7.2.3.2 Solidly earthed systems
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Example in Figure 43 illustrates how the distance protection ZRWPDIS protects a
1
10kV overhead transmission line. The earthing considered is solidly earthed
system.
Out of the six distance protection zones, only the zone 1, zone 2 and zone 3 are
considered in this example. Zones 4, 5 and 6 can be set on similar lines depending
on the application they are being used.
All the settings for impedance are in Ohms Primary.
Z<
A
B
C
Line 1 Line 2
IEC15000385-1-en.vsdx
IEC15000385 V1 EN-US
Figure 43: Considered single line diagram
Table 16: System Data
Parameter Value
System Voltage 110kV
System Frequency 16.7Hz
Full load 50MVA
Short time maximum Power 250% of Full load
Minimum operating voltage 90% of rated voltage
PT Ratio 110kV/110V
CT Ratio 600/1A
Line length A-B 50km
Line length B-C 100km
Positive sequence impedance of line 0.097 + j0.112 Ohm/km = 0.1481 ∟ 49.3°
Ohm/km
Zero sequence impedance of line 0.151 + j0.298 Ohm/km = 0.334 ∟ 63.13°
Ohm/km
Arc resistance 2 Ohm
Tower footing resistance 10 Ohm
General
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Common base IED values for primary current (IBase) and primary voltage (UBase)
are set in a Global base values for settings function GBASVAL.
GlobalBaseSel: It is used to select a GBASV
AL function for reference of base
values.
IBase: Sets the base current in primary ampere. This is 50MVA/110kV = 454.54A.
1MRK 506 375-UEN A Section 7
Impedance protection
Railway application RER670 2.2 IEC 143
Application manual
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