RU2809642C1 - Method for testing aircrafts for selectivity of lightning strikes - Google Patents

Abstract

FIELD: electromagnetic tests.

SUBSTANCE: invention relates to the electromagnetic tests for assessing the areas of an aircraft that are most likely to be hit by lightning. Essence: testing aircraft for selectivity of lightning discharges consists of reproducing spark discharges in an air gap in which a model of an aircraft is located, the largest linear dimension of which is 2.5-3 times less than the length of the air gap. To ensure breakdown of the air spark gap, a resonant transformer is used. The entry and exit points of the lightning leader are determined separately. When determining lightning entry points, the aircraft model is grounded at the bottom. When determining the output points, the model is connected to the high-voltage output of the resonant transformer. The polarity of the voltage at which the breakdown of the air gap occurred is determined by the readings of a pulsed electric field strength sensor located at a short distance from the resonant transformer.

EFFECT: reducing the requirements for the output voltage of testing equipment and reducing its dimensions, reducing the time required for testing.

1 cl, 3 dwg

Description

The invention relates to the field of electromagnetic tests for assessing the areas most likely to damage an aircraft by lightning.

There is a known method for repeatedly reproducing spark discharges of the air gap between a conductive grounded surface and a pointed potential electrode in which a model of an aircraft is located, while the maximum linear size of the model is equal to one meter or more and must have a given ratio with the length of the spark gap [1]. The regulatory and technical documentation determines that the required minimum length of the spark gap consists of the minimum height of the model above the conductive surface, equal to 1 meter, and the minimum height of the potential electrode above the model h:

The distance from the top point of the model to the potential electrode is:

Where - maximum linear size of the model,

- maximum linear size of the aircraft.

For example, for aircraft with a maximum size of 20 m, the length of the spark gap must be at least 3.5 m (with minimum model sizes). The points where the spark hits the model are recorded with photo or video equipment. For reliable statistical processing of test results, it is necessary to reproduce up to a thousand breakdowns of the spark gap.

For such tests, it is necessary to provide high voltage, which is achieved by using various pulse voltage generators (GVG).

Modern GINs make it possible to provide an output voltage of up to 9 megavolts, that is, the length of the spark gap they penetrate can reach 10 m. An example is the GIN from the experimental base of the Federal State Unitary Enterprise “RFNC-VNIIEF” (Istra) [2].

The closest way to achieve the technical result indicated below is the method of generating a high voltage sufficient to break down spark gaps several meters long [3], which uses a pulse voltage generator (GVP) assembled according to the Arkadyev-Marx circuit and having from 10 stages of high-voltage capacitors different nominal capacities. This method is adopted as a prototype.

The reasons preventing the achievement of the technical result indicated below when using the known method, adopted as a prototype, include the fact that in the known method the GIN, consisting of 10 stages of one capacitor with a capacity of 17 nF each, provides an output voltage of up to 1.2 MB, sufficient for breakdown of a spark gap about 1.5 m long. Taking into account the need to ensure uniform charging of all stages, its time is about 3-4 minutes [4]. In addition, GINs with 2-3 MB output voltage and higher are usually located in open areas [5], which makes the tests dependent on weather conditions - in high humidity their operation is unsafe, and in bright sunlight photo and video recording is difficult points where the spark hits the model. Another important feature of such tests is the low reliability of GIN capacitors, which operate to provide the highest output voltages at 80-100% of the rated voltage. With such operation in almost continuous mode, the probability of internal breakdown of capacitors increases sharply, and their diagnosis and replacement are usually very labor-intensive.

Thus, the solution to the problem of ensuring testing of aircraft models for the selectivity of lightning strikes should proceed in the following directions:

1. Rationale for reducing the length of the spark gap to reduce the requirements for the output voltage of test equipment.

2. Determination of technical solutions that reduce the charging capacity and voltage of the testing equipment and, as a consequence, the charging time of the energy storage devices of the testing equipment.

The essence of the proposed method is as follows:

1. The spark entry and exit points into the aircraft are determined separately during testing. Moreover, in the first case, its model is grounded at the bottom, and in the second, it is electrically connected to the high-voltage electrode of the testing equipment. This makes it possible to reduce the length of the spark gap that needs to be pierced, or, accordingly, to enable testing of smaller aircraft models at a constant output voltage. This solution, however, leads to a doubling of the number of required spark gap breakdowns.

2. To reproduce spark gap breakdowns, a resonant transformer (Tesla transformer) is used, which provides the necessary voltage on the secondary winding when using one or two high-voltage (charge voltage up to 60 kV) capacitors in the primary winding. This makes it possible to reduce the capacity and, consequently, the charging time of energy storage devices of testing equipment by up to 10 times or more, as well as reduce its dimensions. This solution, however, does not allow us to estimate the polarity of the voltage at which the breakdown occurred. In addition, a low-stage (2-3 steps) GIN can be used in the primary winding, which makes it possible to reduce the charging voltage of capacitors (up to 30 or 20 kV) with a slight increase in the charged capacitance (2-3 times, respectively) and increase the reliability of their operation.

3. To determine the polarity of the voltage of the secondary winding of the resonant pulse transformer on which the breakdown occurred, a pulse electric field sensor is used, located at a small (5-10 m) distance from the resonant transformer. The temporal shape of the electric field created by the voltage on the secondary winding of the resonant transformer, displayed on an oscilloscope, provides the necessary information in real time.

The technical result consists in reducing the requirements for the output voltage of testing equipment and reducing its dimensions when testing aircraft for the selectivity of lightning strikes, as well as reducing the time required to carry them out.

The specified technical result is achieved by the fact that in a known test method, a reduced model of an aircraft is subjected to electrical breakdown; what is new is that the lightning input and output currents into it are determined alternately, while the model in the first case is grounded at the bottom, and in the second - connects to the high-voltage output of the testing equipment, which is a resonant transformer with an energy storage device - a high-voltage capacitor or a low-step GIN in the primary winding; the polarity of the breakdown voltage is determined using a pulsed electric field sensor. Thus, the required length of the pierced spark gap is reduced due to the absence of its section under (when determining the entry points) and above (when determining the exit points) the model, and the dimensions and charging time of the test equipment are reduced due to the use of one capacitor as an energy storage device. Since in the known test method the GINs used have 10 steps or more, doubling the number of reproducible breakdowns in the proposed one does not lead to an increase in test time, since the capacity and its charging time are reduced by 10 times. In practice, up to 16 capacitors are used in each stage of the GIN, which reduces the charging time by up to 160 times, and in the case of using a low-stage GIN in the primary winding 13 - up to 50-80 times.

The analysis of the state of the art carried out by the applicant, including a search through patent and scientific and technical sources of information and identification of sources containing information about analogues of the claimed invention, allowed us to establish that the applicant did not find a source characterized by features identical to all the essential features of the claimed invention. Identification from the list of identified analogues of the prototype as the analogue closest in terms of the set of characteristics made it possible to establish a set of distinctive features in the claimed method that are essential in relation to the technical result envisioned by the applicant, as set out in the claims. Consequently, the claimed invention meets the “novelty” condition.

To verify the compliance of the claimed invention with the “inventive step” condition, the applicant conducted an additional search for known solutions in order to identify features that coincide with the features of the claimed method that are distinctive from the prototype. The search results showed that the claimed invention does not clearly follow from the prior art for a specialist, since the prior art determined by the applicant did not reveal the influence of the transformations envisaged by the essential features of the claimed invention to achieve a technical result. In particular, the claimed invention does not provide for the following transformations:

addition of a known means with any known part(s) attached to it according to known rules to achieve a technical result in respect of which the influence of such an addition has been established;

replacement of any part (parts) of a known means with another known part in order to achieve a technical result in respect of which the influence of such a replacement has been established;

exclusion of any part (element, action) of a device with the simultaneous exclusion of the function due to its presence and the achievement of the usual result for such exclusion (simplification, reduction of weight, dimensions, material consumption, increased reliability, reduction of process duration, etc.);

increasing the number of similar elements and actions to enhance the technical result due to the presence of just such elements and actions in the product;

execution of a known means or its part (parts) from a known material to achieve a technical result due to the known properties of this material;

creation of a means consisting of known parts, the choice of which and the connection between which are carried out on the basis of known rules and recommendations, and the technical result achieved in this case is determined only by the known properties of the parts of this means and the connections between them.

The described invention is not based on changing a quantitative characteristic(s), presenting such characteristics in a relationship, or changing its appearance. This refers to the case when the fact of the influence of each of these characteristics on the technical result is known, and new values of these characteristics or their relationship could be obtained based on known dependencies and patterns.

Therefore, the claimed invention meets the “inventive step” condition.

List of figures

In fig. Figure 1 shows the appearance of the test equipment and test object.

1 - Tesla installation

2 - High voltage electrode

3 - Pulse electric field sensor

4 - Ground plane

5 - Insulating stand

6 - Model of the aircraft

In fig. Figure 2 shows an electrical circuit diagram of the testing equipment - a resonant transformer.

7 - Resistor

8 - Capacitor IR-100-0.1

9 - Arrester

10 - Pulse transformer

11 - Toroidal container

12 - Spark gap

13 - Low-stage GIN

In fig. Figure 3 shows oscillograms of pulsed electric fields recorded near a resonant transformer.

14 - No breakdown

15 - Breakdown on the negative half-wave

16 - Breakdown on the positive half-wave

Information confirming the possibility of implementing the invention to obtain the above technical result:

To reproduce spark gaps, it is proposed to use a resonant transformer, the pulsed capacitor IK-100-0.1 or a two-three-stage GIN assembled on such capacitors is used as a pulsed power source (PS). The SMPS is placed on a dielectric stand.

The primary winding consists of two flat annular turns of copper foil insulated from each other with an outer diameter of 1.2 m.

The secondary winding consists of 2000 turns of single-core insulated wire wound on a textolite pole 3.2 m high.

The charger consists of a laboratory autotransformer that powers a high-voltage transformer, the output of which is a diode rectifier.

The control system allows you to remotely change the number of turns of the secondary winding of the autotransformer using an electric motor. A schematic electrical diagram of a resonant transformer (when using a three-stage GIN as an SMPS) is shown in Fig. 2.

The operating principle of a high-voltage resonant transformer is as follows [6]. The capacitor, charged to a voltage of 60-90 kV, is discharged into the primary winding. The discharge mode is oscillatory. The voltage on the secondary winding reaches the spark gap breakdown level.

To assess the polarity of the half-wave of the output voltage at the moment of breakdown, a pulsed electric field sensor is used. It is placed at a distance of 5-10 m from the resonant transformer. During the tests, it was found that breakdowns occur with equal probability at different voltage polarities, i.e. the number of reproducible breakdowns during testing is optimal. Typical oscillograms of electric field strengths during breakdowns occurring on the positive and negative half-waves of voltage, as well as in the absence of breakdown, are shown in Fig. 3.

The advantages of the proposed test method are as follows.

1. A practically unlimited number of reproduced pulses in a short time (the charging time of the GIN does not exceed 30 seconds).

2. High maintainability of the installation. Thus, it takes 5-10 minutes to replace a capacitor 8 GIN, 15-20 minutes to eliminate a break in the connecting wires, and 1 hour to eliminate an interturn breakdown of the primary or secondary windings of a pulse transformer.

3. Simplicity of design, mobility within the high-voltage hall and testing area, low cost.

The proposed method has a drawback - the limited dimensions of the tested model are no more than 0.74 m (with 1 m specified in [1]). These dimensions are due to the maximum length of the provided spark gap, equal to 2.84 m. The fact is that, according to the requirements of the NTD, the distance under the model must be at least 1 m.

This drawback is solved by separately studying the lightning entry and exit points into the aircraft.

When determining the “entry” points, the model in the lower part is electrically connected to a grounded plane, due to which the potential electrode is raised above the model to a maximum height (there is no need to ensure a breakdown of the spark gap under the model with a length of at least 1 m). When determining the “exit” points, the model is placed at the maximum height of the potential electrode suspension and electrically connected to it. Thus, the spark gap length provided by the installation (2.84 m) is sufficient for testing models with dimensions of 1/17 of a real aircraft or more. In this case, it is necessary to double the number of breakdowns relative to the requirements of the document, which does not create difficulties in the proposed method.

Thus, the information presented indicates that the following set of conditions are met when using the claimed invention (method):

- the means embodying the claimed method when implemented is intended for use in industry, namely in the aircraft industry;

- for the claimed method in the form as it is characterized in the independent claim of the stated claims, the possibility of its implementation has been confirmed using the means and methods described in the application or known before the priority date.

Therefore, the claimed invention meets the condition of “industrial applicability”.

Information sources

1. RTCA/DO-160G, Environmental Conditions Initiated by: AIR-100 and Test Procedures for Airborne Equipmen.06.22.2011.

2. High-voltage research center [electronic resource], http://www.vei-istra.ru/ 05.29.2023.

3. Fedorov A.A. Pulse voltage generator. RF patent for invention No. 488557/21 dated 10/08/1990.

4. Avrutsky V.A., Kiselev V.Ya., Kuzhekin I.P. Pulse voltage generators, Moscow. 1980.

5. Pichugina M.T. Powerful pulse technology, Tomsk Polytechnic University Publishing House. 2013.

6. Khvitko K.V. Current problems of energy - 2016. Design and principle of operation of the Tesla transformer. Page 516-520.

Claims (1)

A method for testing aircraft for the selectivity of lightning strikes, which consists in reproducing spark discharges in the air gap in which a model of the aircraft is placed, the largest linear dimension of which is 2.5-3 times less than the length of the air gap, in an amount sufficient for statistical processing, and determining, using photo and video recording of the location on the aircraft, areas of lightning strike and exit, characterized in that a resonant transformer is used to ensure breakdown of the air spark gap, and the entry and exit points of the lightning leader are determined separately, while when determining the lightning entry points, a model of the aircraft The device is grounded at the bottom, and when determining the exit points, the model is connected to the high-voltage output of the resonant transformer, while the polarity of the voltage at which the breakdown of the air gap occurred is determined by the readings of a pulsed electric field strength sensor located at a short distance from the resonant transformer.