Fault Locator; Functional Description - Siemens SIPROTEC 4 Manual

Functions

2.16 Fault Locator

2.16 Fault Locator
The measurement of the distance to a short-circuit fault is a supplement to the protection functions. Power
transmission within the system can be increased when the fault is located and cleared faster.

Functional Description

2.16.1
General
The fault locator is a stand-alone and independent function which uses the line and power system parameters
set in other functions. In the event of a fault, it is addressed by the protection functions provided in the 7SJ80
device.
The protected object can e.g. be an inhomogeneous line. For calculation purposes, the line can be divided into
different sections, for example, a short cable followed by an overhead line. In such protected objects, you can
configure each section individually. Without this information, the fault locator uses the general line data (see
Section 2.1.6.2 Setting
The fault locator also calculates double ground faults with different base points, reverse faults and faults that
are located behind the configured sections. For faults that are not located within the configured sections, the
fault locator uses the general line data.
The fault locator can be triggered by the trip command of the non-directional or directional time overcurrent
protection, or by each fault detection. In the latter case, fault location calculations is even possible if another
protection relay cleared the fault. Additionally, the fault location can be initiated via a binary input. However,
it is a prerequisite that pickup of the time overcurrent protection is performed at the same time (directional or
nondirectional).
Fault Location Determination
The measurement principle of the fault locator is based on the calculation of impedances.
Sampled value pairs of short-circuit current and short-circuit voltage are stored in a buffer (at a sampling rate
of 1/16 cycle) shortly after the trip command. At that time, even with very fast circuit breakers, no errors in the
measured values have occurred during the shutdown procedure. Measured value filtering and the number of
impedance calculations are adjusted automatically to the number of stable measured value pairs in the deter-
mined data window. If no sufficient data windows with reliable values could be determined for fault location,
message Flt.Loc.invalid is issued.
The fault locator evaluates the short-circuit loops and uses the loops with the lowest fault impedance (see
margin heading "Loop Selection").
Loop Selection
Using the pickup of the time overcurrent protection (directional or non-directional), the valid measurement
loops for the calculation of fault impedance are selected.
The following table shows the assignment of the evaluated loops to the possible pickup scenarios of the
protection elements.
Pickup by
A B
x
x
x
x
x x
x
232
Notes).
Fault Type
C N
A
B
x C
x N
x A-N
x B-N
x x C-N
A-B
x A-C
Measured Loop
A-N
B-N
C-N
A-N, B-N, C-N
A-N
B-N
C-N
A-B
A-C
E50417-G1140-C343-A8, Edition 12.2017
Signaled Loop
A-N
B-N
C-N
signaled loop
A-N
B-N
C-N
A-B
A-C
SIPROTEC 4, 7SJ80, Manual