Purpose: It could be also called inner sheath or inner jacket, which serves as a bedding under cable armoring to protect the laid up cores and as a separation sheath. Inner sheath is over laid up of cores. It gives Circular Shape of the cable and it also provides Bedding for the armoring.
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Why inner sheath in cables are for?
These intermediate sheaths are called ‘inter-sheaths’; These inter-sheaths are then held at adequate voltage levels. This method improves voltage distribution in the dielectric of the cable and consequently uniform potential gradient is obtained.
What is cable sheath material?
A thermoplastic-sheathed cable (TPS) consists of a toughened outer sheath of polyvinyl chloride (PVC) thermoplastic, covering one or more individual annealed copper conductors, themselves insulated with PVC. This type of wiring is commonly used for residential and light commercial construction in many countries.
What is mainly used for cable sheathing?
PVC Cable. Polyvinyl Chloride (PVC)s is the most common sheath type. It’s low cost, easy to make, and is found on most cables unless a specific requirement for another sheath type exists.
What is sheath in underground cable?
Cable sheath – Protects the cable, against moisture in particular. 2. Wire screen – Controls the electric field and discharges fault currents. 3. Insulating layer – Insulates the electric conductor.
What is cable sheath test?
Sheath Resistance testing is a key onsite diagnostic test for identifying potential cable faults. Commonly known as a Megger Test, it uses a Megohmmeter to measure the resistance of the cross-linked or thermoplastic compound to an applied DC voltage.
Why are sheets used in cables?
It is to protect the metallic sheath against corrosion and from mechanical injury due to armouring.
What is HDPE sheath?
High-density polyethylene sheath (HDPE) can be supplied where greater impermeability to moisture and greater resistance to abrasion is required for adverse installation conditions, but such sheaths are not recommended in areas of fire risk.
What is cable shroud?
CMP Products’ cable shrouds minimise the risk of dirt or foreign substances gathering on the cable gland and point of cable to cable interface. LSF cable shrouds are Low Smoke & Fume (LSF), and Phosphorus Free to suit all CMP SOLO Cable Glands.
Where is lead sheath used?
Prevent ingress of moisture.
What is XLPE cable?
1.2.1 Description of XLPE cable
XLPE is an acronym for cross linked polyethylene. XLPE is a thermosetting polymer meaning that the material (polyethylene (PE)) is cured under heat and in that process forms bonds in all directions forming a three dimensional matrix.
What is lead sheath?
A Lead Sheath is available on many types of wire and cable insulations. This sheath is completely moisture proof and very durable. Where both mechanical strength and moisture resistance are required, a combination of Lead sheath and armor can be used.
What are the three main parts of a sheathed cable?
Cables consist of three major components: conductors, insulation, protective jacket.
What is XLPE insulation?
XLPE or Cross-linked polyethylene is a thermoset insulation material. Crosslinking polymers is a process which changes the molecular structure of the polymer chains so that they are more tightly bound together and this crosslinking is done either by chemical means or physical means.
What type of cable has a lead sheath?
SL and HSL Cables: In SL-type cables, each core is covered separately by a lead sheath. In HSL-type cables each core has both metallized paper covering grounded to zero potential as well as a separate lead sheath for each core.
Why Megger test is done?
The Megger test is a method of testing making use of an insulation tester resistance meter that will help to verify the condition of electrical insulation. Insulation resistance quality of an electrical system degrades with time, environment condition i.e. temperature, humidity, moisture and dust particles.
How do you Megger a cable?
Clamp the alligator clip on one of the megger probes to the wire or cable, touch the other probe to the exposed conductor and press the test button. The megger will generate a current between the probes, and the meter will record the resistance of the jacket to the flow of the current.
What is bedding in cable?
Bedding: Polyvinyl chloride (PVC) bedding is used to provide a protective boundary between inner and outer layers of the cable. Armour: Steel wire armour provides mechanical protection, which means the cable can withstand higher stresses, be buried directly and used in external or underground projects.
Why are seeds used in cables?
To minimize the effect of shocks and vibrations due to gassing vehicles, etc.
What is SL type cable means?
S.L Type Cables: It is similar to the H type cables, with the difference that each of the three cores has its own lead sheath. With this provision, the need for the overall sheath used previously is eliminated. The advantage of such a construction is that the chances of a core-to-core breakdown are greatly minimized.
How do you strip a cable sheath?
Score the plastic sheathing with a sharp knife if you don’t have a special tool. Don’t cut all the way through the plastic. Apply very light pressure with the knife and keep your finger on the opposite side of the cable. Bend and break the sheathing and slide it off.