Methods to combat LPP icing. Method for preventing icing of air lines of AC power lines

Kuvinov A.A., D.T., Togliatti State University;
Karmanov V.F., General Director,
Akhmetzhanov N.G., Chief Specialist of Energy T LLC (Togliatti);
Skuropat I.A., Ph.D., CJSC "GK" Electrical TM-Samara ", Samara;
Galiyev I.T., Postgraduate Student of the Department by Nou Mei,
Aleksandrov N.M., graduate student of the Department of Aero Hesgt;
Khrennikov A.Yu., D.T.N., JSC "NTC FGC UES"

Introduction

When operating air lines (VL) power transmission in a number of regions, there is a serious problem icing of wires in the autumn-winter period, since the average time of elimination of holoid accidents exceeds the average time to eliminate accidents caused by other reasons, 10 or more times. Studies show that holly deposits on the wires of the WL occur at the air temperature of about minus 5 ° C and wind speed of 5-10 m / s. The permissible thickness of the wall of the ice coupling is from 5 to 20 mm for a voltage voltage of 3-330 kV, located in climatic areas of ice I-IV categories.

As a passive measure to combat ice, various high strength wires can be used. For example, AssC Wire (Aluminum Conductor Composite Core - aluminum wire with a composite core from various materials. The Conductor Conductor ACCC is stable in size, since the thermal expansion coefficient (1.6.10-6 ° C-1) is almost an order of magnitude less than steel ( 11.5.10-6 ° C-1). Therefore, the ACCC wires allow for a long time to withstand a high temperature, preventing the formation of ice.

The Aero-Z® wire should also be noted, which consists of one or more concentric layers of round wires (internal layers) and wire with a cross section in the form of "z" (external layers). Each layer of wire has a twist in length, made with a certain step. The smooth surface reduces wind loads by 30-35% and prevents the smell of snow and ice. However, the Aero-Z® wire has a limitation on ice-wing, because it does not allow a long-term increase in the temperature above 80 ° C.

In general, the practical implementation of passive methods of combating ice is possible only when designing and implementing new power lines. The reconstruction of the "old" ll is related to significant costs.

Therefore, it does not lose the relevance of the task of developing active methods for combating holly deposits on wires of the WL. The traditional methods can be attributed to ice floats on the wires of the variable current by artificially creating short circuits or direct current using unmanaged or controlled rectifier blocks. However, in the first case there may be damage to the wires of the WL, and in the second case, expensive rectifier blocks are not used most of the calendar year. At the same time, the current state of the elemental base of power electronics opens additional features and stimulates the development of new methods of combating holly deposits free from these shortcomings. A large number of scientific publications are devoted to issues of research of holly education and combating holly deposits. This paper is set to the task of systematization and comparative analysis of existing methods of combating holly deposits, the solution of which will make it possible to choose from the existing set of technical solutions the most rational for local conditions.

Classification of ways to combat holly

Known devices and methods use the following types of physical impact to remove holly-frozen sediments from power lines wires (Figure 1):

• thermal exposure by heating the wire to a temperature of 120-130 ° C, in which the holled coupling is melted, or by prophylactic heating of wires by 10-20 ° C to prevent the formation of ice;
• the thermodynamic effect by preheating to the formation of a flooded interlayer between the wire and the ice coupling and the subsequent "shaking of the wires of the ampere force" arising from passing a powerful current pulse;
• electromechanical effects by periodic transmission of current pulses causing mechanical oscillations of wires and destruction of the holled coupling; The efficiency of electromechanical effects is enhanced with such parameters of current pulses, which cause mechanical resonance;
• the mechanical effect by moving the screws along the wire using wind energy, the energy of the electromagnetic field of the phase current voltage, permanent magnets, a linear asynchronous motor or the creation of wire vibrations using a mechanical oscillation generator (is not considered in the future, since it is practically not used).

Figure 1 - Classification of methods for removing holled sediments from wires VL:

WC - managed rectifier;

STK - static thyristor compensator;

PC - frequency converter;

Nfch - direct frequency converter;

COP - longitudinal compensation device

One should only note the overall disadvantage of mechanical systems, which consists in the need for manual installation on a wire, removal from the wire, as well as a move from one wire to another. This requires a special technique (auto) and attendant personnel, which increases operating costs and makes it difficult to use in hard-to-reach areas.

Thermal impact of alternating current

Melting ice alternating current is used on a voltage of 220 kV with wires with a cross section of less than 240 mm2. The power source serve as a rule, 6-10 kV tires substations or a separate transformer. The ice melting scheme should be chosen in such a way as to ensure the flow of Current wires by 1.5-2 times higher than a long allowable current. Such an excess is justified by the short-term smelting process (~ 1 h), as well as more intensive wire cooling in the winter. For steel aluminum wires of type AC with a cross section of 50-185 mm2, the approximate value of the one-hour current of ice icewell lies within 270-600 A, and the current warning the formation of ice on the wires - in the range of 160-375 A.

However, only due to the selection of the ice melting scheme, it is often impossible to choose the required short-circuit current. Exceeding the above values \u200b\u200bof the melting current can lead to an annealing of wires, followed by an irreversible loss of strength. With smaller values \u200b\u200bof one-time transmission of short circuit, it may not be enough to completely remove the ice. Then short circuits have to repeatedly repeat, which additionally takes the consequences.

Avoid these negative consequences allows the use of a thyristor alternating voltage regulator, the diagram of which is presented in Figure 2. In the ice melting mode, the switch 7 is turned off, the switch 8 is turned on. Possible methods Melting current control is a pulse-phase by changing the angles of incorporation of power thyristors 1, 2 and 3 or a pulse latitude - by changing the number of voltage flow periods.

Figure 2 - Installation to compensate for reactive power and ice ice

In the reactive power compensation mode, the switch 7 is turned on, and the switch 8 is turned off. In this case, the power thyristors 1, 2, 3 and reactors 4, 5, 6 form a thyristorno - reactor group connected into a triangle, which is an element of a static thyristor compensator. The authors also allow the possibility of using capacitors instead of reactors. In this case, the compensation of reactive power will be carried out using an adjustable capacitor battery.

However, regardless of the method of regulating, the ice drill is carried out by an alternating current of the industrial frequency and requires significant power supply capacities (tens of MB.A), since the active resistance of the airline wires is significantly less inductive resistance. Full power The source increases due to the large and useless for melting ice of the reactive load. It is possible to increase the efficiency of smelting by the longitudinal capacitive compensation of inductive resistance in the case of using capacitors as part of the proposed installation. However, the authors did not consider this opportunity.

The combined installation to compensate for the reactive power and melting ice, the scheme of which is presented in Figure 3, deserves attention. In the ice melting mode, the switch 7 is turned on, by shunting the reactor 6, the switch 9 turns off the condenser battery 8, and the switch 10 is turned on. It is possible to smell on all wires of the airline simultaneously.

Figure 3 - Combined installation for compensation for reactive power and ice ice melting

In the reactive power compensation mode, the switches 7 and 10 are disabled, and the switch 9 is turned on. As a result, a typical scheme of a static compensator based on transistor modules 1, 2 and 3, reactors 5, 6 on the side alternating current and condenser battery 8 on the side direct current. Such a structure can operate both in generation mode and in the consumption mode of reactive power.

An essential deficiency of the installation depicted in Figure 3 is the incomplete use of the valve part in the melting mode. This is explained by the fact that the melting current flows only through the "lower" keys of phases 1, 2 and 3 of the converter bridge. To convert a bridge circuit in three AC keys, additional switching equipment and a significant complication of the power scheme will be required.

Thermal impact of constant current

For the first time, Introduced by a constant current as a promising direction for the struggle against holly deposits on the VL phase wires was noted in. Among the first serial melting plates of ice, the DC-16800-14000 converters, made according to the Larionov scheme on the basis of silicon unmanaged VK-200 valves with a straightened 14 kV voltage, rectified with a current of 1200 A and a 16800 kW output. Wood melting schemes with a straightened current are considered in detail.

The disadvantages of the method should include what should be turned off, and the rectifier block is not used most of the calendar year, since the need for ice melting occurs only in winter. It is possible to note the offer of ice effer the pulsating current without turning off the VL. The rectifier block is turned on in the wrapping of the heated wire so that the constant current does not flow through the windings of power transformers and current transformers. Wiring heating is carried out by a pulsating current containing a variable component determined by the load of the VL, and a constant component determined by the straightened voltage and the active resistance of the melting circuit. However, such a proposal does not increase the use of rectifying blocks, but for practical implementation Requires additional switching equipment.

In this regard, the expansion attempts are fulfilled functionality By combining in one installation of the rectifier block for ice ice and devices for compensating reactive power. This opens up the possibility of year-round operation of equipment, which significantly increases its economic efficiency.

In NIIPT OJSC, a container-type converter device has been developed for the combined installation of ice ice melting and reactive power compensation (Figure 4).

Figure 4 - diagram of a conversion device of a container type (a) and a combined installation (b) ice ice ice and compensation of reactive power

The conversion device (Figure 4) includes:

• transport container 1,
• thyristor modules 2 with control blocks 3,
• forced air cooling system 4,
• disconnector 5 with electromechanical drive 6,
• anode 7, cathode 8 and phase 9 converting bridge conversion,
• control system, regulation, protection and automation 10,
• disconnectors 11, 12 and condenser batteries 13.1, 13.2 and 13.3.

Power equipment is intended for operation in areas with a temperate and cold climate (UHL 1) and placed in a closed steel container, installed on the open part of the substation foundation. Power supply is carried out from the winding of 10 kV of the selected transformer. From the converter devices depicted in Figure 4A, a combined installation is collected, the diagram of which is shown in Figure 4.

In the ice melting mode, disconnectors 11, 12 are closed (Figure 4B), disconnectors 5 (Figure 4a) are open. A diagram of a three-phase bridge rectifier is assembled, which provides a nominal straightened voltage of 14 kV, the rated current of smelting 1400 A and the regulation of the melting current in the range of 200-1400 A.

In the reactive power compensation mode, the disconnectors 11 and 12 are open, and the disconnectors 5 are closed. A circuit of a capacitor battery 13.1, 13.2 and 13.3, controlled by thyristor modules 2, connected ones - in parallel. However, in compensation mode, only stepwise regulation of reactive power is possible.

The last disadvantage can be avoided in a combined installation for ice ice and compensation of reactive power, the scheme of which is presented in Figure 5 (Development of NIIPT OJSC).

Figure 5 - Combined installation for ice ice ice and reactive power compensation

The combined installation includes a supply transformer 1, three-phase disconnectors 2 and 16, three-phase reactors 3 and 15, high-voltage bridge converter 4, DC condenser battery 5, single-phase disconnectors 6 and 7, control system 8, assembly 9-14 fully controlled devices with reverse diodes and resonant transformer 17.

In the ice melting mode, disconnectors 6, 7 and 16 are included. Melting is carried out by constant current. The regulation of the melting current is carried out by the method of high-frequency PWM. For example, when passing a load current through assembly diodes 13 and 10, a fully controlled device from the assembly 9 or 14 is connected in PWM mode. At the same time, the contour of the two-phase short circuit 9 - 10 or 13-14 is briefly formed. The load is spun, and the melting current is adjustable. The rate of increasing the short circuit current is limited to the reactor 3. By selecting the frequency and the coefficient of PWM modulation, the thyristor locking takes place before increasing the short circuit current to a dangerous level. In this case, the conductivity interval of a thyristor is less than in reactive power compensation mode. In reactive power compensation mode, disconnectors 6, 7 and 16 are disabled. The high-voltage bridge converter 4 works in the "Stat" mode.

According to a number of authors who rely on their own experience, only from 7 to 30% of the length of the heated wire during smelting is really covered with ice. This is explained by the fact that the individual sections were due to the corners of the turn and the inability to predict the direction of the wind at the time of the formation of the holly turn out in various climatic conditions. Accordingly, a significant part of electricity is wasted. In this regard, proposed mobile installationwhich allows you to travel to the VL plots in which the wiring is found.

Mobile generator For melting ice on wires, the WL is performed on the car platform, the power supply (0.4 kV) of the three-phase rectifier bridge is carried out from two diesel generators of the ADV320 320 kW each. Conductors with terminals are provided for connecting to wires VL and electric tires for connecting wires on the span between the supports according to the ice melting scheme. The considered technical solution provides ice float at the length of the two flights of the airline on phase wires and a threaker cable.

The general disadvantage of all devices that implement the thermal exposure to constant current is the need to apply the ice-wire ice melting scheme or "wire two wires". In any case, the time of smelting increases and, accordingly, electricity costs. To reduce the melting time, preference should be given to the smelting scheme "Three Wires - Earth", but the grounding devices of substations are not calculated, as a rule, on a relatively long flow of direct current by a value of up to 2000 A.

Thermal impact of the ultra-low frequency

The technical content of this type of exposure is that weaving is produced by a current low frequency generated by a three-phase autonomous voltage inverter, and the effective value of the melting current is set and maintained at the required level by changing the supply voltage value.

At the output voltage frequency of the autonomous inverter in the tenths of Hz and below the current value in the wires of the line is limited to almost only active resistance. As a result, the permissible length of the air line increases compared with the melting of the alternating current of the industrial frequency, simplifies the melting organization, the duration of the ice melting process is reduced, the number of additional switching equipment decreases.

The scheme of the combined installation for ice ice melting and compensation of the reactive power that implements the proposed method is presented in Figure 6.

Figure 6 - Combined installation for ice ice and reactive power compensation

The composition of the combined installation includes three-phase bridge converters on fully controlled semiconductor keys 1 and 7, three-pole switches 2, 5, 8, 9, three-phase chokes 3, 4, capacitor battery 6 and control system 10.

In ice melting mode, the switches 5 and 8 are turned on, and the switch 9 is disabled. The bridge converter 1 operates in a controlled rectifier mode, and the bridge converter 7 operates in a three-phase autonomous voltage inverter mode. Melting is carried out simultaneously on three airline wires. In the reactive power compensation mode, the switches 5 and 8 are turned off, and the switch 9 is turned on. Bridge converters 1 and 7 work in parallel.

The inclusion angle is selected slightly less than 180 °. The network consumes the active power required to maintain the voltage on the condenser battery 6. Alternating voltage is formed on the side of the bridge converters 1 and 7 of the AC. The first harmonic phase is shifted towards the phase voltages of the power supply at the angle. If the amplitude of the first harmonic of the formed voltage exceeds the amplitude of the power supply voltage, then the bridge transducers 1 and 7 generate reactive power, and if less consume reactive power. A change in the modulation coefficient of high-frequency PWM is regulated by the amplitude of the first harmonic of the formed voltage, and, consequently, the value and direction of reactive power.

Thermal exposure to high frequency current

The method is that without disconnecting from consumers to phase wires through the matching device and high-voltage communication capacitors is supplied from the generator of a current of 50-500 MHz. In a uniform conductor, alternating current is concentrated in the surface layer, the thinning of which with increasing frequency leads to an increase in the resistance of the part of the conductor, which passes the current. This means that with the same current flowing over the wire, the higher the signal frequency value, the more thermal power dissipated on the conductor. For example, with MHz, the resistance of aluminum wires increases 600 times or more.

It is shown that with the power of a high-frequency generator, there are several tens of kW of the heating of the wire 10-20 ° C, which should prevent the formation of holled deposits. To eliminate the extremely formed ice and melting ice, it will take heating to a temperature of 100-180 ° C. Accordingly, significantly high electricity costs and a longer smelting procedure will be required.

Therefore, this method is most appropriate to apply in prophylactic purposes to prevent ice-formation, since it is implemented without disconnecting consumers. However, the use of generators with a frequency range of 87.5-108 MHz is fraught with the danger of creating intense radio interference to the VHF range.

Thermodynamic impact

Heated wire with a current high frequency can not only prevent the formation of holling sediments, but also used to facilitate the procedure for the removal of the already formed holled coupling. This is particularly used in the device, the scheme of which is presented in Figure 7.

Figure 7 - Device for removing the snow-ice coating from power lines wires

The automated workplace of the AWP Arm of Dispatcher 6 and the controller 5 ensure the continuous operation of the substation with the display of operational information on the light scoreboard 7.

Electromechanical impact

It is known that when current flows, parallel wires are attracted or repel under the action of the ampere force between them. With a periodic transmission of current pulses, the WL wires will perform mechanical oscillations that destroy holly-frozen sediments. The frequency of current pulses should be close to mechanical resonance and amplitude sufficient to overcome the external and internal friction forces. Changing the transmitted current can be strictly periodic, to have a swinging frequency, change by harmonic law, to have the form of pulse packs with specified laws of changes in frequency, amplitude and wellness. Figure 8 shows one of possible options Sales automated system Delete ice that implements the proposed method.

Figure 8 - Electromechanical Impact System on Airline Wires for Holly Removal

Power transformer 1 converts the supply voltage to the desired value. The power electronics unit rectifies the voltage obtained from the power transformer 1 and generates current pulses of the required value, shape and frequency, transmitted through the wires 2 VL. The control system, which is a programmable logical controller, processes information from the external sensors of holling-wind loads 3, humidity 4 and temperature 5, sets the desired shape and the frequency of current pulses for the power electronics unit and manages the operation of the system as a whole.

With practical use this method A thorough and accurate calculation of the value and frequency of current pulses is needed to eliminate the possible negative consequences of resonance. To increase the efficiency of destruction of holling sediments, current pulses should be passed on wires lying at different levels. This allows you to use ice inertia and gravity, as an additional destructive factor.

This method as well as melting requires a shutdown of the VL. However, the time of mechanical destruction of ice is significantly less than the time spent on smelting. Therefore, the cost of electricity to clean will be lower than when weaving holly deposits.

conclusions

The dominant trend in the development of new means of combating holly deposits on Wire Wires is to use combined conversion facilities capable of carrying out the need for ice ice, and everything else compensation for reactive power.

The most promising should be recognized as a frequency ultra-low current, which combines the advantage of melting by alternating current of the industrial frequency (on three wires at the same time) and melting with a direct current (limited only to active resistance, smooth control of the melting current). An additional advantage is that the installation for ice-ice ultra-low melting is easily transformed into a static reactive power compensator. This allows you to exploit expensive conversion equipment during the calendar year. Nevertheless, such a flaw is preserved as the need to turn off the WL to clean.

Fully free from the last disadvantage can allow the technology of flexible AC power transmission, as part of which is used by conversion equipment, theoretically capable of ensuring, for example, prophylactic heating of wires that prevents the formation of holoid sediments.

Bibliography

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The article "High Energy" ("PM" No. 9 "2015) is mentioned Fighting the icing of LEP wires. To heat the wires using AC, large energy consumption is required, it is economically unprofitable. Therefore, for this purpose a constant electric current is used. However, for LAP With a low voltage value (less than 220 kV), taking into account the system of power supply and technical characteristics, it is quite possible to use and AC. Warning measures are made in preventive heating of wires to prevent them out. With the help of special transformers in the annular system, additional contour currents are created that Allows heating wires and prevent ice education. It is not necessary that the energy is not required here, as in the case of the use of DC, and thus ensures uninterrupted operation of the network. Alexey Grunev

Talk through the earth

The article "On the way to myelofon" ("PM" No. 8 "2015), as an example of the use of ferrimagnets, its use is given to exchange of data with electronics of drilling" shells ". It is worth citing that we are talking about the so-called telemetry systems intended for collecting Data from depth when driving and transmitting information to the surface, for example, to control the drilling head, as well as for prompt decision to change the drilling mode. Ferrimagnetics can really find application, but if you manage to select a beneficial signal against the background of a very high noise level. But in modern Teleysystems The transfer rate of data on the hydraulic communication channel based on a harmonic wave can reach up to 10 bits / s, although it is most often limited to 4 bits for saving batteries. Along with wireless communication channels, such as hydraulic, applied and wired, and electromagnetic , and acoustic, although they have a number of restrictions. Kirill Trukhanov

The king is not real!

The cover "PM" No. 9 "2015 shows an aircraft carrier and the T-50 aircraft carrier, but in the article" Atomic Tsar-Ship "in the photo, signed by Pak Fa, F-22 Raptor. These are really similar in an angle from the nose, however There is one essential detail that allows you to easily and quickly distinguish between these two aircraft. Engines F-22 are located in parallel to each other and on a short distance, while the T-50 engines are under a significant angle relative to each other, and the tail tip is placed between them - the beam tail, where the brake parachute is placed. Evgeny Kunashov

PM: We apologize to all of our readers for a technical error, which led to the placement of improper illustration.

Family ties

In the article "Where to hurry the gentleman" ("PM" number 8 "2015) It is said that the technology got the carrier of the English traditions from the" current German parent BMW ". BMW really became the parent company Rolls-Royce, but call him the parent not at all. correctly. Gennady Dreiger

PM: Until 1998, Rolls-Royce Motors belonged to the Vickers concern. In 1998, the concern was sold by VW, except the right to use the Rolls-Royce brand. The brand was transferred to BMW, where they developed new cars and built a new plant. So BMW is the parent, from which Rolls-Royce got a motor, electronics and pendant parts from the seventh series.

The invention relates to electrical engineering, in particular to devices that impede the formation of ice on the wires of air-voltage power lines (LP) without turning off consumers. The technical result lies in the simplicity and efficiency of the declared device, and, if possible, the removal of existing ice formations without turning off consumers and without complication of the power line, i.e. Without adding duplicate or bypass wires. The device includes an external power source with respect to the power supply, made with the possibility of connecting to the conductor wires of the LEP, while the current source is made in the form of a high frequency generator, made with the possibility of providing the power calculated by the formula P g \u003d Q · A · ΔT, where q is the heat transfer coefficient of the upper hot layer of the air, and the surface area of \u200b\u200bthe wires, Δt is the heating temperature of the wire relative to the ambient temperature; In this case, the generator output is connected to the entrance matching device Capacitive type configured to match the output resistance of the high frequency generator with the power resistance of the power supply and having the number of outputs corresponding to the number of wires of the LPP. 2 N.P. F-lies, 7 yl.

The invention relates to electrical engineering, in particular to devices that impede the formation of ice on the wires of air-voltage power lines (LP) without turning off consumers.

Energy consider loapping icing as one of the most serious disasters. This phenomenon is characterized by the formation of a dense icy precipitate with the altage of the intercooled droplets of rain, seaosi or fog predominantly at temperatures from 0 to -5 ° C on the wires of the PP. The thickness of the ice on the air high-voltage power lines can reach 60-70 mm, significantly weighting the wires. Simple calculations show that, for example, the mass of the AC-185/43 brand wire with a diameter of 19.6 mm. 1 km long with a mass of 846 kg increases with a thickness of ice 20 mm by 3.7 times, with a thickness of 40 mm - 9 times, With a thickness of 60 mm - 17 times. At the same time, the total mass of the power lines of 8 wires in 1 km long increases, respectively, up to 25, 60 and 115 tons, which leads to the breakage of the wires and breakage of the carrier supports.

Such accidents bring significant economic damage, suspending the power supply of enterprises and residential buildings. To eliminate the consequences of such accidents take place at least considerable time and vast means are spent. Such accidents happen annually in many countries of the northern and middle band. Only in Russia, large accidents due to ice for the period from 1971 to 2001 were repeatedly occurred in 44 power systems (see Diagnostics, Reconstruction and Operation of Power Lines in Outflows. / I.I.levchenko, A.S. Zasyptkin, A.A. Allyluev, E.I. Satsuk. - M.: Publishing House MEI, 2007). Only one accident in Sochi power grids in December 2001 led to damage of 2.5 thousand km of electric power lines with a voltage to 220 kV and the cessation of the power supply of a huge area (see).

Numerous ways to combat this phenomenon are known, based on mechanical or thermal effects on ice crust. In this case, preference is given various ways Ice melting, since mechanical impact facilities are often able to be applied in hard-to-reach mountain and wooded areas. Melting current is the most common way to deal with the ice on the wires of the high-voltage power lines. The ice is melted due to the heating of carrier or auxiliary wires by a permanent or alternating current of 50 Hz to a temperature of 100-130 ° C (see, as well as Dyakov A.F., Zatpkin A.S., Levchenko I.I. Prevention and liquidation Outflow accidents in electrical networks. - Pyatigorsk, from the RP "Yuzhenergotehnadzor", 2000 and Rudakov R.M., Vavilova I.V., Golubkov I.E. Fighting the Family in power grid enterprises. - Ufa, Ufa State Aviation Technical University, 1995).

There is a method of removing the ice when the short circuit current is passed on the wires of the split phase of the power line (see A.S. No. 587547). A short-circuit current is an emergency mode for the power line and with a high degree of probability can lead to annealing of wires with a subsequent irreversible loss of strength, which is unacceptable. The problem is aggravated by the one-time transmission current of the short circuit may not be enough to completely remove the ice, and short circuits will have to repeatedly repeat that even more will take effect of the consequences.

Consider the theoretical foundations of the method of combating a hole-followed by a short circuit of the wires.

Let the required current of the ice skipping current due to the heating of the wire on which it is intending, is I pl. Then when weaving constant current, the required power supply voltage

where r Pr is the active resistance of the wires, and when weaving alternating current from the network

where X PR \u003d 2πFL PR \u003d 314L PR is the reactive resistance due to the inductance of the wires L PR at frequency f \u003d 50 Hz. For the relationship of these two stresses with the same melting currents according to (1) and (2) we obtain

Since the value of the U in the lines of considerable length and section due to the relatively large inductance of wires can reach 5-10, it is economically more profitable to produce a constant current, in which the power supply voltage, and, accordingly, its power according to (3) decreases 5-10 times compared to the source of alternating current. True, the use of special powerful high-voltage rectifying plants is required. Therefore, usually weaving by alternating current is used on high-voltage lines with a voltage of 110 kV and below, and constant - above 110 kV. As an example, we indicate that the melting current at a voltage of 110 kV can reach 1000 A, the required power is 190 million volt-amps, melting temperature 130 ° C (see and).

Thus, the ice droplet is a rather complicated, dangerous and expensive event with disconnection when holding all consumers. In addition, clearing the wires from the ice, with the non-changed climatic conditions, they again turn ice, and we need to be wrapped again and again.

Sometimes the heating of the wires are combined with mechanical exposure. So, for example, in Patent of the Russian Federation No. 2666826, a method for removing ice from the wires of the contact network and power lines, which consists in the fact that the alternating current or current pulses are transmitted with a frequency close to mechanical resonance, and amplitude sufficient to overcome the external and domestic forces. friction, with the change in the variable current transmitted, can be strictly periodic, to have a swinging frequency, vary by harmonic law, to have the form of pulse packs with specified frequency changes, amplitude and duty changes. The parameters of the dual or multiple wire of the contact network and the power transmission lines of the electric current are chosen so as to bring the wires to the oscillatory movement. As you know, conductors with unidirectional current flow are attracted. At the same time, when the wires are impaired, the potential energy in the form of elastic deformation is accumulated. Therefore, it turns out a oscillatory system, which, with the corresponding selection of frequency, amplitude and well pulse pulses, can start fluctuate and enter the resonance. Acceleration of the removal of ice is achieved due to the fact that the heating of the wires will be accompanied by mechanical swirling blows. A decrease in electricity costs is achieved due to a significant reduction in the removal time of ice from wires and reduce the magnitude of the transmitted currents. Improving security is achieved by excluding short circuit modes. Reducing the influence on the communication line, preventing the failures of the radio-electronic equipment, also occurs due to the failure of the short circuit modes. This method is very difficult in implementation, and in addition, as in other methods considered, it is necessary to turn off consumers for the period of the defrosting procedure.

The closest to the claimed device is the technical solution described in the Patent of the Russian Federation No. 2316866. The prototype is characterized by the fact that the device consists of two isolated wire groups, which from one end are interconnected and with the subsequent portion of the air line, and from the other end, the first group of the wire is connected to the wire of the previous section of the airline, and between the first and second Wire groups included independent voltage source.

The prototype device to prevent the formation of ice on the air line is shown in FIG. 1 and consists of the first 1 and second 2 isolated wire groups, which from one end are interconnected and with a subsequent section of the LPP 3, and from the other - the first group. The wire is connected to the wire of the previous section of the LPP 4, and between the first 1 and the second 2 groups of the wire connected the independent voltage source 5.

The main line of the line passes from the wires of the previous section of the LEP 4 on the first group of the wire 1 and then on the wire of the next section of the LEP 3. From an independent source 5, the voltage between the first group of the wire 1 and the second group of the wire 2 is applied.

From the theoretical calculations given by the authors of the prototype, it follows that in order to prevent the formation of ice, for example, on a wire of 95/16, the temperature of the wire relative to the environment should be 5 ° C at wind speed 3 m / s. In this case, 36 kW / 10 km should be allocated on the wire. At the rated current of this wire, active losses at a length of 10 km are 28 kW / 10 km. Therefore, the power from an independent voltage source 5 should be 8 kW / 10 km. If the load line is missing, then the power of an independent source 5 should be 36 kW / 10 km.

If the second wire of the wire is an isolated steel wire with a diameter of 4.5 mm, then with the power of loss of this wire, component of 36 kW / 10 km, the voltage of an independent source 5 will be 2.1 kV and current 17 A. with an isolated second group of wire made from Aluminum, with the power of loss of 36 kW / 10 km, the voltage of an independent source will be 0.8 kV and current 45 A.

An independent voltage source may be a voltage transformer that is fed from a 0.38 kV network with 63 kV insulation relative to the Earth for a substation 110 kV, or the transformer away from the substation is powered directly from 110 kV airlines.

The most attractive feature of this solution is the possibility of using it without disconnecting consumers. However, the disadvantage of this method is the complication of the design of the entire LPP due to the creation of the "bypass" groups of wires that make up the burden during the period of defrosting the main wire.

The task of which the claimed invention is directed is to develop a fairly simple and economical device for preventing ice formation on air high-voltage power supply and, if possible, removing existing ice formations without turning off consumers and without complication of the power line, i.e. Without adding duplicate or bypass wires. At the same time, it is desirable to achieve such results so that such a device is based on a new, more effective method. As a prototype of the method, it makes sense to indicate a solution in which the heating of the wire is used using an external current source without turning off consumers.

The technical result in respect of the method is achieved due to the fact that an improved method of warming up the cocked wires of at least two wires is developed by supplying high frequency voltages on them, the distinctive characteristic of which is the use of the skin effect and the effect of the running wave for warming the wires. At the same time, the inventive method provides for the following operations:

Served between two wires of power lines The high-frequency voltage in the range of 50-500 MHz with a power of p \u003d Q · A · ΔT, where q is the heat transfer coefficient of the top hot layer of air, and the surface area of \u200b\u200bthe wires, ΔT is the heating temperature of the wire relative to the temperature Environment.

The technical result regarding the device is achieved due to the fact that the declared device includes a high-frequency generator with a power calculated by the formula: P G \u003d Q · A · ΔT,

where q is the heat transfer coefficient of the top hot layer of the air of the air, and the surface area of \u200b\u200bthe wires, Δt is the heating temperature of the wire relative to the ambient temperature, while the generator output is connected to the input of the matching capacitive type device, configured with the ability to match the output resistance of high frequency generator with input The resistance of the power frame and having the number of outputs corresponding to the number of wires of the power supply lines.

For a better understanding of the being of the claimed invention, its theoretical justification is provided with reference to the corresponding graphics materials.

Figure 1. Prototype device.

Figure 2. Electrical line: 2.1) Short circuit in line, 2.2) Equivalent diagram at constant current, 2.3) Equivalent circuit with alternating current with a frequency of 50 Hz.

Figure 3. Current distribution over the cross section of the conductor: 3.1) at constant current and low frequency; 3.1) at high frequency.

Figure 4. Two-wire line: 4.1) appearance, 4.2) Schedule of the amplitude of the voltage at a running wave, 4.3) with a running and reflected wave.

5. Connection diagram of high-frequency generator to power line.

6. Charts of dependence: 6.1) of the surface layer of current penetration into the conductor, 6.2) of the relative resistivity of the wires depending on the frequency: 601 - steel, 602 - aluminum, 603 - copper.

Fig.7. The dependence of the coefficient of transformation of the electromagnetic energy of the running wave into thermal from the length of the line.

As you know, the term "skin effect" comes from the English word "Skin", i.e. "leather"; At the same time, in the electrical engineering, it is understood that under certain circumstances, the electric current concentrates on the "skin" of the conductor (see RU.Wikipedia.org/Wiki/Skin-effect). It was found that in a homogeneous conductor, alternating current, in contrast to the constant, is not distributed uniformly by cross section of the conductor, and concentrates on its surface, occupying a very thin layer (see figure 3), the thickness of which at the frequency of the AC F\u003e 10 kHz Determined by the formula

where σ (ohm mm 2 / m) is a specific electrical resistance at a constant current; μ o \u003d 1,257 · 10 6 (in · s / a · m) - magnetic constant; μ - relative magnetic permeability (for a non-magnetic material μ \u003d 1) F - frequency in MHz.

The graphs of the function Δ (f) according to (4) for three materials (steel - 601, aluminum - 602 and copper - 603) are shown in Fig.6.1. The thinning of the layer in which the alternating current flows, entails an increase in the resistance of the conductor with a radius R (mm), determined by (R / 2δ)\u003e 10 by the formula

where R o \u003d σ / πr 2 is the resistance of the same conductor with a length of 1 M DC.

The graphs of the function R f (f) // R O at r \u003d 10 mm, showing how the conductor resistance increases with a frequency for three materials (steel - 601, aluminum - 602 and copper - 603), shown in Fig. 6.2. Of these, for example, it follows that at a frequency of 100 MHz and above the resistance of aluminum wires increases by 600 or more times.

As for the effect of the "running electromagnetic wave", then, as you know (see, for example, izob.narod.rn / p0007.html), there are two main ways of propagation of electromagnetic waves: in the free space when the antenna radiation and with the help of waveguides and feeder or so-called long lines - coaxial, striped and two-wire - (see Kaganov V.I. oscillations and waves in nature and technology. Computerized course. - M.: Hot line - Telecom, 2008). In the second case, the electromagnetic wave, as if on the rails, slides along the line. Since the two wires of the power lines can be considered as a two-wire line (Fig. 4.1), we will stop at its analysis. The line itself is characterized by three basic parameters: the wave resistance of ρ, the attenuation of α and phase constant β. Wave resistance Two-wire line stretched in the air

where A is the distance between the centers of the wires, R is the radius of the wire (see Fig. 4.1) constant attenuation

where R f is the resistance of one wire at high frequency, determined according to (5).

The phase constant β \u003d 2π / λ, (1 / m), where λ (m) is the wavelength propagating in the line.

In the two-wire, like other feeder lines, two main modes of operation are possible: only with a running wave in one direction and with two waves - running and reflected from the end or obstacles in the line. Suppose the line is infinitely long. Then there is only a running wave mode in it, the voltage of which depends on the time T and the distance x from the generator (Fig. 4.2):

where U 0 is the amplitude of the voltage at the input of the line to which the generator with the frequency f is connected.

According to (8), the amplitude of the running wave propagating along the line is reduced by exponential law (Fig. 6 and 7). Consequently, the power of the running electromagnetic wave at a distance L from the generator will be:

where P g \u003d (u 0)) 2/2 - the wave power at the beginning of the line equal to the output power of the high-frequency generator.

The difference between the power of the running wave at the beginning of the line and at a distance L will determine the heat heating of the line along which the wave is distributed

The transformation coefficient of the electromagnetic energy of the traveling wave W in the thermal in line L (M) in view (10) will be:

The graphs of the function η (L) at three values \u200b\u200bof the permanent attenuation α (1 / km) are constructed in FIG. 7. It follows that the greater the resistance of the wires of the line R F, determined by (5), and, accordingly, constant attenuation α, determined (7), the greater part of the energy of the electromagnetic field of the running wave along the line is converted to heat. It is this effect of conversion of electromagnetic energy into a thermal, running on the heating of wires at a high frequency of the signal, and is based on the proposed method of preventing ice on the power lines.

In the case of limited dimensions of a line or a high-frequency obstacle, such as a container, in addition to the incident, the reflected wave, the energy of which will also be transformed into heat as it propagates from the obstacle to the generator. Amplitude changes along the line of both waves - falling and reflected - shown in FIG. 4.3.

To calculate the thermal return, we define on a specific example, what power

P g of a high-frequency generator F frequency f connected to the power line will be required to warm up two wires on Δt degrees. We take into account the following circumstances. First, the thin top layer of the wire under the action of an electromagnetic wave warms up almost instantly with a high value of the volumetric heat release. Secondly, it is warmly spent on the heating of the entire wire (o m) and the air surrounding wire by convection (Q b) (see Fig. 3.2).

We will take the following source data: Wire material - aluminum with a diameter of 10 mm, cross section S \u003d 78.5 mm 2, length L \u003d 5000 m, Diens p \u003d 2710 kg / m 3, resistivity on a constant current σ \u003d 0.027 Ohm · mm 2 / m, the specific heat capacity C \u003d 896 J / kg · K, the heat transfer coefficient of the upper hot layer of the air of the air Q \u003d 5 W / m · k.

Mass of two wires:

The surface of two wires:

The amount of heat required to heat the two wires to ΔТ \u003d 13 ° С:

The heat transfer of two wires into the environment when the temperature difference ΔТ \u003d 13 ° C:

where t time in seconds.

From the last expression, we obtain for the required power of the high-frequency generator p d \u003d 20.4 kW, i.e. 2 W Power of high-frequency oscillations per 1 m wires with volumetric heat release in the top layer of the wire 8 MW / m 3. Along the way, we note that with the same type of wire for freeing it from ice by smelting with a cycle of up to 40 minutes, power is 100 V · A 1 meter (see and).

Equating expressions for energy, we will find the amount of time to establish a stationary warning mode of wires:

To check the theoretical provisions expressed above and evidence of the industrial applicability of the proposed method and the device, a laboratory experiment was carried out.

From preliminary calculations it was concluded that the powerful radio transmitters of the VHF broadcasting can be used as a high-frequency signal generator, operating in the frequency range of 87.5 ... 108 MHz, changing only the device for negotiation with the load and connecting to the power line according to the circuit FIG. .five.

In the experimental version, a 30 W generator 502 with a frequency of 100 MHz was connected via the matching device 501 to a two-wire line 50 m long, open at the end, with wires with a diameter of 0.4 mm and a distance between them in 5 mm. Wave resistance of such a line according to (6):

Under the action of a running electromagnetic wave, the heating temperature of the two-wire line was 50-60 ° C with the surrounding air temperature of 20 ° C. The results of the experiment with satisfactory accuracy coincided with the results of the calculation, made according to the above mathematical expressions.

At the same time, the following conclusions were formulated:

The inventive method of heating the power lines by propagating an electromagnetic wave, the energy of which increases to heat to heat, allows you to heat the wires by 10-20 ° C, which should prevent ice formation;

The most appropriate is to use the proposed method and the device to prevent the formation of ice on the wires, since to eliminate the already formed ice "fur coats", significantly large energy consumption and a longer procedure will be required;

Compared to the currently applied method of smelting of the ice, the inventive method has a number of advantages, in particular, given the fact that the method is implemented without disconnecting consumers, it is possible to prophylactic purposes to heat the line before the formation of a dense ice sediment on the wires, which allows you to heat them up to 10-20 ° C, and not to a temperature of 100-130 ° C needed for ice icefall;

Ascending as an ascendibility of the AC frequency increases the resistance of the wires (in the example at a frequency of 100 MHz, the resistance compared with the frequency of 50 Hz increases by three orders of magnitude) allows you to obtain a high coefficient of electrical energy conversion to thermal and, thereby reducing the generator power.

1. The method of combating the hole-read on the power lines, which consists in the fact that without turning off the consumers, the conductive wires, characterized in the external source of the current, differ from the external source, which is supplied between two wires of the power line, high frequency voltage in the range of 50-500 MHz The power R r \u003d Q · a · Δt, where q is the heat transfer coefficient of the upper hot layer of the wire of air, and the surface area of \u200b\u200bthe wires, Δt is the heating temperature of the wire relative to the ambient temperature.

2. A device for dealing with ice, which includes an external current source with respect to the power supply, made with the possibility of connecting to the conductor wires of the LAM, characterized in that external source The current is made in the form of a high-frequency generator, made with the possibility of providing the power calculated using the formula p \u003d Q · A · ΔT, where Q is the heat transfer coefficient of the top hot layer of the air of the air, and the surface area of \u200b\u200bthe wires, Δt - the heating temperature of the wire relative to the temperature environment; In this case, the output of the generator is connected to the input of the matching device of the capacitive type, made with the ability to match the output resistance of the high frequency generator with the power supply resistance of the power supply and having the number of outputs corresponding to the number of power transmission lines.

The invention relates to electrical engineering, in particular to devices that impede the formation of ice on the wires of air high-voltage power lines without turning off consumers

Doctor of Technical Sciences V. Kaganov, Professor Miera.

Over the past fifteen years, ice on high-voltage lines began to occur more and more. With a slight frost, in a mild winter, there are fog or rain droplets on the wires, covering them with a dense ice "fur coat" weighing a few tons on the length of a kilometer. As a result, the wires are torn, and the supports of the power lines break. The frequent accidents on the LEP are associated, apparently with the general warming of the climate and will require a lot of strength and means to prevent them. It is necessary to prepare for them in advance, but the traditional method of melting ice on wires is inffective, uncomfortable, roads and dangerous. Therefore, at the Moscow Institute of Radio Electronics and Automation (Mirea) developed new technology Not just the destruction of already hungry ice, but allowing the ahead of it to prevent his education.

Science and life // illustration

ice socks on wires, insulators and bearing structures sometimes reach significant size and mass.

Multi-button layers of ice on the wires are broken even steel and reinforced concrete supports.

An experimental generator at 100 MHz with a capacity of 30 W collected in Mirea.

Holly - Disaster for power lines

According to Daly, Hollyhold has a different name - an ebeller or a fuel. Holly, that is, a dense icy crust is formed with the intention of the heated droplets, frost or fog at temperatures from 0 to -5 ° C on the surface of the Earth and various items, including wires of high-voltage power lines. The thickness of the ice on them can reach 60-70 mm, significantly weighting the wires. Simple calculations show that, for example, the AC-185/43 brand wire with a diameter of 19.6 mm kilometer has a mass of 846 kg; With a thickness of ice 20 mm, it increases by 3.7 times, with a thickness of 40 mm - 9 times, with a thickness of 60 mm - 17 times. At the same time, the total mass of the power lines of eight wires of kilometer length increases, respectively, up to 25, 60 and 115 tons, which leads to the cliff of the wires and the breakage of the metal supports.

Such accidents bring significant economic damage to their elimination takes several days and vast funds are spent. Thus, according to the materials of the firm "OGRES", major accidents due to ice for the period from 1971 to 2001, many times occurred in 44 Energy Systems of Russia. Only one accident in Sochi power grids in December 2001 led to damage to 2.5 thousand km of power lines with a voltage to 220 kV and the cessation of the power supply of a huge area. Many accidents of holling origin was and last winter.

Holly high-voltage power lines in the Caucasus (including in the area of \u200b\u200bthe winter Sochi Olympiad in 2014), in Bashkiria, in Kamchatka, in other regions of Russia and other countries in 2014. It is a very expensive and extremely uncomfortable way to deal with this disaster.

Melting electric shock

Ice crust on high-voltage lines eliminate, heating the wire with a permanent or alternating current of 50 Hz to a temperature of 100-130 ° C. Make it the easiest way, closed by turns two wires (while the network has to turn off all consumers). Suppose for the effective interpretation of the ice crust on the wires, the current I pl. Then when weaving constant current, the power supply voltage

U 0 \u003d I pl r

where r is the active resistance of the wires, and the alternating current from the network -

where X PR \u003d 2FL is the reactive impedance at a frequency F \u003d 50 Hz, due to the inductance of the wires L.

In the lines of considerable length and section due to relatively large inductance, the voltage of the AC source at a frequency F \u003d 50 Hz, and, accordingly, its power must be 5-10 times more compared to the source of the direct current of the same force. Therefore, it is economically beneficial to melting out the constant current, although this requires powerful high-voltage rectifiers. The alternating current is usually used on high-voltage lines with a voltage of 110 kV and below, and the constant is above 110 kV. As an example, we indicate that at a voltage of 110 kV, the current will reach 1000 A, the required power is 190 million V · a, the temperature of the wire 130 ° C.

Thus, ice ice-current is a rather uncomfortable, complex, dangerous and expensive event. In addition, the purified wires in the surviving climatic conditions again turn ice, which is required to melt and again.

Before setting out the essence of the method of combating holly on the wires of high-voltage power lines, we will focus on two physical phenomena, the first of which is associated with the skin effect, the second - with a running electromagnetic wave.

Skin Effect and Running Waves

The name of the effect comes from the English word "Skin" - leather. The skin effect is that high frequency currents, in contrast to DC, are not distributed uniformly by the cross section of the conductor, and concentrate in a very thin layer of its surface, the thickness of which at a frequency F\u003e 10 kHz is already a fraction of a millimeter, and wire resistance It increases hundreds of times.

High frequency electromagnetic oscillations can spread in free space (with antenna emission) and in waveguides, for example, in so-called long lines, along which the electromagnetic wave slides, as if on the rails. Such a long line can be a pair of power lines. The greater the resistance of the wire of the line, the greater the energy of the electromagnetic field running along the wave line is converted to heat. It is this effect that is based on a new way to prevent ice on the power lines.

In the case of limited dimensions of a line or a high-frequency obstacle, such as a container, in addition to the incident, the reflected wave will also be distributed, the energy of which will also be transformed into heat as it propagates from the obstacle to the generator.

Calculations show that to protect against ice lap length of about 10 km, you need a high-frequency generator with a power of 20 kW, that is, the amount of power to the power meter of the wire. The stationary heating mode of wires occurs after 20 minutes. And with the same type of wire, the use of direct current is required to be 100 W per meter with an output to the mode in 40 minutes.

High-frequency currents generate powerful VHF broadcasting radio transmitters operating in the range of 87.5-108 MHz. They can be connected to the wires of the LAM through the coordination device with the load of the power line.

To verify the effectiveness of the proposed method in Mirea, a laboratory experiment was conducted. A 30 W generator, a frequency of 100 MHz, connected to a two-wire line 50 m long, open at the end, with wires with a diameter of 0.4 mm and a distance between them 5 mm.

Under the action of a running electromagnetic wave, the heating temperature of the two-wire line was 50-60 ° C at an air temperature of 20 ° C. The results of the experiment with satisfactory accuracy coincided with the results of calculations.

conclusions

The proposed method requires, of course, a thorough check in real conditions of the current power grid with full-scale experiments, because the laboratory experiment allows only to give the first, preliminary assessment of a new way to combat holly. But some conclusions from all that have been said can still be done:

1. Heat the power lines of high frequency currents will prevent the formation of ice on wires, since it is possible to heat them up to 10-20 ° C, without waiting for the formation of dense ice. Disconnect from the electrical network of consumers will not have to - the high-frequency signal will not penetrate them.

We emphasize: the method allows you to prevent the appearance of ice on the wires, and not to start to deal with it after the ice "fur coat" envelops them.

2. Since the wires can be heated only by 10-20 ° C, then compared to melting requiring the heating of the wires to 100-130 ° C, the electricity consumption is significantly reduced.

3. Since the resistance of the wires of high frequency currents compared to industrial (50 Hz) increases sharply, the coefficient of transformation of electrical energy into thermal is great. This in turn leads to a decrease in the required capacity. At first, it should be limited to a frequency of about 100 MHz generator with a capacity of 20-30 kW, using existing broadcast radio transmitters.

Literature

Dyakov A. F., Zatpkin A. S., Levchenko I. I. Prevention and elimination of ice-headed accidents in electrical networks. - Pyatigorsk: Publishing House of RP "Yuzhenergotehnadzor", 2000.

Kaganov V. I. oscillations and waves in nature and technology. Computerized course. - M.: Hotline - Telecom, 2008.

Levchenko I. I., Zatpkin A. S., Allyluweva A. A., Satsuk E. I. Diagnostics, Reconstruction and operation of electric lines of power transmission in the ice-free areas. - M.: Publishing House MEI, 2007.

Rudakova R. M., Vavilova I. V., Golubkov I. E. Fight with a holly in power grid enterprises. - Ufa: Ufimsk. State Aviators. tehn University, 1995.

Yavorsky B. M., Detlaf A. A. Handbook of physics. - M.: Science, 1974.