Phase/Ground Fault Quadrilateral Characteristics - GE MiCOM P40 Agile Technical Manual

P44x/EN AP/Hb6
(AP) 5-36
Figure 16: Phase/ground fault quadrilateral characteristics (Ω/phase scheme)
Note:
3.1.2.1.1 Setting
"Zone Setting" menu is used to activate or deactivate individually the 6 zones. The following
text will help you to set the zones:
• The zone 1 elements of a distance relay should be set to cover as much of the
protected line as possible, allowing instantaneous tripping for as many faults as
possible. In most applications the zone 1 reach (Z1) should not be able to respond to
faults beyond the protected line. For an underreaching application the zone 1 reach
must therefore be set to account for any possible overreaching errors. These errors
come from the relay, the VTs and CTs and inaccurate line impedance data. It is
therefore recommended that the reach of the zone 1 distance elements is restricted to
80 - 85% of the protected line impedance (positive phase sequence line impedance),
with zone 2 elements set to cover the final 20% of the line. (Note: Two of the channel
aided distance schemes described later, schemes POP Z1 and BOP Z1 use
overreaching zone 1 elements, and the previous setting recommendation does not
apply).
• The zone 2 elements should be set to cover the 20% of the line not covered by zone
1. Allowing for underreaching errors, the zone 2 reach (Z2) should be set in excess of
120% of the protected line impedance for all fault conditions. Where aided tripping
schemes are used, fast operation of the zone 2 elements is required. It is therefore
beneficial to set zone 2 to reach as far as possible, such that faults on the protected
line are well within reach. A constraining requirement is that, where possible, zone 2
does not reach beyond the zone 1 reach of adjacent line protection. Where this is not
possible, it is necessary to time grade zone 2 elements of relays on adjacent lines. For
this reason the zone 2 reach should be set to cover ≤50% of the shortest adjacent line
impedance, if possible. When setting zone 2 earth fault elements on parallel circuits,
the effects of zero sequence mutual coupling will need to be accounted for. The
mutual coupling results in the Zone 2 ground fault elements underreaching. To ensure
adequate coverage an extended reach setting may be required, this is covered in
Section 3.1.2.1.2.
Ω
1. In a /phase scheme, R must be divided by 1+K
diagram
2. The angle of the start element (Quad) is the angle of the 2Z
positive sequence Z, Z
MiCOM P40 Agile P442, P444
Z
: zero sequence Z)
0
Application Notes
(for a phase/ground
+Z (Z :
1 0 1