Category Archive for: «Energy and Power»

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How to get rid off the harmonics in electrical system?

Nothing good from harmonics… The subject of harmonics is also a contributory factor in electrical noise I already wrote few days ago (Cable spacing as a means of noise mitigation). It also causes several other problems in power circuit components such as motors, transformers and capacitor banks. A load that is purely resistive has the same wave […]

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Cable spacing as a means of noise mitigation

Separation distances In situations where there are a large number of cables varying in voltage and current levels, the IEEE 518-1982 standard has developed a useful set of tables indicating separation distances for the various classes of cables. There are four classification levels of susceptibility for cables. Susceptibility, in this context, is understood to be […]

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Harmonic Distortion and High Frequency Applications

Distortion of the fundamental sine wave The presence of harmonic frequencies in addition to the fundamental 50Hz, bring about distortion of the fundamental sine wave. Considerable problems may arise dependant upon the level of this distortion. Sources of harmonic distortion can be: Variable Speed Drives UPS equipment Non linear load (switch mode power supplies) Special […]

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How the Weather Affects Conductors

Sag Notice how a conductor is strung between poles. It is not pulled tight; it sags. In hot weather it sags even more than in cold weather. Consider the analogy of the clothesline. A tightly strung clothesline as shown in Figure 1a puts a much greater strain on the poles which hold it at either […]

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An example how to calculate voltage drop and size of electrical cable

Input information Electrical details: Electrical load of 80KW, distance between source and load is 200 meters, system voltage 415V three phase, power factor is 0.8, permissible voltage drop is  5%, demand factor is 1. Cable laying detail: Cable is directed buried in ground in trench at the depth of 1 meter. Ground temperature is approximate […]

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2 Most Common Contributing Factors in Insulation Failure

Degradation and breakdown The most frequent failure in electrical equipment is the degradation and breakdown (flashover) of the insulation. Electrical insulation can be liquid or solid, organic or inorganic. Organic insulation material consists of: enamels, varnishes, resins, or polymers that are applied to the steel surface to provide high inter-laminar (between windings) resistance as found on most air-cooled machinery and […]

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Differences between disconnectors, load switches, switch disconnectors and circuit breakers

Device Types Various types of device are available for carrying out the switching and protection tasks listed under title that are specially designed to fulfill the respective requirements. The various parts of IEC 60947 (Low voltage switchgear and controlgear) specify the design, performance and test features of the devices. The most important features of the […]

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6 Factors Influencing Requirements for a Good Grounding System

Six Requirements To Consider In an industrial plant or other facility that requires a grounding system, one or more of the following must be carefully considered (refer to Figure 1 below): 1. Limiting Voltage Limiting to definite values the voltage to earth of the entire electrical system. Use of a suitable grounding system can do […]

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It can happen to experienced engineers too. Stay carefull.

Injuries caused by electric shocks The effect of electricity on the body depends on the amount of current and the length of time the body is exposed to it. The higher the current, the less time a human can survive the exposure. The path of electricity through the body is also critical. For example, current […]

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Main short circuit faults occurring in networks and machines

Short-circuit characteristics Short-circuits can be defined according to three main characteristics: 1. Their origin They may be mechanical: breakdown of conductors or accidental electrical connection between two conductors via a foreign body such as a tool or animal; They may be electrical: following the degradation of the insulation between phases, or between phase and frame or earth, […]

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