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GEK-106237P
MIFII Digital Feeder Relay
A-3
APPENDIX A
A.3 ALGORITHMS
A
A.3ALGORITHMS
Thermal Image algorithms are based on the heating/cooling process of a resistive element due to the current flowing
through it. Let us assume a temperature reference (
θ
a
):
Being:
R =
Ohm Resistance (
Ω
)
I =
Current flowing through the element. (Amps)
m =
Mass of the element (kg)
C
e
=
Specific Heat (Jul/kg/ºC)
θ
=
Element Temperature over ambient temperature (ºC)
a =
Heat Transmission Coefficient, (adding conduction and convection effects (w/m
2
/ºC))
S =
Element Surface (m
2
)
Disregarding the radiation transmission (that at temperatures under 400 ºC is much lower that the considered effects, being
this assumption a conservative one from the protection point of view), the differential equation describing the heating
process of the element can be written as:
We can read this equation as: the heat generated on the resistance during a differential period of time (dt), is used to rise
the element temperature and to rise the ambient temperature.
This separated variables differential equation can be easily integrated, getting the following expression:
Where:
θ
0
:
Initial temperature.
τ
:
Heating Constant, defined as: m * C
e
/ (a * S), according to the defined parameters. It indicates the heating speed
of the element (it is the amount of time it takes to reach the 63% of the final temperature.)
α
:
Parameter which a value equal to: a * S / R
Summary of Contents for MIFII GEK-106237P
Page 91: ...4 28 MIFII Digital Feeder Relay GEK 106237P 4 7 VIEW 4 COMMUNICATIONS 4 ...
Page 124: ...GEK 106237P MIFII Digital Feeder Relay 8 7 8 KEYPAD AND DISPLAY 8 5 MENU TREE 8 8 5MENU TREE ...
Page 125: ...8 8 MIFII Digital Feeder Relay GEK 106237P 8 5 MENU TREE 8 KEYPAD AND DISPLAY 8 ...
Page 126: ...GEK 106237P MIFII Digital Feeder Relay 8 9 8 KEYPAD AND DISPLAY 8 5 MENU TREE 8 ...
Page 127: ...8 10 MIFII Digital Feeder Relay GEK 106237P 8 5 MENU TREE 8 KEYPAD AND DISPLAY 8 ...
Page 128: ...GEK 106237P MIFII Digital Feeder Relay 8 11 8 KEYPAD AND DISPLAY 8 5 MENU TREE 8 ...
Page 129: ...8 12 MIFII Digital Feeder Relay GEK 106237P 8 5 MENU TREE 8 KEYPAD AND DISPLAY 8 ...
Page 130: ...GEK 106237P MIFII Digital Feeder Relay 8 13 8 KEYPAD AND DISPLAY 8 5 MENU TREE 8 ...
Page 131: ...8 14 MIFII Digital Feeder Relay GEK 106237P 8 5 MENU TREE 8 KEYPAD AND DISPLAY 8 ...
Page 185: ...A 10 MIFII Digital Feeder Relay GEK 106237P A 6 MIFII THERMAL CURVES APPENDIXA A ...
Page 203: ...B 18 MIFII Digital Feeder Relay GEK 106237P B 3 IAC CURVES APPENDIXB B ...
Page 245: ...F 8 MIFII Digital Feeder Relay GEK 106237P F 5 CONCLUSIONS APPENDIXF F ...