Electric cables are normally installed on the assumption of a safe working life

Electric cables are normally installed on the assumption of a safe working life
Electric cables are normally installed on the assumption of a safe working life of at least 20 years. Changes in the insulating material take place with the passing of time and these changes, which may eventually result in an electrical breakdown, are accelerated at higher temperatures. Thus, if the working life is fixed, the limiting factor is the temperature at which the cable is required to operate.

During operation, the temperature at which the cable will operate depends upon the ambient temperature and the heating effects of the current produced due to the resistance of the cable conductors.

The heat dissipation of buried cables depends on the depth of laying, ground ambient temperature and its thermal resistivity, these being dependent on their geographical location and the season of the year. Nearby cables would also affect the ground temperature. Cables in air reach steady operating temperatures more quickly than similar cables underground and large cables take longer than small ones.

The heat may cause a change in the properties of an insulating material or in extreme cases, deformation may occur. It is important, therefore, to realise that there is “a cable for the job”.

There is a very wide range of cables designed to operate at voltages up to 400 kV. It is not possible to discuss all these in this book, but the reader is referred to a publication, Copper Cables, published by the Copper Development Association.

The majority of cables have copper conductors and in a cable these may vary from a single conductor to stranded construction.

The number of electric wire contained in most common conductors is 3, 7, 19, 37, 61 or 91. Thus, 37/0·083 indicates that the conductor has 37 wires each having a diameter of 0·083 in.
Study of electric cable used for 18 years outdoors in Romania shows that only 2% of original quantity of di-(2-ethylhexyl) phthalate has been lost during service life. Formulation was stabilized with lead stabilizer. Twenty percent of original stabilizer was used and required replacement in recycling process.3

A similar study in Sweden (see formulation in the next section) showed that only 1% of extractable matter was lost during 30-40 years of cable use, material was thermally stable, and mechanical performance measured by elongation changed very little. Experimental studies conducted in laboratory which simulated service life by thermal aging at 80°C and considering activation energy in Arrhenius equation at 95 kJ/mol showed that cables should perform for at least 44 years. The cables collected from field are suitable for recycling with minimal adjustments to formulation. Figure 13.19 shows that stability of insulation has linear relationship with duration of aging. Figure 13.20 shows that changes in elongation are very small.4
Degradation of insulation performance of electric cables is basically evaluated by tests and analyses. Based on the result of equipment qualification tests, subsequent analyses to confirm the integrity after a 60-year service period of cables and the result of insulation resistance measurement and insulation diagnostic tests, it has been concluded that immediate degradation of insulation performance is unlikely to occur for most types of cables.

Degradation of insulation performance is detected by the insulation resistance measurement, insulation diagnostic tests and performance tests of systems and components, which are performed during the inspection.

The Japanese government commenced a national R&D project on cable ageing to have more accurate prediction. Under this project many experiments are being performed to acquire time dependent data of cable ageing. Superposition of the time dependent data proposed by IEC 1244-2 is proposed as a suitable method to predict cable ageing.

The Japanese plant utilities conduct measurement of insulation resistance to monitor degradation of insulation performance and are planning to perform sample investigation to acquire actual degradation data of cable insulations.
An area of rubber cable technology where much research and development work has been concentrated in recent years is that of the behaviour of cables in fires. Although they may overheat when subject to current overloads or mechanical damage, electric cables in themselves do not present a primary fire hazard. However, cables are frequently involved in outbreaks of fire from other causes which can eventually ignite the cables. The result can be the propagation of flames and production of noxious fumes and smoke. This result, added to the fact that cables can be carrying power control circuits which it is essential to protect during a fire to ensure an orderly shutdown of plant and equipment, has led to a large amount of development work by cablemakers. This work has included investigations on a wide range of materials and cable designs, together with the establishment of new test and assessment techniques.

Although PVC is essentially flame retardant, it has been found that, where groups of cables occupy long vertical shafts and there is a substantial airflow, fire can be propagated along the cables. Besides delaying the spread of fire by sealing ducts at spaced intervals, an additional safeguard is the use of cables with reduced flame propagating properties. Attention has also been focused on potential hazards in underground railways, where smoke and toxic fumes could distress passengers and hinder their rescue. Initially, compounds with reduced acidic products of combustion were incorporated in cables which have barrier layers to significantly reduce the smoke generated. In the meantime, other cablemaking materials have been developed which contain no halogens and which also produce low levels of smoke and toxic fumes as well as having reduced flame propagating properties. These are now incorporated in British Standards such as BS 6724 and BS 7211.

A different requirement in many installations, such as in ships, aircraft, nuclear plant and the petrochemical industry (both on and off-shore), is that critical circuits should continue to function during and after a fire. Amongst the cables with excellent fire withstand performance, mineral insulated metal sheathed cables are particularly suited for use in emergency lighting systems and industrial installations where ‘fire survival’ is required. As fire survival requirements on oil rigs and petrochemical plants become more severe, new control cable designs have been developed to meet fire tests at 1000°C for 3h with impact and water spray also applied, and also to have low smoke and low toxic properties.

Another novel approach to fire protection in power stations and warehouses is the use of fire detector cables (Figure 31.4). These are used in a system which both detects and initiates the extinction of a fire in the relatively early stages of its growth. These cables have also been installed in shops, offices and public buildings, where the cables can be used to operate warning lights or alarms.
The starting point is the real-life cable installations, simply because any fire regulation aims at addressing real-life fires. However, realistic cable installations cannot be used in a testing and classification system. The costs will be enormous as the number of different installations is almost infinite. The solution is therefore based on the assumption that certain large-scale reference scenarios can be representative of real-life hazards and that performance requirements of the cables can be identified in these reference scenarios. The term reference scenario is here used for an experimental set-up that is deemed to represent real life.

In exact terms the representation will never be true. However, a reference scenario is created in such a way that experimental fires in the scenario will be representative of a large number of real practical cases sufficiently accurately for a regulator. The burning behaviour of cables in the reference scenarios can then be linked to the burning behaviour in standardised test procedures. This is achieved by analysing fire parameters like heat release rate, flame spread and smoke production from experiments in the reference scenario and comparing them to the standard rate. When this link is established it is possible to use measurements in the standardised tests for classification. Thus the classification of a table in a standard test will reflect a certain burning behaviour in the reference scenario which in turn is linked to real-life hazard situations.
The test used to determine the flame resistance of electric cables, signal cables, and cable splice kits is described in Title 30, Code of Federal Regulations, Part 7, Subpart K (CFR 30, 2005). The principal parts of the apparatus are a test chamber or a rectangular enclosure measuring 17 inches deep by 14 inches high by 39 inches wide (43.2 cm deep by 35.6 cm high by 99.1 cm wide) and open at the top and front. The floor or base of the chamber is lined with a noncombustible material to contain burning matter which may fall from the test specimen during a test. Permanent connections are mounted to the chamber and extend to the sample end location. The connections are used to energize the electric cable and splice specimens. The connections are not used when testing signaling cables. A rack consisting of three metal rods, each measuring approximately 3/16 inch (0.48 cm) in diameter is used to support the specimen during a test. The horizontal portion of the rod which contacts the test specimen shall be approximately 12 inches (30.5 cm) in length. A natural gas type Tirrill burner, with a nominal inside diameter of 3/8 inch (0.95 cm), is used to apply the flame to the test specimen.
For tests of electric cables and splices, a source of either alternating current or direct current is used for heating the power conductors of the test specimen. The current flow through the test specimen is regulated and the open circuit voltage is not to exceed the voltage rating of the test specimen. An instrument is used to monitor the effective value of heating current flow through the power conductors of the specimen. Also, a thermocouple is used to measure conductor temperature while the cable or cable splice kit is being electrically heated to 400 °F (204.4 °C). For the electric cable test, three specimens each three feet (0.91 m) in length are prepared by removing five inches of jacket material and two inches of conductor insulation from both ends of each test specimen.
For splice kits, a splice is prepared in each of three sections of a MSHA-approved flame-resistant cable. The cable used is the type that the splice kit is designed to repair. The finished splice must not exceed 18 inches (45.7 cm) or be less than 6 inches (15.2 cm) in length for test purposes. The spliced cables are three feet in length with the midpoint of the splice located 14 inches (35.6 cm) from one end. Both ends of each of the spliced cables are prepared by removing five inches of jacket material and two inches of conductor insulation. The type, amperage, voltage rating, and construction of the power cable must be compatible with the splice kit design.
The test specimen is centered horizontally in the test chamber on the three rods. The three rods are positioned perpendicular to the longitudinal axis of the test specimen and at the same height. This arrangement permits the tip of the inner cone from the flame of the gas burner to touch the jacket of the test specimen. For splices, the third rod is placed between the splice and the temperature monitoring location at a distance 8 inches (20.3 cm) from the midpoint of the splice. The gas burner is adjusted to produce an overall blue flame five inches (12.7 cm) high with a three-inch (7.6 cm) inner cone and without the persistence of yellow coloration. The power conductors of the test specimen are connected to the current source. The connections must be compatible with the size of the cable’s power conductors to reduce contact resistance. The power conductors of the test specimen are energized with an effective heating current value of five times the power conductor ampacity rating at an ambient temperature of 104 °F (40 °C).
The electric current is monitored through the power conductors of the test specimen with the current measuring device. The amount of heating current is adjusted to maintain the proper effective heating current value until the power conductors reach a temperature of 400 °F (204.4 °C). For electric cables, the tip of the inner cone from the flame of the gas burner is applied directly beneath the test specimen for 60 seconds at a location 14 inches (35.6 cm) from one end of the cable and between the supports separated by a 16 inch (40.6 cm) distance. For the splices made from the splice kits, the tip of the inner cone from the flame of a gas burner is applied for 60 seconds beneath the midpoint of the splice jacket. After subjecting the test specimen to the external flame for the specified time, the burner flame is removed from beneath the specimen while simultaneously turning off the heating current. The amount of time the test specimen continues to burn is recorded after the flame from the burner has been removed. The burn time of any material that falls from the test specimen after the flame from the burner has been removed is added to the total duration of flame. The length of burned (charred) area of each test specimen is measured longitudinally along the cable axis. The procedure is repeated for the remaining two specimens. For a cable or splice kit to qualify as flame resistant, the three test specimens must not exceed a duration of burning of 240 seconds and the length of the burned (charred) area must not exceed 6 inches (15.2 cm). The flame test of an electric cable is shown in Fig. 13.4 – the electric cable did not meet the test criteria.


USB (an acronym for Universal Serial Bus) is a standard of communication that is commonly used for transferring data and powering devices. This standard introduced a new type of cable that was developed in the 1990s and has continuously evolved in the decades that followed. In this section, we outline the evolution of the USB cable and describe the types that exist today.

USB types
USB connectors come in several types: the default sizes (USB A, USB B and USB C), Mini USB type A and B and Micro USB A and B.
USB A has an elongated, rectangular form and can carry power and data. The USB A plug is used to provide a downstream connection to controllers or hubs.
USB B is narrower, squarer shaped and commonly used for connecting peripheral devices such as printers and scanners, or as an upstream port for USB hubs. USB B connectors are still in use today but slowly being phased out and replaced with USB C connectors and ports.
USB C is the newest USB interface, launched in 2014. With a narrower, more elongated shape than USB A, USB C has more pins enabling it to transfer a larger amount of power and data. USB typc C cable is currently compatible with Apple MacBooks with Thunderbolt 3 ports, Chromebooks and the most recent laptop models.
USB Mini plugs were designed for use on USB peripheral devices such as older smartphone models or digital cameras While still in use on some devices, USB Mini is now broadly seen as a legacy connector, and not certified as compatible with newer devices.
USB Micro is an even slimmer version of the USB mini-plugs, being better suited to newer models of OTG (on-the-go) devices while enabling the same level of connectivity. USB Micro is now the standard connection type for charging smartphones.

USB versions
USB 1.0 is the original USB standard, where the limit for data transfer is 12Mbps. USB 1.0 was originally designed to connect peripheral devices such as mice, keyboards and game controllers. As the simplicity of the USB connector interface grew in popularity, the USB standard evolved to USB 2.0 in 2000.
USB 2.0 provided a much higher connection speed with a throughput of 480Mbps. The cable is also known as High Speed. The standard length of USB 2.0 passive cables is 5 meters. Active cables, on the other hand, can have a length of up to 20 meters. 
The USB 3.0 specification was released in 2008. This type is also known as SuperSpeed, being able to transfer data at a speed up to 5.0Gbps. SuperSpeed USB cables can be told apart with the SS logo and the blue color in the internal part of plugs and port. The standard length for passive cables is 3 meters, while active cables can be up to 20 meters long. The 2nd generation of USB 3.1 can transfer up to 10Gbps of data.

HDMI, an acronym for High-Definition Multimedia Interface, is an interface for transmitting digital audio and video data from a source device to a presentation/output device such as a projector or display or digital audio device. The initial HDMI standard HDMI 1.0 was created in 2002 as a collaboration between major technology manufacturers including Panasonic, Phillips, Sony and Toshiba. Since then, this data transmission interface has evolved and improved, and several versions of HDMI are now available. Each new HDMI version has brought about an exponential increase in audio/video capacity, resolution, improved color spaces, and advanced features such as CEC (Consumer Electronics Control), 3D and Ethernet data connection.

HDMI Cable Types
HDMI Standard cables work with resolutions up to 720p and 1080i with bandwidth capacity up to 5 GB/s. It is suitable for HDMI versions 1.0 to 1.2a.
HDMI High-Speed cables work with resolutions of 1080p, as well as 4K@30Hz, 3D, and Deep Color. This type of cable has a bandwidth capacity of up to 10 GB/s. It is recommended to use this type of HDMI cable if you are connecting a 1080p HD display to a 1080p HD content source. It is suitable for HDMI versions 1.3 to 1.4a. With the HDMI 1.4 standard, this cable can also be used for 3D video.
Premium HDMI Cable is a certification that ensures the HDMI has been tested for reliable performance of advanced display technology such as 4K@60Hz, HDR and expanded color range including BT.2020. The bandwidth capacity is 18 Gbps and it is optimized for HDMI version 2.0.
The latest HDMI cable type – the Ultra-High-Speed HDMI cable – is the only one that complies with the specifications required to support the HDMI 2.1 specification. This includes uncompressed 8K@60Hz and 4K@120Hz, and a bandwidth capacity of 48GBps.

Notable HDMI specifications
HDMI 1.4 HDMI 1.4 came out in 2009 and was a significant game-changer in the AV industry. Worthy of mention is the addition of the HDMI Ethernet Channel, which allows HDMI cables to act as ethernet cables, 3D over HDMI, ARC (Audio Return Channel), the HDMI micro connector and 4K@30Hz data transfer speed.
HDMI 2.0 The HDMI 2.0 standard was released in September 2013. With this standard, the HDMI bandwidth was increased to 18 Gb/s, 4K support increased to up to 60Hz, and added support to the 21:9 aspect ratio, mostly used in theatres.
HDMI 2.1 The HDMI 2.1 stand was released in November 2017, adding support to even higher resolutions and refresh rates, now reaching 4k@120Hz and 8K@120Hz. The HDMI 2.1 standard’s features require the Ultra-High-Speed cable to function smoothly. Other features include Dynamic HDR, DSC 1.2 (Display Strem Compression), and enhanced eARC (enhanced Audio Return Channel).

How long should HDMI cables be?
With rooms getting bigger and packed with more and more devices, your AV equipment might not be as close to each other as you would like it to be. You will need to route long enough cables to connect equipment that is located quite far from each other. The electronics industry’s maximum recommendation for HDMI cable length is 50 feet or 15.24m to ensure optimal video and audio quality. Most HDMI cables available on the market reach a maximum of 25 feet or 7.62m, making that length a safe bet
With longer cables, you risk reducing the quality of the signal and experience audio lag and image degradation and screen flashing. To ensure signals with higher resolutions and refresh rates, such as 4K@60Hz, it is recommended that you use shorter cables, active cables (containing a processing chip that ensures the signal travels without loss), fiber optic cables or an HDMI extension over shielded CAT5e/6/7 via HDBaseT.

Tidier cables with Neets Input Panels
In larger rooms or more complex equipment setups, the number of cables and their lengths can quickly escalate, causing issues of safety, performance and pure aesthetics. Safety is a primary concern, as cables trailing on the floor are an obvious tripping hazard. Trailing cables are also exposed to frequently trampling and being run over by office chair wheels, damaging them and reducing the quality of the connection. Finally, trailing cable connections makes the room look messy and unprofessional.
Luckily, there are cable management solutions on the market that can eliminate these problems simultaneously. We’re talking about what are known as wall sockets or plates such as Neets’ own range of Input Panels.
With an input panel installation, you can run your desired length cables through the wall or ceiling, connecting each end to the back of the input panels. The input panels are installed in strategic locations around a room, making it easy to connect different HDMI components and send bi-directional audio and video signals between the components, all the while having a neat and clean look in your meeting room, conference hall, classroom or auditorium.

Perhaps surprisingly, the main reason for buying wireless headphones is not to support the tireless efforts of the Bluetooth Special Interest Group. No, the number one reason for picking up Bluetooth headphones is of course because they’re wireless. Not that I have anything in particular against cables, per se, but the freedom going wireless offers you is unparalleled.
No more tangled headphone cords, no need to take your device with you as you walk around the house, no accidentally yanking your earphone cable out or knocking your phone off the table, no wear and tear, no safety worries with the new breed of the smartphone with no analog port. The first time you head to the gym with a pair of wireless TWS earphone on, I guarantee you’ll become an instant convert.

Connect Cables in pc and it’s affect

Is there anyway I can know if the cable I use to charge my phone in it was connect to my pc before or not? Is there something in pc can let me see that because my pc contain some malware and spy files that comes to it through another phone because I used to use all cables and connect them to pc so I decided to format my other iphone in charger while charging it in the wall during deleting your data and setting the phone turned off so I connect it to the charger and it start to format and delete all data and settings while connect to charger so I format it again and I am afraid that the malware will be inside the iPhone system and even formatting it will no help

iphone cables

Shenzhen Runray Technology Co., Ltd, found in 2004,  located in Bao’an area ShenZhen city. Company production area covers about 6000 square meters. Runray is a professional enterprise with strong capability in research and development, industrial product appearance design, production and sales.
Runray has a strict and standardized organization structure, equipped with administration department, finance department, engineering department, marketing department, design department, purchasing department, after-sales department, quality department, production department, material control department. We are a vigorous and rapidly developing company now.
At present, we are dedicated in all kinds of electronic products and mobile phone accessories’ design, research and development, productions and sales. Our staple products almost are personal mount, which include Car Charger, Wall Charger, Mobile phone cable , Power Bank, Car Purifier,Mini USB LED light, USB Fan, and other mobile phone accessories. Our products have already obtained CE、ROHS、FCC certification.Also all of our car chargers are with Patent.
Our company has also passed ISO9001 quality management system certification. Our products are popular in Europeans and other clients from all around the world due to novel style, fast delivery time, reasonable price, and high-qualified service.  
Company will make every effort to realize development demands of “systematically organization, scientific decision, standardized management, programmatic work, standardized efficiency”. And we will strive for providing more products with high quality and competitive price.iphone cables

How can I evaluate the safety of these Magsafe 2 USB-C Charge Cables?

They look like and claim to be USB-C to Magsafe 2 cables, that allow you to charge up on the go from a USB-C wall adaptor.

Link 1: https://jgotech.com/collections/usb-c-power-delivery/products/magsafe2-to-usb-c-charging-cable

Link 2: https://www.aliexpress.com/item/NEW-Replacement-USB-C-Type-C-To-Macsafe-2-Cable-Cord-For-Macbook-Retina-Pro-Air/32981363404.html

Can anyone comment on the viability and safety of products like these?

Rasperry Pi as a WiFi Router, but without using Ethernet cables?

I have the Raspberry Pi 2, and the official WiFi dongle that comes from the makers of Pi. I’d like to mention that I’m very new to understanding technology, code, and how things work in general so I may be trying to do something that’s entirely impossible.

I was wanting to set up a sort of private router on the Pi in my room nearby, but noticed that all the tutorials for setting up Pi routers are for when you’re connected to the main router via eth0. My question is: Is it possible for other devices to connect to the Pi like a router, and have all the traffic go through wlan0 to the main router and back?

I’m guessing that modifying the tutorials to apply to wlan0 could be what I’m asking, but I’m unsure if you can even have wlan0 as both an access point for other devices and the Pi’s own connection to the internet at the same time. I feel like to someone with actual understanding of the topic, this may seem a very stupid question, so I apologise in advance.