0.01
0.1
1
10
100
1000
10000
0.5 5 50
IEEE Very Inverse Curve
0.05
0.5
1
5
10
30
50
70
100
TD
Time in seconds
Current in Multiples of Setting
0.01
0.1
1
10
100
1000
10000
0.5 5 50
IEEE Extremely Inverse Curve
0.05
0.5
1
5
10
30
50
70
100
TD
Time in seconds
Current in Multiples of Setting
E00759
Figure 32: IEEE very and extremely inverse curves
2.1.5 DIFFERENCES BETWEEN THE NORTH AMERICAN AND EUROPEAN STANDARDS
The IEEE and US curves are set differently to the IEC/UK curves, with regard to the time setting. A time multiplier
setting (TMS) is used to adjust the operating time of the IEC curv
es, whereas a time dial setting is used for the
IEEE/US curves. The menu is arranged such that if an IEC/UK curve is selected, the I> Time Dial cell is not visible
and vice versa for the TMS setting. For both IEC and IEEE/US type curves, a definite time adder setting is available,
which will increase the operating time of the curves by the set value.
2.1.6 PROGRAMMABLE CURVES
As well as the standard curves as defined by various countries and standardising bodies, it is possible to program
custom cur
v
es using the User Programmable Curve Tool, described in the Settings Application Software chapter.
This is a user-friendly tool by which you can create curves either by formula or by entering data points.
Programmable curves help you to match more closely the withstand characteristics of the electrical equipment
than standard curves.
2.2 PRINCIPLES OF IMPLEMENTATION
The range of protection products provides a very wide range of protection functionality. Despite the diverse range
of f
unctionality pr
ovided, there is some commonality between the way many of the protection functions are
implemented. It is important to describe some of these basic principles before going deeper into the individual
protection functions.
A simple representation of protection functionality is shown in the following diagram:
P14x Chapter 6 - Current Protection Functions
P14xEd1-TM-EN-1 95
To Next Page
Loading...
Need help?
General
