Table of Contents
Advertisement
Thermal phase overload protection
(THOL)
For other parameters: see description in the setting table in the Technical Reference
Manual.
6HWWLQJ H[DPSOH
Assume the following data:
•
I1b: 5 A
•
Temperature increase of the conductor: 90°C at continuous load current 4.5 A.
•
Max. permissible temperature of the conductor: 125°C
Time constant τ = 20 min
•
•
Max. ambient temperature: 30°C
•
Max. temperature increase due to radiant power from the sun: 5°C
([DPSOH 7+2/ ZLWK QR WHPSHUDWXUH FRPSHQVDWLRQ
I
= 4.5 A = 4.5/5 x 100 = 90% of I1b
base
= 90°C, τ = 20 min
T
base
The thermal function assumes 20°C ambient temperature as a fixed value instead of the
actual value 30°C. Also, the 5°C temperature increase due to the sun radiant power is
not included in the calculated temperature increase. Hence, the function calculates con-
tinuos conductor temperature 20 + 90 = 110°C at 4.5 A whereas the max. value is 30 +
90 +5 = 125°C. Hence the setting should be TTrip = 125 - (125 - 110) = 110°C.
([DPSOH 7+2/ ZLWK WHPSHUDWXUH FRPSHQVDWLRQ
Assume temperature measuring elements with output 4 mA at -20°C and 20 mA at
100°C. Settings of Ibase, T
MI11-1_Max= 20.00mA MI11-MaxValue = +100°C
MI11-I_Min= 4.00mA MI11-MinValue = -20°C
The influence of the ambient temperature is included in the calculated values. The 5°C
temperature increase due to the sun radiant power, however, is not included. Hence the
setting should be T
= 125 - 5 = 120°C.
trip
The current transformer secondary setting current (Is
I
S EC
⋅
------------- - Is
Is
=
SEC
I
PRIM
and τ same as above.
base
&KDSWHU
) is:
SEC
&XUUHQW
(Equation 58)
121
Advertisement
Table of Contents
