When you consider about power transmission and distribution in an urban area the usage of underground cables play a major role. If you are interested in the field of electrical engineering you must have some basic pieces of information about underground cables. Following are some important guidelines on the cable use of electrical supply.
Underground cable is a one or more conductor which covers insulation to protection. There is some properties conation in underground cables such as
Properties of Underground Cables:
Here you can find several properties of electrical underground cables:
- Conductors in cable should be a very high conductivity
- Need good flexibility for the conductor
- The cable should not get overheated
- The cable must have a better thickness
- The suitable mechanical protection is required while the cable is laying
- The materials should contain good chemical and physical stability
Construction of Cables:
The construction of an underground electrical cable as follows:
Conductor: Conductor may have one or more conductor which made out of copper or aluminum
Paper insulation: Each core conducted by the suitable thickness of the insulation. There are several insulation materials which is used such as
- Impregnated paper
- Varnish Cambric
- Rubber Mineral
Lead Sheath: Lead sheaths are used to protect the cable from the moisture and it also protects against acids and alkaline in the soil. Lead or Aluminum is mostly used in this protection system.
Bedding: The layer of bedding applies over lead or metallic sheath. The main purpose of the bedding is to protect the lead sheath.
Armoring: Armoring is laid over beading. The armoring consist of one or two layers of steel wire or tape. The main objective of armoring is to protect against mechanical faults.
Serving: This is to use to protest the armoring of the cable. It’s also a protection of the conductor insulations.
The properties of Insulation Materials of Cables
- Insulations materials of the cable should not get affected by acids and alkalines
- Materials should contain high mechanical strength
- Low cost
- Noninflammable
- Should contain high dielectric strength
- High insulation resistance
Types of insulation materials used for Underground cables
- Rubber
- Vulcanized Rubber
- Impregnated Paper
- Varnish Cambric
- Polyvinyl Chloride (PVC)
Underground cable classification according to its voltage limits
- Low tension cables (LT) – Voltage bellow 1000 V
- High tension cables (HT) – Voltage up to 11,000V
- Super tension cables (ST) – Voltage Between 22kV to 33kV
- Extra high tension cables (EHT) – Voltage Between 33kV to 66kV
- Extra Super Voltage cables (EHT) – Voltage more than 132 kV
Hope that you have got some basic idea about the underground electrical cables and its usage in the electrical industry.
