Power Systems 2 ELE3015. Lecture 1: Transmission Lines

Transcription

1 Power Systems 2 ELE3015 Lecture 1: Transmission Lines

2 Transmission Lines: Introduction Use to carry electrical power from point of generation to the point of use. Usually over large distances. Made with electrical conductors.

3 Transmission Lines: Introduction Transmission lines are normally operated at high voltages to reduce the line current for a given power level. Lower current results in lower I 2 R losses. Lower losses means a more efficient transmission system that is more economical for system operators.

4 Transmission Lines: Introduction Standard voltage levels (ANSI C84.1)

5 Transmission Lines: Introduction Example transmission lines

6 Transmission Lines: Introduction Example transmission lines

7 Transmission Lines: Introduction Example transmission lines

8 Transmission Lines: Introduction Transmission lines consists of: Three phase conductors Insulators to support and isolate the conductors Supporting structure which holds the conductors and insulators Foundation and grounding Optional lightning protection shield wires

9 Transmission Lines: Introduction Transmission line basic overview:

10 Transmission Lines: Conductors The conductors carry the actual electric current. They must be of adequate rating to carry the required power without overheating. For overhead lines they are generally made primarily of aluminum. Underground lines are normally made with cables and will be considered later.

11 Transmission Lines: Conductors Types of aluminum conductors: All Aluminum Conductor (AAC) Concentric lay stranded All Aluminum Conductor ( AAC) is made up of one or more strands of hard drawn 1350 aluminum alloy. AAC has seen extensive use in urban areas where spans are usually short but high conductivity us required. Because of its relatively poor strength to weight ratio, AAC had limited use in transmission lines and rural distribution because of long spans utilized

12 Transmission Lines: Conductors Types of aluminum conductors: Aluminum Conductor Steel Reinforced(ACSR) Aluminum Conductor Steel Reinforced (ACSR) is concentrically stranded conductor with one or more layers of hard drawn 1350-H19 aluminum wire on galvanized steel wire core. ACSR conductors combine the light weight and good conductivity of aluminum with the high tensile strength and ruggedness of steel. ACSR can therefore provide higher tensions, less sag, and longer span lengths than obtainable with most other types of overhead conductors.

13 Transmission Lines: Conductors Types of aluminum conductors: All Aluminum Alloy Conductor (AAAC) Concentric lay stranded Aluminum Alloy Conductors (AAAC) are made out of high strength Aluminum- Magnesium-Silicon Alloy. AAAC has better strength to weight ratio and offer improved electrical properties, excellent sag-tension characteristics, and superior corrosion resistance when compared with ACSR. AAAC can be used on the distribution system and for medium & high voltage transmission lines but is more expensive than ACSR.

14 Transmission Lines: Conductors Examples of available ACSR conductors (Midal Cables)

15 Transmission Lines: Insulators Insulators are used to support and isolate the conductors from the tower. They require both mechanical strength and excellent electrical insulating properties. They are generally made of ceramics or composite materials.

16 Transmission Lines: Insulators Insulators are used to support and isolate the conductors from the tower. They require both mechanical strength and excellent electrical insulating properties. They are generally made of ceramics or composite materials. They must be rated for the voltage levels they are required to insulate from.

17 Transmission Lines: Insulators Example ceramic insulator.

18 Transmission Lines: Insulators Ceramic insulators can be chained for higher voltages.

19 Transmission Lines: Insulators Example composite insulator.

20 Transmission Lines: Insulators Example composite insulator. Alternating diameter silicone weather sheds Fiberglass insulating rod Silicone also serves as rod covering Galvanized steel end fitting