DEMA CPM 310 G, User Manual

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IEC Protection Curves
“IEC (International Electro-technical Commission) 60255-3, Electrical relays - Part 3: Single input energizing
quantity measuring relays with dependent or independent time” standard describes the protection curves
named as below.
1. IEC STI: IEC Short Time Inverse Curve.
2. IEC SI: IEC Standard Inverse Curve.
3. IEC VI: IEC Very Inverse Curve.
4. IEC EI: IEC Extremely Inverse Curve.
5. IEC LTI: IEC Long Time Inverse Curve.
6.
IEC Thermal Overload Curve.
𝒕 = [
𝑨
(
𝑰
𝑰
𝑺
)
𝜶
− 𝟏
+ 𝑩] × 𝑻𝑴𝑺
Universal trip time delay formula is given above, while IEC constants for various curves are given on the below
table.
t Trip delay (s).
A A constant for the characteristic (s).
I Momentary current (A).
Is Set current threshold (A).
α A constant for the characteristic (-).
B A constant for the characteristic (s).
TMS Time Multiplier Setting (-).
□
Curve Type Trip Delay Formula Reset Delay Setting Range
IEC STI
Short Time Inverse
𝒕 =
[
𝟎. 𝟎𝟓 𝒔
(
𝑰
𝑰
𝑺
)
𝟎.𝟎𝟒
− 𝟏]
× 𝑻𝑴𝑺,
𝒕𝑹𝒆𝒔𝒆𝒕 = 𝑫𝑴𝑻 (𝟎. 𝟎𝟒 − 𝟏𝟎𝟎) 𝒔
IEC SI
Standard Inverse
𝒕 =
[
𝟎. 𝟏𝟒 𝒔
(
𝑰
𝑰
𝑺
)
𝟎.𝟎𝟐
− 𝟏]
× 𝑻𝑴𝑺
𝒕𝑹𝒆𝒔𝒆𝒕 = 𝑫𝑴𝑻 (𝟎. 𝟎𝟒 − 𝟏𝟎𝟎) 𝒔
IEC VI
Very Inverse
𝒕 = [
𝟏𝟑. 𝟓 𝒔
(
𝑰
𝑰
𝑺
) − 𝟏
] × 𝑻𝑴𝑺 𝒕𝑹𝒆𝒔𝒆𝒕 = 𝑫𝑴𝑻 (𝟎. 𝟎𝟒 − 𝟏𝟎𝟎) 𝒔
IEC EI
Extremely Inverse
𝒕 =
[
𝟖𝟎 𝒔
(
𝑰
𝑰
𝑺
)
𝟐
− 𝟏]
× 𝑻𝑴𝑺
𝒕𝑹𝒆𝒔𝒆𝒕 = 𝑫𝑴𝑻 (𝟎. 𝟎𝟒 − 𝟏𝟎𝟎) 𝒔
IEC LTI
Long Time Inverse
𝒕 = [
𝟏𝟐𝟎 𝒔
(
𝑰
𝑰
𝑺
) − 𝟏
] × 𝑻𝑴𝑺 𝒕𝑹𝒆𝒔𝒆𝒕 = 𝑫𝑴𝑻 (𝟎. 𝟎𝟒 − 𝟏𝟎𝟎) 𝒔