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necessary to determine suitable settings and selection of proper scheme
communication.
Fault resistance
GUID-115D7410-1398-45FB-BDDD-E778740E1641 v1
The performance of distance protection for single phase-to-ground faults is very
important, because normally more than 70% of the faults on transmission lines are
single phase-to-ground faults. At these faults, the fault resistance is composed of three
parts: arc resistance, resistance of a tower construction, and tower-footing
resistance.The resistance is also depending on the presence of ground shield conductor
at the top of the tower, connecting tower-footing resistance in parallel. The arc
resistance can be calculated according to Warrington's formula:
1.4
28707 L
Rarc
I
×
=
EQUATION1456 V1 EN-US
(Equation 220)
where:
L
represents the length of the arc (in meters). This equation applies for the distance protection zone
1. Consider approximately three times arc foot spacing for the zone 2 and wind speed of
approximately 30 m/h
I
is the actual fault current in A.
In practice, the setting of fault resistance for both phase-to-ground
RFPG
and phase-to-
phase
RFPP
should be as high as possible without interfering with the load impedance
in order to obtain reliable fault detection.
8.9.3
Setting guidelines
IP14962-1 v1
8.9.3.1
General
GUID-FE2F8421-83BA-47FF-AB07-77C242D9650D v1
The settings for Distance measuring zones, quadrilateral characteristic ((ZMRPDIS,
21) are done in primary values. The instrument transformer ratio that has been set for
the analogue input module is used to automatically convert the measured secondary
input signals to primary values used in (ZMRPDIS, 21).
The following basics must be considered, depending on application, when doing the
setting calculations:
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI
337
Application manual
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