Abstract
Transformers belong to the main equipment of power plants, raising, lowering and distribution substations, as well as various types of converter devices. In the process of operating oil transformers, damage or defects can occur, the timely detection of which enables taking measures to prevent their furtherance and to keep the equipment intact. Severe consequences are caused by damage to the windings and main insulation of the transformers as it might bring about malfunctions in the cooling system. Existing cooling devices are not always efficient. We have developed a complementary cooling system for power transformers with thermoelectric converters. The operating principle of the device is based on the following: at night, when the ambient temperature is the lowest, water ice is produced the melting of which keeps the transformer oil cold in the hottest daytime. Two operating states of the developed device are described. We also herein present a mathematical description of the water cooling process. We have analyzed the results of studies consisting in evaluating the alteration in the heat flow drawn by vertical ground-coupled heat exchangers. The results of the research show it is possible to use the system for thermoelectric module- and VGHE-enabled liquid cooling of power oil transformers that will allow to draw up to 50% of heat at peak thermal loads, whereas the transformer power is expected to increase by 25–40% depending on the specifications.
Highlights
Введение Воздействие на силовой трансформатор тока подмагничивания как постоянного, так и в виде импульса существенно изменяет режим его работы, т. е. магнитная система переходит в режим насыщения
We have developed a complementary cooling system for power transformers with thermoelectric converters
The results of the research show it is possible to use the system for thermoelectric module- and VGHE-enabled liquid cooling of power oil transformers that will allow to draw up to 50% of heat at peak thermal loads, whereas the transformer power is expected to increase by 25–40% depending on the specifications
Summary
Для определения конструктивных и режимных параметров работы ВГТО, предназначенных для предварительного охлаждения воды перед подачей в емкость используется математическая модель, предложенная в работе [16]. ВГТО для условия переменной температуры поверхности скважины приводится к частному решению для постоянной температуры. Теплоносителя (воды), кг/с; cp – удельная массовая теплоемкость воды, Дж/(кг·К); tL1 – температура воды на входе в ВГТО, К; tL2 – температура воды на выходе из ВГТО, К; kl – линейный коэффициент теплопередачи, Вт/(м·К); L – длина ВГТО (глубина скважины), м; n – количество ВГТО; tL – средняя температура воды в ВГТО, К; tG – температура грунта, К. Линейный коэффициент теплопередачи с учетом термического сопротивления слоя заполнителя скважины можно определить по формуле: kl. D1 2 s d1 2 z d2 где α – коэффициент теплоотдачи, Вт/(м2·К); λs – коэффициент теплопроводности материала трубы ВГТО, Вт/(м·К); λz – коэффициент теплопроводности заполнителя скважины, Вт/(м·К); d1 – внутренний диаметр трубы ВГТО, м; d2 – наружный диаметр трубы ВГТО, м; δz – толщина слоя заполнителя скважины, м. Коэффициент теплоотдачи при обтекании прямых труб можно найти по известным уравнениям [17, 18] в зависимости от режима течения теплоносителя:
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