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Idmt Curve

The document describes the inverse time-current characteristics of two types of relays: ABB relays and GEC ALSTHOM relays. It provides the equations used to calculate the operation time for different characteristic curves for each relay type based on measured current, pickup current setting, and other constants. It also includes example operation times and currents for each curve type at specified times and currents.

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887 views2 pages

Idmt Curve

The document describes the inverse time-current characteristics of two types of relays: ABB relays and GEC ALSTHOM relays. It provides the equations used to calculate the operation time for different characteristic curves for each relay type based on measured current, pickup current setting, and other constants. It also includes example operation times and currents for each curve type at specified times and currents.

Uploaded by

benwkg
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as XLS, PDF, TXT or read online on Scribd
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IDMT Characteristic for ABB Relay

Item Curve Formular Service Setting Pick-Up Time multiplier Time at Specifix current Current Seconds Current at Specifix time Seconds Current Remark

1..

Normal t(s) = Inverse

kxb ( I/I>) - 1
a

0.5

15

3.151

2.49

19.999

a = 0.02 , b = 0.14 a = 1.0 , b = 13.5

2..

Very Inverse

t(s) =

kxb ( I/I>) - 1
a

0.5

15

3.375

3.375

15.000

3..

Extremely t(s) = Inverse

kxb ( I/I>) - 1 kxb ( I/I>) - 1


a a

0.5

20

2.667

2.667

19.999

a = 2.0 , b = 80.0 a = 1.0 , b = 120.0

4..

Long-time t(s) = Inverse

0.5

40

8.571

8.571

40.002

Where : t = Operation time Seconds k = time multiplier I = measured current value I> = set start current value

Note: The relationship between current and time complies with the BS 142.1966 and IEC 255-4 standard.

IDMT Characteristic for GEC ALSTHOM Relay


Item Curve Formular Service Setting Pick-Up Time multiplier Time at Specifix current Current Seconds Current at Specifix time Seconds Current Remark

1..

Short time t(s) = K x(TMS) Inverse ( I/Is) - 1


a

0.5

15

0.556

0.556

15.014

a = 0.04 , K = 0.05 a = 0.02 , K = 0.14 a = 0.7 , K = 9.4 a = 1.0 , K = 13.5

2..

Standard t(s) = K x(TMS) Inverse** ( I/Is) - 1


a

0.5

15

3.151

3.151

15.000

3..

Inverse t(s) = K x(TMS) ( I/Is) - 1


a

0.5

15

4.060

4.06

15.000

4..

Very Inverse**

t(s) = K x(TMS) ( I/Is) - 1


a

0.5

15

3.375

3.375

15.000

5..

Extremely t(s) = K x(TMS) Inverse** ( I/Is) - 1


a

0.5

15

5.000

15.000

a = 2.0 , K = 80.0 a = 1.0 , K = 120.0

6..

Long-time t(s) = K x(TMS) Inverse ( I/Is) - 1 Where :


a

0.5

15

30.000

30

15.000

t = Operation time Seconds K = Constant I = Fault current Is = Current threshold setting

a = constant
TMS = time multiplier Note: ** IEC standard characteristic

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