ES2922882A1 - Device for detecting and measuring electrical currents associated with corona discharges during storm activity (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Device for detecting and measuring electrical currents associated with corona discharges during storm activity that, comprising a sensor (1) in question, has cascade connections from the current transformer, through the protection devices (4), the wave shaper circuit (5), the noise cancellation circuit (6), the signal extractor circuit (7) up to the measurement circuit (8). (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

Device for detecting and measuring electrical currents associated with corona discharges during storm activity

OBJECT OF THE INVENTION

The invention, as expressed in the title of this specification, refers to a low amplitude electrical current sensor of atmospheric origin, optimized for corona discharges in conductors, providing, to the function for which it is intended, advantages and characteristics, which are described in detail later, which represent an improvement on the current state of the art.

More particularly, the object of the invention focuses on a system for measuring and detecting electric currents through a conductive section, producing a measurable signal proportional to the electric current. To do this, it comprises a magnetic sensor that is coupled to the driver's environment and does not affect the circuit to which it is inserted. The signals obtained at the meter output can be used in the production of alarms to detect impulsive currents through the conductor, in the calculation of currents and electrical charges transferred during corona discharge events.

FIELD OF APPLICATION OF THE INVENTION

The field of application of the present invention falls within the lightning protection sector, focusing particularly on the field of industry dedicated to installations with lightning warning systems.

Lightning protection systems are made up of three subsystems, designed to intercept a lightning strike to the structure (through the capture subsystem); Conduct lightning current to ground safely (through the downconductor subsystem) and disperse lightning current to ground (through the grounding subsystem).

Currently, it is not possible to obtain absolute protection against lightning. The degree of protection is defined at the international level according to a risk analysis, specifying a level of protection (I, II, III, IV). The highest level of protection is level I, which offers the highest probability of catching a lightning strike for a given range of intensity (current).

In addition to the protection offered by these devices, there is interest in the information that can be obtained from the electrical currents that flow through the sensor. In this context, corona discharges and upward tracers are physical phenomena that precede atmospheric discharge, caused by an intense and usually rapid increase in the level of the local electric field at the tip of the lightning rod.

Within the clouds, the collisions of different ice particles are responsible for the production of electrical charges. Macrophysical and microphysical processes occur simultaneously and through the separation of charges, the storm cloud is formed.

The formation of electrically charged structures in the atmosphere significantly alters the electric field at ground level, establishing a considerable potential difference between the lower parts of the cloud and the ground. In structures connected to the ground, such as poles, towers, and even in non-conductive bodies, such as trees and buildings in general, electrical charges move and concentrate at the ends of said surfaces, increasing the density of electrical charges and promoting a elevation of the local electric field.

The acceleration of free electrons in the vicinity of these surfaces can produce collisions with neutral molecules in the medium, ionizing them. This process releases additional electrons that speed up and collide with more atoms, starting a chain reaction, called an avalanche effect. If the local electric field exceeds a critical value (in air, at atmospheric pressure, the dielectric strength value is approximately 30 kV/cm), small ionized regions appear where corona discharges occur.

Corona discharges are characterized by the formation of plasma (regions of ionized air) at the ends of surfaces with high local electric fields. In grounded conductors with exposed elements characterized by their pointed shape, corners, metal edges, or small diameter cables, the first stage of such discharges is characterized by an impulsive (pulsing) current and accompanied by emissions of ultraviolet radiation. Lightning and its associated rapid electric field variations also can cause corona discharges in grounded structures.

The measurable electrical current in the early stage of sharp element corona discharges has an impulsive characteristic, its waveform having an extremely fast rise time of a few tens of nanoseconds and a duration of the order of a few hundred nanoseconds. The maximum current observed depends on the structure in question and can vary from tens of microamps to tens of amps.

During thunderstorms, the rapidly rising electric field can contribute to the formation of upstream tracers or streamers from grounded structures, which in turn can trigger lightning. The possibility of detecting and measuring corona discharge currents, which can be a precursor to lightning, in protection systems is a novelty that allows evaluating how low current levels affect said systems and how this information can be used in the production of alarms for electrical protection.

BACKGROUND OF THE INVENTION

As a reference to the current state of the art, it should be noted that, although different types of current sensors and lightning protection systems are widely known. However, systems that focus on measuring low impulsive currents from corona discharges that are resistant to high-amplitude currents produced by lightning are unknown.

EXPLANATION OF THE INVENTION

The device for detecting and measuring electrical currents associated with corona discharges during storm activity that the invention proposes represents an improvement over the current state of the art, with the characterizing details that make it possible and that distinguish it conveniently collected in the final claims accompanying this description.

Specifically, what the invention proposes, as noted above, is a sensor comprising a system for detecting and measuring electric currents that occur through a conductor, and that a measurable signal can be obtained, proportional to the current variations. The sensor must have a bandwidth compatible with the frequencies of the impulsive signals of the corona discharge, sensitivity to low currents and withstand high currents, resulting from the impact of lightning directly on the conductors in which the sensor can be installed.

The signals obtained through the sensor can be used for various applications related to the measurement and detection of corona discharges, and other small currents that can flow in the conductive section to which the sensor is attached. By way of example, mention should be made, in the field of electrical protection against atmospheric discharges, of lightning rods and lightning rods with primer devices (PDCs) and Franklin-type spikes. The sensor can be used in the field, providing information on currents by protection devices, or in validation tests of these devices, in which it is sought to verify the first emissions of corona discharges. Another possible application is related to wind turbines, in which the device can be used for the detection and/or measurement of electrostatic discharges from the blades of the wind turbine and its nacelle.

The signals obtained by the device can be used to feed detection or measurement algorithms for corona discharges. Electrical current waveforms can be integrated and an estimate of the electrical charge transferred can be obtained. Being a device for measuring impulsive currents with very fast discharges, the sensor must be coupled to a conductor connected a few meters from the point of discharge, in order to minimize inductive effects and other interference caused by noise in the signals obtained. .

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, a plan is attached to this descriptive report, as an integral part of it, in which for illustrative purposes and not limitation, the following has been represented:

- Figure 1 shows a schematic representation of the measurement circuit coupled to the conductor, where the current transformer used, and the elements that handle the input signals in the preferred embodiment of the invention have been represented.

- Figure 2 shows a schematic representation of a possible sensor application together with a control and acquisition system, which provides functions and user interface.

- Figure 3 shows the typical waveform that the device is designed to measure.

PREFERRED EMBODIMENT OF THE INVENTION

In view of the aforementioned figures, it can be seen in them a non-limiting example of an embodiment of the electrical current meter associated with corona discharges during storm activity, which includes what is described in detail below, in accordance with the following list of references assigned to each element:

1.sensor

2. Downstream Driver

3. Inductive sensor

4. Protection devices

5. Wave shaping circuit

6. Noise cancellation circuit

7. Signal extraction circuit

8. Measurement circuit

9. Voltage output, proportional to density of corona pulses detected

10. Voltage output, proportional to noise level detected

11. Pulse output, corona presence indication

12. Pulse output, lightning pulse detection

13. Processing unit

14.Digital Controller

15. Communications module

16. User interface module

17. Data logging module.

Thus, as can be seen in Figure 1, the sensor (1) in question has cascade connections from the inductive sensor (3) to the measurement circuit (8). The intermediate circuits are, respectively, the protection devices (4), the wave shaper circuit (5), the noise cancellation circuit (6) and the signal extractor circuit (7).

The inductive sensors (3) produce an output voltage proportional to the current variation measured in a specific bandwidth. Power transfer to the measurement circuit is limited by the intrinsic characteristics of the inductive sensor. The overvoltage protection devices (4) limit the amplitude of the overvoltages induced by the impulse currents of great magnitude in the downconductor (2), which safely conducts the lightning current to earth. These devices act quickly against these overvoltages and guarantee the least possible interference in the measurement carried out.

The wave shaper circuit (5) applies a non-linear transfer function to condition the signal within the desired range for the measurement circuits, as well as to guarantee the limitation of the signal through the saturation of some components.

The frequency content of the corona discharge signals is very similar to the VHF impulsive radiation that can be detected during lightning formation processes. In this way, the noise cancellation circuit (6) attenuates unwanted components in the measurement and increases the signal-to-noise ratio.

The signal extractor circuit (7) separates the detections of corona discharges from the detections of impulsive currents related to the formation of leaders, or even the occurrence of lightning strikes. This circuit contributes to minimizing detection errors produced by the system.

The measurement circuit (8) provides: a voltage output (9) that is proportional to the density of corona pulses detected, a voltage output (10) proportional to the noise level detected, a pulse output (11) of corona presence indication and a pulse output (12) for lightning pulse detection.

In Figure 2, in an optional embodiment, the sensor (1) is connected to a monitoring unit. processing (13) comprising the following elements: a digital controller (14), a communications module (15), a user interface module (16) and a data recording module (17). The communications module (15) can include different communication possibilities, such as Wi-Fi, Bluetooth, optical cables, Ethernet or serial cable. The user can interact to obtain system information or modify its parameters through the user interface (16).

In Figure 3, a schematic of the waveforms that the device is capable of measuring is shown. In general, the device responds to the excitation of impulsive discharges with such a waveform in a wide range of amplitudes, in which the Peak currents (Ip) can range from tens of microamps to tens of amps. The device's read bandwidth includes waveforms with rise times (Ts) from tens of nanoseconds to tens of microseconds, and duration times (Td) from hundreds of nanoseconds to hundreds of microseconds. In addition to the ability to measure currents in this wide range of values, the device is characterized by resisting and detecting electrical currents from ascending leaders and lightning strikes, which have rise times and durations that can reach tens of milliseconds and amplitudes that can reach hundreds of kiloamps.

Having sufficiently described the nature of the present invention, as well as the way of putting it into practice, it is not considered necessary to make its explanation more extensive so that any person skilled in the art understands its scope and the advantages derived from it, stating that, within its essentiality, it may be put into practice in other forms of embodiment that differ in detail from the one indicated by way of example, and to which it will also reach the protection that is sought as long as its fundamental principle is not altered, changed or modified. .

Claims (1)

1. - Device for detecting and measuring electrical currents associated with corona discharges during storm activity, comprising : - an inductive sensor (3), connected to a down conductor (2) that conducts the lightning current to ground safely, producing an output voltage proportional to the current variation measured in a specific bandwidth; - protection devices (4) against overvoltages, which limit the amplitude of the overvoltages induced by the impulse currents of great magnitude in the down conductor (2); - a wave shaper circuit (5), which applies a non-linear transfer function to condition the signal within the desired range for the measurement circuits, while guaranteeing the limitation of the signal through the saturation of some components; Y - a measurement circuit (8), which has at least one voltage output (9) that is proportional to the density of corona pulses detected; in which all these circuits are connected in cascade and successively starting from the down conductor (2). 2. - Device according to claim 1, characterized in that, following the wave shaping circuit (5), it comprises a noise cancellation circuit (6), which attenuates unwanted components in the measurement and increases the signal ratio /noise; and in that the measurement circuit (8) includes a measurable voltage output (10) indicating the noise level of the measurement. 3. - Device according to any of the preceding claims, characterized in that, following the wave shaping circuit (5), it comprises a signal extractor circuit (7) that separates the corona discharge detections from the current detections impulsive ones related to the formation of the leaders, or even the occurrence of lightning strikes, in order to minimize the detection errors produced by the system; and because the measurement circuit (8) includes a pulse output (11) indicating the presence of the corona effect and a measurable pulse output (12), which provides detection of electrical currents of ascending leaders and lightning. 4 - Device according to claim 1, characterized in that the measurable signal of the voltage output (9), proportional to the intensity of the corona discharges observable through a down conductor (2), provides measurements in: - a range of peak currents (Ip) from tens of microamps to tens of amps, - rise times (Ts) from tens of nanoseconds to tens of microseconds, and - duration times (Td) from hundreds of nanoseconds to hundreds of microseconds. 5. - Device according to claim 3, characterized in that the pulse output signal (11) provides detection of discharges due to the corona effect in: - a range of peak currents (Ip) from tens of microamps to tens of amps, - rise times (Ts) from tens of nanoseconds to tens of microseconds, and - duration times (Td) from hundreds of nanoseconds to hundreds of microseconds. 6. - Device according to any of the preceding claims, characterized in that it comprises a processing unit (13) associated therewith that includes a digital controller (14) to be used by a digital data acquisition system. 7. - Device according to claim 6, characterized in that the digital controller (14) comprises a communications module (15). 8. - Device, according to claims 6-7, characterized in that the processing unit (13) comprises a user interface (16), through which a user accesses the data registered in a data registration module (17) to obtain system information or modify its parameters. 9. - Use of the device of the preceding claims for measurement and/or detection of electrostatic discharges of wind turbine blades and their nacelle.