Design Guide for Underground Transmission Line

Design Guide for Electrical Energy Transmission in Underground Cable Network

The voltage level of the transmission line network is the key consideration in the design guide factor for both overhead transmission systems and underground cable transmission systems.

Schematic line diagram below, the specific voltage level guide is used for conventional overhead transmission and a new concept underground transmission network system for-

1. Power Generation;
2. Bulk Transmission;
3. Sub-Transmission; &
4. Distribution System.

What The Distribution Voltage Level Is?

In electrical power transmission and distribution systems, voltage levels are divided into different categories considering the equipment operating capability, such as-

1. Low Voltage (LV)              - up to 1000Volt;
2. normalVoltage (MV)       - 1000 Volt ~ 35 kilo Volt;
3. High Voltage (HV)            - 35kilo Volt ~ 230 kilo Volt;
4. Extra High Voltage (EHV)  - above 230 kilo Volt; &
5. Ultra High Voltage (UHV)  - above 800 kilo Volt.

Also, very safe low voltage, like less than 70 Volt is known as extra low voltage (ELV).

What is the common Transmission & Distribution Voltage Level?

Sponsored:

The above line diagram from the power generation station to the end user consumer, passing through different levels of transmission voltage systems, shows the most common transmission and distribution voltage levels. Very common Low Voltage (LV) is 120V, 230V,385V,420V, 625V, etc.; normalVoltage (MV) is 11kV, 19kV, 33kV, etc.; High Voltage (HV) is 110kV,132kV, 220kV, 230kV, etc.; Extra High Voltage (EHV) is 230 kV, 400kV, 500kV, 765kV, etc. It differs from country to country.

The selection of the transmission voltage level depends on the load flow distance. If the energy is necessary to travel a long distance or a comparatively short distance, but the energy is a bulk amount, then the voltage level needs to be higher.

During energy transmission, a certain percentage of energy is lost; to minimize or reduce these losses voltage needs to increase.

“A voltage of (nominally) 230 V and a frequency of 50 Hz is used in Europe, most of Africa, most of Asia, much of South America and Australia. In North America, the most common combination is 120 V and a frequency of 60 Hz. Other voltages exist, and some countries may have, for example, 230 V but 60 Hz. This is a concern to travelers, since portable appliances designed for one voltage and frequency combination may not operate with or may be destroyed by another”.

Why is an underground transmission network necessary?

Underground Energy Transmission is costly compared to conventional overhead transmission. It needs less maintenance, but takes more time to find out some cable fault.

Though the initial cost is high for underground cable energy transmission, it is the first priority to energy transmission network administrator to change the network to underground.

Advantages are less maintenance, less environmental trouble like storms or cyclones, easy monitoring,g and ensure a reliable power supply.

Now XLPE insulated copper or alluminium core power cable is widely using for large scale of advantages on reliable power supply”.

Read about: High Voltage Power Line and Health Risk

Underground network requires less land use, destroys less forest/vegetation, keeps the city clean, trouble free power supply, etc.

What Is The Main Equipment Used In Underground Energy Transmission?

Sponsored:

The main equipment for underground electrical energy transmission networks is as follows-

1. Power Cable;
2. Insulated & Straight Through Cable Joint;
3. Gas Insulated Cable Termination
4. Indoor or Outdoor Cable Termination;
5. Cable Sheath Earthing Link Box;
6. Fiber Optic Cable for Communication & Monitoring System, etc.

The Design Guide for both underground and overhead electrical energy transmission line systems is not a span; it’s need divert rules considering the site situation and international and local standard codes.