ABB Relion 670 Series Product Manual page 38

Phasor measurement unit RES670
Pre-configured
Product version: 1.2
Table 25. Thermal overload protection, one time constant LPTTR
Function
Reference current
Reference temperature
Operate time:
æ ö
2 2
-
I I
p
t ç ÷
= ×
t ln
ç ÷
2 2
-
I I
è ø
b
(Equation 1)
EQUATION1356 V1 EN
I = actual measured current
I = load current before overload
p
occurs
I = base current, IBase
b
Alarm temperature
Trip temperature
Reset level temperature
38
Range or value
(0-400)% of IBase
(0-
Time constant t = (0–1000) minutes
(0-200)°C, (0-400)°F
(0-400)°C, (0-600)°F
(0-400)°C, (0-600)°F
1MRK 511 266-BEN -
Accuracy
± 1.0% of I
r
± 1.0°C, ±2°F
IEC 60255-8, ±5% + 200 ms
± 2.0% of heat content trip
± 2.0% of heat content trip
± 2.0% of heat content trip
ABB