Experimental investigations of electro-thermal resistibility of conductors and cables to action of rationed on the International Standard IEC 62305-1-2010

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UDC 621.3. 022: 621. 319. 53

doi: 10. 20 998/2074−272X. 2016.1. 09

M.I. Baranov, S.V. Rudakov

EXPERIMENTAL INVESTIGATIONS OF ELECTRO-THERMAL RESISTIBILITY OF CONDUCTORS AND CABLES TO ACTION OF RATIONED ON THE INTERNATIONAL STANDARD IEC 62 305−1-2010 APERIODIC IMPULSE OF CURRENT OF ARTIFICIAL LIGHTNING

Purpose. Experimental researches of electro-thermal resistibility of cable-explorer products, applied in the power electric circuits of objects of electric-power industry, to action on its copper and aluminum parts bearings a current rationed on the International Standard of IEC 62 305−1-2010 aperiodic impulse 10/350 ps of current of artificial lightning. Methodology. Electrophysics bases of technique of high tensions and high pulsed currents (HPC), and also scientific and technical bases of planning of devices of high-voltage impulsive technique and measuring HPC in them. Results. Experimental a way the quantitative levels of maximal values maximum ofpossible and critical closenesses of aperiodic impulse 10/350 ps of current of artificial lightning with rationed on the international standard of IEC 62 305−1-2010 peak-temporal parameters and admittances on them in copper (aluminum) parts bearings a current of send-offs and cables with a polyethylene (PET) and polyvinylchloride (PVCH) isolation. Originality. First in world practice on the unique powerful high-voltage generator of HPC of artificial lightning experimental researches of resistibility to lightning of pre-production models of send-offs (cables) are conducted with copper (aluminum) tendons, PET and PVCH by an isolation, in-use in power electric circuits of electric-power industry objects. Practical value. The use in practice of protecting from lightning of the got results will allow substantially to promote functional and fire-prevention safety of engineering communications of objects of industrial electroenergy in the conditions of action on them of short shots of linear lightning. References 16, figures 12.

Key words: high impulsive current of lightning, wires and cables of electric chains of objects of electric-power industry, generator of high pulsed current of artificial lightning, electro-thermal resistibility to lightning of cable-conductor products.

Приведены результаты экспериментальных исследований электротермической стойкости образцов ряда проводов и кабелей электрических цепей объектов промышленной электроэнергетики с медными (алюминиевыми) жилами (экранами), поливинилхлоридной и полиэтиленовой изоляцией к действию короткого удара большого импульсного тока искусственной молнии с нормированными по международному стандарту IEC 62 305−1-2010 амплитудно-временными параметрами и допусками на них. Библ. 16, рис. 13.

Ключевые слова: большой импульсный ток молнии, провода и кабели электрических цепей объектов электроэнергетики, генератор большого импульсного тока искусственной молнии, электротермическая молниестойкость кабельно-проводниковой продукции.

Introduction. One of the ways for reliable electrothermal and fire protection from direct (indirect) lightning power facilities (PF) and their utilities is the informed choice of cables and wires installed in their primary and secondary circuits, and complies with strict conditions of lightning resistance. According to the requirements of existing International and national Standards [1−6] with a short lightning in the wire and cable power circuits of the PF can occur pulse currents of positive polarity amplitude ImL, with aperiodic temporary form t/tp=10 ps/350 ps, where Tf, tp are, respectively, the acceleration time between the levels (0.1 — 0. 9) ImL and duration of the current pulse at the level 0. 5ImL. In [1−6], the normalized amplitude-time parameters (ATP) and the tolerances are specified for the aperiodic impulse lightning current corresponding to I-IV levels of protection against lightning of the PF and their utilities. Thus, for example, a lower level IV of the lightning protection of the PF set of ATPs and other characteristics affecting the current pulse are aperiodic 10/350 ps lightning characterized by the following normalized quantitative values [1−7]: tp = 350 ps (with a tolerance of ± 10%) — ImL = 100 kA (with a

tolerance of ± 10%) — specific energy (the integral of the action of the lightning current) JL=2. 5T06 A2-s (with a tolerance of ± 35%) — fluxed charge gL=±50 C (with a tolerance of ± 20%). With regard to the numerical value of Tf, it is, with a tolerance of ± 20% is according to [1−7] and the secondary character may be in the range 10 ps & lt- Tf & lt- 15 ps. Furthermore, the time t"p1,6Ty, corresponding to a current amplitude ImL, according to the requirements [1−5] must not exceed 25 ps, and by [6] - 50 ps. Currently there are no methodological and other data that can be used to select the specified wire and cable electrical circuits of the PF that meets the existing requirements [1−6]. In this regard the holding of a high-current high-voltage equipment in the experimental studies on the definition of electrothermal lightning resistance of cables and wires of the PF is an actual scientific and technical problem.

Problem definition. Consider widely used in electrical power circuits of the PF wires and cables with copper (aluminum) conductor (screen) in polyvinylchloride (PVC) and polyethylene (PET) insulation. For their

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electrothermal tests on lightning resistance we use straight test samples (TS) of given wires (cables) with length of

0.5 m, rigidly clamped in a high-current discharge circuit of the generator of the pulsed lightning current (GPLC). As GPLC we select created in 2014 by the Institute «Molniya» of the NTU «KhPI» a powerful high voltage generator ГИТМ-10/350 [7], which reproduces at low impedance and low-inductive electrical load aperiodic current pulses 10/350 ps artificial lightning with positive polarity normalized ATP and tolerance to them, meet the requirements of existing International and national Standards [1−6]. During consideration of experimental studies on the generator ГИТМ-10/350 containing in its structure four concurrent high-voltage pulse current generator (PCG) it is required as a first approximation to determine at room temperature 00 = 20 °C maximum limit values 5m1d and critical 5m1k densities of the aperiodic current pulse 10/350 ps of the artificial lightning with normalized ATP [1−6] in the current-carrying parts of mentioned TS of wires and cable of electrical circuits of the PF.

Electrical circuit and parameters of the powerful high-voltage generator ГИТМ-10/350. Fig. 1 shows a circuit diagram of the generator ГИТМ-10/350 used for electrothermal tests on the lightning resistance of the TS of chosen wire and cable of power circuits of the PF.

Fig. 1. Circuit diagram of high-current discharge circuits of the generator ГИТМ-10/350 for forming in the TS of wires (cables) of electrical circuits of the PF aperiodic current pulses 10/350 ps of the artificial lightning with normalized ATP and tolerance to them (GHVIP — generator of high-voltage ignitor microsecond pulses of voltage of amplitude up to ± 100 kV- Fb F2 — respectively three and two-electrode high-voltage air-spark switches PCG-1 — PCG-4- Cp=180 pF — blocking capacity for pulse voltage up to ± 120 kV of the GHVIP circuit controlling the actuation of the spark switches F1 and F2-

TS — test sample of the wire (cable), CS — coaxial shunt type ШК-300 for measuring of pulse current of artificial lightning amplitude from ± 10 A to ± 300 kA- ±U313, ±U34 — charging voltage, respectively of PCG-1 — PCG-3 and PCG-4- L1 — L4, R1 — R4 and C1 — C4 — respectively intrinsic inductances, resistances and capacitances of discharge circuits of PCG-1 — PCG-4- L30, L40 — forming inductances of discharge circuits of PCG-3 and PCG-4) [7]

It can be seen that its four individual PCG (PCG-1 -PCG-4) work in parallel on the total electrical load -tested TS of wires and cables. Note that the PCG-1 -PCG-3 were collected on the basis of 171 parallel included high-voltage pulse capacitor ИК-50−3 (16 for

PCG-1, 44 for PCG-2 and 111 for PCG-3), and PCG-4 -on the basis of 288 high-voltage pulse capacitors ИМ2−5-140 consistently included two in each of its 144 connected in parallel sections [7, 8]. Intrinsic electrical parameters of the generator type ГИТМ-10/350 are the following [7]: for PCG-1 — Rj-0. 375 Q- Lj~1 pH- Q~48 pF- for PCG-2 — R2~0. 136 Q- L2~1.3 pH- C2~132 pF- for PCG-3 — R3~0. 057 Q- L3~2.5 pH- C3~333 pF- for PCG-4 — R4~0. 083 Q- L4~1.5 pH- C4~10. 08 pF. Forming inductance L30 in the discharge circuit of the PCG-3 is about 40 pH, and forming inductance L40 in the discharge circuit of the PCG-4 — about 7 pH.

The nominal value of stored electrical energy in a generator-type ГИТМ-10/350 at a charging voltage for capacitors U31−3 of PCG-1 — PCG-3 at ± 50 kV and a charging voltage for capacitors U34 of PCG-4 at ± 5 kV is about 1145 kJ [7]. And, for the PCG-1 — 60 kJ, for PCG-2 — 165 kJ, for PCG-3 — 416 kJ, for PCG-4 — 504 kJ. These data highlight the high levels of energy consumption such as capacitor banks generator ГИТМ-10/350, and point to «hidden» from the reader difficulties for maintenance personnel with such powerful energy storage [9, 10]. To avoid devastating consequences in capacitor banks generator type ГИТМ-10/350 and ensure safe working conditions for maintenance of their personnel in the emergency mode of its work due to electrical breakdown at the stage of the charge (discharge) of the inner or outer insulation of at least one of its 459 capacitors all high-voltage output pulse capacitors in PCG-1 — PCG-4 were installed protective resistance made on the basis of parallel connected high graphite-ceramic volume fixed resistors TBO-60 with par value of 24 Q at DC voltage up to ± 25 kV [10, 11]. Parallel operation of PCG-1 — PCG-4 in the mode of the high-current discharge of high-voltage capacitor oscillator type ГИТМ-10/350 on the TS wires (cables) is provided as shown in Fig. 1 simultaneous actuation of the high-voltage three-electrode-managed air switch F1 with graphite main electrodes having a hemispherical working surface at a nominal voltage of ±50 kV [12] and the high-voltage two-electrode air switch F2 with graphite rectangular electrodes containing a flat working surface, for a rated voltage of ±10 kV [13]. Synchronous actuation of switches Fi and F2 in the presented in Fig. 1 circuit diagram is performed by applying a high voltage across the capacitance Cp dividing by the average graphite spherical electrode F1 switch from generator of high-voltage ignitor microsecond pulse (GHVIP) of microsecond duration pulse voltage amplitude up to ± 100 kV [7, 10]. When electrical breakdown due to the work of the GHVIP of one of the two air gaps switch F1 and its subsequent activation occurs surge voltage to the TS of the wire (cable) results simultaneously with F1 triggered and switch F2, subsequent discharge to a load (TS) of charged capacitors PCG-1 — PCG-4 and the flow of

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simulated lightning current pulse with the required ATP through the samples studied wires (cables).

The results of tests of wires and cables for resistance of the PF to current pulse 10/350 ps of the artificial lightning. Fig. 2 is a perspective view of the working table of the generator ГИТМ-10/350 is rigidly fixed to its high-current discharge circuit solid round copper wire diameter of 3.5 mm and a cross-section mm2 Si~9.6 mm2 of the TS of the RF coaxial cable РК Д2−3,5/9 [14] to the flow by it of the aperiodic current pulse 15/335 ps of the artificial lightning amplitude of about ImL-85.6 кА.

Fig. 2. The view of the workingtable of thepowerful high-voltage generator ГИТМ-10/350 with rigidly fixed to its massive steel electrodes solid round copper wire cross-section of Sy=9.6 of the TS of the RF coaxial cable РК Д2−3,5/9 with semi-air PET insulation of length of 0.5 m, removed protective sheath and PET twisted copper screen before exposure to the aperiodic current impulse 15/335 ps of the artificial lightning with amplitude ImL~85.6 кА (U313=16.5 kV- U34=4.2 kV)

Fig. 3 presents fixed with the help of calibrated by the state metrological service of the measuring shunt type ШК-300 [7, 10] and DSO Tektronix TDS 1012 aperiodic waveform current pulse 15/335 ps of artificial lightning flowing in the discharge circuit of the generator ГИТМ-10/350 via the copper core of the TS of the mentioned cable of the length of 0.5 m. After exposure to the amplitude of the current pulse ImL~85.6 кА the TS of the RF coaxial cable РК Д2−3,5/9 was visually as a whole and, accordingly, electrodynamically and electrothermally not damaged.

The maximum current density in the copper conductor on the particular cable was about § mi~ImL/Si~8.9 kA/mm2. Found in a copper conductor RF cable РК Д2−3,5/9 with PET insulation for the case (ImL~85.6 кА- Jl~2T06 A2-s) calculated by taking into account [15] The peak value of the maximum permissible density 5m1d current pulse 15/335 ps of the artificial lightning from the ratio 5m11. 353T08TmL/(. /L)½ is approximately equal to 5m1d=8.2 кА/mm2. It is known that at this average density 5m1d pulsed current in a copper

conductor of said cable, the maximum permissible shortterm temperature heating 01t it will not exceed 120 °C [15, 16]. From the obtained approximate data that the calculated value of the current density 5m1d=8.2 кА/mm2 different from its experimental value 5m1d=8,9 кА/mm2 about 8%.

Fig. 3. Oscillogram of the aperiodic artificial lightning current pulse generator circuit type ГИТМ-10/350 in the discharge of its PCG-1 — PCG-4 on the solid round copper conductor of cross-section S1=9.6 mm2 of the RF cable brand РК Д2−3,5/9 with semi-air PET insulation of the length of 0.5 m, and removal of the protective sheath of PET and twisted copper screen (ImL~85.6 kA- 8m1~ImL/S1~8.9 kA/mm2- Ту=Г5 ps- fm=25 ps- ip=335 ps- Jl=2−106 A2-s- qL~42 C- U31. 3=16.5 kV- U34=4.2 kV- vertical scale — 22. 52 kA / cell- the horizontal scale — 50 ms / cell)

Fig. 4 shows a working table of the generator ГИТМ-10/350 with electrodes attached to his split round copper conductor cross-section of S1~3.2 mm2 of the TS of the RF coaxial cable РК 50−7-11 with solid PET insulation [14] of the length of 0.5 m before exposure to the current pulse of 15/335 ps of the artificial lightning amplitude up ImL~85.6 kA.

Fig. 5 shows the initial stage of the electrical explosion (EE) of the copper conductor of the crosssection of S1~3.2 mm2 tested in the discharge circuit of the generator type ГИТМ-10/350 of the TS of the RF coaxial cable РК 50−7-11 with a solid of length of 0.5 m. Filming of the EE of the indicated copper wires made with the help of a digital camera s Canon M307E with its subsequent storyboard. The examination of the investigated TS after its electrothermal test indicates total sublimation of its copper from the interior of PET belt insulation cylindrical configuration of radio frequency coaxial cable РК 50−7-11.

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Fig. 4. The view of the working table of the generator ГИТМ-10/350 with rigidly fixed to its massive steel electrodes split round copper conductor with cross-section S3.2 mm2 of the TS of the RF coaxial cable РК 50−7-11 with a solid PET insulation of the length of 0.5 m and «plugged» with electrothermal tests its braided copper shield-up exposure to the aperiodic current pulse 15/335 ps of the artificial lightning amplitude of about 4−85.6 кА (U313−16.5 kV- U34−4.2 kV)

Fig. 5. The initial stage of EE of the copper conductor with cross-section of Sj=3.2 mm2 of the TS of the RF coaxial cable РК 50−7-11 with a solid PET insulation of the length of 0.5 m in the high-current discharge circuit of the generator ГИТМ-10/350

Fig. 6 shows in enlarged form an end cutting of the TS of the RF coaxial cable РК 50−7-11 with solid PET insulation of length of 0.5 m after exposure to the test current pulse 17/310 ps with amplitude 4−82.9 кА according to the oscillogram, shown in Fig. 7 and EE of its split round copper conductor cross-section of S1~3.2 mm2. The average peak value of pulse current density in the exploding electrical copper conductor was in this case 5m1−44−25.9 кА/mm2.

Fig. 6. View of the end cutting of the TS of the RF coaxial cable РК 50−7-11 with a solid PET insulation of the length of 0.5 m after passing on his split round copper conductor of the crosssection of Si=3.2 mm2 of the test current impulse 17/310 ps by the artificial lightning from the generator ГИТМ-10/350 and its EE with complete sublimation of copper (4−82.9 кА- 5^-44−25.9 кА/mm2- x/-17 ps- tm-28 ps- Tp-310 ps-

Jl-1. 76−106 АЧ- qL-37.9 C)

The calculated estimation for this electro-thermal case (4−82.9 кА- ,/l-L76−106 АЧ) of the maximum value of the critical density of the current pulse 17/310 ps of the artificial lightning ratio 5m1k-4. 416−1084/(JL)½ [15] indicates that 5m1k-27,6 кА/mm2. It can be concluded that for copper conductor cable brand РК 50−7-11 estimated value of the current density 5m1k-27.6 кА/mm2 from its experienced values 5m1k-25.9 кА/mm2 differs by about 6%.

We note that used in Fig. 3, 6 and 7, the value passed through the current-carrying parts of the TS wires and cables in the discharge circuit of the generator type ГИТМ-10/350 electric charge qL was determined by the ratio qL-kL4(1. 32xp+0. 27tm), where kL is the normalizing factor for changing our experience in the range (1. 092 — 1. 112).

Fig. 8 captures the moment of preparation for electrothermal tests in high-current discharge circuit from the generator ГИТМ-10/350 of the TS of the wire ПНП 2×2,5 with PVC insulation of the length of 0.5 m, comprising two parallel connected to the massive steel electrodes desktop used high voltage pulse current solid round copper conductor of the cross-section of S1−5 mm2.

Fig. 9 shows of the wire ПНП 2×2,5 with a PVC insulation, experienced the impact of its two parallel-connected to the discharge circuit of the generator type ГИТМ-10/350 solid round copper conductor of the total section of S1−5 mm2 of the aperiodic current pulse 17/335 ps of the artificial lightning amplitude 4−83.8 кА. The average peak value of pulse current density of large veins in the copper wires of the test in this case was equal to about 5m1−44−16.8 кА/mm2.

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Fig. 7. Oscillogram of the aperiodic artificial lightning current pulse in the circuit of the generator ГИТМ-10/350іп the discharge of its PCG-1 — PCG-4 to the electrically exploding digested a round copper conductor of the cross-section of Si=3.2 mm2 of the RF coaxial cable РК 50−7-11 with a solid PET insulation of the length of 0.5 m without the use of tests at its copper-braided screen (ImL~82.9 кА- 8m1~ImL/S1~

=25.9 кА/mm2- Tf=17 ps- tm=28 ps- xp=310 ps- JL=1. 76−106 A2-s- qL=37.9 C- U31−3=16.5 kV- U34=4.2 kV- vertical scale — 22. 52 kA / cell- the horizontal scale — 50 ms / cell)

Fig. 8. View of the working table of the generator ГИТМ-10/350 with rigidly fixed on its massive steel electrodes with solid round copper conductors of the total section of S1=5 mm2 of the TS of the wire ПНП 2×2,5 with a PVC insulation of the length of 0.5 m to the impact on them aperiodic current pulse 15/335 ps of the artificial lightning of amplitude of about ImL=85.6 кА (U31−3=16.5 kV- U34=4.2 kV)

considered aperiodic pulse 17/335 ps of the artificial lightning current amplitude ImL=83.8 кА.

Fig. 9. View of the fragment of the TS of the wire ПНП 2×2,5 with PVC insulation with two parallel-connected in the discharge circuit of the generator ГИТМ-10/350 with round copper conductors of the total section of S1=5 mm2 after flowing over them aperiodic pulse test current 17/335 ps of the artificial line lightning (ImL=83.8 кА- 5m1=ImL/S1=16.8 кА/mm2- Tf=17 ps- tm=28 ps- xp=335 ps- JL=1. 91T06 А2^- qL=41.2 C-

U31−3=16.5 kV- U34=4.2 kV)

At considerable heating of the PVC insulation in this type of testing also indicates that the average maximum density pulse current 5m1=16.8 кA/mm2copper wire ПНП 2×2,5 about 1.8 times the estimated maximum amplitude value allowable density used therein pulse current equal 5m1d=1. 506−108-ImL/(. /L)½=9.1 кА/mm2 [15]. In addition, the estimation of the temperature 01 of the pulse Joule heating by flowing 17/335 ps pulse current copper wires of said wire on the settlement ratio (2) from [15] shows that she was about 01=912 °С. Of course, what is the value of 01 is much higher than the maximum permissible short term temperature 01k heating wires (cables) with PVC insulation, is about 150 °C [15, 16]. These data indirectly confirm the accuracy of the experiment we found the maximum allowable maximum density of 15/335 ps pulse current linear artificial lightning current carrying parts of copper wires (cables) with PET and PVC insulation, strength totaled about 5m1d=9 кА/mm2.

Fig. 10 shows view of electrodes attached to the working table of the generator ГИТМ-10/350 of the TS of the continuous circular aluminum АППВнг2×6 conductor of the cross section S1=6 mm2 of the wire with PVC insulation length of 0.5 m (second aluminum conductor wire was tested by us «muffled»).

Oscillogram acting on the TS of solid round copper wire conductors ПНП 2×2,5 with PVC insulation by the aperiodic pulse current artificial lightning in this case, virtually the same waveform shown in Fig. 3. Copper wire strands of weathered rendered them strong electro and electrodynamic effects, and its PVC insulation — no. In this case, there has been a local destruction of its PVC insulation because of its heat from flowing through the veins of copper wire

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Fig. 10. View of the working table of the generator ГИТМ-10/350 with rigidly fixed to its massive steel electrodes solid circular core section of the TS of the continuous circular aluminum АППВнг2×6 conductor of the cross section S1~6 mm2 of the wire with PVC insulation length of 0.5 m before exposure by the aperiodic current pulse 15 / 335 gs of the artificial lightning of amplitude of about 4=85.6 кА (U31. 3=16.5 kV- U34=4.2 kV)

Fig. 11 oscillogram of the test pulse 17/265 gs of the artificial lightning current of amplitude 4=83.8 кА

flowing through electrically exploding in high-current

discharge circuit of the generator ГИТМ-10/350 aluminum conductor with cross-section of Si =6 mm2 of the АППВнг2×6 wire with PVC insulation 5m1=ImL/S1=14 кА/mm2) is presented.

Fig. 11. Oscillogram of the aperiodic artificial lightning current pulse in the circuit of the generator ГИТМ-10/350 at the discharge of its PCG-1 — PCG-4 to electrically exploding solid circular aluminum conductor of the of cross-section S1=6 mm2 of the АППВнг2×6 wire with PVC insulation of the length of 0.5 m (4=83.8 кА- 5m1=ImL/S1=14 кА/mm2- xy=17 gs- tm=28 gs- Tp=265 gs- JL=1. 58−106 АЧ- qL=33.3 C- U31. 3=16.5 kV-

U34=4.2 kV- vertical scale — 22. 52 kA / cell- the horizontal scale — 50 ms / cell)

Fig. 12 shows an intermediate stage of the EE of the tested in the generator ГИТМ-10/350 discharge circuit [7] of the aluminum cord of the cross-section of S1=6 mm2 of

the TS of the wire АППВнг2×6 with PVC insulation of the length of 0.5 m (4=83.8 кА- 5m1k=14 кА/mm2).

Fig. 12. An intermediate stage of EE of the continuous circular aluminum conductor of the cross-section of S1=6 mm2 of the TS of АППВнг2×6 wire with PVC insulation of the length of 0.5 m in the high discharge circuit of the generator ГИТМ-10/350

The estimated maximum value of the critical density of the current pulse 17/265 gs of the artificial lightning for the aluminum core of the wire АППВнг2×6 with PVC insulation by the approximation ratio 5m14=2. 863T08TmL/(. /L)½ [15] indicates that in this electrothermal case it is about 19 kA / mm2. Obtained empirically for the aluminum core value 5m1k=14 кА/mm2 is different from the calculated value 5m1k=19 кА/mm2 approximately 26%. Made in further experiments on the generator ГИТМ-10/350 of the TS of АППВнг2×6 wire with PVC insulation length of 0.5 m and its two parallel electrodes are connected to the discharge circuit of said high-current pulse current generator artificial lightning aluminum conductors general section S1=12 mm2 (Fig. 13) showed that the test was carried out at virtually survived have had a strong electro and electrodynamic effects.

Fig. 13. View of the wire АППВнг2×6 with PVC insulation of the length of 0.5 m with its parallel electrodes connected to working table of the generator ГИТМ-10/350 with two aluminum cords of total section of S1=12 mm2 to exposure by the pulse current 15/335 gs of the artificial lightning of amplitude 4=83.8 кА (on the right the measurement shunt ШК-300 [7, 10] included in the high-current discharge circuit of the generator is clearly shown)

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Oscillogram of the test pulse 15/335 ps of the simulated lightning current with amplitude /,*-83.8 кА in this case, virtually the same as the waveform shown earlier in Fig. 3. The peak pulse current density in the mentioned aluminum wire cord of the TS was about 5m1-/mL/S1−6.9 кА/mm2. Assessment of the maximum allowable limit of the current density in the TS of the aluminum wire of with PVC insulation at 15/335 ps pulse current on the settlement ratio 5m1d-0,975−108-/,*/(JL)½ [15] leads us to the fact that in this case 5m1d -5.9 кА/mm2. We can see that obtained with electrothermal tests experienced the peak value of the maximum permissible density 5m1d-6.9 кА/mm2 of the used pulse 15/335 ps pulse of current of the artificial lightning in the aluminum cord of the wire АППВнг2×6 with PVC insulation from the corresponding calculated value 5m1d -5.9 кА/mm2 is different by about 14%.

Conclusions.

1. For the first time experimentally it was found that when dealing with actual applications of lightning protection of electrical circuits of industrial electric power to a short stroke of lightning discharges in accordance with the requirements of a number of currently valid international and national standards must be assumed that the maximum allowable pulse density of 15/335 ps lightning current in the current-carrying parts of copper wires (cables) with PET and PVC insulation equals about 5m1d-9 кА/mm2, and in the current-carrying parts of their aluminum wires (cables) with PVC insulation — 5m1d-6 кА/mm2.

2. From the results experimental studies, carried out in the Institute «Molniya» of the NTU «KhPI» for lightning resistance of samples of cables and wires of the PF on a unique high-voltage current pulse generators of artificial lightning type ГИТМ-10/350 it is follow that the critical density of its impulse 15/335 ps of the current in the copper current-carrying parts of wires (cables) with PET and PVC insulation is about 5m1k-26 кА/mm2 and for aluminum current-carrying parts of wires (cables) with PVC insulation — about 5m1k-14 кА/mm2. When reaching in copper (aluminum) cords (screens) of the wires and cables of the electrical circuits of the PF of such a density of the current pulse of lightning they will be subject to EE and failure.

3. Found experimental values of densities 5m1d and 5m1k of normalized according to the requirements of existing International and national Standards of 15/335 ps pulse current artificial lightning in the aluminum and copper live parts of cables and wires of electric circuits of thePF are the appropriate choice and reasonable installation with their view of similar products in electrical power circuits of the PF will help to improve their operational and fire safety in the active thunderstorm activity in a constantly environmental aspects of industrial electric power air atmosphere.

REFERENCES

1. IEC 62 305−1: 2010 «Protection against lightning. Part 1: General principles». Geneva, IEC Publ., 2010.

2. IEC 62 305−2: 2010 «Protection against lightning.- Part 2: Risk management». Geneva, IEC Publ., 2010.

3. IEC 62 305−3: 2010 «Protection against lightning.- Part 3: Physical damage to structures and life hazard». Geneva, IEC Publ., 2010.

4. IEC 62 305−4: 2010 «Protection against lightning.- Part 4: Electrical and electronic systems within structures». Geneva, IEC Publ., 2010.

5. GOST R MEK 62 305−1-2010. Nacional'-nyj standart Rossi-jskoj Federacii «Menedzhment riska. Zashhita ot molnii. Chast'- 1: Obshhie principy» [GOST R IEC 62 305−1-2010. National Standard of the Russian Federation. Risk management. Protection from lightning. Part 1: General principles]. Moscow, Stan-dartinform Publ., 2011, 46 p. (Rus).

6. Deutsche Norm DIN EN 50 164−1: 2008 (VDE 0185−2001). Blitzschutzbauteile. — Teil 1: Anforderungen an Verbindungs-bauteile [German Norms DIN EN 50 164−1: 2008 (VDE 1 852 001). Protecting from Lightning of Buildings and their Parts. Part 1: Requirements on Parts Buildings and of Connection]. Berlin, Publ. DS, 2008. 16 p. (Ger).

7. Baranov M.I., Koliushko G.M., Kravchenko V.I., Rudakov S.V. A powerful high-voltage generator of aperiodic impulses of current of artificial lightning with the peak-temporal parameters rated on an International Standard IEC 62 305−1-2010. Elektro-tekhnika і elektromekhanika — Electrical engineering & amp- electromechanics, 2015, no. 1, pp. 51−56. (Rus).

8. Berzan V.P., Gelikman B. Yu., Guraevsky M.N., Ermuratsky V.V., Kuchinsky G.S., Mezenin O.L., Nazarov N.I., Peregudova E.N., Rud'- V.I., Sadovnikov A.I., Smirnov B.K., Stepina K.I. Elektricheskie kondensatory i kondensatornye ustanovki. Spra-vochnik [The electrical capacitors and condenser options. Directory]. Moscow, Energoatomizdat Publ., 1987, 656 p. (Rus).

9. Dashuk P.N., Zayents S.L., Komel'-kov V.S., Kuchinskiy G.S., Nikolaevskaya N.N., Shkuropat P.I., Shneerson G.A. Tehnika bol'-shih impul'-snyh tokov i magnitnyh polej [Technique large pulsed currents and magnetic fields]. Moscow, Atomizdat Publ., 1970. 472 p. (Rus).

10. Baranov M.I., Koliushko G.M., Kravchenko V.I., Nedzel-skyi O.S., Dnyschenko V.N. A current generator of the artificial lightning for full-scale tests of technical objects. Pribory i tekhnika eksperimenta — Instruments and experimental techniques, 2008, no. 3, pp. 81−85. (Rus).

11. Baranov M.I. Selection and installation of high-voltage ceramic protective resistors in the charge-discharge circuit powerful capacitive energy storage. Visnyk NTU «KhPI» — Bulletin of NTU «KhPI», 2014, no. 50(1092), pp. 13−20. (Rus).

12. Baranov M.I., Koliushko G.M., Nedzel'-skiy O.S., Plichko A.V., Ponuzhdaeva E.G. High voltage-controlled high-current spark gap with graphite electrodes RVGU-50. Visnyk NTU «KhPI» — Bulletin of NTU «KhPI», 2014, no. 50(1092), pp. 28−37. (Rus).

13. Baranov M.I., Koliushko G.M., Kravchenko V.I., Nedzel'-skiy O.S. High-voltage high-current generator air gaps of the current artificial lightning. Pribory i tekhnika eksperimenta — Instruments and experimental techniques, 2008, no. 6, pp. 58−62 (Rus).

14. Belorussov N.I., Saakjan A.E., Jakovleva A.I. Elektricheskie kabeli, provoda i shnury. Spravochnik [Electrical cables, wires

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and cords. Directory]. Moscow, Energoatomizdat Publ., 1988. 536 p. (Rus).

15. Baranov M.I., Kravchenko V.I. Electrothermal resistance wire and cable to the aircraft to the striking action pulsed current lightning. Elektrichestvo — Electricity, 2013, no. 10, pp. 7−15. (Rus).

16. Orlov I.N. Elektrotehnicheskij spravochnik. Proizvodstvo i raspredelenie elektricheskoj energii. Tom 3, kn. 1 [Electrical Engineering Handbook. Production and distribution of electric energy. Vol. 3, book 1]. Moscow, Energoatomizdat Publ., 1988, 880 p. (Rus).

Received 11. 09. 2015

M.I. Baranov1, Doctor of Technical Science, Chief Researcher, S.V. Rudakov2, Candidate of Technical Science, Associate Professor,

1 Scientific-& amp--Research Planning-& amp--Design Institute «Molniya», National Technical University «Kharkiv Polytechnic Institute», 47, Shevchenko Str., Kharkiv, 61 013, Ukraine.

phone +38 057 7 076 841, e-mail: eft@kpi. kharkov. ua

2 National University of Civil Protection of Ukraine,

94, Chernyshevska Str., Kharkiv, 61 023, Ukraine. phone +38 057 7 073 438, e-mail: serg_73@i. ua

How to cite this article:

Baranov M.I., Rudakov S.V. Experimental investigations of electro-thermal resistibility of conductors and cables to action of rationed on the International Standard IEC 62 305−1-2010 aperiodic impulse of current of artificial lightning.

Electrical engineering & amp- electromechanics, 2016, no. 1, pp. 48−55. doi: 10. 20 998/2074−272X. 2016.1. 09.

ISSN 2074−272X. Electrical Engineering & amp- Electromechanics. 2016. no. 1

55

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