Toshiba GRT100 Series Instruction Manual page 123

6.5.1.5 Restricted earth fault element REF
The restricted earth fault element is checked on the following items.
 Operating current value
 Percentage restraining characteristic
Note: Set all the CT ratio matching settings (1kct1 - 1kct3 to 3kct1 - 3kct3) to "1", because the
operating value depends on the settings.
Operation current value
The testing circuit is shown in Figure 6.5.7.

Single-phase
current
source


DC
power

supply

DC
voltmeter

Figure 6.5.7 Operating Current Value Test of REF element (Model 100s, 200s)
The test current input terminal number and output signal number of the REF element is as
follows:
Element
1REF
2REF
3REF
 Press 4 (= Logic circuit) on the "Test" sub-menu screen to display the "Logic circuit"
screen.
 Enter the signal number 71 to observe the 1REF output at monitoring jack A and press the
ENTER key.
 Apply a test current to TB1-7 and -8 and change the magnitude of the current applied and
measure the value at which the element operates.
Check that the measured value is within 15% of the theoretical operating value.
A
Input terminal Output signal
number number
TB1-7 and –8 71
TB1-15 and –16 74
TB1-23 and –24 77
 122 
6 F 2 S 0 7 8 9
GRT100
TB 1
-7
I N
-8
A
Monitoring
jack
0V
TB 4
- A16
- A17
E