Travelling-wave based fault protection of high-voltage transmission lines
View Patent ↗An improved method of fault detection in a high-voltage direct current (HVDC) power transmission line is provided. The fault detection is based on fault-induced travelling waves. The method comprises estimating an amplitude of fault-induced travelling waves at the fault location, and calculating a fault resistance (R f ) based on the estimated amplitude, an estimated pre-fault voltage at the fault location, and a surge impedance of the transmission line. The estimated fault amplitude and the estimated pre-fault voltage are calculated from voltage measurements performed at both ends of the transmission line. Further, a fault detection device is provided.
1. A method of fault detection in a high-voltage power transmission line, the method comprising:
estimating a pre-fault voltage V 0 at a fault location of the high-voltage power transmission line by:
measuring a first pre-fault voltage V 0 A at a first end of the transmission line,
measuring a second pre-fault voltage V 0 B at a second end of the transmission line, and
calculating the estimated pre-fault voltage as
V
0
=
V
0
A
+
V
0
B
2
estimating a voltage amplitude V f , at the fault location, of a fault-induced travelling wave by:
measuring a first fault-induced voltage change ΔV A at the first end of the transmission line,
measuring a second fault-induced voltage change ΔV B at the second end of the transmission line, and
calculating the estimated amplitude of the fault-induced travelling wave as V f =ΔV A +ΔV B , and
calculating a fault resistance R f based on the estimated amplitude V f , the estimated pre-fault voltage V 0 at the fault location, and a surge impedance Z 0 of the transmission line as
R
f
=
Z
0
V
0
-
V
f
2
V
f
.
2. The method according to claim 1 , further comprising:
comparing the calculated fault resistance to a threshold value, and
deciding that a high-impedance fault has occurred if the calculated fault resistance exceeds the threshold value.
3. The method according to claim 2 , further comprising:
initiating, in response to deciding that a high-impedance fault has occurred, protective measures.
4. A fault detection device comprising:
first measuring means being arranged for measuring, at a first end of a high-voltage power transmission line, a first pre-fault voltage V 0 A and a first fault-induced voltage change ΔV A , and
second measuring means being arranged for measuring, at a second end of the transmission line, a second pre-fault voltage V 0 B and a second fault-induced voltage change ΔV B ,
estimating means being arranged for estimating a voltage amplitude V f , at a fault location of the high-voltage power transmission line, of a fault-induced travelling wave by calculating an estimated amplitude of the fault-induced travelling wave as V f =ΔV A +ΔV B , the estimating means being further arranged to calculate an estimated pre-fault voltage as
V
0
=
V
0
A
+
B
0
B
2
,
and
calculating means being arranged for calculating a fault resistance R f based on the estimated amplitude V f , the estimated pre-fault voltage V 0 at the fault location, and a surge impedance Z 0 of the transmission line, the fault resistance R f being calculated as
R
f
=
Z
0
V
o
-
V
f
2
V
f
.
5. The device according to claim 4 , further comprising comparing means being arranged for:
comparing the calculated fault resistance to a threshold value, and
deciding that a high-impedance fault has occurred if the calculated fault resistance exceeds the threshold value.
6. The device according to claim 5 , wherein the comparing means is further arranged for:
initiating, in response to deciding that a high-impedance fault has occurred, protective measures.