A new aluminum wiring in Russia

Introduction

S 20 March 2019 Year in Russia enacted №2 Change to SP 256.1325800.2016 "Electrical residential and public buildings". Changing №2 permits the use of cables and wires with cores made of aluminum alloys brands 8030 and 8176 (таблица 1) в электропроводке при строительстве жилых и общественных зданий. This change also introduces some additional rules for working with aluminum conductors and cables.

Changed rulebook JV 256.1325800.2016 It enables the use of wires and cables with conductors made of aluminum alloys, not only in the distribution networks of buildings, who exercise the power of apartments, but in the apartments themselves.

Table 1 - Chemical composition of the aluminum alloys 8176 and 8030
GOST P 58019-2017 (с учетом поправки по ИУС №5 2018 г.)

Below is an overview of the problems and solutions of the aluminum wiring, as well as the practice of the aluminum wiring in the US and Canada.

The "old" aluminum wiring

aluminum wiring, which are installed in residential buildings from the mid-1960s, It is believed, It was the cause of many fires. Therefore, 2003 , in Russia it has been banned for use in housing construction. The conductors of the wiring while the wire was cold-worked aluminum AD0E mark GOST 4784 (таблица 2). The main cause of the problems with this aluminum wiring was weakening and overheating of contact connections of aluminum wire with so-called wiring products, ie with rosettes, switches, etc.. P.

Similar problems occurred with the aluminum wiring and abroad. for instance, in the US and Canada, these problems started after, as, beginning with 1965 года, due to the shortage and high cost of copper began to massively use aluminum wires and cables, including, for routing of electrical wiring within buildings. This wiring was a conductor of aluminum brand 1350 in the cold-worked condition H19. Chemical composition of the aluminum brand 1350 (таблица 3) практически совпадает с химическим составом АД0Е [1].

Table 2 – Химический состав марки алюминия АД0E (ГОСТ 4784-97)

Table 3 - Chemical composition of the aluminum brand 1350 по стандарту ANSI H35.1 [2]


aluminum brand 1350 It has been successfully used and is still used in overhead transmission lines from power plants to transformer substations. In this case, the aluminum has advantages over the copper because of its low specific weight.

Problems “old” wiring and their solutions

causes problems with "old" with the aluminum wiring conductors made of aluminum or brand marks AD0E 1350 считаются следующие особенности его свойств по сравнению с медной проводкой [2,3]:

  • creep up
  • lower ductility
  • higher thermal expansion
  • oxidation of the contact surfaces
  • galvanic corrosion in contact with brass and steel.

1) Ползучесть

Проблема:

  • Алюминий марки АД0Е (1350) под постоянной нагрузкой в контактном соединении проявляет ползучесть, что приводит к ослаблению электрического контакта (рисунок 1). Creep - it, simplistically, slow plastic deformation at stresses below the yield stress. See. more here.


Figure 1 – Ползучесть алюминия и ослабление контакта [13]

Решение:

  • Aluminum alloy wires 8030 and 8017 have a higher resistance to creep, which is close to the, which have copper wires. This is achieved, primarily, за счет повешенного содержания железа (рисунок 2).

Figure 2 [13]

2) Пластичность

Проблема:

Of aluminum wire 1350 used in the aluminum wiring in the fully cold-worked condition H19. In this state, the tensile strength only slightly higher than the yield stress, and elongation is only 1,5-2 % (drawing 3) [6]. A related "fragility" of the aluminum wire and its notch sensitivity and dents.

Figure 3- Change ultimate strength and ductility
при нагартовке и отжиге алюминия [5]

Решение:

  • Aluminum alloy wires 8030 and 8176 have a condition H2X, i.e. with intermediate annealing, which gives an elongation of not less than 10 % [7].

3) Температурное расширение

when heated aluminum increases its size and volume to a greater extent, than other materials, who are with him contact connections, for example, brass or steel. This causes thermal stresses and, often, plastic deformation, что приводит к уменьшению площади контакта и к еще большему его нагреву (рисунок 4) [8].

(а)

(б)

Figure 4 [9]

Решение:

  • Коэффициент температурного расширения алюминия практически не зависит от легирующих элементов или технологии [2]. To compensate for the high thermal expansion of aluminum wiring special contact devices of the materials used, близких по температурному расширению (рисунок 5) [8].
  • For aluminum wiring categorically do not use the so-called plug-in contacts, когда провод «втыкается» в контактное устройство [9]. These contacts are very sensitive to the differences of thermal expansion of the materials of the contact device and the aluminum conductor.

Figure 5 [8]

4) Окисление поверхности контакта

Проблема:

  • Fresh aluminum surface immediately covered with a film of aluminum oxide. Alumina is an electrical insulator. The thickness of this film depends on the temperature and humidity of the environment.

Решение:

  • At a temperature 25 ºC oxide thickness is only 2-50 nm. mechanical force, which is attached to the aluminum wire screw or plate easily "breaks through" brittle layer of aluminum oxide. Moreover, voltage, которое применяется в распределительных сетях зданий (обычно от 120 by 480 В) достаточно, чтобы преодолеть изолирующие свойства естественного оксида алюминия [3,4].
  • For, to get the highest good connection is better to remove the oxide layer from the surface of the aluminum wire and cause it conductive grease. This is especially important for conductors, which operate in a humid or corrosive atmosphere,, at high temperature or during long-term service life. Conductive grease prevents further growth of the oxide film and, Moreover, excludes the ingress of moisture at the contact surface or another electrolyte, что исключает гальваническую коррозию (см. below).

5) Гальваническая коррозия алюминия

Проблема:

  • materials, which are used in contact with the aluminum compound, may be other metals, for example, steel or brass. При наличии влаги это может приводить к образованию гальванической пары и вызывать гальваническую коррозию алюминия (см. Figure 3). This deteriorates the contact corrosion conditions and also can cause overheating of the contact connection.

Решение:

  • The use of special contact devices from materials, не вызывающих гальваническую коррозию алюминия (см. Figure 4);
  • Применение специальной контактной смазки (см. above item 4)).

The "new" aluminum alloys in the United States and Canada

Electrical alloys series 8000

Back in the early 1970s, a number of new aluminum alloys have been developed in the United States and Canada for the production of aluminum wire and cable. Standard ASTM B 800 [8] включает 6 such alloys, some of them have been patented. They all have a high iron content, as well as some other additive elements. The main differences of the chemical composition, for example, aluminum alloy 8030 and aluminum brand 1350 shown in Figure 6.

Figure 6 – Comparison of the chemical composition
aluminum alloy 8030 and aluminum brand 1350 [13]

At the present time for the production of aluminum wire and cable used only two aluminum alloy - 8030 and 8176 (таблица 4) [8-12]. The European standard EN 573-3 also includes a series of 8000 только эти два электротехнических алюминиевых сплава (таблица 5). For ease of comparison, the table also shows the 6 Alloys with a chemical composition 8030 and 8176 GOST P 58019.

Table 4 - alloys 8030 and 8176 в ASTM B 800

Table 5 - alloys 8030 and 8176 в IN 573-3

Table 6 - Chemical composition of alloys 8176 and 8030 GOST P 58019-2017

"American" and "Russian" alloys 8030 and 8176

note, that Russian alloys 8030 and 8176 существенно отличаются от своих американских и европейских аналогов (см. tables 4-6). In figures 7 and 8 shows the limits of the content of the main alloying elements in the alloy 8030 (железо-медь) и 8176 (железо-кремний) по ASTM B 800 and GOST R 58019. Russian alloys have a much lower content of alloying elements – gland, copper and silicon.

Figure 7 - Limits of iron and copper in the alloy 8030
by ASTM B 800 and GOST R 58019

Figure 8 - Limitation of silicon and iron content in the alloy 8176
by ASTM B 800 and GOST R 58019

Aluminum conductors in the US NEC

Согласно американскому Национальному электрическому кодексу (NEC) все алюминиевые жилы должны изготавливаться из электротехнических алюминиевых сплавов серии 8000:

  • whole – dimensions 12, 10 and 8 AWG
  • stranded – from 8 AWG and more.

Aluminum wires less 12 AWG (3,31 мм2) в Кодексе не рассматриваются.

Справка:

  • American wire gauge (AWG) – это стандартизированная система размеров для диаметров круглых токопроводящих жил – от 40 by 0000(4/0). The greater the number of AWG, the smaller the physical size of the core. Detail table AWG cm. on the image 9.


Figure 9 Detail AWG table

The use of aluminum conductors in the US and Canada

In the US and Canada is currently the aluminum alloy wire 8030 and 8176 available on the market only since the size of AWG 8 (8,37 мм2) [10]. It can also be seen in catalogs and presentations of manufacturers of aluminum wire and cable, who in the 1970s were the first to use alloys 8030 and 8176 – Alcan Cable и Southwire [11-13]. For internal wiring need aluminum wire sizes AWG 10 и AWG 12.

В презентации компании Alcan представлена наглядная схема стандартного применения алюминиевых проводов и кабелей для передачи электроэнергии от электростанций к жилым домам (рисунок 10) [13]: везде, но не внутри самих домов!


Figure 10 – Применение алюминиевых проводов в США и Канаде [13]

During the construction of new homes for wiring internal wiring, usually, применяют медные провода – об этом прямо указано и на сайте американской Алюминиевой Ассоциации [14].

At the same time, to connect major residential consumers of electricity - dryers, conditioners, boilers, Cooktop - usually used is aluminum cables. Moreover, in many American homes for supplying electric power from a common power grid to the home electrical panel is also used cables with aluminum conductors. In these cases, use aluminum conductors 8 and 6 AWG (8,37 и 13,3 mm2) [6].

For the last 20 лет значительно возросло применение алюминиевых проводов в качестве «фидерных» (подводящих) электрических линий для высотных зданий, hospitals, hotels, stadiums and, It has recently, дата-центров [3].

Learning to work with aluminum wires and cables

American Aluminum Association is making great efforts to promote the production of aluminum, including, aluminum cable products. An example of this is the, for example, объемное руководство по алюминиевым электрическим проводникам Aluminum Electrical Conductor Handbook [15].

Американская Алюминиевая Ассоциация и Национальная Ассоциация Электротехнических Подрядчиков (NECA) совместно разработали и регулярно обновляют Стандарт NECA/AA 104-2012 [9] по правилам установки алюминиевых проводов и кабелей в электрических сетях зданий. This standard provides guidance on working with aluminum conductors and cables, which includes a lot of detailed illustrations.

conclusion

1. Working with aluminum conductors and cables for internal and external wiring of buildings, including, alloys 8030 and 8176 It requires additional knowledge and skills compared to working with copper wires and cables. For this, for example, US and Canada, developed and distributed by special standards, guidelines and recommendations, as well as seminars and workshops.

2. In the US and Canada, cords and cables from aluminum alloys 8030 and 8176 used mainly, from size 8 AWG. These cables are used to connect large residential consumers, such as dryers, boilers, air conditioning, as well as for power supply from the network to the general distribution panel individual houses. For wiring internal wiring in the construction of new homes Aluminum wires and cables with dimensions 10 AWG и 12 AWG hardly used.

3. Over the past two decades in the United States and Canada has increased the use of wires and cables made of aluminum alloys 8030 and 8176 для подводящих (фидерных) линий подачи электроэнергии для высотных жилых, office buildings and data centers, as well as large structures, for example, stadiums.

Sources:

  1. Change №2 to the joint venture 256.1325800.2016 – 19.09.2018.
  2. Aluminum and Aluminum Alloys / ed. J.R. Davis - ASM International, 1993.
  3. Power cables with the conductors of aluminum alloys for wirings in residential buildings / Kamensky MK, Nedayhlib TA, Frik A.A. - Cables and wires – №3, 2018.
  4. Aluminum Alloy Conductors: 45 Years of Reliable Installations /Christel Hunter – Îäèí News magazine – January 18, 2016.
  5. Design of Aluminium structures: Selection of Structural Alloys Structural Design according to Eurocode 9 /R. Gitter – EUROCODES: Background and Applications, 2008.
  6. ASTM B 230 Standard Specification for Aluminum 1350–H19 Wire for Electrical Purposes.
  7. ASTM B 800 Standard Specification for 8000 Series Aluminum Alloy Wire for Electrical Purposes – Annealed and Intermediate Tempers.
  8. Evaluation of Aluminum Cable / Breck Booker, Southwire – 2011.
  9. NECA/AA 104-2012 Recommended Practice for Installing Aluminum Building
    Wire and Cable.
  10. The Evolution of Aluminum Conductors Used for Building Wire and Cable – National Electrical Manufactures Association (NEMA), 2012.
  11. Building Wire – Product Catalog – Alcan Cable
  12. https://www.southwire.com/Building-Wire/c/building-wire
  13. Stabiloy, Aluminum or copper? /Alex Mak – Alcan – 2008
  14. Technical Information on Electrical AluminumAluminum Association, 2019
  15. Aluminum Electrical Conductor Handbook /Aluminum Association, 1989.