GE T60, Instruction Manual

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5-308 T60 Transformer Protection System GE Multilin
5.7 CONTROL ELEMENTS 5 SETTINGS
5
g) THERMAL OVERLOAD PROTECTION (ANSI 49)
PATH: SETTINGS

CONTROL ELEMENTS

MONITORING ELEMENTS

THERMAL OVERLOAD PROTECTION

THERMAL
PROTECTION 1(2)
The thermal overload protection element corresponds to the IEC 255-8 standard and is used to detect thermal overload
conditions in protected power system elements. Choosing an appropriate time constant element can be used to protect dif-
ferent elements of the power system. The cold curve characteristic is applied when the estimated
I
p
current is less than
10% of the base current. If I
p
current is greater or equal than 10% than the base current, then the hot curve characteristic is
applied. I
p
current is estimated with a fixed time constant for both cooling and heating that reaches to the final value in two
seconds on a step change (either step up or step down) signal.
The IEC255-8 cold curve is defined as follows:
(EQ 5.50)
The IEC255-8 hot curve is defined as follows:
(EQ 5.51)
In the above equations,
• t
op
= time to operate
•
τ
op
= thermal protection trip time constant
• I = measured overload RMS current
• I
p
= measured load RMS current before overload occurs
• k = IEC 255-8 k-factor applied to I
B
, defining maximum permissible current above nominal current

THERMAL

PROTECTION 1
THERMAL PROTECTION 1
FUNCTION: Disabled
Range: Disabled, Enabled
MESSAGE
THERMAL PROTECTION 1
SOURCE: SRC1
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
MESSAGE
THERMAL PROTECTION 1
BASE CURR: 0.80 pu
Range: 0.20 to 3.00 pu in steps of 0.01
MESSAGE
THERMAL PROTECTION 1
k FACTOR: 1.10
Range: 1.00 to 1.20 in steps of 0.05
MESSAGE
THERM PROT 1 TRIP
TIME CONST: 45 min.
Range: 0 to 1000 min. in steps of 1
MESSAGE
THERM PROT 1 RESET
TIME CONST: 45 min.
Range: 0 to 1000 min. in steps of 1
MESSAGE
THERM PROT 1 MINIM
RESET TIME: 20 min.
Range: 0 to 1000 min. in steps of 1
MESSAGE
THERM PROT 1 RESET:
Off
Range: FlexLogic operand
MESSAGE
THERM PROT 1 BLOCK:
Off
Range: FlexLogic operand
MESSAGE
THERMAL PROTECTION 1
TARGET: Self-reset
Range: Self-reset, Latched, Disabled
MESSAGE
THERMAL PROTECTION 1
EVENTS: Disabled
Range: Disabled, Enabled
t
op
τ
op
I
2
I
2
kI
B
( )
2
–
--------------------------
 
 
 
ln ×
=
t
op
τ
op
I
2
I
p
2
–
I
2
kI
B
( )
2
–
--------------------------
 
 
 
ln ×
=