Toshiba GRT100 Series, Instruction Manual

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6 F 2 S 0 7 8 9
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
A
TB 1
DC
voltmeter
TB 4
-7
-8
- A16
- A17
E
GRT100
DC
power
supply


Monitoring
jack
A
0V




I N
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 Input terminal
number Output signal
number
1REF TB1-7 and –8 71
2REF TB1-15 and –16 74
3REF TB1-23 and –24 77

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.