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Compact Fluorescent Lamp (CFL) The compact fluorescent lamps are becoming very useful nowadays, because of consumption of power, cost, longer life, attractive look, smooth light and low maintenance. These lamps are available in different sizes and designs. They have single rod, double rod, triple rod or spiral rod. These lamps are available in different power […]
Fluorescent lamp It is a low pressure mercury vapour lamp. It consists of a glass tube 25 mm in diameter and 0.6 m, 1.2 m and 1.5 m in length. The inner portion of the tube is coated with phosphorous. The tube contains argon gas at low pressure and a drop of mercury is added. […]
Mercury vapour lamp On the basis of pressure inside the discharge tube, the mercury vapour lamps are classified as High pressure mercury vapour lamp and Low pressure mercury vapour lamp. High pressure mercury vapour lamps are classified as: 1. MA type (Mercury vapour lamp with auxiliary electrode) These are operated at 220 ‐ 250 volt, […]
Sodium vapour lamp Sodium vapour lamps are some of the most efficient lamps in the world. They have an efficiency of up to 190 lumens per watt compared to an incandescent street lamp which has between 15 and 19 lumens per watt. This sodium vapour lamps comes in two major groups: 1. High pressure sodium […]
Incandescent lamp The filament of this lamp is heated up to the incandescent stage of heat. So these types of lamps are called as incandescent lamps. There are two types. 1. Vacuum type lamp and 2. Gas filled type lamp In this type of lamp, the sphere shaped glass cover is used. The glass stem […]
Arc lamp The principle of an arc lamp is that when two electrodes carrying current are separated through a small distance, an arc is struck between them. The arc lamps were used in the past for street lighting purposes but nowadays these are used when extreme brightness is required. Carbon arc lamp is most commonly […]
Laws of illumination The illumination on a surface depends upon the luminous intensity, distance between the source and surface and the direction of rays of light. It is governed by following laws. 1. Inverse square law 2. Lambert’s cosine law Inverse square law It states that the illumination of a surface is inversely proportional to […]
Introduction Almost all human activities are based on light. Natural light is obtained from the sun. Artificial light plays an important role in our everyday life. In places where natural light is not available, artificial light is obtained by electric lamps. Lighting plays an important role because of its belief, consistency, simple control and low […]
Difference between Overhead line and Underground cables
Three phase cable Commonly, underground cables are used to transmit three phase power supply. For three phase service, the following cables are used. a. Belted cable up to 11 KV b. Screened cable 22KV to 66 KV c. Pressure cable above 66 KV a. Belted cable up to 11 KV The crosssection view of the […]
Classification of cables a. According to the rating of voltage the cables are classified into i. Low tension cables up to 1 KV ii. High tension cable up to 11KV iii. Super tension cables 22 KV to 33KV iv. Extra high-tension cables 33KV to 66 KV v. Oil filled cables 66KV to 132 KV vi. […]
Power distribution system The medium voltage transformer using transmission lines are reduced by step down transformer (415V, or 240V) are used to the consumer. This system includes the feeder lines, distributors and service mains. Feeder line The feeder line is nothing but similar as power transmission conductors. It connects the power from sub-station and power […]
Types of insulators i. Pin type insulator ii. Suspension insulators a. Hewlett suspension type b. Cemented cap type c. Core and link type iii. Strain insulator iv. Shackle insulator v. Stay type insulator i. Pin type insulator This type of insulator is fixed in the crossing arm of the pole. The conductor is placed in […]
Line insulators The overhead line conductors should be supported with the poles or towers by means of insulators. These insulators act as supports in order to avoid any leakage of current from the conductor to earth. Properties of insulators Here are some of the properties of line insulators i. Mechanical strength should be very high. […]
Types of overhead lines The transmission line has three parameters, resistance, inductance and capacitance distributed uniformly along the whole length of the line. The resistance and inductance forms series impedance. The capacitance existing between conductor for single phase line and a conductor, to neutralize the three-phase line, forms a shunt path through the length of […]
Effects of transmission 1. Skin effect When an alternating current flows through a conductor, a flux will be produced in it. This flux will be higher at the center of the conductor than outer surface. The high reactance of center area causes the alternating current to flow near the surface of the conductor. This is […]
Types of poles Line supports or the poles which hold the conductors to a height they are above the ground level. In general, four types of poles are used, depending on the size and shape of the conductor used. i. Wooden poles ii. Concrete poles iii. Tubular steel poles iv. Latticed steel tower i. Wooden […]
Overhead line transmission The overhead lines are used to transmit electricity from power plants to consumers. A network of electrical power lines are used to transmit the electricity over a geographic area is called power grid. Main components used in overhead lines i. Electric conductors ii. Poles and towers iii. Insulators iv. Cross arm that […]
Alternative transmission From the power generating stations, a large amount of AC supply is produced and is transmitted through transmission lines. The layout of a typical AC power supply system. The transmission is done caried by 3 phase 3 wire and 3 phase 4 wire systems. Other methods are also used for some special reasons. […]
Direct Transmission Let us see the transmission of DC power from the AC power. The single line diagram of high voltage direct current transmission is given in Alternative current is generated and stepped up to high voltage through the sending end transformer. This high voltage alternating current is converted to the direct current by a […]