CHAPTER 5: SETTINGS
CONTROL ELEMENTS
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
5-373
5
I
n
is the measured overload RMS current at index n
E
n
is the accumulated energy at index n
E
n – 1
is the accumulated energy at index n – 1
The thermal overload protection element removes the
THERMAL PROT 1 OP
output operand when E < 0.05. In case of
emergency, the thermal memory and
THERMAL PROT 1 OP
output operand can be reset using
THERM PROT 1 RESET
setting.
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 5-41: Typical time constants
The figure shows the logic for the thermal overload protection element.
Figure 5-214: Thermal overload protection logic
5.8.11.10 Broken conductor detection
SETTINGS
CONTROL ELEMENTS
MONITORING ELEMENTS
BROKEN CONDUCTOR 1(2)
Protected equipment
Time constant
Minimum reset time
Capacitor bank
10 minutes
30 minutes
Overhead line
10 minutes
20 minutes
Air-core reactor
40 minutes
30 minutes
Busbar
60 minutes
20 minutes
Underground cable
20 to 60 minutes
60 minutes
BROKEN CONDUCTOR 1
BROKEN CONDUCTOR 1
FUNCTION: Disabled
Range: Disabled, Enabled
BROKEN CONDUCTOR 1
SOURCE: SRC 1
Range: SRC 1, SRC 2, SRC 3, SRC 4
BROKEN CONDUCTOR 1
I2/I1 RATIO: 20%
Range: 20.0% to 100.0% in steps of 0.1%
BROKEN CONDUCTOR 1
I1 MIN: 0.10 pu
Range: 0.05 to 1.00 pu in steps of 0.01