FR2676547A1 - Lightning alarm device - Google Patents

Abstract

The device is designed to deliver warnings relating to the proximity of lightning strikes by using the sudden changes in the electric field which are caused by the space charge when the lightning strikes approach. Use is made, as a synthesized lightning-strike detection sensor, of a group of corona-current point electrodes 53 arranged radially on a hemispherical metal electrode 59 for detecting the electric field variations, with the interposition of insulators 54 in the shape of an umbrella. These electrodes are fixed to a support pole, whilst being insulated therefrom. A corona-current detection circuit and an electric-field variation detector 4 are attached to them. …<??>The device is particularly useful for protecting computer systems. … …

Description

The invention relates to a lightning alarm device designed for

decrease the risk of accident, which can lead to death or injury, due to lightning strikes occurring in a limited area which receives a certain number of visitors, spectators, players, etc. and to reduce accidental damage caused in places where many computers are used, forecasting from a long distance the approach of storm clouds and

correctly judging thunderstorm activities.

In recent years, automation has grown remarkably in factories, research laboratories and offices, and the use of computers in such places has become widespread, and such a trend is only continuing. At the same time, the troubles caused to computers by lightning have

remarkably increased.

Factories and offices that use many computers have an urgent need for lightning alarm systems which can announce in advance the explosion of thunder and deliver a suitable warning in good time so that in these factories and these offices, operators can take effective countermeasures beforehand, such as switching the power supply to the computers to a private power generator or removing the floppy disks from the computers in order to save.

their memories.

So many people want to be able to

have a safe lightning alarm system.

As conventional techniques relating to methods for predicting lightning strikes, there may be mentioned a radar method, a radio wave reception method, an electric field measurement method, etc. a radio wave with a wavelength of 3 to 10 cm, and groups of precipitation particles (raindrops, snowflakes, ice particles, hailstones, etc.) which fall from clouds by gravity are detected as producing an echo As convection clouds turn into thunderstorm clouds when the precipitation zone becomes greater than 7 km in summer and 3 km in winter, we can refer to this to detect thunderstorm clouds The advantages and disadvantages of radar method are as follows: (1) Carefully measure, from time to time, the

position and scale of precipitation.

(2) As a lightning explosion is judged indirectly from the top of the area of

haste, reliability is rather limited.

(3) The radar method is expensive and requires specially trained technicians for its implementation. 2 Radio wave reception method This method consists of receiving electromagnetic waves produced by lightning discharges and judging the lightning activities, to determine whether or not they are vigorous and / or whether the lightning is approaching or not, by based on the intensity and on the frequency of the received signals However, this method has the following drawbacks: (1) As it consists in capturing the radio waves produced by thunderstorm discharges, it is not possible to predict lightning before its explosion. (2) There is a certain probability that the radio waves produced by artificial noise sources can be mistaken for a discharge.

lightning.

(3) A correct estimate of the distance to

place of lightning discharges is difficult.

(4) It is difficult to distinguish a weak radio wave from nearby thunderstorm clouds from a strong radio wave from distant thunderstorm clouds. (5) A similar prediction can be obtained by practicing noise reception, by means of a

ordinary radio receiver.

(6) It is impossible to differentiate between

lightning strikes and cloud discharges.

As seen above, radio wave reception, using only a receiver, is not very efficient and, for recent times, has

is therefore not widely used.

However, a similar but more sophisticated system, called "Method for determining and locating lightning", has recently been implemented. The main characteristics of this method are as follows: The method uses more than three stations, each of which receives electromagnetic waves from lightning discharges, determine their directions of propagation and analyze their waveforms so as to

distinguish lightning strikes from cloud discharges.

The results obtained are gathered in a main station and quickly processed by computer, and the

lightning strikes positions are determined.

This method can cover a large area, such as an area having a radius of 400 km, with relatively high accuracy. However, since this method uses radio waves, errors in determining the directions cannot be avoided. In addition, this process requires the installation of expensive equipment as well as the use of a large number

specialists for operation and management.

3 Electric field measurement method: In addition to methods 1 and 2 mentioned above, there is an electric field measurement method This method proposes to measure the surface electric field and triggers an effective alarm

when the electric field exceeds a certain value.

To measure the surface electric field, there are the following three methods:

(1) Measurement of rotating electric field.

(2) Corona current measurement.

(3) Detector of variations in the electric field. Although the rotating electric field meter is capable of measuring the surface electric field consecutively, it includes rotating mechanical parts and requires a

careful and expensive maintenance.

The corona current meter has the disadvantage that the current measurement becomes unstable in the critical area of corona current formation.It is impossible to measure a corona current unless the lightning strikes are closer together than 10 km and, in order to predict the approach of lightning strikes from a long distance, it is necessary to install a lot of corona current measuring devices in a wide area. At the same time, it is necessary to install a complicated communication system linking these

devices between them.

This device is intended to measure the surface electric field which has the most intimate relation to nearby lightning strikes Although the device is suitable for knowing the risk of local lightning strikes, it is difficult to accurately predict the production lightning strikes close simply from the strength of the surface electric field because this is also affected by the charge

of accumulated space right above the ground surface.

To avoid the effect of such a space charge, one must have the corona current needles for corona current measurement at a height such that they pass through the surface space charge layer. suitably a large area with such devices, great construction expenses are necessary, since a considerable number of support poles for the needles have to be constructed and cables have to be run down

Communication.

The detector of variations of the electric field is intended to detect and count the variations of the electric field caused by lightning discharges, by measuring the variation of electric voltage induced on a metal electrode fixed to a support above the surface of the ground, but connected to the ground by means of a large counting system The number of electric field variations counted is integrated for the predetermined time interval and, when this number exceeds a value fixed in advance, an alarm is triggered According to this process, an alarm can be triggered when thunderstorm clouds are produced within a radius of about 30 km.However, to trigger the above alarm, setting the value set in advance is rather difficult and judgment as to whether thunderstorm clouds produced will or will not approach east

also difficult.

In the case where convection clouds develop just above, the detection of changes in the electric field begins only after lightning discharges have started and, therefore,

the alarm will not be triggered in time.

Among the three conventional methods mentioned above, the one which seems relatively

reliable is the electric field measurement method.

The present invention firstly proposes, by studying and developing the function of said corona current measuring apparatus (2), a method for predicting the approach of nearby lightning strikes which

could cause a fatal and serious disaster.

Second, by combining said technique (3) for detecting variations in the electric field and the corona current measuring apparatus (2), the present invention provides a multiple object lightning alarm device, which is based on on the information relating to the total lightning activity over an area ranging from a long distance of about 30 km in radius to a very short distance just above The present invention makes use of the following nature of the electric field and of the variation of the electric field The minimum amplification of the variation of the electric field detector for distant lightning discharges is proportional to the distances of the discharges, in the case where they have the same discharge value The corona current due to the electric field

surface area varies with the square of the electric field.

The multi-object lightning alarm device, according to the present invention, is simple and is also capable of providing the user with the information as to whether or not lightning discharges occur at a great distance, whether or not they occur. are approaching or not, and whether or not convection clouds just above are growing in thunderstorm clouds All of this information is essential to prevent serious lightning accidents and to protect electronic property and instruments from damage. damage caused

by lightning.

Use of the present invention may be more practical than installing expensive systems such as radar stations or so-called lightning tracking systems. Use of the present invention simultaneously with such systems will increase.

enormously the efficiency of the complete system.

Two characteristics will be described below

important aspects of the present invention.

1 Detection of nearby lightning strikes According to the present invention, when a sudden change in the polarity of the corona current is caused by a lightning strike, the currents measured just before and just after this sudden change provide valuable information. There is a large difference between the current before the change and the current after the change, and the greater the load consumed by the lightning strike In addition, the greater the ratio of the current before the change to the current after the change, and the greater the l The effect of the space charge near the ground surface is large As this space charge forms to be greatest just below the center of the charged cloud, the larger ratio indicates that the charge density d space is stronger and therefore the center of the

cloud is closer to the observation site.

The user of the present invention can note the approaching arrival of lightning strikes by observing a graph displayed on the chart recorder connected to the device, or by adjusting the predetermined positions of the positive and negative relay hands attached to the relay. from the measuring device, or by actuating the logic circuit which automatically triggers a nearby lightning strike warning. 2.New arrangements of electrodes for measuring the corona current and detecting variations in the

electric field.

With regard to needle electrodes with corona current and electrodes for detecting variations of the electric field, several problems still remain For the problems due to the fact that the corona current varies irregularly at the level of the critical electric field during the installation of the crown current, according to the present invention the number of needle electrodes with crown current is increased in order to equalize the irregularity For this purpose five groups of six isolated needle electrodes with crown current are installed. radially on a hemispherical electrode. Under a strong electric field, a pulsed corona current flows from the electrode for detecting variations in the electric field and disturbs the detection of variations in the field When raindrops or snowflakes strike the electrode for detecting -variations of the electric field under the same condition, a disturbing pulsed current also circulates To avoid a faulty operation caused by the pulsed currents, provision is necessary so that the electrode for detecting the variations of field is not exposed to a very strong electric field Seloon the present invention, this problem has been successfully solved by adopting a synthesized electrode system, that is, groups of corona current needle electrodes are arranged radially on one electrode hemispherical detection of electric field variations, which detects the variations of the magnetic field and reduces the

electric field applied to a hemispherical electrode.

In the accompanying drawings: Figure 1 is a representation which shows the relationship between a storm cloud serving as a model and a surface electric field; Figure 2 shows the changes over time of the surface electric field recorded at a point (A) in Figure 1, as the storm cloud moves in the direction shown by an arrow Figure 3 is a representation which shows the relationship between needle electrodes and the space charge above the ground surface, under a usual thunderstorm cloud; FIG. 4 is a representation which shows the distribution of the space charge at the periphery of the needle electrodes, just after a lightning strike; Fig. 5 is a representation which shows the charge distribution in a thunderstorm cloud, the space charge above the ground surface and the distribution of lines of electric force which indicates the main electric field; FIG. 6 is a representation just after a lightning strike (discharge of the cloud towards the ground). It shows how the electric field of the

figure 5, -

Figures 7 (a) and 7 (b) are examples of recordings of sudden changes in the surface electric field caused by nearby lightning strikes; FIG. 8 is a block diagram showing a system for detecting variations in the electric field; Fig. 9 is a view which shows a microammeter with two preset needles forming relay contacts which are fixed on both sides of the zero point. The preset zero point is disposed in the center of the microammeter; Fig. 10 is a side view which shows a synthesized lightning detection sensor consisting of a hemispherical metal electrode for detecting variations in the field and groups of corona current needle electrodes disposed radially on the hemispherical electrode detecting variations in the field; FIG. 11 is a diagram of the lightning alarm device according to the invention, in which the circuit for detecting nearby lightning strikes is connected to the synthesized lightning detection sensor of FIG. 10; and FIG. 12 is a block diagram of the lightning alarm device according to the invention, which triggers an object lightning alarm

multiple.

We first refer to Figure 1 which shows a storm cloud model and the corresponding electric field In the figure, the observation site indicated in (A) corresponds to a region with good weather o

the surface electric field is directed downwards.

The site indicated in (B) is just below a thunderstorm cloud where the surface electric field is directed upwards, and the site indicated in (C) is a site where the surface electric field changes direction Figure 2 is a recording over time of the surface electric field observed initially at the site (A) of Figure 1 and continuously during the period when the storm cloud moves in the direction shown by the arrow The electric field changes suddenly and its absolute value is reduced, as represented by the small arrows, each time lightning discharges occur. The nearby lightning strike detection circuit monitors sudden variations in the surface electric field on the graph of a recorder connected to the microammeter, detects sudden variations of very large amplitude as shown in P in figure 2, and judges whether the shots

lightning approaching near the observation site.

We will now describe how

works each part of the device according to the invention.

1 Detection of nearby lightning strikes.

It is well known that under the base of a cloud (usually the lower part of clouds are negatively charged), above the ground surface a space charge of opposite polarity to that of the cloud charge forms. Figures 3 and 4 show the distribution of the space charge in the vicinity of a synthesized lightning detection sensor, before and after lightning strikes Figure 5 shows typically an example of the distribution of the electric charge d 'a stormy cloud and the electric field just before lightning strikes Due to the negative electric charge at the lower part of the cloud, a space charge is formed under the base of the cloud, represented by D The electric field becomes strongest at the lower edge of the negative electric charge in the cloud, and a lightning strike starts from this position The electric field is directed upwards at the location of the observation site A in figure The field electric is of about 5-v 10 kv / m due to the effect of space charge Figure 6

shows what the state is immediately after a lightning strike.

Although most of a cloud's negative charge is discharged into the ground during a lightning strike, the space charge remains as it was As a result the surface electric field changes direction, as is indicated by the lines of force in the figure, and the absolute value of the surface electric field remains roughly the same or becomes a little higher than that just above the

love at first sight.

As the surface electric field is continuously recorded on a diagram, its sudden variation caused by the lightning strike can be digitally processed.Xa represents the absolute value of the surface electric field measured at the observation site A of figure 5 just before lightning strikes and by Xb that measured at the same site just after lightning strikes The absolute value of the electric field at the same place just before lightning strikes, assuming that there is no space charge, is represented by X This electric field X is obtained by subtracting the electric field Xb due to the space charge from the electric field Xa, i.e. X = Xa (-Xb) = Xa + Xb On the other hand, according to the present results of the lightning study, it is estimated that the electric potential of the center of the negative charge in thunderstorm clouds is 10 V, and its height above the ground is 5 x 10 m We can therefore sketch the following relation X = 10 = 2 x 10 V / m = 20 k V / mx 103 Therefore, even when the present device does not obtain a correct reduction factor for an absolute measurement, an estimate can be made of an approximate absolute value of the surface electric field For example , if the values Xa and Xb are equal before and after the lightning strike as shown in figure 7 (a and b), we can obtain the following approximate estimate: Xa + Xb = X 20 k V / m, Xa = Xb therefore Xa = Xb = 10 k V / m, Xa and Xb are directed towards the

up and down respectively.

If Xb is approximately twice Xa in absolute value as shown in Figure 7 (b), we can

get the following relation.

Xa + Xb = 20 k V / m, Xb = 2 Xa So approximately Xa = 7 k V / m and Xb = 13 k V / m Similarly, Xa and Xb are directed upwards and

down.

The above is an estimate

approximate numerical value for a typical storm cloud.

The fact that the magnitude of the sudden change in the electric field Xa + Xb = X is large, means that the amount of the electric charge expended by a lightning strike is large Similarly, the fact that the ratio Xb / Xa is large means that the effect of the space charge is important As the space charge formed is greater just below the center of the thunderstorm cloud, we can estimate that the greater the ratio Xb / Xa, the greater the center of the thunderstorm cloud is close to the observation site For example, if the magnitudes 8 X, in Figures 7 (a) and 7 (b) are approximately the same and if the value of Xb / Xa in Figure 7 (b) is two times that of figure 7 (a), we estimate that the center of the storm cloud is much closer to the observation site in the situation of figure 7 (b) by

comparison with that of Figure 7 (a).

In this regard, the fact that the two quantities mentioned above are gradually increasing indicates that a strong thunderstorm cloud is approaching. Also, according to the present invention, the approach of lightning strikes can be automatically detected either by means of the preset positive and negative relay needles of a microammeter with relay contacts, or by using a logic circuit of a semiconductor.

2 Multi-object lightning alarm device.

It comprises a hemispherical metal electrode for the detection of variations in the electric field, which is fixed to the surface of the ground, and a corona current needle electrode, this electrode being mounted, through an insulator, on the The hemispherical metal electrode being integral with it Detection of nearby lightning strikes has the additional function of delivering a first warning when either a detector of variations in the electric field connected directly to the hemispherical metal electrode for detecting variations of the field, or a crown current detection circuit connected directly to the crown current hands, is activated separately, and to issue a second warning when these

are activated simultaneously.

Since the value of the surface electric field and the value of its sudden variations are sufficiently large in the area indicated at K in Figures 1 and 2, the detector of the variations of the electric field and the corona current detection circuit connected to the microammeter operate. little

nearly simultaneously.

As already mentioned, the device of the present invention also includes the near lightning strike detection circuit and delivers a "near lightning strike warning" as a final emergency alarm. Accordingly, the multi-object lightning alarm device of the present invention can easily judge whether a thunderstorm is approaching, whether the risk of lightning strikes increases due to the approaching lightning.

lightning strikes, and if the storm recedes.

3 Adjusting the sensitivity of the variation detector

of the electric field.

FIG. 8 is a block diagram showing an electric field variation detector which comprises a low frequency amplifier 41 with gain switch, an electric field variation counting circuit 42, a timing circuit 43, and a trigger circuit 44. The sensitivity of the detector to variations in the electric field is proportional to the gain (the unit of which is db) of the low-frequency amplifier (in the figure, i represents the input side and O the

output side).

Assuming that the gain of the low frequency amplifier remains the same, the sensitivity of the detector to changes in the electric field becomes high when activated by counting a small number of changes over a period of time.

relatively long (the unit is the minute).

Accordingly, the basic sensitivity adjustment is achieved by operating a switch on the low-frequency amplifier (usually equipped with

a three-position switch of the Odb / 20 db / 30 db).

A fine adjustment is achieved by the combination of the circuit for counting the variations of the electric field (usually equipped with a five-position switch going from the first time to the fifth time) and the timing circuit (usually equipped with a switch to three one-minute positions, three

minutes and five minutes).

In figure 8, the sensitivity becomes strongest when the low-frequency amplifier is at the 30 db position, the electric field variation counting circuit is at the "once" position, and the timer circuit is at the position five minutes, and monitoring can be carried out over an area of one

little more than 30 km radius.

4 Synthesized lightning detection sensor.

With reference to FIG. 10, a synthesized lightning detection sensor will be described consisting of the combination of synthesized lightning constituted by the combination in a single element of a hemispherical metal electrode for detecting the variations of the field and of a group of 'crown-current needle electrodes disposed radially on an electrode

hemispherical through an insulator.

An umbrella-shaped insulator is mounted at the top of each of the metal tubes 55 which are installed radially on a hemispherical metal electrode 59 for detecting field variations. Several tapered bosses 52 are arranged on the top surface of a metal base 51 of rounded shape mounted at the end of the insulator Crown current needle electrodes 53, having a somewhat pointed tapered end are mounted radially on the metal base 51, removably, at suitable intervals These needle electrodes corona current are all electrically and integrally connected, by means of a conductive wire, to the internal face of the hemispherical metal electrode for detecting the variations of the field, in an isolated state of the current needle electrodes The crown-current needle electrodes 53, the metal base 51 of rounded shape, etc. are made of a material conductive such as stainless steel However, the present invention is not limited to this material The number of needles ext fixed so that a metal tube element 55 comprises six corona current needle electrodes 53 As the electrode hemispherical metal 59 for detecting the variations of the field is equipped with five elements in metal tubes, it is a total of thirty needle electrodes with crown current 53 which are disseminated radially to detect the crown current One can use, as needles of the electrodes needle with a crown current, medical needles or similar needle electrodes (hereinafter referred to simply as

as "injection needles").

Reference numeral 51 denotes a rounded metal base, which is a true circular ball. The rounded metal base 51 is not necessarily a circular ball; it * can also be a ball of any similar configuration or of an elliptical shape as long as it is of a configuration which makes it difficult to break

by the corona current.

Reference numeral 52 denotes tapered bosses which protrude radially on the upper surface of the metal base 51 at suitable intervals An injection needle 53 for constituting the crown current needle electrodes is mounted, so that they can be replaced, on each of the bosses 52 by engaging means, etc. In the drawing the reference numeral 54 designates the umbrella-shaped insulators, the numeral 55 the metal tubes, the numeral 56 the insulators, the numeral 57 the shafts, the number 58 the connection terminals, and the number 59 a hemispherical metal electrode for detecting the variations of the field If we equip an element with too many needle electrodes with crown current 53, the

corona current is saturated and therefore undesirable.

As such a group of corona current needle electrodes 53, installed radially on a hemispherical electrode, is normally disposed outside, these are subject to nuisance from birds and insects. corona current needle electrodes 53 are provided, this does not result in significant damage even if several corona current needle electrodes are damaged The corona current produced by the bursting of a thunderstorm varies significantly over the course of a storm.

level of the current value at the start of the storm.

However in this case, since several needles are used, the corona current discharges are averaged. In addition, the action on the electric field may be from a diagonal direction, depending on the geographical conditions and the place of installation However, this does not result in any significant difference in the sensitivity of the device of the present invention, due to its construction. When the device is installed in a high place, which can be subjected to heavy rain from a lateral direction, the configuration of the hemispherical metal electrode 59 for detecting the variations of the field does not necessarily require a hemispherical shape. use a shape very close to that of a ball Also, when the installation takes place on a high mountain where the storm approaches from a lower altitude, several metal tubes are sometimes installed radially, fixed to the metal base 51 of rounded shape, provided at their upper end with needle electrodes 53 with crown current, so that they

look down.

As the storm clouds approach, a large amount of corona current flows from the corona current needle electrode group

installed radially on a hemispherical electrode.

As a result, when a significant amount of negative charge is at the base of the clouds, as shown in Figures 3 and 4, a weak crown erupts from grass, trees, rocks or other substances that make protrudes near the surface of the ground, and a discharge of positive ions occurs. However, since ions in particularly large numbers are produced at the top of the synthesized electrode of the present invention, due to its structure, the sensitivity detection of nearby lightning strikes is improved and extremely efficient. In general, when the pulsed current flows to the electrode to detect changes in the electric field, sometimes the sensor for changes in the electric field may malfunction. One of the reasons for such malfunction is that the current crown flows to the electrode (because the crown current is a pulsed wave), another reason is that the raindrops or snowflakes hit the electrode or attach themselves to it (in this case, it there is also a circulation of a pulsed current) In any case, a large amount of electric field acts on the electrode for detecting variations in the electric field. However, the hemispherical metal electrode 59 for detecting variations in the field according to the present invention has a rounded shape and the head portion of each of the metal tubes 55 is also covered by a round umbrella-shaped insulator In addition to the end portions of several of the needle-curved electrodes 53 t crown are positioned on the upper part of the hemispherical metal electrode 59 for detecting field variations As a result, the electric field is concentrated on the ends of the needles of the group of crown current needle electrodes which are installed radially on a hemispherical electrode, just below the thunderstorm clouds It follows that the hemispherical metal electrode 59 for detecting the variations of the field does not directly receive a large quantity of electric field and there is therefore no reason to fear a malfunction of the sensor

variations in the electric field.

It also happens that an abnormal current flows through the corona current needles, causing a malfunction. This is the case when electrified raindrops hit the hemispherical metal electrode part 59 for detecting the variations of the field, the charge of the raindrops being transferred to the hemispherical metal electrode 59 for detecting the variations of the field and this charge accumulates in the electrode 59, although this is for a short period of time Even if the state of the electric field is not such that corona current flows from it, sometimes current flows from the hemispherical metal electrode for detecting field variations to the corona current needle electrodes, causing malfunction. , as the umbrella-shaped insulator 54 achieves perfect insulation, the charge of raindrops cannot be a cause of

malfunction.

Embodiment synthesized from the above Figure 11 shows an embodiment of a lightning alarm device connected to a nearby lightning strike detection circuit using the close lightning strike detection according to the present invention. resistor 20 of high value is connected between the hemispherical metal electrode 59 for detecting the variations of the field and an earth electrode 2 At 53, crown-current needle electrodes have been designated, at 54, umbrella-shaped insulators, at 7 a direct current amplifier, at 8 'a microammeter with relay contacts, the center of which is zero and both sides of which are provided with preset relay tips, as shown in figure 9, and at 10 a relay circuit attached to the microammeter 8 ', the latter and the relay circuit 10 being connected to the direct current amplifier 7 A contact for positive current of the relay circuit 10, attached to the micro ammeter 8 ', is connected to relay 11 and a contact for negative current is connected analogously to relay 12 Numbers 13 and 14 denote auxiliary circuits (return time: 0.1 G-, 0.5 sec), 15 designates a relay which is actuated when the positive current contact and the negative current contact are actuated simultaneously, and 19 designates an alarm circuit for

to produce a "near thunderbolt warning".

In this embodiment, the microammeter with the relay contacts is used to detect sudden changes in the polarity of the corona current.However, this part can be replaced

by a logic circuit of a semiconductor.

Finally, FIG. 12 shows an embodiment of a lightning alarm device which uses a multiple object lightning alarm device according to the present invention. At 59, a hemispherical metal electrode of detection of variations in the electric field, at 2 an earth terminal, and at 4 a detector of variations in the electric field which outputs signals for a predetermined time (approximately 30 sec). In 53, crown-current needle electrodes have been designated , at 54, umbrella-shaped insulators, at 7 a direct current amplifier whose sensitivity can be adjusted, at 8 and 8 'micro-ammeters (see figure 9) with relay contacts, the center of which is zero and whose two sides are provided with pre-set needles, and at 9 and 10 relay circuits attached to the microammeters 8 and 8 ', elements 8 and 9 and elements 8' and 10 being connected to the DC amplifier 7 The circuitrelay 9 attached to a micro-ammeter 8 is actuated by the pre-set needles in relation to the quantities of positive current and negative current On the other hand a contact for positive current of the relay circuit 10 attached to the micro-ammeter 8 'is connected to relay 11 , and a contact for negative current is connected analogously to relay 12 Reference numbers 13 and 14 designate auxiliary circuits (return time: 0.1 -v 0.5 sec), 15 designate a relay which is actuated when the contact for positive electric current and the contact for negative electric current are actuated approximately simultaneously, 17 designates a circuit giving a "first warning" 18 designates a circuit giving a "second warning" and 19 designates a circuit giving a "warning of love at first sight ". When the electric field variation detector 4 is actuated to produce an output signal or when corona current flows through the corona current needle electrodes 53 and when the relay circuit 9 attached to the microammeter 8 is actuated so as to pass the pre-set needles (both positive and negative side) of microammeter 8 to output a warning signal, the "first warning" warning circuit 17 is controlled provided one

any of the warning signals is output.

When the two above-mentioned signals are output almost simultaneously, the warning circuit 18 of the "second warning" is controlled. In the case of nearby lightning strikes, for example, a thunderstorm cloud is near and the corona current already exceeds the preset negative needle of the 8 'microammeter When lightning strikes then occur, the polarity of the corona current suddenly changes and a positive corona current sometimes escapes beyond the positive preset needle.However, as the negative charge at the base of the cloud increases as time passes, the current value of the microammeter is reduced and the needle returns to the position that was his

before lightning strikes occur.

The corona current value just before this change is represented by Ixa and the corona current value just after this change is represented by Ixb The position of the microammeter needle suddenly moves from Ixa to Ixb due to lightning strikes When the two relays 11 and 12 are controlled almost simultaneously by passing the preset positive and negative needles which are determined taking into account the values of Ixb Ixa and Ixb / Ixa, the relay circuit is controlled by the auxiliary circuits 13 and 14 for activate warning circuit 19 of

the near lightning strike warning ".

If the preset needles of the microammeter 8 'have been positioned taking into consideration the value of Ixb Ixa and the value of Ixb / Ixa, so that Ixa and Ixb can be compared, a warning can be issued when the probability of a stroke close lightning strike increases Also, the measuring relay part can be replaced by a

logic circuit using a semiconductor.

Even in the event that a lightning strike strikes a metal pylon supporting power transmission lines that is at a remote distance, factories and offices with a computer-controlled system that uses a lot of power may be found. computers suffer enormous damage due to interruption of service or instantaneous voltage drop According to the lightning alarm device of the present invention, the detector of variations in the electric field can detect relatively lightning activity. distant and semi-distant and rapidly developing lightning activity just above it is immediately picked up by the corona current detector and

corresponding alarms can be triggered.

The approach of a nearby lightning strike point can also be detected by the near lightning strike detection circuit indicated above and

a nearby lightning strike alarm will be triggered.

In this way, by foreseeing the possibilities of significant damage due to lightning in factories and computer-controlled offices on a large scale, by means of a lightning alarm device according to the present invention based on the device of lightning. multiple object lightning alarm, a disaster can be avoided by using effective countermeasures such as

connection to a private power supply.

In addition, since the lightning alarm device of the present invention is capable of correctly delivering a timely warning of the outbreak of a thunderstorm in a limited area, such as a soccer field, a baseball field or construction sites, where there are a large number of people, it can be of great help in preventing a lightning accident that may have

resulting in many deaths or injuries.

The lightning alarm device of the present invention can also be used to predict lightning strikes and the accompanying abnormal air blasts, which make aircraft take-off and landing operations dangerous, and to locate aircraft. storms by an appropriate adjustment of its

sensitivity.

As is evident from a description which

above, the present invention makes possible the early delivery of a warning signal by correct prediction of lightning strikes regardless of whether the lightning strikes are those that enter a monitored area or consist of a lightning strike.

lightning burst just above.

Since the lightning alarm device according to the present invention does not require a large space or location for its installation and does not require large support posts, since it takes advantage of the phenomenon of space charge, its maintenance proves easy The application of the invention is particularly suited to places such as airports, where obstacles of great height are not welcome. Furthermore, if the invention is used at the same time as information obtained by radar In an airport, predictions of high probability can be obtained. As the device is inexpensive and the installation costs are low, the lightning alarm device according to the present invention is economical In addition, as even a hobbyist can use it easily and since the invention is hardly likely to cause discomfort, there is little maintenance which is a significant advantage.

Claims (4)

1 Lightning alarm device, characterized in that its essential part consists of a nearby lightning strike detection circuit which measures the corona current flowing through needle electrodes to corona current (53), which compares a value of corona current Ixa just before the sudden changes in polarity due to the lightning strike and a value of corona current Ixb just after the sudden changes in polarity which indicates the presence of lightning strikes, and which automatically delivers a warning of stroke lightning strike when a preset value is exceeded, which is set taking into account the first the values of Ixb Ixa and of Ixb / Ixa. 2 A lightning alarm device according to claim 1, characterized in that the nearby lightning strikes detection circuit measures the corona current by means of a group of corona current needle electrodes (53) which are disposed radially on a hemispherical shaped electrode (59), and automatically delivers a "near thunderbolt warning". 3 A lightning alarm device according to claim 1, characterized in that it further comprises a synthesized lightning detection sensor which is integrally formed of a group of needle ring current electrodes (53) installed radially on a hemispherical electrode comprising a hemispherical metal electrode for detecting variations in the electric field (59), metal tubes (55) disposed radially on said metal electrode (59) insulators (54) in the form of an umbrella mounted on the parts tops of said metal tubes (55), a plurality of tapered bosses (52) projecting radially from an upper surface of a rounded metal base (51) mounted on each of said insulators (54), and current needles ring which are each removably mounted on each of said tapered bosses (52), said group of ring current needles installed radially on an electro hemispherical (59) being connected to said nearby lightning strike detection circuit and to a corona current detection circuit, said hemispherical metal electrode (59) for detecting variations in the electric field being connected to a field variation detector electric (4), a "first warning" being triggered when said electric field variation detector (4) and said crown current detection circuit are actuated separately, a "second warning" being triggered when said field variation detector electric (4) and said crown current detection circuit are actuated simultaneously, and a "near lightning strike warning" being triggered when said detection of nearby lightning strikes is activated. 4 A lightning alarm device according to claim 3, characterized in that the detector of variations in the electric field (4) consists of a combination of switches with several positions capable of adjusting the gain of an amplifier (41) , the number of counts of an integrator of sudden changes in the electric field (42), a timer circuit (43), etc. among circuits for counting the frequency of sudden changes of the electric field. electric field for a predetermined time.