# US 2019/0245343 A1 · Method to detect utility disturbance and fault direction

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- Number: US 2019/0245343 A1
- Document ID: US20190245343A1
- Status: Published application
- Kind: A1
- Application number: 16/176,180
- Filed: 2018-10-31
- Published: 2019-08-08
- Earliest claimed: 2018-02-02
- Assignees: S&C Electric Company
- Applicants: S&C Electric Company
- Inventors: David Glenn Porter; Stephen E. Williams
- Web page: https://patentgrep.com/patent/US20190245343A1

## CPC

- H02H 7/28: for meshed systems
- G01R 19/02: Measuring effective values, i.e. root-mean-square values
- G01R 19/16528: {using digital techniques or performing arithmetic operations (using digital techniques to measure a voltage or a current, see G01R19/25)}
- G01R 19/2506: {Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values (G01R19/003 takes precedence); Details concerning sampling, digitizing or waveform capturing (displaying waveforms G01R13/00; analog sampling G01R19/0053)}
- G01R 19/2513: {Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging}
- G01R 31/08: Locating faults in cables, transmission lines, or networks
- H02H 1/0007: {concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445)}
- H02H 3/42: responsive to product of voltage and current
- H02J 3/00: Circuit arrangements for AC mains or AC distribution networks
- H02J 3/14: by switching loads on to, or off from, the networks, e.g. progressively balanced loading
- H02J 13/16: the power network being controlled at grid-level, e.g. using aggregators
- H02H 1/0092: {concerning the data processing means, e.g. expert systems, neural networks}
- H02J 3/381: {Dispersed generators}
- H02J 2101/24: Photovoltaics
- H02J 2101/28: Wind energy
- H02J 2105/52: for limitation of the power consumption in the networks or in one section of the networks, e.g. load shedding or peak shaving
- Y02B 70/3225: Demand response systems, e.g. load shedding, peak shaving
- Y02E 10/56: Power conversion systems, e.g. maximum power point trackers
- Y02P 80/14: District level solutions, i.e. local energy networks
- Y04S 20/222: Demand response systems, e.g. load shedding, peak shaving
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS

## Abstract

A method for detecting a voltage disturbance in a utility having a micro-grid. The method transforms current and voltage measurements into first and second voltage values and first and second current values in a stationary reference frame, and transforms the first and second voltage values and the first and second current values to third and fourth voltage values and third and fourth current values in a rotating reference frame, where the third voltage value defines an average magnitude of the three-phase power signals. The method multiplies the third current value by the third voltage value to obtain an instantaneous power value and multiplies the fourth current value by the third voltage value to obtain an instantaneous volt-ampere reactive (VAR) value. The method opens the switch if the VAR value has a magnitude above a predetermined value and a direction indicating the fault is outside of the micro-grid in the network.

## Claims

### Claim 1

A method for detecting a voltage disturbance in an electrical power distribution network that includes an electrical system having one or more power sources that can be disconnected from the network by a disconnect switch provided in an electrical line, where the network provides three-phase electrical AC power signals to the electrical system, said method opening the disconnect switch in response to detecting the voltage disturbance only if the voltage disturbance is in the network outside of the electrical system, said method comprising:
reading instantaneous voltage measurements of each of the three-phase power signals on the electrical line;
reading instantaneous current measurements of each of the three-phase power signals on the electrical line;
detecting whether a fault is occurring in the distribution network by using the voltage measurements to detect a voltage disturbance on the electrical line;
transforming the voltage measurements into first and second voltage values in a stationary reference frame;
transforming the first and second voltage values in the stationary reference frame to third and fourth voltage values in a rotating reference frame, where the third voltage value defines an average magnitude of the three-phase power signals and the fourth voltage value provides an indication of whether the third voltage value is locked to a network voltage;
correcting the fourth voltage value over time to maintain the third voltage value locked to the network voltage;
transforming the current measurements into first and second current values in the stationary reference frame;
transforming the first and second current values in the stationary reference frame to third and fourth current values in a rotating reference frame;
multiplying the third current value by the third voltage value to obtain an instantaneous power value;
multiplying the fourth current value by the third voltage value to obtain an instantaneous volt-ampere reactive (VAR) value; and
opening the switch if the VAR value has a magnitude above a predetermined value and a sign indicating the voltage disturbance is outside of the electrical system in the network.

### Claim 2 (depends on 1)

The method according to claim 1 wherein detecting a voltage disturbance includes calculating a sliding window root mean squared (RMS) voltage for each three-phase power signal over a first predetermined sample period using the instantaneous voltage measurements.

### Claim 3 (depends on 1)

The method according to claim 1 wherein transforming the voltage measurements into first and second voltage values and transforming the current measurements into first and second current values includes employing a Clarke transformation, and wherein transforming the first and second voltage values into third and fourth voltage values and transforming the first and second current values includes into third and fourth current values includes employing a Park transformation.

### Claim 4 (depends on 3)

The method according to claim 3 wherein transforming the first and second voltage values and transforming the first and second current values includes using a sine and cosine of a frequency correction angle.

### Claim 5 (depends on 4)

The method according to claim 4 wherein employing the Park and Clark transformations includes using the equations:
V
ds
=
2
3

V
a
-
1
3

(
V
b
+
V
c
)
,

V
qs
=
1
3

(
V
b
-
V
c
)
,

V
dr
=
V
ds

cos

(
θ
)
+
V
qs

sin

(
θ
)
,

V
qr
=
V
qs

cos

(
θ
)
-
V
ds

sin

(
θ
)
,

I
ds
=
2
3

I
a
-
1
3

(
I
b
+
I
c
)
,

I
qs
=
1
3

(
I
b
-
I
c
)
,

I
dr
=
I
ds

cos

(
θ
)
+
I
qs

sin

(
θ
)
,

I
qr
=
I


cos

(
θ
)
-
I
ds

sin

(
θ
)
,
where Va, Vb and Vc are the instantaneous voltage measurements of the three-phase power signals, Ia, Ib and Ic are the instantaneous current measurements of the three-phase power signals, Vds is the first voltage value, Vqs is the second voltage value, Vdr is the third voltage value, Vqr is the fourth voltage value, Ids is the first current value, Iqs is the second current value, Idr is the third current value, Iqr is the fourth current value and θ is the frequency correction angle.

### Claim 6 (depends on 4)

The method according to claim 4 wherein correcting the fourth voltage value over time includes providing the fourth voltage value to a proportional-integral (P-I) regulator that generates a correction frequency that changes a base frequency of the network, where the frequency correction angle is determined from the changed base frequency.

### Claim 7 (depends on 1)

The method according to claim 1 further comprising filtering the power value and the VAR value to remove transients therefrom.

### Claim 8 (depends on 1)

The method according to claim 1 wherein the electrical system is a critical load or a micro-grid.

### Claim 9 (depends on 1)

The method according to claim 1 wherein opening the switch further includes looking at the current direction of the power signal.

### Claim 10

A method for detecting a voltage disturbance in an electrical power distribution network that includes an electrical system having one or more power sources that can be disconnected from the network by a disconnect switch provided in an electrical line, where the network provides three-phase electrical AC power signals to the electrical system, said method opening the disconnect switch in response to detecting the voltage disturbance only if the voltage disturbance is in the network outside of the electrical system, said method comprising:
reading instantaneous voltage measurements of each of the three-phase power signals on the electrical line;
reading instantaneous current measurements of each of the three-phase power signals on the electrical line;
transforming the voltage measurements into first and second voltage values in a stationary reference frame using a Clarke transformation;
transforming the first and second voltage values in the stationary reference frame to third and fourth voltage values in a rotating reference frame using a Park transformation, where the third voltage value defines an average magnitude of the three-phase power signals and the fourth voltage value provides an indication of whether the third voltage value is locked to a network voltage;
transforming the current measurements into first and second current values in the stationary reference frame using a Clarke transformation;
transforming the first and second current values in the stationary reference frame to third and fourth current values in a rotating reference frame using a Park transformation;
multiplying the third current value by the third voltage value to obtain an instantaneous power value;
multiplying the fourth current value by the third voltage value to obtain an instantaneous volt-ampere reactive (VAR) value; and
opening the switch if the VAR value has a magnitude above a predetermined value and a sign indicating the voltage disturbance is outside of the electrical system in the network.

### Claim 11 (depends on 10)

The method according to claim 10 wherein transforming the first and second voltage values and transforming the first and second current values includes using a sine and cosine of a frequency correction angle.

### Claim 12 (depends on 11)

The method according to claim 11 further comprising correcting the fourth voltage value over time to maintain the third voltage value locked to the network voltage, wherein correcting the fourth voltage value over time includes providing the fourth voltage value to a proportional-integral (P-I) regulator that generates a correction frequency that changes a base frequency of the network, where the frequency correction angle is determined from the changed base frequency.

### Claim 13 (depends on 10)

The method according to claim 10 wherein the electrical system is a critical load or a micro-grid.

### Claim 14

A detection system for detecting a voltage disturbance in an electrical power distribution network that includes an electrical system having one or more power sources that can be disconnected from the network by a disconnect switch provided in an electrical line, where the network provides three-phase electrical AC power signals to the electrical system, said method opening the disconnect switch in response to detecting the voltage disturbance only if the voltage disturbance is in the network outside of the electrical system, said detection system comprising:
means for reading instantaneous voltage measurements of each of the three-phase power signals on the electrical line;
means for reading instantaneous current measurements of each of the three-phase power signals on the electrical line;
means for detecting whether a fault is occurring in the distribution network by using the voltage measurements to detect a voltage disturbance on the electrical line;
means for transforming the voltage measurements into first and second voltage values in a stationary reference frame;
means for transforming the first and second voltage values in the stationary reference frame to third and fourth voltage values in a rotating reference frame, where the third voltage value defines an average magnitude of the three-phase power signals and the fourth voltage value provides an indication of whether the third voltage value is locked to a network voltage;
means for correcting the fourth voltage value over time to maintain the third voltage value locked to the network voltage;
means for transforming the current measurements into first and second current values in the stationary reference frame;
means for transforming the first and second current values in the stationary reference frame to third and fourth current values in a rotating reference frame;
means for multiplying the third current value by the third voltage value to obtain an instantaneous power value;
means for multiplying the fourth current value by the third voltage value to obtain an instantaneous volt-ampere reactive (VAR) value; and
means for opening the switch if the VAR value has a magnitude above a predetermined value and a sign indicating the voltage disturbance is outside of the electrical system in the network.

### Claim 15 (depends on 14)

The detection system according to claim 14 wherein the means for detecting a voltage disturbance calculates a sliding window root mean squared (RMS) voltage for each three-phase power signal over a first predetermined sample period using the instantaneous voltage measurements.

### Claim 16 (depends on 14)

The detection system according to claim 14 wherein the means for transforming the voltage measurements into first and second voltage values and the means for transforming the current measurements into first and second current values employ a Clarke transformation, and wherein the means for transforming the first and second voltage values into third and fourth voltage values and the means for transforming the first and second current values includes into third and fourth current values employ a Park transformation.

### Claim 17 (depends on 14)

The detection system according to claim 14 wherein the means for transforming the first and second voltage values and the means for transforming the first and second current values use a sine and cosine of a frequency correction angle.

### Claim 18 (depends on 17)

The detection system according to claim 17 wherein the means for correcting the fourth voltage value over time provides the fourth voltage value to a proportional-integral (P-I) regulator that generates a correction frequency that changes a base frequency of the network, where the frequency correction angle is determined from the changed base frequency.

### Claim 19 (depends on 14)

The detection system according to claim 14 wherein the electrical system is a critical load or a micro-grid.