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6.5.1.7 Inverse time overcurrent elements OCI, EFI
The testing circuit is shown in Figure 6.5.11.
Single-phase
current
source
A
TB1
-2
-1
-7
-8
I
a
I
N
GRT100
Monitoring
j
ack
A
0V
TB4
-
A
16
-
A
17
E
DC
power
supply
+
−
Time
counter
Start
Stop
OV
Figure 6.5.11 Testing OCI and EFI (Model 100s, 200s)
One of the four inverse time characteristics can be set, and the output signal numbers are as
follows:
Element Signal number
1OCI, 2OCI, 3OCI 50, 56, 62
1EFI, 2EFI, 3EFI 73, 76, 79
Fix the time characteristic to test by setting the OCI or EFI on the "OC" screen.
"Setting (change)" sub-menu
→ "Protection" screen → "Trip" screen → "Protection element"
screen
→ "OC" screen
The testing procedure is as follows:
• Press 4 (= Logic circuit) on the "Test" sub-menu screen to display the "Logic circuit" screen.
• Enter a signal number to observe the OCI or EFI output at monitoring jack A and press the
ENTER
key.
• Apply a test current and measure the operating time. The magnitude of the test current should
be between 1.2
× I
s
to 20 × I
s
, where I
s
= (CT secondary rated current) × (OCI or EFI current
setting).
• Calculate the theoretical operating time using the characteristic equations shown in Section
2.11.4. Check that the measured operating time is within the error mentioned below.
Accuracy: Standard, Very and Long-time inverse: IEC 60255-3 class 5
Extremely inverse: IEC 60255-3 class 7.5