Frequently Asked Questions
With many years of experience within the cable industry, the Nexans Olex team have been assisting customers on a wide range of cable related topics. To assist you, we have listed our most commonly asked questions by product category. Should you have a question that is not answered in these pages, please feel free to send your question to Nexans Olex via the Contact Us form and one of our experienced sales or technical team will respond to your request.
Why would a contractor want to use a flat sheathed cable instead of a circular cable?
Flat sheathed cable has one less operation in manufacture, contains less PVC than a circular cable and is therefore cheaper and being relatively flat it can be easier to install where space is confined. The disadvantage of flat sheath is that any twists makes neat installation difficult and it is very difficult to handle as conductor sizes increase.
PVC is available at various temperature ratings, ie 75°C, 90°C and 90°C-HT. As XLPE is rated at 90°C what's the difference between that and the higher rated PVC?
All grades of PVC are nominally rated at a 75°C operating temperature for normal installations however the higher PVC rated cables can operate at higher temperatures under certain conditions. These conditions are outlined in AS/NZ 3000:2000, but generally limit the time at which they can operate at those temperatures and restrict their usage where there is no potential for mechanical damage (PVC softens considerably at these temperatures). XLPE does not soften at 90°C and hence does not have the installation and operation restrictions of PVC.
Does the change of V105 to V90-HT mean that this grade of PVC has been down rated?
Some contractors interpreted the V105 rating as a continuous operating temperature of 105°C, which is incorrect. The V105 grade should only be operated at this temperature for limited periods under certain conditions. In order to avoid this confusion, the name has been changed to V90-HT, ie indicating that the cable can operate at high temperatures for limited times. The actual composition of the PVC has not changed.
What does the 0.6/1kV designation mean?
This is the method adopted generally by Australia, UK, Asia and Europe in indicating the voltage rating of a cable. The first number indicates the voltage rating of the insulation to ground and the second number indicates the voltage rating from one insulated conductor to another insulated conductor. Generally if a cable is only referred to by one voltage, the second number is used. For example a 19/33kV cable is often referred to as a 33kV cable.
Why are generally used cables designated as 450/750V when only 240 volts are being carried?
A minimum thickness of insulation is required to offer a reasonable level of resistance to mechanical damage. If only enough insulation was used to insulate to 240 volts, the covering would be too easily damaged.
Is your PVC sheathed flat cable suitable for installation against polystyrene insulation?
Most people are familiar with the "rigid" PVC compound used to make conduits and the "flexible" PVC compound used to make cables. The essential difference between the two is that the "flexible" material contains a kind of oil known as a plasticiser. It should be noted that the commonly employed plasticisers may migrate from the PVC and into other contacting materials, such as polystyrene or polyurethane. Once the plasticiser has migrated from the PVC compound it becomes less flexible and more brittle leading to eventual cable damage in the long term. The rate of plasticiser migration is dependent on many factors but it is largely affected by the size of the contact area between the PVC and other contacting material (i.e. larger contact area results in a quicker rate of migration of the plasticiser) so the rate of deterioration of the cable will vary depending on the installation conditions. There are two ways of preventing the migration of the plasticiser from cable. Either by installing the cable so there is no direct contact between the cable and other offending material (e.g. by installing in a conduit, or by applying an addition barrier tape), or by selecting alternative cable that does not include migratory type plasticiser (e.g. Alsecure® Envirolex® Flat TPS cable). At present the Alsecure® Envirolex® Flat TPS cable is not stocked but it may be supplied subject to minimum order quantity and manufacturing lead time and in this regard recommend that further enquiries are made with your Nexans Olex representative.
Can Nexans Olex manufacture submarine cables?
Olex have manufactured a range of cable designs for underwater applications. With our technical expertise and manufacturing experience, Olex are able to customise cable designs to provide the optimum mechanical and moisture protection to the cable. Consequently, Nexans Olex are able to provide cables which meet the customer’s various installation requirements.
Extra High Voltage
What is DTS?
Distributed Temperature Sensing (DTS) is a branch of condition monitoring whereby the temperature of an optical fibre, at any point long its route, can be determined with a high degree of accuracy.
Increasingly, high and extra high voltage underground cables are being manufactured with an optical fibre incorporated in such a way that it is either adjacent to the conductor insulation or as close as is practical. A profile of the conductor/s temperature can then be extrapolated from the fibre temperature and this temperature can then be used as a basis for a system rating calculation.
What is the purpose of the screens in instrumentation cables?
The presence of large machines, welders and other processes in industrial environments create a lot of electrical interference (noise). This noise has the potential to distort the clarity of signals that are transmitted between equipment, which may lead to false readings, For example, a system monitoring the temperature of a boiler may not report the correct temperature. A metallic screen will shield the cores of a cable from interference, thus improving the clarity of a signal.
Why are there individually screened pairs or triples as well as overall screened pairs or triples?
The overall screen will protect the interior of the cable from external interference, however individual pairs or triples may create interference between themselves, which has the potential to distort signals in adjacent pairs. The use of individually screened pairs or triples reduces this distortion.
Data cables have screens also – what is the difference between a data cable and an instrumentation cable?
Instrolex instrumentation cables are in fact a “heavy” duty” or industrial type of data cable. The wires are larger and the cable tends to be more substantial, making the whole assembly less fragile. In addition, the high level of noise in an industrial environment places extra demands upon the screening that is required. Hence, pairs are often individually screened as well as overall screened (as explained in the previous question).
There are cheaper instrumentation cable types available in the market. What are the differences?
Some instrumentation cables on the market reduce costs by reducing the amount of twist in the pairs and using a PVC compound with a lower temperature rating. The fewer twists increases the manufacturing speed and with the reduced rating of the PVC, reduces the overall cost of the cable.
Olex continue to use a PVC compound that has reduced flame propagation and a temperature rating of 90°C for superior performance. It still utilises varying twist rates between adjacent pairs for superior crosstalk immunity.
Are Instrolex cables manufactured to any standards and do they comply with the Hazardous Area Standards?
Instrolex cables are not made to any Australian Standard. The Instrolex design is identical to the Olex manufactured Dekoron product and is an internationally recognised and proven design for industrial instrumentation applications.
Individual components of the product however, do conform to various Australian Standards such as AS/NZS 1125 for the conductors, AS/NZS 3808 for the insulation and sheathing materials and AS3863 for the armouring materials. In addition, the Instrolex cables are manufactured in accordance with the Olex certified Quality Management System complying with AS/NZS ISO 9001.
With regards to the Hazardous Area Standards, Instrolex complies with this standard for Intrinsically Safe circuit provided that it is installed in accordance with the requirements of the relevant Australian Standard.
What is the voltage rating of Instrolex cables?
The standard Olex range of instrumentation cables have been tested in our factory at 2kV core-core and will withstand operating voltages in excess of 500 V AC without failure.
However, their insulation thickness of 0.4mm radial thickness does not meet Australian Standard requirements for mains voltage operation (250/440 or 0.6/1kV), hence the cables are supplied for use in Australia in instrumentation and similar applications with nominal working voltage of 110 V AC or 150 V DC. For export use, where Australian Standards compliance is not a requirement, the Instrolex cables are rated 300 V AC/DC.
Why are some conductors tinned and others are not?
Tinned conductors resist corrosion and are therefore very suitable for marine applications. It is also necessary to tin conductors where a rubber insulation comes in direct contact with the conductor. The use of tinned conductors also assist in making the conductor easier to solder.
What is the difference between a cord and a cable?
There are two main differences between a cord and a cable.
A cord includes conductor sizes up to and including 4mm2 and up to five cores, and is generally rated at 240/440 volts (although some heavy duty flexible cords are rated at 0.6/1kV).
A cable includes conductor sizes of 6mm2 and above and is generally rated at 0.6/1kV. Cables with flexible conductors less than 6mm2 and with a core count greater than five core are also classified as flexible cables.
Flexible cables are often used with oil or chemicals. How do you determine which cables will be suitable for these applications?
The circumstances of an installation have a large bearing upon the suitability for exposure to chemicals and oils. This includes the anticipated length of exposure, the type of chemicals or oil involved, operating temperature, environment and application. If you are asked for a recommendation, obtain as much information as you can and refer to your local Olex sales office.
Why don’t manufacturers mix PVC and rubber in building a cable? For example, a PVC insulation and CSP sheath.
In determining the construction of a cable, the designer looks at the environment in which the cable will operate. For example, does it need to operate at low temperature, in oil or chemicals, will it be subject to mechanical damage, etc. This generally then determines the sheath that will be required. In selecting the insulation, the operating voltage and current need to be considered and then a selection is made so that it is compatible with the sheath. For example, PVC and CSP could not be combined because the PVC would melt when the CSP is cured at high temperature.
What type of flexible cord or cable is used on hot appliances?
The relevant application standards specify that for those appliances the cable must resist heat deformation. This is achieved by using either a rubber sheath or cotton covered PVC insulated cords for some appliances.
Are the Olex 4 core flexible cord core colours (Brown, Light Blue, White, Green/Yellow), in contradiction with AS/NZS 3000?
The Olex flexible cord colours are in accordance with the requirements set out in AS/NZS 3191 and are not intended to apply to flexible cords used in fixed wiring as outlined in AS/NZS 3000. The standard range of flexible cords (with colours highlighted below), should not be used as fixed wiring, as they have incorrect insulation colours. Flexible cords can be used as fixed wiring if the alternative insulation colour scheme (ie. as per fixed cables) is used and they are of the heavy duty type or installed in the appropriate wiring enclosure.
The standard range of Olex insulation colours for fixed and flexible cables designed to Australian Standards are as follows:
Fixed cables (450/750V & 0.6/1kV)
Active Cores: red, white (uncoloured), blue
Neutral Core: black
Flexible Cords (ordinary duty & heavy duty – standard)
Active Cores: brown, white (black), orange
Neutral Core: light blue
Can I use Flexolex® in reeling applications?
The flexible 3, 4 and 5 core cables offered are part of the standard and stocked Olex range of products. These cables are renowned for their flexibility and have been designed for ease of handling and bending. Under conditions of reeling with low tension and appropriate bending diameters, these cables will provide good performance for many years.
However, such designs do not suit tight bending and reeling under tension where the sheath can be squeezed and induced to move toward one end, thereby exhibiting the characteristics of “corkscrewing”. Another effect of reeling under tension with misaligned rollers or guides, is for the cables to roll on their axis which eventually causes conductor wire breakages.
What is the relationship between Austel and the Australian Communications Authority (ACA)?
Before July 1997, all telecommunications products needed Austel approval, involving an exhaustive and expensive system of testing and approval, which Olex met. Since the disbanding of Austel in 1997 and the establishment of the Australian Communications Authority (ACA), testing has become the responsibility of the manufacturer or supplier. Companies are now issued with an ACA Merchant Number which must appear on all products along with the “A tick” symbol to signify compliance with the ACA requirements. All Olex communication products comply with these regulations and are all marked in this way. In 2005, the Australian Communications and Media Authority took over the ACA. Regulations however have not changed.
What is Olex’s ACA Merchant Number?
Olex’s ACA Merchant Number is N10594.
Where is the Austel approval number?
The Austel approval number has been replaced with the ACA Merchant Number.
Is Figure 8, 24/0.20mm (Olex code JSF.75) 240 volt rated?
Yes. It is rated in accordance with Australian Standard 3191. This product is also approved for use to AS/ACIF S008:2001.
What does the term Extra Low Voltage (ELV) mean?
Extra low voltage is cable that is rated at 50V AC/ 120V DC. This is defined as such in AS/NZS 3000:2000, known as the “Wiring Rules”.
Why is solid copper conductor preferred over copper clad steel conductor in closed circuit television applications?
The copper clad steel conductor was specifically developed for use in coaxial cables intended for RF use. RF implies that the signal being carried by the coax is of “high frequency”. All conductors that carry alternating currents have losses that are associated with the conductor’s resistance. Due to skin effects, the resistance increases when an alternating current flows in it. This effect causes the current to flow more in the outer region of the conductor and not in the centre, and is due to inductive effects. This effect also increases with the magnitude of the frequency of the alternating current. So much so that at RF, only the very thin surface layer is useful for carrying currents.
Therefore, to reduce the cost of the cable, the centre of the conductor is replaced with a low cost material such as steel. Closed circuit television applications employ the base video signal, which consists of alternating currents of much lower frequency than RF. At these frequencies, the skin effect is not as significant so a greater proportion of the conductor can be utilised for carrying the video signal current. Therefore, the solid copper conductor will have a lower loss for video signal when compared to a copper clad conductor, so it is preferred for CCTV applications.
Which cables are approved for use in mines?
The answer is dependent on the State in which the mine is located.
In NSW, the system is that approval is needed from the Department of Mineral Resources for compliance to the NSW Coal Mines Regulation Act, 1982.
Olex have a Certificate of Approval. Olex is covered by Approval No: MDA ex 1355 – File No: M82/2882, Dated 27th February. 1985. The approval covers all cables made to AS1802 and AS1972 where applicable. I also understand there are amendments which Alfred Eiden had and could have covered AS2802.
In QLD, the system is that approval is needed from the Department of Minerals and Energy for compliance to the Queensland Coal Mining Act, 1925-1990. This Act stated that cable made and in conformance with Australian Standards 1802, 2802 and 1972 is deemed suitable to be used subject to the cable being installed, operated, maintained and overhauled in accordance with the provisions of the Act.
For cables made to other Standards, then specific approval must be obtained from the Inspector of Coal Mines at the Department. As our equipment is of an electrical nature, the approval would come from the Principal Electrical Inspector.
Olex have a Certificate of Approval, number QMD 91 6984 X for the use of 95mm2 XLPE 12.7/22kV PVC SWA PVC.
In Western Australia, Western Power (formerly SECWA) that hold jurisdiction in this area and authorises approvals.
If a cable has a fire rating, does this mean that it won’t burn?
Fire rated cables are designed to continue functioning during the course of a fire for a specific period of time which allows for safe evacuation of a building by maintaining smoke handling systems, emergency lighting etc. The cable will burn however in a manner that ensures circuit integrity during the fire. The tests to determine the fire rating of a cable system are documented in AS/NZS 3013:2005.
Can a cable with a fire rating operate continuously in hot environments, for example, very close to a furnace?
No, a cable with a fire rating does not necessarily mean that is it suitable for use in a hot environment. It is necessary to design cables using special materials such as silicone or glass fibre to withstand relatively high temperatures (in excess of 110°C on a continuous basis.)
What does a two hour fire rating mean?
The fire test for determining the fire rating of a cable consists of exposing a cable and fittings to extreme temperature in a furnace over a period of two hours. The temperature builds throughout the period to a final temperature of around 1030°C. The cables are subjected to their round operating voltage and a current flows through the conductors. If the insulation fails, ie shorts to ground, or if the current stops flowing, the test has failed. This test permits comparisons between different manufacturer’s products and provides a benchmark on which installation standards can be based.
How is the resistance to mechanical impact measured?
A length of cable is energised and the impacted with a device, loaded with a predetermined weight. The impact point will consist of two different points, a blunt crushing type of point and a sharp cutting type of point. If the cable maintains circuit integrity through this test, it attains a mechanical rating. Different loads can be applied to attain different levels of rating.
What does the cable system consist of?
The AS/NZS 3013:2005 fire test requires that all of the items that comprise a cabling system operating in the fire rated zone must be tested and pass as a system. In other words, it is no longer possible to test the cable in isolation. Other components that may comprise a system include fasteners, saddlers, ladders, cable trays, clamping systems, etc. Joints only need to be tested if they are installed in the fire rated zone. Alsecure® is available in lengths to suit the contractor, hence this requirement should not be necessary.
Is it OK to use EPR/PCP Mine Trailing Cables in submersible applications?
Olex does not view our PCP sheathed cable as being a long term solution for submersible applications. The PCP contains Magnesium Oxide (as a curing agent) which will absorb water.
A better solution would be to utilise a CPE sheath, as used on our Flexolex® range, which does not contain Magnesium Oxide. It has also been tested at elevated water pressures and has been found to be suitable for submersible applications such as submersible pump motor connections.
Both cables contain cores which are insulated with EPR. The insulation itself gives good protection from water penetration although it would be preferable for the sheath to do so also. Therefore, for this application, CPE is the preferred sheathing material rather than PCP.
How do I determine the rating of a cable?
The continuous current rating of a cable is determined by the ability of the cable to dissipate the heat generated by the current passing through its conductor. It depends on a number of parameters, but the most important are the:
•Conductors’ DC resistance;
•Thermal resistance of the insulating sheathing materials; and
•Ambient conditions of the environment where the cable is installed (for example the surrounding air temperature).
For standard cables such as PVC building wire, XLPE SDI or circular cables (all rated 0.6/1kV), the ratings have all been calculated and are tabulated in Australian Standard AS/NZS 3008.1.1. This standard includes various circuit configurations such as single and three phase and various installation arrangement such as “in air”, “direct buried in ground”, “in ducts”, etc.
Olex has included the same tables from AS/NZS 3008.1.1 in the Standard Product Search our customer’s convenience.
For ratings of HV XLPE cables, please see the attached HV PDF in the products sections.
If ratings are required for non-standard cables or for cables in non-standard installation or environmental conditions, Olex have specialised software available for performing the rating calculation to suit specific customer requirements.
How do I measure the amount of current a cable can carry over a particular distance?
A current which flows in a conductor will cause a voltage drop over the conductor’s length. This voltage drop is due to the resistance of the conductor. The Wiring Rules AS/NZS 3000:2000 states a maximum limit for voltage drop of 5% for low voltage systems. Therefore there is a simple calculation which can be done that relates the percentage volt drop, the cable length, and the voltage drop factor for a particular cable. This calculation and voltage drop factors (in mV/A.m –milliVolt per Amp metre) are given in AS/NZS 3008.1.1. The formulae for how much current is:
I = 5 x V x 1000
100 L x Vc
I = cable current that produces the maximum voltage drop
V = system voltage (ie normally 400V for 3 phase and 230V for single phase)
Vc = mV/A.m volt drop factor for cable from AS/NZS 3008.1.1
L = circuit length
Note: In addition to performing this voltage drop calculation, the continuous current rating of the cable must be checked.
How do I determine the size of cable required for a particular current of a distance?
A current which flows in a conductor will cause a voltage drop over the length of conductor due too its resistance. The cable size can be determined to find Vc as shown below:
Vc = 5 x V x 1000
100 L x I
When Vc is found, it is then necessary to look up the appropriate table of volt drop factors in AS/NZS 3008.1.1 to find a cable size which has a lower voltage drop factor than that just calculated. After obtaining the cable size, the continuous current rating must again be checked. If the cable size meets or exceeds the required current, I, then this is the answer. If not, the cable size must be increased until the current, I, is obtained.
Are orange circular PVC cables suitable for use outdoors exposed to sunlight? Is the orange PVC “UV stabilised”?
Yes, orange circular PVC are suitable for use outdoors, since they have an outer sheath which protects the core insulation. Whilst some fading of the colour of the sheath is expected over time, this is restricted to just the outer surface layer and does not penetrate into the bulk of the sheath material. Therefore the sheath will continue to provide protection of the core insulation. In addition AS/NZS 3000:2000 states in Note 1 to Clause 3.3.12 - “Sheathed cables exposed to direct sunlight do not require further protection from ultraviolet radiation as the sheath is considered to provide the necessary protection.”
The term “UV stabilised” has an understanding in the cable industry to mean the addition of a minimum amount of carbon black to a material (2%). In reality, this is only essential for Polyethylene exposed to UV, such as XLPE Aerial Bundled cable or in high density PE in High Voltage cables. This will obviously render the material black and is regarded as the best means of UV protection of a material. Even black PVC sheathed cables, using only 0.5% carbon black, will not suffer from fading. The orange circular PVC cable does not contain carbon black, but the material is still “UV resistant”.
What is the correct lug for use on compacted conductors?
Compacted conductors have a smaller diameter compared to standard stranded conductors, but their nominal cross sectional area is equivalent and a lug designated for the same cross sectional area must be used on the compacted conductor. Even though the lug will appear to fit more loosely, when crimped in accordance with the lug manufacturer’s recommendations, the end result is the equivalent to the crimping of a standard conductor. Compacting the conductor by the cable manufacturer is just the action of pushing all the wires together, getting rid of the air gaps, ahead of time.
Note: The general practice is for lug manufacturers to manufacture a range of lug sizes that suits both the compacted and standard conductors. However, if there are any concerns, please consult your lug manufacturer.
What is the correct lug for use on flexible conductors?
Flexible conductors have a larger diameter compared to a nominal stranded conductor of the same nominal cross-sectional area. Since the diameter of the flexible conductor is larger, it is difficult to insert into the barrel of a lug of the same cross-sectional area.
One method of terminating is by using the next largest lug size and crimping with a half hex and flat dye. Alternatively, a special lug suited to flexible conductors can be sought.
Further information on crimping techniques can be obtained from lug manufacturers.
The terminology below refers to frequently used terms which are unique to Nexans Olex.
Ceramifiable® Registered Trade Name for a type of polymer composition that becomes a ceramic when burned, continuing to provide insulation to the conductor.
CPE Chlorinated Polyethylene. An oil, ozone and heat resistant sheathing compound.
CSP, CSPE Chlorosulphonated Polyethylene. Oil, ozone and heat resistant sheathing material. DuPont Trade Name for this product is Hypalon.
EPR Ethylene Propylene Rubber. A water and ozone resistant, flexile, cross linked high grade insulation material.
Fire Resistant The property of cables to continue to function while under the influence of fire. Olex cables that are Fire Resistant provide circuit integrity even when burned and maintains integrity after the fire has extinguished. In most cases, the cables will withstand a water spray and still provide circuit integrity.
Flame Retardant The property of cables to retard or slow the progress of fire and flame along the cable. This is achieved through the use of materials that do not readily burn and will tend to self-extinguish.
Flexolex® Registered Trade Name for a range of cables insulated with EPR and sheathed with CPE. These cables include flexible conductors and are suitable for flexing applications. The cables are constructed to comply with AS/NZS 5000.1 (power and control), AS/NZS 3191 (cords), AS/NZS 1995 (welding), and IEC 60245.4 (cords). The range includes TCWB screened cables. A range is also available with pilot cores for use with submersible pumps.
FR Flame Retardant.
GSWB Galvanised Steel Wire Braid.
HDPE High Density Polyethylene, generally used as a sheathing material where it provides high resistance to water penetration, is very hard, has low coefficient of friction, and is abrasion resistant.
HF Halogen Free.
HFFR Halogen Free Flame Retardant.
HOFR Heat, Oil and Flame Retardant.
Instrolex® Registered Trade Name for a range of Instrumentation cables insulated and sheathed with a flame retardant PVC. The standard range includes up to 50 pairs and up to 36 triples in either 0.5mm2 or 1.5mm2 conductors. Larger conductors may be specified, as can options of Lead Sheathing, SWA, or HF insulation and sheath materials.
LSZH, LS0H Low Smoke Zero Halogen.
PCP Polychloroprene (DuPont Trade Name for this product is Neoprene). This is an oil resistant, tough sheathing material, that is used mainly in mining cables as an outer sheath.
Powerlex™ Trade Name for a range of PVC flexible cords and cables compliant with all relevant Australian standards.
Pyrolex® Registered Trade Name for a range of fire resistant and flame retardant cables made of materials that are LSZH and pass tests such as AS/NZS 3013, IEC 60332 (all parts), IEC 60754, BS 4066, and BS 6387. The Pyrolex® range includes cables insulated with Ceramifiable®.
SWA Steel Wire Armour. This is used to provide mechanical protection for the cable.
TCWB Tinned Copper Wire Braid.
TPE Thermoplastic Elastomer. A plastic material compounded so it displays characteristics like an elastomer. TPE is normally tough, cut resistant, flexible, smooth, with vibrant colouring.
Varolex® Registered Trade Name for a range of cables suitable as Variable Speed Drive supply cables. The cables are insulated with XLPE, overall copper screened, and sheathed with PVC. The range available includes fixed conductors with copper tape screen, or flexible conductors with copper braid screen. The key features include low capacitance of the power cores, high electrical strength insulation, and three earth conductors of maximum size disposed in the cable interstices. These cables are constructed to comply with AS/NZS 5000.1 (0.6/1kV power), but include the extra features to provide a low impedance path to ground for high frequency signals and to withstand the higher voltages at the motor terminal ends.
Versolex® Registered Trade Name for a range of cables insulated with a cross linked flexible polyolefin and sheathed with a TPE. These cables include flexible conductors and are suitable for both fixed and flexing applications. The cables are constructed to comply with AS/NZS 5000.1 (power and control), AS/NZS 3191 (cords), AS/NZS 1995 (welding), IEC 60227.4 (PVC cords), and IEC 60245.4 (EPR cords). The range includes TCWB screened cables. A range is also available with pilot cores for submersible pumps.
XLPE Cross Linked Polyethylene. A high grade insulation material.
ZH Zero Halogen.