Fault Locator; Description - Siemens SIPROTEC 7SJ62 Manual

Functions

2.15 Fault Locator

2.15 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.
2.15.1

Description

General
The fault locator is an autonomous 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 7SJ62/64
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).
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 pro-
tection, or by each fault detection. In the latter case, fault location calculations is even possible if another pro-
tection 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 non-
directional).
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").
Note
If in Power System Data 1 address 213 Vab, Vbc, VGnd was selected for the voltage connection (con-
nection of two phase-to-phase voltages as well as the displacement voltage), but without connecting a dis-
placement voltage to the device, the fault locator cannot function properly and must be taken out of service.
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SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008