NOJA-7481-00 Application Note - Fault Locator
NOJA-7481-00 Application Note - Fault Locator
NOJA-7481-00 Application Note - Fault Locator
NOJA Power
Application Note
Fault Locator
www.nojapower.com.au
NOJA-7481-00
Revision History
NOJA Power® and OSM® are registered trademarks of NOJA Power Switchgear Pty Ltd. This document
is copyright and is intended for users and distributors of NOJA Power Switchgear product. It contains
information that is the intellectual property of NOJA Power Switchgear and the document, or any part thereof,
should not be copied or reproduced in any form without written permission from NOJA Power Switchgear.
NOJA Power® and OSM® are registered trademarks of NOJA Power Switchgear and should not be
reproduced or used in any way without written authorisation.
NOJA Power Switchgear applies a policy of ongoing development and reserves the right to change product
without notice. NOJA Power Switchgear does not accept any responsibility for loss or damage incurred as a
result of acting or refraining from action based on information in this User Manual.
Table of Contents
1. Introduction ........................................................................................................................................... 1
2. Calculation ............................................................................................................................................. 1
2.1. Fault Type Selection ........................................................................................................................ 1
2.2. Distance to Fault Calculation ............................................................................................................ 2
2.3. Fault Loop Impedance Calculation .................................................................................................... 3
2.4. Fault Impedance Calculation ............................................................................................................ 3
2.5. Single Phase Switchgear .................................................................................................................. 4
2.6. Basic Settings .................................................................................................................................. 5
2.7. Accuracy of Estimated Fault Location ................................................................................................ 5
3. Sample Faults ........................................................................................................................................ 6
3.1. BC Fault .......................................................................................................................................... 6
4. Sample Simulations ................................................................................................................................ 8
4.1. BC Faults ........................................................................................................................................ 8
4.2. Running the simulationS .................................................................................................................. 9
4.3. Event Log...................................................................................................................................... 10
NOJA-7481-00
1. INTRODUCTION
The Fault Locator (21FL) functionality provides one-end impedance based fault location estimation in a radial
distributed system. The 21FL function operates based on the measurements of current and voltage phasors in
the fundamental frequency (50 or 60Hz) on one side of the line.
The fault location algorithm utilises zero and negative phase sequence current as the polarising values which
eliminates dependency on load, source and load impedances and improves accuracy.
Note that in fault location estimation, fault impedance is considered to be purely resistive as the Arc Fault is
resistive.
Note: The fault locator algorithm for single phase to earth faults is only suitable for grounded networks and it is not
suitable for ungrounded and Petersons’ coil grounded systems. As the fault type detection depends on the operation
of overcurrent elements, high impedance faults will not be detected if overcurrent elements do not operate.
2. CALCULATION
The fault location algorithm is applicable to OC, EF, SEF, OCLL, EFLL and SEFLL elements when enabled. When
the calculation is completed the fault type and the following values are reported:
m Distance to Fault (km)
Zf Magnitude of Fault Impedance
θf Angle of Fault Impedance (degree)
ZLoop Magnitude of Fault Loop Impedance
XLoop Measured Positive Sequence Reactance from the Relay to Fault Location
θLoop Angle of Fault Loop Impedance (degree).
Distance to fault is calculated in two steps. First the fault type is determined then the distance to fault is
calculated based on the detected fault type.
After a protection operation, the detected fault type is determined using the following table. The numbering
convention for fault type is consistent with IEC 61850.
Fault Type
Fault Type Selection method (at the time of protection operation)
Number
0 None Any condition other than Fault type declared in 1 to 11.
1 AE P(PhA)=True AND P(PhB)=False AND P(PhC)=False AND [A(PhA)=True OR A(PhN)=True]
2 BE P(PhA)=False AND P(PhB)=True AND P(PhC)=False AND [A(PhB)=True OR A(PhN)=True]
3 CE P(PhA)=False AND P(PhB)=False AND P(PhC)=True AND [A(PhC)=True OR A(PhN)=True]
P(PhA)=True AND P(PhB)=True AND P(PhC)=False AND P(PhN)=False AND [A(PhA)=True OR
4 AB
A(PhB)=True]
P(PhA)=False AND P(PhB)=True AND P(PhC)=True AND P(PhN)=False AND [A(PhB)=True OR
5 BC
A(PhC)=True]
P(PhA)=True AND P(PhB)=False AND P(PhC)=True AND P(PhN)=False AND [A(PhC)=True OR
6 CA
A(PhA)=True]
P(PhA)=True AND P(PhB)=True AND P(PhC)=True AND P(PhN)=False AND [A(PhA)=True OR
7 ABC
A(PhB)=True OR A(PhC)=True]
P(PhA)=True AND P(PhB)=True AND P(PhC)=False AND P(PhN)=True AND [A(PhA)=True OR
8 ABE
A(PhB)=True OR A(PhN)=True]
P(PhA)=False AND P(PhB)=True AND P(PhC)=True AND P(PhN)=True AND [A(PhB)=True OR
9 BCE
A(PhC)=True OR A(PhN)=True]
Fault Type
Fault Type Selection method (at the time of protection operation)
Number
P(PhA)=True AND P(PhB)=False AND P(PhC)=True AND P(PhN)=True AND [A(PhC)=True OR
10 CAE
A(PhA)=True OR A(PhN)=True]
P(PhA)=True AND P(PhB)=True AND P(PhC)=True AND P(PhN)=True AND [A(PhA)=True OR
11 ABCE
A(PhB)=True OR A(PhC)=True OR A(PhN)=True]
The following table summarizes the fault location algorithms for each individual selected fault using the modified
Takagi Method.
Fault Type
Fault Type Distance to Fault, m (km)
Number
0 Not Detected -
Im[VA I 0* ]
1 AE m
Im[ Z1 ( I A K 0 3I 0 ) I 0* ]
Im[VB I 0* ]
2 BE m
Im[ Z1 ( I B K 0 3I 0 ) I 0* ]
Im[VC I 0* ]
3 CE m
Im[ Z1 ( I C K 0 3I 0 ) I 0* ]
*
Im[(V1 aV2 ) (aI 2 )]
4 or 8 AB or ABE m *
Im[ Z1 ( I1 aI 2 )(a I 2 )]
*
Im[(V1 V2 ) ( I 2 )]
5 or 9 BC or BCE m *
Im[ Z1 ( I1 I 2 )(I 2 )]
*
Im[(V1 a 2V2 ) (a 2 I 2 )]
6 or 10 CA or CAE m *
Im[ Z1 ( I1 a 2 I 2 )(a 2 I 2 )]
Im[V1 I1* ]
7 or 11 ABC or ABCE m
Im[ Z1 I1 I1* ]
where:
m= the distance to fault in km.
Im = the imaginary part of a complex number
“*” = conjugate e.g. I 0* ( I 00 )* I 0 0
Z 0 Z1
K0 = the compensation factor which is calculated as follows: K0
3Z1
Z1 = the positive sequence impedance where Z1 R1 jX 1
Z0 = the zero sequence impedance where Z 0 R0 jX 0
a 1120 and a 2 1240
The fault loop impedance which includes both resistance and reactance of the faulted loop is calculated
according to the following table.
Fault Type
Fault Type Fault Loop Impedance
Number
0 None -
VA
1 AE Z loop Z loop loop
( I A K 0 3I 0 )
VB
2 BE Z loop Z loop loop
( I B K 0 3I 0 )
VC
3 CE Z loop Z loop loop
( I C K 0 3I 0 )
V1 aV2
4 or 8 AB or ABE Z loop Z loop loop
I1 aI 2
V1 V2
5 or 9 BC or BCE Z loop Z loop loop
I1 I 2
2
V a V
6 or 10 CA or CAE Z loop Z loop loop 1 2 2
I1 a I 2
V1
7 or 11 ABC or ABCE Z loop Z loop loop
I1
Fault Type
Fault Type Fault Impedance
Number
0 None -
( I A K 0 3I 0 )
1 AE Zf Z f f ( Z loop mZ1 )
3I 0
( I B K 0 3I 0 )
2 BE Zf Z f f ( Z loop mZ1 )
3I 0
( I C K 0 3I 0 )
3 CE Zf Z f f ( Z loop mZ1 )
3I 0
( I aI )
4 or 8 AB or ABE Z f Z f f 1 2 ( Z loop mZ1 )
I1
Fault Type
Fault Type Fault Impedance
Number
( I1 I 2 )
5 or 9 BC or BCE Z f Z f f ( Z loop mZ1 )
I1
2
(I a I )
6 or 10 CA or CAE Z f Z f f 1 2 ( Z loop mZ1 )
I1
7 or 11 ABC or ABCE Z f Z f f (Zloop mZ1 )
The fault locator for single phase reclosers is only applicable for Single Wire Earth Return (SWER) systems.
The detected fault type is determined using the following table.
Fault Type
Fault Type Selection method (at the time of protection operation)
Number
0 Not Detected Any condition other than Fault type declared in 1
1 AE P(PhA)=True AND A(PhA)=True
Fault Type
Fault Type Distance to Fault, m (km)
Number
0 Not Detected -
Im[VA I A* ]
1 AE m
Im[ Z A I A I A* ]
Fault Type
Fault Type Fault Loop Impedance
Number
VA
1 AE Z loop Z loop loop
IA
Fault Type
Fault Type Fault Impedance
Number
1 AE Z f Z f f Z loop mZ A
Where ZA = the impedance where Z A RA jX A
Please refer to the OSM User Manual for measurement accuracy of the fault locator functionality.
The accuracy of the estimated fault location depends on the following conditions:
Measurement accuracy
Fault Resistance and reactance effect
Zero sequence mutual effects
Line parameters uncertainty, especially error in obtaining zero-sequence impedance (Z0).
Presence of shunt capacitors and reactors
Series compensated networks
Non-homogenous lines, tapped lines and spurs
Excessive harmonic content.
3. SAMPLE FAULTS
3.1. BC FAULT
For an 11kV distribution system where we have voltages and currents as follows:
Ia Ib Ic Va Vb Vc
RMS 11.1 478.9 471.9 6.3 4.8 4.1
Angle -28.50 -158.20 22.80 -0.40 -139.40 130.60
V1 = 1/3 (Va + aVb + a2Vc)
=1/3 (6.3 -0.40 + 4.8 (-139.40 +1200) + 4.1 130.60 +2400)
= 1/3 (6.3 -0.40 + 4.8 -19.40 + 4.1 370.60)
= 1/3 [(6.3 + 4.53 + 4.03) + j(-0.04-1.59+0.75)]
= 1/3 (14.86 -j0.85]
= 4.95 – j0.28
= 4.96 -3.240
Similarly:
V2 = 1/3 (Va + a2Vb + aVc)
= 1.35 +0.27j
= 1.38 11.250
I1 = 1/3 (Ia + aIb + a2Ic)
= 278.73 -66.980
= 109.00 - j256.53
I2 = 1/3 (Ia + a2Ib + aIc)
=270.23 111.550
= -99.26 + j251.34
Notice that we have multiplied the numerator by 1000 as the voltage should be in Volts not Kilovolts.
= Im (500176 + j878548)
Im (-41480-j282408)
= 878548
282408
= 3km
4. SAMPLE SIMULATIONS
4.1. BC FAULTS
Event log should indicate the faults as per simulation sequence (as shown below).
BC Fault 1
Note:
The “Distance to Fault” event indicates that the fault locator calculation has commenced.
BC Fault 2
BC Fault 3