GE L90 Instruction Manual page 538

CONTROL ELEMENTS
I is the measured overload RMS current at index n
n
E is the accumulated energy at index n
n
E is the accumulated energy at index n – 1
n – 1
The thermal overload protection element removes the
emergency, the thermal memory and
All calculations are performed per phase. If the accumulated energy reaches value 1 in any phase, the thermal overload
protection element operates and only resets when energy is less than 0.05 in all three phases.
Table 5-40: Typical time constants
Protected equipment
Capacitor bank
Overhead line
Air-core reactor
Busbar
Underground cable
The figure shows the logic for the thermal overload protection element.
5
5.8.11.10 Broken conductor detection
SETTINGS  CONTROL ELEMENTS  MONITORING ELEMENTS  BROKEN CONDUCTOR 1(2)
 BROKEN CONDUCTOR 1

5-352
THERMAL PROT 1 OP
output operand can be reset using
THERMAL PROT 1 OP
Time constant Minimum reset time
10 minutes 30 minutes
10 minutes 20 minutes
40 minutes 30 minutes
60 minutes 20 minutes
20 to 60 minutes 60 minutes
Figure 5-202: Thermal overload protection logic
BROKEN CONDUCTOR 1

FUNCTION: Disabled
BROKEN CONDUCTOR 1

SOURCE: SRC 1
BROKEN CONDUCTOR 1

I2/I1 RATIO: 20%
BROKEN CONDUCTOR 1

I1 MIN: 0.10 pu
output operand when E < 0.05. In case of
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 20.0% to 100.0% in steps of 0.1%
Range: 0.05 to 1.00 pu in steps of 0.01
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
setting.
THERM PROT 1 RESET