ABB Relion 670 series, Technical Manual

Page: 322 / 1432

For Zone 1,
Z R PEZ j X PEZ
RVset
1 1 1 1 1
= + ⋅
IECEQUATION15025 V1 EN-US
(Equation 93)
For Zone 2-5 and RV,
Z R Zx j X Zx
RVset
1 1 1
= + ⋅
IECEQUATION15026 V1 EN-US
(Equation 94)

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 158: Simplified offset mho characteristic and voltage vector for phase A-to-ground
fault
Operation occurs if 90 °≤β≤270 °.
7.8.7.7 Load encroachment
GUID-6785BF05-2775-4422-8077-A663D01C6C07 v4
In some cases the measured load impedance might enter the set zone characteristic without any
fault on the protected line. This phenomenon is called load encroachment and it might occur when
an external fault is cleared and high emergency load is transferred onto the protected line. The
effect of load encroachment is illustrated on the left in figure 159 . The entrance of the load
impedance inside the characteristic is of course not desirable and the way to handle this with
conventional distance protection is to consider this with the resistive reach settings, that is, to
have a security margin between the distance zone characteristic and the minimum load
impedance. Such a solution has the drawback that it will reduce the sensitivity of the distance
protection, that is, the ability to detect resistive faults.
Section 7 1MRK 502 066-UUS B
Impedance protection
316
Technical manual