Application Guide - NP900 Series
337 (504
)
A996A
Basically in between these presented restraint calculation modes the characteristics are
now set to equally sensitive.
Also the variations of Turnpoint1 setting either to 0.01xIn or 1.0xIn are presented (Figures
A, C with Turnpoint 1 set to 1.00 xIn and B, D with Turnpoint 1 set to 0.01 xIn).
1.1.1.6
Z
ERO SEQUENCE COMPENSATION FOR EXTERNAL EARTH FAULTS
This example did present only one type of transformer and its properties. Very common
variation in this kind of transformer is when the star side, no matter HV or LV or both, is
grounded thus forming a route outside of the “Differential zone”.
Figure 1.1.1.6-159 Transformer grounding and external fault.
The grounding needs to be known in the differential current calculation since if it is not
compensated any low impedance earthfault outside of the differential zone shall cause
differential current measured and possible tripping of the differential protection. For this
purpose the calculated zero sequence compensation is used. This has to be told to the
Содержание NP900 Series
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Страница 49: ...Application Guide NP900 Series 49 504 A996A Figure 3 2 1 3 25 Definite time operating characteristics...
Страница 50: ...Application Guide NP900 Series 50 504 A996A Figure 3 2 1 3 26 IEC predefined characteristics NI VI LTI and EI...
Страница 52: ...Application Guide NP900 Series 52 504 A996A Figure 3 2 1 3 28 IEEE predefined characteristics EI MI and VI...
Страница 243: ...Application Guide NP900 Series 243 504 A996A Figure 3 3 2 1 122 NPS biased thermal trip curves with kNPS values 7 and 10...
Страница 491: ...Application Guide NP900 Series 491 504 A996A 3 7 5 6 SETTING EXAMPLE...
Страница 504: ...Application Guide NP900 Series 504 504 A996A A996A...