ES2758531A1 - SYSTEM AND METHOD OF LOCATION OF GROUND FAULTS IN ALTERNATING CURRENT FACILITIES (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Method and system for locating earth faults in alternating current electrical installations based on the measurement of the voltages (Uin) and the impedances (Zi) in each phase of alternating current, and the quotient between the impedance (Zgnd) and the voltage (Ugnd), or current measurement in case of having a rigid system to ground, of a grounding device placed in a neutral point that allows calculating the phase that has the fault, as well as the percentage of failure over the equivalent impedance of said phase. (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

SYSTEM AND METHOD OF LOCATION OF EARTH FAULTS IN

ALTERNATING CURRENT FACILITIES

OBJECT OF THE INVENTION

The present invention refers to a system and method of locating earth faults in alternating current electrical installations capable of locating this type of defect being at any point of the electrical circuit, with it in operation.

The system and method for locating earth faults according to the present invention is useful in electrical installations connected to an electrical network by means of a transformer that has a neutral output secondary. The present invention has application, for example and without limitation, in the electrical automotive sector and in that of renewable energies.

BACKGROUND OF THE INVENTION

Electrical installations must have protection systems that make them safe against all kinds of faults for equipment and people. In the event of earth faults, usually caused by a bare cable that touches the installation's chassis or another similar defect, the actuation devices against this type of fault are of various technology, and thus are not detection and diagnostic devices. intended for these.

In the field of diagnosis, the detection and location of ground or chassis faults is complicated due to the various factors that can influence the estimation. Diagnostic devices are of fundamental importance to equipment if they want to estimate the existence or not of a fault and if so, the location and severity of the damage that this fault is causing in the system in question.

In electrical installations with an isolated neutral configuration, a ground point does not cause a fault current. In case of having a fault detector installed in the system and it is connected to ground, the current with a point to ground is small due to the fault limiting impedance, and in cases of rigid ground systems, ground faults can cause severe overcurrents in the system as they do not have this limiting impedance.

The need to detect a possible defect occurs by trying to locate this shunt as soon as possible, because if a first earth fault occurs, a low residual current flows through the grounded limiting impedance, but a second fault would lead to a fault. in the system of considerable gravity, taking into account the magnitude of the residual current that circulates between both points. This would cause a short circuit between some elements of the same phase or a biphasic fault.

In the already known ground fault detection systems it is usual to have the following means for the detection and location of these faults:

• Detection by injection of alternating current of a frequency different from that of operation between a point in the electrical installation and ground that gives a reading of said current if there is a ground fault.

• Detection by current injection in the electrical installation that reads the current if there is a ground fault.

• Location by voltage injection between a point of the electrical installation and earth in a measurement resistance that stops reading or decreases it if there is a ground fault.

These fault detection systems require an active component between the system neutral and ground.

There are also technologies such as minimum impedance relays that can distinguish where the fault is located in the system by measuring the phase current and phase voltage at a point in the circuit from which you want to start locating and protecting. , without the need to introduce current or voltage sources to the system.

These latest fault detection systems can alert that there is a defect and not locate it, or if it is located, it cannot operate correctly if the system has intermediate DC buses because they do not know how to differentiate if the fault is downstream or upstream of these buses.

The state of the art corresponding to the present invention is described, in more detail, in the following documents:

PCT / US1995 / 002802 (08/15/1995) US5661664 A (08/26/1997) ABB Power T&D Company Inc., Raleigh, N.C. ONE-TERMINAL DATA FAULT LOCATION SYSTEM AND PROCESS FOR LOCATING A FAULT.

PCT / ES2011 / 000278 (19.09.2011) WO2012 / 038564 A2 (29.03.2012) UNIVERSIDAD DE SEVILLA (100.00%) DEVICE AND METHOD FOR THE LOCATION OF FAULTS IN LINES OF ELECTRICAL DISTRIBUTION.

ES2716482 A1 (06.12.2019) UNIVERSIDAD POLITÉCNICA DE MADRID (100.00%) SYSTEM AND METHOD OF DETECTION OF LAND FAULTS OR AGAINST CHASSIS IN CONTINUOUS CURRENT SYSTEMS WITH BATTERY-FEED INVERTERS.

P. Tian, CA Platero, F. Blázquez and JM Guerrero, "Ground Faults Location System for Powertrain of Electric Vehicles”, 2019 IEEE 12th Intemational Symposium on Diagnostics for Electrical Machines, Power Electronics and Drives ( SDEMPED) ^, Toulouse, France, 2019 , pp. 488-492.

In the first two documents described above, it is necessary to take measurements, both intensity and voltage, to locate the earth fault.

Despite the known ground fault detection systems and methods, there is a need in the sector to develop new systems and methods that are capable of detecting ground faults in alternating current electrical installations regardless of the specific configuration of said installation (single-phase, two-phase, three-phase or successive configurations) and that said installations may also be provided with direct current buses.

Likewise, it is convenient to develop new systems and methods for detecting earth faults, capable of detecting in which phase and in what percentage of phase this fault occurs, since this would speed up the repair and / or maintenance tasks. Furthermore, it would be advantageous if such detection systems and methods were capable of detecting earth faults using only voltage measurements, since this would considerably reduce their manufacturing and / or implantation cost.

DESCRIPTION OF THE INVENTION

The present invention aims to address all the limitations, disadvantages and disadvantages of the prior art ground fault detection systems and methods described above.

For this purpose, a first object of the invention refers to a system for locating earth faults in at least one alternating current electrical installation, said electrical installation being provided with at least one alternating current phase, a ground connection and a neutral point, characterized by comprising:

a) a grounding device, consisting of a passive element arranged between the neutral point of the electrical installation and the ground connection;

b) at least one measuring equipment, configured to measure the following quantities:

i) the voltages of each phase of alternating current (Uin) and calculate the phasor of all the voltages of each phase of alternating current as:

where:

Ti: is the period of the voltage wave;

uin (tj): is the instantaneous value of the alternating current phase voltage wave for a given instant tj;

0u.in: is the argument of the first harmonic of the wave performing a fast Fourier transform (FFT);

a1in: is the amplitude value of the FFT first harmonic sine filter for the phase-neutral voltage wave (Uin);

b1in: is the amplitude value of the FFT's first harmonic cosine filter for the phase-neutral voltage wave (Uin);

ii) the impedances of each alternating current phase (Zi),

iii) the value of (■ U = ( ( n 2 d )), corresponding to the quotient between the grounding impedance (Zgnd), and the voltage (Ugnd) at the grounding device; and

c) a calculation equipment, configured to identify the phase of alternating current in which an earth fault occurs by comparing the angle between voltages, such that:

where:

0Ugnd: is the phase of the voltage read at the measurement equipment terminals;

0Uin: is the phase of the voltage that carries the earth fault;

A0gnd: is the own impedance of the measurement equipment;

The calculation equipment is also configured to calculate the percentage (k) over the phase impedance of the alternating current where the earth fault occurs, said percentage (k) being:

where

k: is the percentage as a unit over the phase impedance where the fault occurs;

Uin: is the voltage of the alternating current phase "i";

Zi: is the impedance of the alternating current phase "i";

N is the total number of phases of the installation;

Zgnd is the impedance of the grounded device; and

Ugnd is the voltage read at the impedance of the grounded device.

In a first embodiment of the invention, the fault location system is provided with a measuring equipment configured to measure the voltage at the neutral point of the electrical installation and to measure the voltage in the grounding device. In this embodiment of the invention the value of the quotient ^{(U ^)} U gnd is determined from said voltage measurement, calculated as:

where:

Tgnd: is the period of the voltage wave;

ugnd (tj): is the instantaneous value of the voltage wave in the grounding device for a given instant tj;

0Ugnd: is the argument of the first harmonic of the wave performing a fast Fourier transform (FFT) in a conventional way;

a1gnd: is the amplitude value of the FFT first harmonic sine filter for the voltage wave at the impedance of the grounding device (Ugnd);

b1gnd: is the amplitude value of the FFT first harmonic cosine filter for the voltage wave at the impedance of the grounding device (Ugnd).

Unlike the prior art, this embodiment of the invention allows ground faults to be located by taking voltage measurements only.

Likewise, the system and method according to the present invention allow the location of earth faults in alternating current electrical installations, regardless of the type of configuration it has, being able to be single-phase, two-phase, three-phase or successive dispositions in addition to being able to include in its configuration direct current buses.

In the present invention, the impedances of each phase of alternating current (Zi) can be measured a priori or, if said impedances are variable, by means of a suitable instrument for estimating variability (for example: in an asynchronous machine, where the impedance varies with slip, by means of a shaft speed meter). Likewise, the value of the grounding impedance (Zgnd) can be known -optionally- a priori of the installation.

Likewise, in the present invention the voltage (Ugnd) in the grounding device is calculated in the same way as the phase-neutral voltages on the AC side.

The residual current is defined as the result of the sum of the line currents that circulate through a circuit (or electrical installation). In the event of a fault (ground fault) this residual current is non-zero and there is a return to ground of said current by the grounding device, which consists of a passive element, also previously installed to ground at a neutral point in the system to which you want to adhere, or in the case of a grounded network (type rigidly grounded, TT, or grounded by an impedance, IT), installed in series in the corresponding grounding system.

Said first embodiment of the fault location system of the invention is therefore provided with a device configured to measure the voltage to which the grounding device is subjected, thus characterizing the residual current.

In a second embodiment of the fault location system of the invention, an ammeter configured to measure current (in TT systems where there is no ground impedance) is provided directly in the grounding device, since:

. _ U gnd

6 res 3 _{3 g nd}

where:

Ires: is the residual current flowing through the grounding device;

Ugnd: is the voltage measured at the grounding device;

Zgnd: is the grounding impedance.

Therefore, in said second embodiment of the fault location system, according to the invention, it is provided with an ammeter configured to measure the residual current flowing through the grounding device (Ires) and determine the value of (- U = ((n n d d ) as

3 g n d _ 1

M g n d L res

Returning to the first embodiment, in case of earth fault, the residual voltage Measurement, Ugnd, will have a series of characteristics according to where the defect has occurred, so that these proportionally resemble the waveform and magnitude of the voltage where said failure has occurred. A non-limiting example of this case would be to record a PWM wave (Pulse width modulated wave by an electronic converter by controlled opening and closing of switches) in the grounding device, which would imply a fault on the current side toggles of an inverter (see Figure 1 and Figure 2).

The identification of the phase with the defect, once you have a voltage reading in the grounding device, is obtained by comparing the angle between the voltage in the grounding device (which is, for example, an impedance grounding) and phase voltages on the AC side. This is located as:

^{® U gnd ~ ® U in =} 180 ° ^{A 9 * nd}

Where:

0Ugnd: is the phase of the voltage read at the terminals of the measuring device;

0Uin: is the phase of the voltage that carries the earth fault;

A0gnd: is the own impedance of the measurement device (a non-limiting example may be a calibrated measurement resistance R that would have an added offset of 0 °).

Its operation is analogous if you have an intensity measurement (second embodiment). Being the measurement of the phase this time:

^{@ Ires ~ @ Ui.n =} 180 ° ^^ gnd

Where:

0ires: is the phase of the residual fault current reading that circulates through the grounding device;

The fault location system and method according to the present invention (which will be described below), once the phase is known, is based on the following equation:

N

^{2 _ Z gnd} V ^{U jn}

^{M gnd 4 —1} 3

For i being the number of phases of the electrical installation. In the case of a three-phase electrical installation (with three phases of alternating current a, b and c) it would have:

Where:

k: is the percentage as a unit over the phase impedance where the fault occurs;

Zgnd: is the impedance of the grounded device;

Ugnd: is the phasor of the voltage read in the impedance of the grounded device;

Uan: is the phasor of the phase a voltage;

Ubn: is the phasor of the phase b voltage;

Ucn: is the phasor of the phase c voltage;

Za: is the impedance of phase a;

Zb: is the impedance of phase b;

Zc: is the impedance of phase c.

The present invention contemplates measuring each phase voltage of the alternating current part of the system. If the neutral of the system is not accessible, an artificial neutral will be made.

Some embodiments of the invention also contemplate measuring the voltage on the DC side passive measuring element. In the event that the system is rigidly grounded, alternatively, other embodiments of the invention contemplate reading the current in the grounding device circulating towards the ground, instead of the voltage through a grounding device, leaving The expression:

And in the case of a three-phase system:

The present invention contemplates calculating the modulus and argument voltage phasor to be able to operate in the previously described formulas and the neutral current one in case of measuring residual current.

The present invention contemplates calculating the phase impedances or obtaining them by means of previous tests or a mixture of both (they can be variable in the case of an electric drive) and these can be calculated by means of measures of mechanical magnitudes that are appropriate. A non-representative example of these would be to obtain the impedances of the equivalent circuit of an asynchronous motor by pre-testing the motor, and adjusting the rotor parameters according to the slip of the machine, for which the measurement of the speed measurement of the shaft rotation, in addition to the network frequency obtained from the frequency of the stator neutral phase voltage.

The present invention also contemplates pre-testing the impedance of the grounded device.

The installation of the grounding device can be in both the DC bus areas and AC points, as long as it is between a neutral potential connection point between the circuit and ground.

A second aspect of the present invention refers to a method of locating earth faults in at least one alternating current electrical installation, said electrical installation being provided with at least one alternating current phase, a ground connection and a neutral point , characterized by comprising the following stages:

a) provide a grounding device, consisting of a passive element, between the neutral point of the electrical installation and the ground connection;

b) measure the voltages of each phase alternating current (Uin);

c) measure the impedances of each alternating current phase (Zi);

d) calculate the phasor of all the voltages of each phase of alternating current as:

where:

Tgnd: is the period of the voltage wave;

ugnd (tj): is the instantaneous value of the voltage wave in the grounding device for a given instant tj;

0Ugnd: is the argument of the first harmonic of the wave performing a fast Fourier transform (FFT);

a1gnd: is the amplitude value of the FFT first harmonic sine filter for the voltage wave in the impedance of the grounding device (Ugnd);

b1gnd: is the amplitude value of the FFT's first harmonic cosine filter for the voltage wave at the impedance of the grounding device (Ugnd).

e) measure the value of ( ^{= s ^))}

U-gnd corresponding to the quotient between the grounding impedance (Zgnd) and the voltage (Ugnd) in the grounding device;

f) calculate the location of the earth fault by comparing the angle between voltages of each phase, such that

^{@ U gnd ~ @ Ui.n =} l - 0 ° ^{A 9 gnd}

where:

0Ugnd: is the phase of the voltage read at the measurement equipment terminals;

0Uin: is the phase of the voltage that carries the earth fault;

A0gnd: is the own impedance of the measurement equipment; and

g) calculate the percentage (k) on the phase impedance of alternating current where the earth fault occurs, said percentage (k) being:

where

k: is the percentage as a unit over the phase impedance where the fault occurs;

Uin: is the voltage of the alternating current phase "i";

Zi: is the impedance of the alternating current phase "i";

N: is the total number of phases of the installation;

Zgnd is the impedance of the grounded device; and

Ugnd is the voltage read at the impedance of the grounded device.

In a first embodiment of the fault locating method of the invention, the value of the quotient ( U U gn ^ d ) is determined by measuring the voltage at the neutral point of the electrical installation and measuring the voltage at the grounding device.

In a second embodiment of the fault location method of the invention, the value of the quotient ( U '( g n n d d ) is determined by measuring the residual current flowing through the grounding device (Ires) and determining the value of ^{( ' gn)} ) as:

U-gnd

DEFINITIONS

Throughout the present description, a "passive element" should be understood to be an electrical element that lacks voltage or current sources.

BRIEF DESCRIPTION OF THE FIGURES

In the following, a series of drawings that help to better understand the invention are described very briefly, which are expressly related to an embodiment of said invention and are presented as non-limiting examples thereof.

Figure 1 is a schematic view of a first embodiment of the fault location system according to the invention, in which the electrical installation is fed through the electrical network;

Figure 2 is a schematic view of a second embodiment of the fault location system according to the invention, in which the electrical installation is powered by batteries; and

Fig. 3 is a schematic view of a third embodiment of the fault location system according to the invention, in which the electrical installation whose neutral is connected to ground through an impedance.

NUMERICAL REFERENCES OF THE FIGURES

(1) Grounding device;

(2) Midpoint of the DC bus;

(3) Voltage measurement equipment in the grounding device;

(4) Positive pole of the DC bus of the converter;

(5) Negative pole of the DC bus of the converter;

(6) IGBT;

(7) AC bus;

(8) Measurement and calculation of phase-neutral voltage of phase a;

(9) Measurement and calculation of phase-neutral voltage of phase b;

(10) Measurement and calculation of phase-neutral voltage of phase c;

(11) Measurement of auxiliary parameters to calculate the phase impedance; (12) Electric drive;

(13) Calculation of phasor and phase with defect by comparison of voltage phasor arguments;

(14) Calculation of the percentage of phase impedance where the earth fault is located;

(15) Power transformer.

PREFERRED REALIZATIONS

A description is now made of various cases of preferred uses for the invention.

The design of Figure 1 represents the ground fault location system in the case of a variable speed drive, with an average DC stage that is fed from the electrical network. In this specific embodiment of the invention, the location system consists of:

• A grounding device (1) connected at the midpoint of the direct current bus (2) where the voltage between this point and ground is measured by means of a voltage measuring device in the grounding device ( 3), which is the second connected point of the passive element, this voltage is called Ugnd.

• The zero potential point of the direct current zone is located at the midpoint of the direct current bus (2). From this midpoint, the positive pole of the DC bus of the converter (4) will form in the upper part, and in the lower part it will be the negative pole of the DC bus of the converter (5).

• The converter on the left, (which is part of the electrical installation), transforms the alternating current from the grid into direct current and the inverter on the right (which is also part of the electrical installation), transforms the direct current into current alternates. Both are connected between the positive and negative poles of the direct current bus (4) (5) by means of switching elements. In this case they are insulated gate bipolar transistors, IGBTs (6), arranged on three bridges that make up a converter and an inverter of 6 pulses each.

• Alternating current flows from the inverter to a three-phase electrical installation, or alternating current bus (7), which supplies an electric drive (12). The measurements of the voltages of each phase-neutral of phases a, Uan (8), b, Ubn (9) and c, UCn (10) are collected from this three-phase installation. Additionally, the motor speed is also measured for this particular case in the auxiliary parameters measuring equipment for calculating the phase impedance (11) in order to calculate the equivalent impedance of the electric drive (12).

• Finally, we proceed to the calculation of the phasor and phase with defect by comparing the arguments of the voltage phasor (13) and knowing the phase, we proceed to calculate the percentage of phase impedance where the earth fault is located (14).

Figure 2 represents the location system for a variable speed drive powered directly from batteries. It is a variant of the previous scheme of the system for locating earth faults in alternating current, where only measurements of the phase-neutral voltage of phases a (8), b (9) and c (10) are made on the alternating side , the measurement of the speed of the machine by means of auxiliary parameter measurement equipment for calculating the phase impedance (11) and the voltage measurement in the voltage measurement equipment in the grounding device (3), since the measurement of the currents is not necessary for the location of the fault. This specific case could be applied to the power train scheme of an electric vehicle, in this case the ground faults would be faults to the vehicle chassis.

Figure 3 shows the case of a machine fed directly from an electrical network whose neutral is connected to earth through an impedance, so that the defect value is limited. Where the following points are observed:

• Grounding device (1) where the fault voltage is measured by means of the voltage measuring equipment in the grounding device earth (3) connected to the star center of the secondary of a power transformer (15).

• The power transformer (15) is connected to both sides by alternating current buses (7). The high voltage side goes to the network and the low voltage side to the electric drive (12).

• To locate the defect, the phase-neutral voltages of phases a (8), b (9) and c (10) must be measured. Additionally, the motor speed is also measured for this particular case in the auxiliary parameters measuring equipment for calculating the phase impedance (11).

• Finally, we proceed to the calculation of phasor and phase with defect by comparison of arguments of the voltage phasor (13) and the unknown k is cleared by calculating the percentage of phase impedance where the earth fault is located. (14).

AC drive controlled by an inverter and powered by batteries.

Its application is mainly for electrical systems with conversion between direct current and alternating current, since the device can be installed in any neutral point and locates only the defect in alternating current. A non-limiting example of such an application can be seen in the electric power train of an electric vehicle that corresponds to Figure 2.

Variable speed drive with double converter and direct current stage powered from an electrical network

It can also be used for the application in generation groups with a converter and an inverter such as wave power systems or wind generators with PMSG technology subsequently connected to the grid, both examples can be modeled with Figure 1.

In these systems, the grounding device (1) can be placed both in the midpoint of the DC bus (4) between rectifier and inverter and on the AC bus (7) of the network if there is any neutral point accessible for connect the device to ground.

The phase-neutral voltage measurements of phases a (8), b (9) and c (10) must be carried out on the system's variable frequency alternating current bus (7) and the residual voltage will be measured at terminals of the device regardless of where it is positioned.

Drives or loads directly connected to the electrical network at industrial frequency.

This invention is also valid for systems connected directly to the network, that is, for loads with power supply at industrial frequency. In this case, you may or may not include a device that limits the return current through the device, or you can only measure the current in a rigid connection to ground at a point of zero potential. A non-limiting example of this application can be a SCIG wind turbine or a synchronous machine directly connected to the network.

The device in these cases must be connected to an artificial neutral or, if the system configuration allows it, to the low voltage side of the power transformer (15) that supplies the loads to be diagnosed (see Figure 3).

Claims (6)

Ground fault location system in at least one alternating current electrical installation, said electrical installation being provided with at least one alternating current phase, a ground connection and a neutral point, characterized in that it comprises: a) a grounding device (1), consisting of a passive element arranged between the neutral point of the electrical installation and the ground connection; b) at least one measuring equipment, configured to measure the following quantities: i) the voltages of each phase of alternating current (Uin) and calculate the phasor of all the voltages of each phase of alternating current as:

where: Ti: is the period of the voltage wave; uin (tj): is the instantaneous value of the alternating current phase voltage wave for a given instant tj; 0Uin: is the argument of the first harmonic of the wave performing a fast Fourier transform (FFT); a1in: is the amplitude value of the FFT first harmonic sine filter for the phase-neutral voltage wave (Uin); b1in: is the amplitude value of the first harmonic cosine filter of the FFT for the phase-neutral voltage wave (Uin); ii) the impedances of each alternating current phase (Zi)); iii) the value of ^{(= snd),} u 'nd corresponding to the quotient between the grounding impedance (Zgnd) and the voltage (Ugnd) in the grounding device; c) a calculation equipment, configured to identify the alternating current phase in which an earth fault occurs by comparing the angle between voltages such that:

where: 0Ugnd: is the phase of the voltage read at the measurement equipment terminals; 0Uin: is the phase of the voltage that carries the earth fault; A0gnd: is the own impedance of the measurement equipment; The calculation equipment is also configured to calculate the percentage (k) over the phase impedance of the alternating current where the earth fault occurs, said percentage (k) being: 1

where k: is the percentage as a unit over the phase impedance where the fault occurs; Uin: is the voltage of phase "i"; Zi: is the impedance of phase "i"; N is the total number of phases of the installation; Zgnd is the impedance of the grounded device; and Ugnd is the voltage read at the impedance of the grounded device. 2. A ground fault location system according to claim 1, in which a measuring equipment configured to measure the voltage at the neutral point of the electrical installation and to measure the voltage in the grounding device is provided. 3. Ground fault location system according to claim 1, in which an ammeter configured to measure the residual current flowing through the grounding device (Ires) and determine the value of U-gnd ) is provided as Z .g n d 1 M) n d L res 4. Method for locating earth faults in at least one alternating current electrical installation, said electrical installation being provided with at least one alternating current phase, a ground connection and a neutral point, characterized in that it comprises the following stages: - arranging a grounding device (1), consisting of a passive element, between the neutral point of the electrical installation and the ground connection; - measure the voltages of each phase of alternating current (Uin); - measure the impedances of each alternating current phase (Zi); - calculate the phasor of all the voltages of each alternating current phase as: I heard ^ U.V, M in U in

and for the voltage in the grounding device such as:

where: Ti: is the period of the voltage wave; uin (tj): is the instantaneous value of the alternating current phase voltage wave for a given instant tj 0Uin: is the argument of the first harmonic of the wave performing a fast Fourier transform (FFT): a1in: is the amplitude value of the FFT first harmonic sine filter for the phase-neutral voltage wave (Uin); b1in: is the amplitude value of the FFT's first harmonic cosine filter for the phase-neutral voltage wave (Uin); Tgnd: is the period of the voltage wave; ugnd (tj): is the instantaneous value of the voltage wave in the grounding device for a given instant tj .; 0Ugnd: is the argument of the first harmonic of the wave performing an FFT; a1gnd: is the amplitude value of the FFT's first harmonic sine filter for the voltage wave at the impedance of the grounding (Ugnd); b1gnd: is the amplitude value of the FFT first harmonic cosine filter for the voltage wave at the impedance of the grounding device (Ugnd); - measure the value of (.U ^), corresponding to the quotient between the impedance U-gnd grounding (Zgnd) and the voltage (Ugnd) in the grounding device; and - calculate the location of the earth fault by comparing the angle between the voltages of each phase such that:

where: 0Ugnd: is the phase of the voltage read at the terminals of the measuring device; 0Uin: is the phase of the voltage that carries the earth fault; A0gnd: is the impedance of the measurement device. and calculate the percentage (k) on the phase impedance of alternating current where the earth fault occurs, said percentage (k) being: 1

where k: is the percentage as a unit over the phase impedance where the fault occurs; Uin: is the voltage of the alternating current phase "i"; Zi: is the impedance of the alternating current phase "i"; N: is the total number of phases of the installation; Zgnd is the impedance of the grounded device; and Ugnd is the voltage read at the impedance of the device set to Earth. 5. Ground fault location method according to claim 4, in which the value of the quotient (= ^{2 ^ 1} ) is determined by measuring the voltage at el _{= gnd} neutral point of the electrical installation and measuring the voltage in the grounding device. 6. Ground fault location method according to claim 4, in which the value of the quotient (- = ^nd -) is determined by measuring the current _{= gn d} residual circulating through the grounding device (Ires) and determining the value of ^{(& gn (} ) as: _{= gn d} Z .g n d 1 M) n d L res