CC BY
17
Назим
Ярослав
Викторович
кандидат технических наук, доцент кафедры «Металлические конструкции». Донбасская национальная академия строительства и архитектуры, Строительный институт, кафедра «Металлические конструкции»
e-mail: ksv@donnasa.ru
Танасогло Антон
Владимирович
кандидат технических наук, доцент кафедры «Металлические конструкции», Донбасская национальная академия строительства и архитектуры, Строительный институт, кафедра «Металлические конструкции»
e-mail: a.v.tan@mail.ru
Гаранжа Игорь
Михайлович
кандидат технических наук доцент кафедры «Металлические конструкции». Донбасская национальная академия строительства и архитектуры, Строительный институт, кафедра «Металлические конструкции»
e-mail: garigo@mail.ru
УДК 624.014
NAZI M Y. V. TANASOGLO A. V. GARANZHA I. M.
Double circuit large transmission line crossing 150 kv on the Dnieper river
This paper presents the reconstruction of the double circuit large transmission line crossing 150 kV "Kremenchuk Hydroelectric Station - Kremenchuk Heat and Power Station" through the Dnieper River due to the suspension of new conductors. The responsibility of the given construction is not established only by that fact, that given overhead transmission line is one of power supply lines of Kremenchuk, but also its intersystem value. During calculation of stress-strain state of steel towers whole number of interdependent factors is taken into account, which are climatic conditions, overhead lines design parameters (length of span, sag, clearances), terrain profile and scheme OPTL, difference between the tensions in adjacent anchor sites, calculation modes and load combinations, etc. Attention is accented to a local strengthening of metal structures of transition supports and foundations. Using the new conductors with a large cross section allowed to increase the energy reliability of Kremenchug city due to the power increasing of the line without replacing the existing towers.
Keywords: overhead transmission power line (OPTL), large transmission line crossing, reconstruction, conductor line, tower, calculation modes.
НАЗИМ Я. В., ТАНАСОГЛО А. В., ГАРАНЖА И. М.
ДВУХЦЕПНЫЙ БОЛЬШОЙ ПЕРЕХОД ВОЗДУШНОЙ ЛИНИИ 150 КВ ЧЕРЕЗ Р. ДНЕПР
В статье рассматривается реконструкция двухцепного большого перехода воздушной линии 150 кВ «КремГЭС — КремТЭС» через р. Днепр вследствие подвески новых проводов. Ответственность данного сооружения обусловлена не только тем, что данная ВЛявляется основной энергоснабжающей линией г. Кременчуг, но и ее межсистемным назначением. При расчете напряженно-деформированного состояния опор учитывается целый ряд взаимозависимых факторов, каковыми являются климатические условия, конструктивные параметры ВЛ (длина пролета, стрела провеса, габарит), профиль и план (схема) трассы, разность тяжений в смежных анкерованных участках, расчетные режимы работы и сочетания нагрузок и др. Предложено решение локального усиления металлоконструкций переходных опор и фундаментов. Применение новых проводов большего сечения позволило повысить энергетическую надежность г. Кременчуг вследствие увеличения передаваемой мощности данной линии без замены существующих опор.
Ключевые слова: воздушная линия электропередачи (ВЛ), большой переход воздушной линии, реконструкция, токоведущий провод, переходная опора, расчетные режимы.
1. Topic actuality
One of the main power lines, which supply energy Kremenchug city infrastructure (Poltava region, Ukraine), is overhead power transmission line 150 kV «Kremenchuk Hydroelectric Station — Kremenchuk Heat and Power Station». This power transmission line has been built more than sixty years ago using bronze conductors B-120.
However to provide the necessary throughput of OPTL 150 kV a conductor with an aluminum cross section 500 mm2 is required.
This power transmission line crosses the Dnieper River. Large transmission lines crossings are complex engineering structures [1, 2]. Taking into account that the impossibility of a long shutdown of the power line, its reconstruction with
Fig. 1. The large transmission line crossing through the Dnieper river: а) scheme; b) general view
supports and conductors replace is unworkable. Building of new OPTL 150 kV requires the significant material resources and huge investments, and most importantly will take more than a dozen of months.
That is why it was decided to reconstruct the existing OPTL without towers' replace, and only with partial strengthening of steel structure towers and foundations. Specialists of Donbas national academy of civil engineering and architecture have developed and implemented the working project of reconstruction in 2013 [3, 4].
Accomplishment of a technical measures complex for replace of electrical conductors and ground conductor on the existing OPTL 150 kV allowed to provide a higher level of exploitation of the energy object under consideration and to improve the stability of its functioning and reliability of power supply in Kremenchug city.
2. Brief characteristic of the object
The project of double circuit large transmission line crossing 150 kV «Kremenchuk Hydroelectric Station — Kremenchuk Heat and Power Station» through the Dnieper River (a site of towers 17-20) performed by Kharkov department of «HeatEnergoProject» institute in 1955. Length of transition is over 1.4 km (Fig. 1).
A characteristic feature of the OPTL 150 kV under consideration is that the power line crosses the Dnieper River on the islands. The tower number 17 is located on the Dnieper River coast, the tower №18 on a peninsula, the tower 19 on the Erik Island, the towers 20a and 20b are on the Didok Island. Therefore, span number 17-18 is the transition through the fairway, towers 18-19 and 19-20 are transitions through the ducts of Dnieper River (Fig. 2).
The maximum level of water space in the field of a ship navigation is 65.00 m of the Kremenchug hydroelectric station's lower pool.
This transmission power line, built and put into operation at the end of the 1950s, is the set of main Krenenchug city «supply ring». During an exploitation period of OPTL 150 kV «KremHPP — KremTPP» through the Dnieper river in the span 17-18 all bronze conductors B-120 were broken off by masts of ships and replaced to the conductor mark AC 240/32.
Supports 17, 18, 19 are double circuit transition tower type. They are spatial grid welded metal structures with mounting bolt connections (Fig. 3, a). Portal supports 20a, 20b consist of welded grid metal sections with mounting weld connections (Fig. 5, a).
Conductors on the site between towers 17-20 are bronze of mark B-120, ground-wire cable of mark C-50 in the span 18-19, in other spans — mark C-35.
According to chapter 2.5 regulations [5] climatic conditions of the OPTL 150 kV are the following: characteristic ice value — 15 N/m; characteristic value of wind pressure — 450 MPa; characteristic load of wind pressure to conductors and wires with diameter 10 mm, covered with icing — 8
Fig. 2. The longitudinal profile along the axis of the large transmission line crossing through the Dnieper River
N/m; an average annual air temperature +8 °C; minimal air temperature — 36 °C; maximal air temperature +38 °C.
3. The determination of sag conductor while under construction
For the calculation of electrical conductors and ground-wire cables used software package «MISI1» [6], developed at Donbas National Academy of Civil Engineering and Architecture. Software package implements the algorithm for determining the stress-strain state of flexible filaments with a certain weight, wind and critical spans for a given terrain profile and specific meteorological conditions [7].
To calculate the tension and sag of conductor in various modes the equation of state of wire has been used, which sets a mathematical relationship between stress load and temperature:
El2 YnEl2 vu t v ,,,
- %- -E(ti - ^ (1)
where aJ , on — tension in conductor (ground-wire cables) and in the original and calculated modes, respectively, Pa;
, ^jj — unit load on the conductor (cable) in the original and calculated modes, respectively, N/(m • m2);
l — calculated span of conductor, m;
E — reduced modulus of elasticity of conductor (cable),
Pa;
a — coefficient of linear thermal expansion of conductor (cable);
tj , tn — temperature in the original and calculated modes, respectively, °C.
Taking into account domestic [8-12] and foreign experience [13-20] recalculation was performed for two options of the conductors: traditional steel-aluminum conductor ACSR (AC-500/64) and homogeneous compact conductor AAAC (Aero-Z 504-2Z), for which the tests were
Table 1. Compare sag conductor In calculation modes
Span Span length, m Sag in calculation modes for options conductor, m АЕRО-Z 504-2Z АС-500/64
I II III IV V VI VII VIII IX X
17-18 435.0 12.94 13.04 12.57 12.91 11.56 13.59 11.41 13.66 11.69 13.99 9.56 11.51 13.05 15.03 10.54 12.57 11.71 14.00 10.51 12.56
18-19 551.0 27.08 32.46 26.92 32.34 25.61 31.75 25.48 31.20 25.87 31.45 22.89 29.57 27.79 32.26 24.23 30.36 25.89 31.46 24.21 30.36
model
performed in a climate chamber [21]. Ground-wire cable C70 has been used.
While calculating several interdependent factors have been taken into account: climatic conditions, overhead lines design parameters (length of span, sag, clearances), terrain profile and scheme PTL, difference between the tensions in adjacent anchor sites, calculation modes and load combinations, etc.
In result of the calculation in software package «MISI1» have determined arrows sag of conductors and ground-wire cables by 10 design modes. Maximal arrow sag is observed at the following conditions: a) conductors and ground-wire cable covered with icing when t = -5 °C, a velocity head of the wind at ice [mode I];) the maximal velocity head of the wind when t = -5 °C, no ice [mode III];) the maximal temperature t = +38 °C, no wind and ice [mode VII].
All these affect the stress-strain state of the OPTL, as the conductors and ground-wire cables loads depend directly from the sag and different heights of suspension points on towers. In this case software package allows to keep track the clearance from conductors to the ground, water level, ships and crossed engineering structures and others OPTL according to regulations [5].
The sags of conductors shows Table 1.
4. Recalculation and reinforcement of metal structures and pole basements
Recalculation of structures towers of large transmission line crossing was carried out on loads for all calculation modes with using of software complex «Structure CAD», the additional verification with using of software complex «LIRA».
Fig. 3, b shows the spatial computational model for calculating
the tower of line crossing in «Structure CAD». Fig. 5, b shows the computational model of portal tower.
For each mode the efforts in elements of tower have been determined. In the function of calculated efforts maximum rating has been taken up. Comparison of calculated efforts in elements of tower number 18 (% difference of the effort for two variants of the suspension conductors AC-500/64 and Aero-Z 504-2Z) is given in Table 2.
Analysis of the obtained results showed that the use of conductor AC-500/64 (compared to conductor Aero-Z 504-2Z) on a large transmission line crossing 150 kV «Kremenchuk Hydroelectric Station — Kremenchuk Heat and Power Station» through the Dnieper river leads to the reduces of the values of calculated efforts in the belt elements at the bottom of towers up to 18.6%, in the belts of console towers — 15.3%, diaphragms — 18.7%. At the same time, in the case of using the embodiment of AC-500/64 values of calculated efforts in lattice elements console increase to 27.4%, in lattice elements tower — to 22.8% (excluding lattice elements tower in area near of the lower console where the values of effort decrease by 26.5%).
As a result of the recalculation of a section as a part of a unified system the reserves of the bearing capacity of the tower of large crossing have been identified, as the further analysis of the stresses in the belts of supports in play of maximum loads allowed to state that the tension only in the elements of the middle and upper console exceed the design resistance of steel by 14.8%.
That is why a decision has been made to strengthen the side and bottom faces of middle and top console (Fig. 3) using the installation of additional elements — diagonal lattice element (Fig. 4). It allowed to reduce the calculated length, and thus the flexibility, and also to reduce tension of the values, given in the calculation sheet of the tower. Thus, towers number 17, 18, 19 after the local strengthening can take the load from the conductor's suspension of new cross sections 500 mm2 and a new ground-wire cables C70.
Description and number of the element Efforts in elements of tower Change of the calculated efforts for options suspension conductor, %
Project effort (on calculation sheet), kN Recalculation effort, kN (for conductor АС-500/64) Recalculation effort, kN (for conductor АЕRО-Z 504-2Z)
Belt elements of tower U1 -921.0 -1258.8 -1492.6 18.6
u2 -855.0 -1221.6 -1414.5 15.8
U3 -783.0 -1169.6 -1320.9 12.9
U4 -721.5 -1106 -1231.1 11.3
U5 -625.5 -996.4 -1157.9 16.2
U6 -470.8 -490.7 -455.3 -7.2
U7 -113.5 -173.9 -174.6 0.4
Elements of the lattice of tower Si -61.5 -67.4 -65.0 -3.6
s2 0.0 -92.9 -88.1 -5.2
S3 0.0 -55.4 -51.6 -6.9
S4 -78.3 -65.4 -50.5 -22.8
S5 -87.0 -74.1 -64.8 -12.6
s6 -100.5 -82.9 -65.8 -20.6
S7 -111.5 -94.5 -82.6 -12.6
S8 -126.0 -107.1 -96.5 -9.9
S9 -142.0 -121.9 -104.4 -14.4
S10 -146.5 -126.3 -145.3 15.0
S11 -214.0 -261.8 -331.2 26.5
S12 -156.0 -195.8 -159.4 -18.6
S13 -84.6 -177.1 -148.9 -15.9
S14 -34.4 -80.0 -80.4 0.5
Belt elements of traverse (console) N1 -51.7 -69.5 -67.2 -3.3
N'1 -101.6 -102.7 -118.4 15.3
n2 -68.2 -97.2 -98.1 0.9
N2 -41.3 -137.3 -155.0 12.9
N3 -85.6 -112.2 -118.7 5.8
N'3 -53.3 -179.7 -186.3 3.7
N4 -46.3 -34.3 -34.2 -0.3
N4 -11.0 -79.2 -77.8 -1.8
Elements of the lattice of traverse (console) S15 -22.3 -24.7 -25.4 2.83
S16 -30.5 -35.2 -33.3 -5.40
S17 -23.5 -50.7 -39.9 -21.30
S18 -25.2 -29.2 -27.2 -6.85
S19 -36.8 -43.1 -38.9 -9.74
S20 -30.4 -61.5 -47.9 -22.11
S21 -27.7 -25.1 -21.8 -13.15
S22 -29.8 -34.0 -30.2 -11.18
S23 -40.5 -46.4 -33.7 -27.37
S24 0.0 -59.9 -50.3 -16.03
S25 -12.9 -14.0 -15.1 7.86
S26 -18.5 -20.0 -21.4 7.00
S27 -14.1 -29.1 -29.0 -0.34
Fig. 4. Strengthening of lateral facet of the top console tower
Fig. 5. Scheme of the portal tower: a) geometrical scheme; b) spatial model
/
Fig. 7. The installing of the new conductors: a) the conductors unrolling by the water surface while erection procedure; b) the Installation and tension of conductors
The analysis of maximal stresses in metal elements of portal supports number 20a, 20b from new conductors and ground-wire cables showed that they do not exceed the values shown in the calculation sheet of this support. However, it was decided to strengthen the foundations of portal tower by pinch monolithic grillage (Fig. 6).
Decrease of metal consumption in the reconstruction of double circuit large transmission line crossing 150 kV through the Dnieper River composed 90%, as the tower replace was not required.
5. The installing of the new conductors and ground-wire cables
On the basis of a techno-economic justification of the comparison of the variants of two types of conductors applying, taking into account the considerable cost of conductor Aero-Z 504-2Z and applied line fittings, as well as the cost of the works and technological solutions for its installation, there was accepted the variant of reconstruction with the use of traditional conductor AC 500/64.
During the reconstruction of the OPTL 150 kV «Kremenchuk Hydroelectric Station — Kremenchuk Heat and Power Station» at the site between towers number 17-20 the bronze conductor B-120 has been replaced to conductor AC 500/64. Replacement conductors on span were performed by unrolling the new wires using existing conductors. The conductors were being replaced sequentially by one in each span (Fig. 7).
Hook sheave were being installed directly to the support's console or to
insulator strings. In the inaccessible to machinery lots the unrolling has been carried out with the help of pulling winches on the off-road car using the displaced into the hook sheaves the existing conductor and overhead ground-wire cable as wired rope. At the same time conductors unrolling to their full length was carried out on the surface of the water without a diving to the bottom of the river. For this purpose swollen rubber bags have been used (Fig. 7, a). The unrolling and installation of conductors and ground-wire cables were performed by a specialized element of an integrated electrician's team.
As an illustrative example Fig. 7, b shows the installation and tension of conductors using the equipment which is installed on a barge.
6. Concluding Remarks
The decisions made concerning the reconstruction of double circuit large transmission line crossing 150 kV through the Dnieper River allowed to enhance reliability of Kremenchug power supply scheme due to increase of capacity and transmitted power of this line by 18% without changing the existing towers.
Analysis of the results of recalculation of the OPTL allows to make a conclusion that the reserve of the carrying capacity can cover the loss of strength by increasing the load from the conductors and ground-wire cables (while their replacing on larger cross-section) in connection with the use of methods of mechanical calculation of overhead power lines as part of unified system [7], allowing to take into account the specified values of atmospheric
loads, orographic terrain conditions
and design factors of the overhead line.
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