIME CONSTANT FOR THE STATOR ANDOR FOR THE
ROTOR THE RELAY MUST RECOGNIZE WHETHER THE MOTOR IS RUNNING OR AT STAND STILL 4HE CRITERION IS THE CURRENT FLOW
THE LIMIT OF WHICH IS SET IN ADDRESS "2+ #,/3%$ ADDITIONAL PLANT DATA 3ECTION !BOVE THIS CUR
RENT THE BREAKER IS ASSUMED TO BE CLOSED IE THE MOTOR IS ASSUMED TO BE RUNNING 4HIS PARAMETER IS PROCESSED
BY SEVERAL PROTECTION FUNCTIONS 4HE THERMAL OVERLOAD PROTECTION AND THE RESTART LOCKOUT OPERATE WITH THE COOL
ING DOWN TIME CONSTANT K
Ç
|
Ç
WHEN THE MEASURED CURRENT IS SMALLER THAN THE ABOVE MENTIONED LIMIT
)N ORDER TO DISTINGUISH CORRECTLY BETWEEN RUNNING MOTOR AND STAND STILL THE LIMIT "2+ #,/3%$ MUST BE HIGHER
THAN THE SMALLEST LOAD CURRENT EG IDLE CURRENT
)N SECONDARY VALUES THE FOLLOWING RESULTS
)
NOLOAD SEC
)
.
! !
7HEN CONSIDERING A TOLERANCE OF )
.
THE SETTING VALUE OF "2+ #,/3%$ IS CHOSEN
|
))
.
&OR
SHORT CIRCUIT PROTECTION
THE FOLLOWING SHOULD BE ASSUMED
3HORT CIRCUIT CURRENTS OF THE FEEDER
THREE PHASE
)
SCPH
K!
TWO PHASE
)
SCPH
K!
!SSUMED THE MAXIMUM START UP CURRENT IS NOT HIGHER THAN TIMES THE RATED START UP CURRENT )
3424
4HE
SETTING VALUE ) OF THE OVERCURRENT TIME PROTECTION RESULTS
|
)
3424
) )
SCPOL
! ) K!
3ETTING MUST BE ABOVE THE MAXIMUM START UP CURRENT 3ELECTED VALUE ! )N SECONDARY VALUE
))
.
!
!
4HE FACTOR CONSIDERS HIGHER START UP CURRENTS BY INCREASED VOLTAGE 4HE STAGE CAN BE SET INSTANTANEOUS OR
WITH ONLY A SMALL DELAY MS
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