GE D60 User Manual

5-318 D60 Line Distance Protection System GE Multilin
5.7 CONTROL ELEMENTS 5 SETTINGS
5
To ensure element accuracy for high overcurrent conditions, the maximum value of I/(k x I
B
) is limited to 8, even when real-
istically it is exceeding this value.
The reset time of the thermal overload protection element is also time delayed using following formula:
(EQ 5.29)
In the above equation,
• τ
rst
= thermal protection trip time constant
• T
min
is a minimum reset time setting
Figure 5–163: IEC 255-8 SAMPLE OPERATE AND RESET CURVES
The thermal overload protection element estimates accumulated thermal energy E using the following equations calculated
each power cycle. When current is greater than the pickup level, I
n
> k × I
B
, element starts increasing the thermal energy:
(EQ 5.30)
t
rst

rst
kI
B

2
I
2
kI
B

2
–
-----------------------------



ln T
min
+=
0.1
1
10 100
I / I
pkp
t (min)
0.01
0.1
1
10
100
τ = 30
rst
τ = 30
op
T = 10
min
827724A1.CDR
E
n
E
n 1–
t
t
op In
---------------
+=

GE D60 Specifications

General

Frequency	50/60 Hz
Manufacturer	General Electric (GE)
Communication Protocols	DNP3
Mounting	Panel mount
Operating Temperature	-20°C to +60°C