Thermal Overload Protection, Two Time Constants Trpttr - ABB RET670 Product Manual
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Also See for RET670:
- Applications manual (1016 pages) ,
- Commissioning manual (328 pages) ,
- Installation and commissioning manual (240 pages)
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Transformer protection RET670 2.0
Product version: 2.0
Table 48. Thermal overload protection, one time constant LCPTTR/LFPTTR
Function
Reference current
Reference temperature
Operate time:
é
ê
-
2
I
I
ê
t
=
t
ln
-
ê
T
2
-
2
-
Trip
I
I
ê
p
ë
T
EQUATION13000039 V2 EN
T
= set operate temperature
Trip
T
= ambient temperature
Amb
T
= temperature rise above ambient at I
ref
I
= reference load current
ref
I = actual measured current
I
= load current before overload occurs
p
Alarm temperature
Operate temperature
Reset level temperature
Table 49. Thermal overload protection, two time constants TRPTTR
Function
Base current 1 and 2
Operate time:
æ
2
2
ö
-
I
I
p
ç
÷
t
= ×
t
ln
ç
÷
2
2
-
I
I
è
ø
ref
(Equation 2)
EQUATION1356 V2 EN
I = actual measured current
Ip = load current before overload
occurs
Iref = reference load current
Alarm level 1 and 2
Operate current
Reset level temperature
ABB
Range or value
(2-400)% of IBase
(0-300)°C, (0 - 600)°F
Time constant t = (1–1000)
minutes
ù
ú
2
ú
p
ú
T
Amb
×
2
I
ú
ref
û
ref
(Equation 1)
ref
(0-200)°C, (0-400)°F
(0-300)°C, (0-600)°F
(0-300)°C, (0-600)°F
Range or value
IBase
(30–250)% of
I
= load current before overload
p
occurs
Time constant τ = (0.10–500.00)
minutes
(50–99)% of heat content operate
value
IBase
(50–250)% of
(10–95)% of heat content trip
Accuracy
±1.0% of I
r
±1.0°C, ±2.0°F
IEC 60255-8, ±5.0% or ±200 ms whichever is greater
±2.0°C, ±4.0°F
±2.0°C, ±4.0°F
±2.0°C, ±4.0°F
Accuracy
±1.0% of I
r
±5.0% or ±200 ms whichever is greater
±2.0% of heat content trip
±1.0% of I
r
±2.0% of heat content trip
1MRK 504 141-BEN C
67
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