Wide area fault detection method using PMU data
The embodiments herein are directed to monitoring in real time, power system data so as to provide insights into global operation of a power grid. Such a scheme disclosed herein utilizes rules, which are created by analyzing PMU measurement data, in order to detect the fault location (bus and line) and fault type. Three common types of faults in a power grid, single-line-to-ground (SLG), line-to-line (LL), and three phase faults, can be detected using the methods herein.
1. A method for wide-area real time line fault detection in a power grid system, the power grid comprising a plurality of phasor measurement units (PMUs) and other sensors individually coupled to various system components of the power grid and supervisory control and data acquisition facilities, the method comprising:
(a) using the PMUs to measure one or more current phasors and one or more voltage phasors at a monitored bus of a load center of the supervisory control and data acquisition facilities, wherein the supervisory control and data acquisition facilities include a logic processor device; and
(b) using the logic processor device of the supervisory control and data acquisition facilities to:
take out transmission lines without a stable steady-state positive sequence current value;
acquire the measured one or more current and voltage phasors obtained from the PMUs;
identify an event as one or more faulted buses in the power system via calculating a maximum three phase total average voltage deviation (ΔV i ), wherein a magnitude of the one or more measured voltage phasors is utilized to calculate the maximum three phase total average voltage deviation (ΔV i );
determine the event as one or more fault types using at least one methodology selected from: a first method that uses the magnitude of the one or more voltage phasors and a second method that uses both the magnitude and a phase angle of the measured one or more voltage phasors, wherein the first method and the second method enables determination of the one or more fault types with at least one fault type selected from: single line-to-ground faults (SLG), line-to-line faults (LL), and three-phase faults;
detect the one or more faulted lines using the magnitude of positive sequences of the one or more current phasors as the parameter; and
issue an auditory and/or user interface warning concerning the one or more faulted lines detected.
2. The method of claim 1 , wherein calculation of the maximum three phase total average voltage deviation (ΔV i ) to identify the event further comprises:
calculating a voltage sag (V sag ) at a bus;
determining a voltage deviation of each phase using (ΔV i )=V ssi −V sagi ; and
thereafter calculating the three phase total average voltage deviation ΔV i , using:
Δ
V
t
=
(
Δ
V
A
)
2
+
(
Δ
V
B
)
2
+
(
Δ
V
C
)
2
3
.
(
2
)
3. The method of claim 1 , wherein the first method that uses the magnitude of the one or more voltage phasors to determine the one or more faulted lines further comprises:
determining the single line-to-ground faults (SLG) via a threshold that requires a first phase to have one or more voltage sag values to be less than 0.95 per-unit (p.u.) with a second and a third phase to have one or more voltage sag values to be above 0.95 per-unit (p.u.).
4. The method of claim 1 , wherein the first method that uses the magnitude of the one or more voltage phasors to determine the one or more faulted lines further comprises:
determining the line-to-line faults (LL) via a threshold that requires one or more voltage sag values from two of the three phases selected from a first phase, a second phase, and a second phase to be in a range between 0.35 per-unit (p.u.) and 0.95 per-unit (p.u.).
5. The method of claim 1 , wherein the first method that uses the magnitude of the one or more voltage phasors to determine the one or more faulted lines further comprises:
determining the three-phase faults via a threshold that requires all three phases selected from a first phase, a second phase, and a second phase to have one or more voltage sag values to be in a range between 0.0.0 per-unit (p.u.) and 0.8 per-unit (p.u.) and wherein all voltage sags among the three phases have a value within 10% of a defined unbalanced threshold using:
DV
sag
_
max
%
=
DV
sag
_
max
V
sag
_
ave
×
100
%
.
6. The method of claim 1 , wherein the second method that uses both the magnitude and the phase angle of the measured one or more voltage phasors to determine the one or more faulted lines further comprises:
determining the single line-to-ground faults (SLG) by satisfying at least one of the following: a voltage change in per-unit (p.u.) of a zero sequence voltage (ΔV 0 ) is larger than that of a negative sequence voltage (ΔV 2 ):|ΔV 0 |>|ΔV 2 |, and if the “voltage change in per-unit p.u.” of the zero sequence voltage (ΔV 0 ) is less than that of the negative sequence voltage (ΔV 2 ): |ΔV 0 |<|ΔV 2 |, and
Δ
V
2
Δ
V
0
<
4
and
the following all are satisfied including: the phase angles of the negative or zero sequence voltage phasors at the peak point have an angle variation from the steady-state values that satisfies Δθ 2 >100° or Δθ 2 >100°, and using
1
∠0°
-
V
_
1
_
peak
V
_
2
_
peak
<
50
and
a ratio of “voltage change in per-unit (p.u.) of a positive first (ΔV 1 ) to negative second (ΔV 2 ) sequence voltage is provided satisfying
Δ
V
1
Δ
V
2
<
3
and if only one phase has a voltage sag of at least 0.1.
7. The method of claim 1 , wherein the second method that uses both magnitude and phase angle of the measured one or more voltage phasors to determine the one or more faulted lines further comprises:
determining a line-to-line fault (LL) by satisfying at least one of the following: a zero-sequence voltage magnitude measured at a local peak is obtained that satisfies
|V 0 _ peak |<0.004 p.u.
wherein if the zero sequence voltage peak |V 0 _ peak |>0.004 p.u., determine if the zero sequence voltage (ΔV 0 ) is less than the negative sequence voltage (ΔV 2 ) based on: |ΔV 0 |<|ΔV 2 |, and
the following all are satisfied including: the phase angles of one or more negative and zero sequence voltage phasors at the peak point have an angle variation from the steady-state values: Δθ 2 >100°, OR, Δθ 0 >100°, and
1
∠0°
-
V
_
1
_
peak
V
_
2
_
peak
<
50
,
and
the ratio of “voltage change in p.u.” of the positive (ΔV 1 ) to negative (ΔV 2 ) sequence voltage is small:
Δ
V
1
Δ
V
2
<
3
,
and
any two phases have voltage sags of at least 0.1.
8. The method of claim 1 , wherein the second method that uses both magnitude and phase angle of the measured one or more voltage phasors to determine the one or more faulted lines further comprises:
determining a balanced three phase fault if the following are both satisfied: a positive and a negative sequence of voltages measured at their respective local peaks satisfy:
1
∠0°
-
V
_
1
_
peak
V
_
2
_
peak
>
50
;
and
the phase angles of the negative or zero sequence voltage phasors at the peak point have a large angle variation from the steady-state values based on: Δθ 2 >100°, or Δθ0>100°.
9. A wide-area real time line fault detection computing system, comprising:
a logic processor device in supervisory control and data acquisition facilities of a power grid system;
a plurality of phasor measurement units (PMUs) and other sensors individually coupled to various system components of the power grid;
a memory operatively coupled to the processor, the memory containing instructions that when executed by the processor causes the logic processor device to perform a process including:
acquiring measurements from said plurality of PMUs and other sensors at a monitored bus of a load center configured within the power grid system;
take out transmission lines without a stable steady-state positive sequence current value;
identifying an event as one or more faulted buses in the power system via calculating a maximum three phase total average voltage deviation (ΔV i ), wherein the magnitude of the one or more measured voltage phasors is utilized to calculate the maximum three phase total average voltage deviation (ΔV i );
determining the event as one or more fault types using at least one methodology selected from: a first method that uses the magnitude of the one or more voltage phasors and a second method that uses both the magnitude and a phase angle of the measured one or more voltage phasors, wherein the first and the second method enables determination of the one or more fault types with at least one fault type selected from: single line-to-ground faults (SLG), line-to-line faults (LL), and three-phase faults;
detecting the one or more faulted lines using the magnitude of positive sequences of the one or more current phasors as the parameter; and
issue an auditory and/or user interface warning concerning the one or more faulted lines detected.