ABB Relion 670 series, Technical Manual

Page: 362 / 1432

where
X1RvPEZx is the positive sequence reactance reach for phase-to-ground
fault opposite to zone direction for zone x (x=1-5 and RV)
R1RvPEZx is the positive sequence resistive reach for phase-to-ground
fault opposite to zone direction for zone x (x=1-5 and RV) and
expressed by,
R RvPEZx X RvPEZx
R FwPEZx
X FwPEZx
1 1
1
1
= ⋅ 





IECEQUATION15024 V1 EN-US
(Equation 109)

A
V
( 3 0 ) 1
A N set
I I K Z
  
I
A
• jX
2
( 3 0 ) 1 )
comp A A N RVset
V V I I K Z
 
     
 
1
( 3 0 ) 1
comp A A N set
V V I I K Z
    
( 3 0 ) 1
A N RVset
I I K Z
  
I
A
• R
ANSI15000057-1-en.vsdx
ANSI15000057 V1 EN-US
Figure 181: Simplified offset mho characteristic and voltage vector for phase A-to-ground
fault
Operation occurs if 90 °≤β≤270 °.
7.9.7.8 Load encroachment
GUID-D846C3D9-4C79-40B5-9ED2-23934214AADB v5
In some cases the load impedance might enter the zone characteristic without any fault on the
protected line. The phenomenon is called load encroachment and it might occur when an external
fault is cleared and high emergency load is transferred on the protected line. The effect of load
encroachment is illustrated in the left part of figure 182 . The entrance of the load impedance
inside the characteristic is not allowed and the previous way of handling this was to consider it
Section 7 1MRK 502 066-UUS B
Impedance protection
356
Technical manual