ENGINEERING ARTICLES

FUEL SUPPLY SYSTEM OF DIESEL POWER PLANT It consists of storage tank, strainers, fuel transfer pump and all day fuel tanks. The fuel oil is supplied at the plant site by rail or road. The oil is stored in the storage tank. From the storage tank, oil is pumped to smaller all day tank at daily or short intervals. From this tank, fuel oil is passed through strainers to remove suspended impurities. The clean oil is injected into the engine by fuel injection pump. AIR INTAKE SYSTEM OF DIESEL POWER PLANT This system supplies necessary air to the engine for fuel combustion. It consists of pipes for the supply of fresh air to the engine manifold. Filters are provided to remove dust particles from air which may act as abrasive in the engine cylinder. Because a diesel engine requires close tolerances to achieve its compression ratio, and because most diesel engines are either turbocharged or supercharged, the air entering the engine must be clean, free of debris, and as cool as possible. ...

A generating station in which diesel engine is used as the prime mover for the generation of electrical energy is known as diesel power station. In a diesel power station, diesel engine is used as the prime mover. The diesel burns inside the engine and the products of this combustion act as the working fluid to produce mechanical energy. The diesel engine drives alternator which converts mechanical energy into electrical energy. As the generation cost is considerable due to high price of diesel, therefore, such power stations are only used to produce small power. Although steam power stations and hydro-electric plants are invariably used to generate bulk power at cheaper costs, yet diesel power stations are finding favor at places where demand of power is less, sufficient quantity of coal and water is not available and the transportation facilities are inadequate. This plants are also standby sets for continuity of supply to important points such as hospitals, radio stations, cinema ho...

There are many different types of electronic fuses and every manufacturer has their own solution. The principle is the same though; a sensor measures the current and some kind of controller or comparator, often a micro processor, controls a transistor, typically of a MOSFET kind. By master the opening and the closing of the MOSFET, the controller sets if the current should be cut off. Since a controller is programmable, an electronic fuse has a wide range of applications. One controller can be in command of many MOSFET’s which individually can be put on or off remotely and has an electronic fuse state memory to know in which state it is during disconnection. Control equipment can be connected for monitoring voltage and current level. Sometimes the electronic fuses are constructed with two MOSFET’s as seen in Figure 2.9. At start-up, the transistor M1 opens first and once steady state has been reached, M2 will be switched on. Because of the higher resistance R, the current will flow th...

As mentioned previously, circuit breakers can detect a fault either thermally or magnetically. The magnetic hydraulic circuit breaker is an all round device and can operate in many different areas. The magnetic hydraulic circuit breaker can be divided into two different categories; sealed and unsealed breakers. Sealed breakers, made for currents below 20 A, are less dependent of the surrounding environment. The trip of a magnetic hydraulic circuit breaker is achieved by a solenoid. As the current flows through the breaker, it also passes through a coil which creates a magnetic force. When a fault current occurs, the magnetic force of the solenoid increases until it reaches a certain level where a sear is trigged and opens the breaker. This level is called “the ultimate trip current” and it is the lowest current that still guarantees a break. The most usual at Ericsson Power Solutions is to use a time delayed magnetic hydraulic circuit breaker that make it susceptible to some curren...

A simple circuit breaker was developed by Edison as early as 1878 when he worked on his electric light circuit. Even though he did not use his mechanical breaker in his commercial circuit, the function was based on the same principle that is used in a modern circuit breaker. The circuit breaker is, in contrast to the melting fuse, resettable. This basically means that a circuit breaker can be seen as a switch with high current handling capabilities. Depending on the area of use, there are many different types of circuit breakers but the function in general is the same. When an over current occurs, a thermal or a solenoid sensor detects the fault current and presses the breaker apart with mechanically stored energy, e.g. a spring or compressed air. As for a melting fuse, an arc is created in the break. Since the circuit breaker must be able to handle the high current and the high temperature created from the arc without being destroyed, the arc has to be extinguished. Some ways to handl...

The first type of fuse developed was of a melting kind. The word fuse comes from the Latin word to melt, “fusus”. As Thomas Edison developed his electric light circuit in the late 1870’s, he needed a protective mechanism “to provide against accidental crossing of the conductors leading from the mains”. Edison used a simple wire fuse in a wood-block holder. In 1890 Edison patented an enclosed fuse “to prevent or diminish the liability to surface creeping of lightning or other powerful current”. The general idea of a melting fuse is (as the name reveals) to melt and make a galvanic break. A metal wire with smaller cross-section compared to the surrounding conduction line is placed in series with the conductor, see Figure 2.1. Figure 2.1: Cross section of a melting fuse If the current increases, the resistance in the small wire results in excessive power dissipation. This energy will eventually cause the smaller wire to melt. As the melting starts, the current in the line will crea...

ELECTROMECHANICAL RELAYS: Early relay designs utilized actuating forces that were produced by electromagnetic interaction between currents and fluxes, much as in a motor. These forces were created by a combination of input signals, stored energy in springs, and dash pots. The plunger type relays are usually driven by a single actuating quantity while an induction type relay may be activated by a single or multiple inputs (see Figs. 3.9 and 3.10.). Although existing protection is provided primarily by electromechanical relays that is because the cost and complexity of replacing them may be prohibitive; never the less, new construction and major system or station revisions are witnessing the replacing of electromechanical relays with solid state or digital relays. FIGURE 3.9 Plunger type relay. FIGURE 3.10 Principle of construction of an induction disk relay. Shaded poles and damping magnets are omitted for clarity. SOLID STATE RELAYS: The expansion and growing complexity ...