Category Archive for: «High Voltage»

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An Example of Choosing 138 kV Line Circuit Breaker

Let’s choose 138 kV line #3 circuit breaker To better understand a process of high voltage equipment selection, let’s discuss an example of choosing 138 kV Line #3 Circuit Breaker, shown in Figure 1, assuming that the following information about the system is available: Continuous current for all the lines: Line #1 – 1,000 A, […]

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How to mitigate effects of very fast transients (VFT) on HV equipment

VFT overvoltages The level reached by very fast transients (VFT) overvoltages originated by disconnector switching or line-to-ground faults inside a gas insulated switchgear (GIS) are below the basic insulation level (BIL) of substation and external equipment. However, aging of the insulation of external equipment due to frequent VFT must be considered. Transient enclosure voltages (TEV) […]

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An example of calculating the technical losses of T&D lines

Introduction to Losses There are two types of losses in transmission and distribution line. Technical Losses and Commercial Losses. It’s necessary to calculate technical and commercial losses. Normally technical losses and commercial losses are calculated separately. Technical losses of the distribution line mostly depend upon electrical load, type and size of conductor, length of line […]

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Hey Mom, look at that big HVDC Transformer!

Key component HVDC transformers are key components of HVDC stations. HVDC converter and inverter stations terminate long-distance DC transmission lines or DC sea cables. This type of transformer provides the interface between AC grids and high power rectifiers and are used to control the load flow over the DC transmission lines. Design options The design […]

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8 Main Disadvantages of HVDC Transmission

High Voltage Direct Current (HVDC) Few weeks back I posted an article about advantages of HVDC over HVAC transmission systems. Advantages of HVDC are numerous and very well recognized, but like everything on this earth this system has other side too. The eight main disadvantages of HVDC transmission systems, including DC links connecting HVAC systems area, […]

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Electrical Thumb Rules You MUST Follow (Part 7)

Continued from: Electrical Thumb Rules You MUST Follow (Part 6) 8 electrical thumb rules to follow: Overhead conductor / cable size Transmission / distribution  line (span, height of tower) Types of towers Tower swing angle clearance (metal part to live part) Cable coding, IS 1554 (A2XFY, FRLS, FRPVC, FRLA, PILC) Corona ring size Load as per […]

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Advantages of HVDC over HVAC transmission

AC as preferred option Despite alternating current being the dominant mode for electric power transmission, in a number of applications, the advantages of HVDC makes it the preferred option over AC transmission. Examples include: Undersea cables where high capacitance causes additional AC losses (e.g., the 250-km Baltic Cable between Sweden and Germany). Endpoint-to-endpoint long-haul bulk […]

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15 hypothesis responsible for the aging of composite insulators

Major causes of aging in composite insulators Most technical work concentrates on the aging of nonceramic insulators and the development of test methods that simulate the aging process. Transmission lines operate in a polluted atmosphere. Inevitably, insulators will become polluted after several months in operation. Fog and dew cause wetting and produce uneven voltage distribution, […]

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General principles of electricity supply systems

Transmission of electricity The generation of electricity in most modern power stations is at 25 kV, and this voltage is then transformed to 400 kV for transmission. Virtually all the generators of electricity throughout the world are three-phase synchronous generators. The generator consists of a prime mover and a magnetic field excitor. The magnetic field […]

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Special Transformers for Industrial Applications

Specific Industrial Transformers A number of industry applications require specific industrial transformers due to the usage of power (current) as a major resource for production. Electric arc furnace transformers (EAF) DC electric arc furnace transformers (DC EAF) Rectifier transformers Converter transformers Line Feeder Electric arc furnaces (EAF), ladle furnaces (LF) and high-current rectifiers need a […]

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