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Tuesday, January 19, 2021

The World of High Voltage Power

The World of High Voltage Power

Depending on the convention of the local electrical power industry, high voltage is from 52 kV to 72.5 kV, and has a practical upper limit of about 1,200 kV, although earlier studies and demonstration projects are as high as 1,500 kV. The technical challenge from the beginning for high-voltage products has been the battle between mechanical, thermal and dielectric properties of the materials used to make them, starting with paper and oil for insulation, and air, oil and sulfur-hexafluoride-gas-immersed switching devices to interrupt the current. Besides the power transformers, which at that time already existed, other high-voltage components had to be developed to complete the grid, including power capacitors, high-voltage resistors, overvoltage protection devices and, of course, measurement transformers for current and voltage. All of these devices were connected to electromechanical relays to control and monitor the primary equipment.

Beta Tdworld Com Sites Tdworld com Files Gas Insulated Switchgear Sempersteig Zurich 1967 201402031 Gas-insulated switchgear (GIS)

Since those early times, electromechanical equipment has undergone significant improvement as a more detailed understanding has emerged of the basic physics of materials under electrical and thermal stress, in particular understanding of the dominant insulation media oil, paper and porcelain. For switching devices, bulk oil breakers were later replaced by minimum oil breakers, where the oil volume was reduced to the amount needed for extinguishing the arc. Later on, it was found that oil could be replaced by introducing a high-pressure air flow into the arcing zone. Only later were the phenomenal dielectric properties of sulfur hexafluoride (SF6) gas discovered, which resulted in the introduction of the first high-voltage gas-insulated switchgear (GIS)

1. From then on the focus was on improving the understanding of breaker physics, which resulted in more powerful interrupters capable of interrupting short-circuit currents from 25 kA typically up to 80 kA, and from many series-connected interrupters to a maximum of one interrupting unit for up to 420 kV and even 550 kV circuit breakers. As an example: In 1998 ABB was the first manufacturer to provide a dead tank breaker (DTB) with 245 kV and rated short-circuit currents of 80 kv.

Beta Tdworld Com Sites Tdworld com Files Dead Tank Breaker Us 201402032. Dead tank breaker

Additionally, the increased knowledge of thermal and dielectric gas properties paired with computer simulations of hot gas flow helped to further develop basic switchgear function to a level where, according to latest Cigre statistics, the reliability of SF6 circuit breakers improved to a low value of 0.3 failures per 100 circuit- breaker-years of operation, which is an order of magnitude better than the first two pressure SF6 breakers, and cannot even compare with devices based on earlier oil technology.

Beta Tdworld Com Sites Tdworld com Files Failure Rate Of Different Breaker Technologies 201402035. Failure rate of different breaker technologies

➔ 3 shows 420 kV live tank breakers (LTBs) from in comparison with a modern type of LTBET2, with two interrupting units in series and no need for grading capacitors.

Beta Tdworld Com Sites Tdworld com Files 420k V Circuit Breaker Airblast Technology From 1955 With 10 Interrupting Units In Series 201402033. 420 kV circuit breaker airblast technology with 10 interrupting units in series

Beta Tdworld Com Sites Tdworld com Files Modern 420k V Sf6 Circuit Breaker With Two Interrupting Units In Series 201402034 Modern 420 kV SF6 circuit breaker with two interrupting units in series

Innovation in high-voltage equipment

Different global requirements have led to the emergence of various types of high-voltage switchgear 

6. Primarily, these include LTBs, in which the main insulation is air and the active part on high-voltage potential is connected to overhead power lines; DTBs, a version predominantly used in the United States, in which the interrupter is contained in a pressurized metal tank on ground potential; and GIS, which is used mainly indoors or wherever a small footprint is essential. Liberalized electric power markets in various countries have made reliability, compactness and efficient use of substation area more and more important. ABB pioneered the development of switchgear products with additional integrated functions like the Plug and Switch System (PASS), which led to the development of mixed technology switchgear that provide a functional blend of AIS (air-insulated switchgear) and GIS technologies.

Beta Tdworld Com Sites Tdworld com Files Abb Comprehensive Hv Switchgear Portfolio Depending On Space And Reliability Reqs 201402036.ABB has a comprehensive HV switchgear portfolio depending on space and reliability requirements.

Launched in the PASS is a modular concept that combines the main breaking function in a metal enclosure (as in a DTB) with a combined disconnecting/ earthing switch and current measurement. PASS is a very versatile HV product. It can be configured to fit all AIS substation layouts, such as single busbar, double busbar or H-bridge, and can be installed in new installations or retrofitted into existing substations for substantial space savings. This new HV switching machine comes fully factory assembled and tested, which means minimum time for field installations, as well as reduced lead times in tendering and overall project execution. PASS and in general mixed-technology switchgear solutions are becoming more and more popular, in particular because they offer greater flexibility in new substation layouts. Since its introduction, ABB has sold more than 8,000 PASS or hybrid switchgear bays worldwide.

Beta Tdworld Com Sites Tdworld com Files Pass Versatile And Modular Hv Switching Machine For New And Retrofit Applications 201402037.The PASS is a versatile and modular HV switching machine for new and retrofit applications.

Another example of pioneering HV switchgear concepts is the disconnecting circuit breaker (DCB) first launched by ABB in 2000. The most unreliable switching device in AIS substations is the open-air disconnector, used primarily to isolate circuit breakers or other HV components for maintenance purposes. In a DCB, the air-insulated disconnector is simply avoided and becomes part of the SF6 gas protected main breaker. As the maintenance interval of modern HV SF6 circuit breakers is now 15 years or more, keeping unreliable air disconnectors makes no sense in many cases. With the introduction of the IEC standard for DCBs (IEC 62271-108) in 2005, the acceptance of this technology grew significantly, resulting in more than 1,500 ABB DCB installations worldwide for all voltage levels up to 550 kV.

Beside compactness, the most important advantage of integrating functions is reliability, because more components are in a protected gas environment. The move from electromechanical relays to digital protection devices has replaced bulky instrument transformers used to measure voltage and currents as well as multiple redundant electromechanical tripping relays. In their place are a few sensors with local preprocessing intelligence, connected to numerical bay and station control devices by low-power analog signals, or fiber-optic digital connections. Pioneered by ABB, these devices represent the first step into the world of digital substations, later to become widely known as smart substations. For example, ABB introduced a smart GIS solution featuring electronic current sensors with optical voltage transducers, supervision of actuators and integrated digital protection and control.

The big breakthrough for digital substations came with the emergence of the international substation automation standard IEC 61850, which solved the engineering nightmare of integrating various proprietary solutions. Not only was the problem of interoperability between devices from different suppliers solved, but IEC 61850 also created a future-proof standard that is immune to the fast developing and ever-changing digital world.

Recent developments and outlook

The continuous drive to increase reliability and availability of electrical power is reflected in the latest revision of the HV switchgear standard where new tough requirements were set for mechanical (M2) and capacitive switching (C2), as well as electrical endurance (E2). These efforts, in combination with smart grid initiatives, have resulted in an increased trend toward online monitoring of all primary switchgear functions at the bay and substation level. This is necessary to move away from fixed maintenance schedules, and to be able to plan well ahead for revised maintenance schedules, minimizing outage times. The new generation of smart substations will implement what has been learned in the past, increasing the safe, reliable and flexible operation of HV equipment that is capable of meeting future demands on the AC power grid.

Another HV challenge is the efficient transmission of bulk power over long distances. Recently, new installations of ultrahigh- voltage (UHV) technology demonstration projects have emerged in China and India. One can say that the rise of UHV technology (defined as voltages above 800 kV for AC transmission, and 800 kV and above for direct current or DC transmission) was triggered by energy-hungry emerging countries, where abundant but remote energy supplies had to be flexibly connected to mega-cities and fast-growing industrial load centers far away.

Beta Tdworld Com Sites Tdworld com Files 1100k V Uhv Ac Hybrid Gis Designed By Abb Jinmeng Substation China 201402038.1,100 kV UHV AC hybrid GIS, designed by ABB 

Beta Tdworld Com Sites Tdworld com Files 1100k V Uhvdc Surge Arrester In The Testing Hall In 2012 201402039.1,100 kV UHVDC surge arrester in the testing hall in 2012

10.Despite the controversy over UHV transmission – in particular its commercial viability – State Grid Cooperation of China decided to boost HVDC technology to UHV levels as well. Starting with +/– 500 kV to 800 kV DC, the first commercial installations went into operation in 2010. ABB has in recent years successfully completed tests of all 1,100 kV UHVDC components, and is ready for future HV grids in the years to come.

11.As a world leader in HV products, ABB is committed to improving and exploring advanced HV technologies, and investing in pilot installation projects to explore new technologies that sustainably support the growth in demand of electric power around the world.


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