Power Cables

Major Differences Between Power Cables and Control Cables

Power cables and control cables are instrumentation cable types used in industrial environments and electrical power generation. These cables are almost similar in certain aspects but also have numerous differences. Both kinds of cables for power and control applications are created with PVC, XLPE, PE, steel-wire or sheathed armour, single and multi-conductor, and jacket.

Basically, a power cable is a cable type used for transmitting power from its source to devices. It may also be utilised in manufacturing industrial establishments and in the internal supplies of power. On the other hand, a control cable is a type of cable that connects different field devices from the control room. It is usually created for sending signals from a control device, automation control, and measurement and regulation. Read on to learn more about the differences between power and control cables.

Function
Power cables are considered the cornerstone of the electrical system for huge power transmission and distribution. Low energy and high energy are both transmitted to the equipment from the source. These power cables are typically utilised on the power system’s main lines to transfer and distribute power at every voltage level, from 1 kV to 500 kV and beyond.

On the other hand, control cables are primarily used to distribute power from distribution points to different instrumentation and electrical equipment. The current flowing through the control cable is much less than that of the power cable. One can find control cables with a minimum voltage class of 300 V to 500 V and a cross-section of 0.75 mm2. Meanwhile, the power cable’s cross-sectional area is multiple times larger than the control cables, sometimes reaching 630 mm2.

In terms of function, power cables are utilised in power generation, transmission, transformation, distribution, and power supply lines. On the other hand, control cables are used to directly transmit electrical energy from the power distribution point to the various electrical appliances and equipment.

Shielding
A power cable is usually used for the transmission and distribution of the power of huge functions in the power system’s main line. On the other hand, control cables are often utilised for the purposes of automation, control, and measurement. Control cables provide excellent resistance to interference or signal noise.

Hence, control cables are considered suitable for sending low-voltage signals, whereas power cables have the capability to transfer higher energy. During the laying of control cables, it is essential to provide a gap with electrical cables of around 0.2 meters in order to overcome the effects of electromagnetic interference (EMI).

Coating And Insulation
When it comes to power cables, there are usually requirements for resistance to traction, temperature, corrosion, and compression. On the contrary, the requirements of control cables are relatively low. Thus, most of the time, the sheath and insulation of the power cables are thicker than those of the control cables.

Because power cables are utilised in active environments and transfer plenty of energy, they require excellent sheathing. The sheath in power cables is vigorous and resists an array of external factors, such as temperature and corrosion. The same sheath is not required in control cables, and they commonly have conventional PVC insulation.

4 Reasons Why Copper Is Used in Electrical Power Cables

Copper has many benefits, making it a common material in manufacturing. One of the areas where copper is most valuable is in electrical wiring. Copper power cables are found in electrical applications nearly everywhere. Electricians, data centers, construction companies, and more use copper cabling for various reasons. Keep reading to learn four reasons why copper is used for electrical power cables.

High Conductivity

Copper is one of the most highly conductive metals on the market. In fact, copper is only second to silver in conductivity rankings. Thanks to its high conductivity, copper can easily transmit electricity, which makes it an ideal material for electrical wiring. Copper allows electrical currents to travel a greater distance, enabling manufacturers to create longer cables. Cables crafted from copper materials have superior performance and efficiency than those made with other materials like aluminum.

Superior Ductility

Copper is a convenient metal to work with due to its ductility, which is how much you can deform it without it breaking. This material is highly malleable and flexible, ideal for manufacturing power cables. Because many power cables snake through ceilings, walls, floors, and
appliances, they need to be flexible and fit a variety of spaces.

Copper wires can bend and conform to various shapes without losing power or efficiency. This enhanced ductility also ensures there’s less damage to a cable while in tight storage spaces or wrapped around a column, providing long-lasting usability.

Useful Resistances

Copper also has useful resistances for use in electrical wiring. It features corrosion resistance, which is ideal for safety and performance. This corrosion resistance occurs due to the oxide layer that forms on its surface over time. Because of this layer, this material has a very slow corrosion rate, boosting its longevity and preventing rusting, ensuring it maintains its functions in environments where moisture is present in the air.

Copper also features superior heat resistance. This helps keep power cables from overheating and causing fires. Copper electrical wiring can help lessen the occurrences of home and commercial building fires. These resistances are ideal for use in wiring because they promote safety in any wiring application.

Inexpensive And Accessible

This material is more affordable than other metals. Copper is less expensive than its other conductive counterparts, which include silver and gold. You can achieve better conductive results with copper for a lower price. Additionally, copper is more accessible due to its usefulness in cabling and other applications. You can find many copper suppliers and mines worldwide that supply copper sheets, wires, and more for manufacturing.

Power Cables Market Trends

What You Need To Know About Power Cables

 

The Actual Current Rating Of a Cable - Derating Factors Are Real

The tables of current rating of electric cables, as published by cable manufacturers, give the value of ‘standard current rating’. This is the maximum safe continuous current that the cable can carry under standard conditions. In South Africa, the standard conditions assume an air temperature of 30 °C, that the cables are shaded from the sun, that the maximum soil temperature of buried cables is 20 °C, and that there are no multiple cables touching, or in close proximity to each other.

There are also other standard conditions for altitude, soil resistivity, depth of burial, etc. If any of the actual site conditions are worse than standard or can become worse during the life of the cable, then an appropriate derating of the standard current rating is necessary so that the electric cable does not overheat. The opposite also applies; for example, a cable buried in swampy soil will probably have a soil thermal resistivity much better than standard, and the cables’ current rating can be appropriately re-rated upwards.

 

Single Core Cables Are Very Different From Three Or Four Core Cables And Should Be Installed Differently

When the cable’s conductor size is required to be quite large, often there is no possibility of obtaining the cable as a three or four core cable as it would simply be too big to handle. In such cases, it’s necessary to use single core cables. These cables need to be installed with care and treated differently from three or four core cables for the following reasons:

Within a three or four core cable, there is a balanced electromagnetic field within the armour and, as a result, there can be no voltage induced into this armour. In the case of single core cables, within the metallic screen or armour of each core, there is an electromagnetic field arising from only one phase, and this will induce a voltage into any surrounding metallic sheath. These metallic sheaths include copper tape screens, lead sheaths, and armour.

In the case of a three or four core cable, it’s common practice to bond the armour on both sides of the cable to earth. In the case of single core cables, this is not always recommended, because the induced currents can drive large circulating currents in the armour loops.

Where the metallic sheaths of single core cables are single point bonded (earthed on one side only), induced voltages will appear at the other end (the unearthed end) of the cable, between the metallic sheaths and earth, and between the metallic sheaths themselves. When installing single core cables, whether LV or MV, it’s advisable to consult with an expert, in order to arrive at an optimum solution and avoid embarrassing cable failures as a result of these induced voltages or circulating currents.