Countermeasures For Magnetising Inrush; Inrush Current Detector; Icd Element Characteristic; Icd Block Scheme - Toshiba GRE110 Instruction Manual

2.9 Countermeasures for Magnetising Inrush

GRE110 provides the following two schemes to prevent incorrect operation from a magnetising
inrush current during transformer energisation.
- Protection block by inrush current detector
- Cold load protection

2.9.1 Inrush Current Detector

Inrush current detector ICD detects second harmonic inrush current during transformer
energisation and blocks the following protections:
- OC1 to OC4
- EF1 to EF4
- SEF1 to SEF4
- NPS1 and NPS2
- BCD
The blocking can be enabled or disabled by setting the scheme switches [OC∗-2F], [EF∗-2F],
[SEF∗-2F], [NPS∗-2F] and [BCD-2F].
The ICD detects the ratio ICD-2f between second harmonic current I2f and fundamental current I1f
in each phase current, and operates if its ratio is larger than the setting value. Figure 2.9.1 shows the
characteristic of the ICD element and Figure 2.9.2 shows the ICD block scheme. When ICD
operates, OC, EF, SEF, NPS and BCD elements are blocked independently. The scheme logic of
each element is shown in the previous sections.
ICD-2f(%)
Setting
The setting elements necessary for the ICD and their setting ranges are as follows:
Element
ICD-2f
ICDOC
I /I
2f 1f
0
ICDOC
Figure 2.9.1
261
A
262
ICD
B
263
C
Figure 2.9.2
Range Step
10 – 50% 1%
1.00 – 25.0 A 0.01 A
 46 
|I |/|I |≥ICD-2f(%)
2f 1f
|I |≥ICDOC
1f
I
1f

ICD Element Characteristic

≥1

ICD Block Scheme

Default Remarks
15% Second harmonic detection
1.00 A ICD threshold setting
6 F 2 T 0 1 7 2
&
ICD
ICD