The residual voltage (Vres) is passed through a bandpass filter tuned to 220 Hz, which also adds 90° to it. The
residual current (Ires) is also passed through a 220 Hz bandpass filter, but no phase shift is applied. The resulting
components which we shall call V
H1
and I
H2
are therefore in antiphase with each other for forward faults and in
phase if the forward line is not faulted.
The VH1 and IH2 components are passed through a sign filter and multiplied to create a reactive power
component in the range of -1 to +1. This is the transient reactive power Q
tran
. If Q
tran
> 0, then there forward line is
healthy. If Q
tran
< 0, then the forward line is faulty.
There are two modes of operation for the direction detector; Standard and Advanced. Standard mode is used in
most cases and is described here. Advanced mode is for special situations, and involves dynamically altering the
Q
tran
thresholds. For details of Advanced mode, please contact General Electric.
The inputs to this module are:
● The residual voltage
● The residual current
● Dir> Vnf Thresh (defines the threshold for the residual voltage sign filter).
● Dir> Inf Thresh (defines the threshold for the residual current sign filter
The DD outputs two signals to indicate a forward fault and a reverse fault
Sign Filter Thresholds
The Dir> Vnf Thresh setting is used to get the sign of instantaneous voltage value by sign filter. If the input value is
larger than Vnf, the output is +1. If the input value is less than -1*Vnf, the output is -1. Otherwise the output is 0.
The Dir> Inf Thresh setting is used to get the sign of instantaneous current value by sign filter. If the input value is
larger than Vnf, the output is +1. If the input value is less than -1*Vnf, the output is -1. Otherwise the output is 0.
9.2
TRANSIENT EARTH FAULT DETECTION LOGIC
9.2.1 TRANSIENT EARTH FAULT DETECTION LOGIC OVERVIEW
VN
V00905
TEF> Start
TEF VN> Start
TEF Detection
Enabled
TEF> Timer Block
VN
Dir>Vnf Thresh
IN
Dir>Inf Thresh
TRP
Direction
Detector Module
Forward
Reverse
&
&
&
TEF>DIR FWD
TEF>DIR REV
TEF> Steady
TEF> Intermit
TEF>Dir Status
Enabled
FA
Fault Type
Detector Module
Steady
Intermittent
FTD> Time Window
FTD> Fault Count
FTD> Status
Enabled
&
&
VN
FTD> VN
Figure 228: Transient Earth Fault Logic Overview
P543i/P545i Chapter 13 - Current Protection Functions
P54x1i-TM-EN-1 393
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