Zone Reach Setting Higher Than Minimum Load Impedance - ABB RELION 670 SERIES REG670 Applications Manual

Section 8
Impedance protection
8.3.4.9
276
times the load-impedance angle, more accurate calculations are necessary according to
equation 138.
é
£ × ×
0.8
RFPG Z
ê
ë
load min
GUID-11DD90FA-8FB5-425F-A46F-6553C00025BE V1 EN-US
Where:
ϑ is a maximum load-impedance angle, related to the maximum load power.
To avoid load encroachment for the phase-to-phase measuring elements, the set
resistive reach of any distance protection zone must be less than 160% of the minimum
load impedance.
RFPPZx  
1.6 Z
load
EQUATION579 V3 EN-US
Equation 139 is applicable only when the loop characteristic angle for the phase-to-
phase faults is more than three times as large as the maximum expected load-
impedance angle. More accurate calculations are necessary according to equation 140.

 
 
RFPPZx 1.6 Z

load min
IECEQUATION2307 V2 EN-US
All this is applicable for all measuring zones when no Power swing detection function
ZMRPSB (78) is activated in the IED. Use an additional safety margin of
approximately 20% in cases when a ZMRPSB (78) function is activated in the IED,
refer to the description of Power swing detection function ZMRPSB (78).

Zone reach setting higher than minimum load impedance

The impedance zones are enabled as soon as the (symmetrical) load impedance crosses
the vertical boundaries defined by RLdFwd and RldRev or the lines defined by ArgLd.
So, it is necessary to consider some margin. It is recommended to set RLdFwd and
RldRev to 90% of the per-phase resistance that corresponds to maximum load.
The absolute value of the margin to the closest LdAngle line should be of the same
order, that is, at least 0.1 • Z
The load encroachment settings are related to a per-phase load impedance in a
symmetrical star-coupled representation. For symmetrical load or three-phase and
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
× +
2 R 1 R 0
¶ - ×
cos sin
× +
2 X 1 X 0

R1Zx
 
 
cos sin


X1Zx
.
load min
1MRK 502 071-UUS A
ù
¶
ú
û
GUID-78D0227F-2568-4C9A-8921-45812B4ABAF2 v5
Application manual
(Equation 138)
(Equation 139)
(Equation 140)