Determination of Hot-Spot Temperature for ONAN Distribution Transformers with Dynamic Thermal Modelling

It is normal practice when designing electrical machines to design for operation within the maximum temperature limits of the insulation. If part of the winding is not effectively cooled under these conditions, the resulting temperature rise can damage the insulation and seriously reduce the length of operational service of the machine. This paper discusses a method of detecting high-temperature regions within a winding and of estimating the ‘hot spot’ temperature. The investigation has been concentrated on the design associated with a direct water-cooled winding, although the results could be applied generally on other electrical machines.

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Real-Time Temperature On-Line Monitoring and Analysis System for Transformers

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.521.409 ◽

2014 ◽

Vol 521 ◽

pp. 409-413 ◽

Cited By ~ 1

Author(s):

Ya Bo Chen ◽

Yue Sun ◽

Xu Ri Sun ◽

Ge Hao Sheng ◽

Xiu Chen Jiang

Keyword(s):

Real Time ◽

Hot Spot ◽

Load Ratio ◽

Distribution Transformers ◽

Insulation Aging ◽

On Line ◽

Analysis System ◽

Operation Status ◽

Process Fault Diagnosis ◽

Spot Temperature

The safe operation of power transformers mainly depends on proper functioning of insulation, whose status is revealed by temperatures. Applying ZigBee wireless network, a real-time temperature on-line monitoring and analysis system is developed to view the operation status of underground distribution transformers and process fault diagnosis. Furthermore, using the top-oil and hot-spot temperature calculation method in IEEE Std C57.91-1995, the system can compute a prediction of those temperatures with current load ratio and ambient temperature. System will display early warnings if temperatures are much higher than expected ones, in which way insulation aging can be handled in advance. Insulation fault and big disasters will be prevented.

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Environment Influence on Lifetimes of Power Transformers

Electrotehnica, Electronica, Automatica ◽

10.46904/eea.21.69.2.1108004 ◽

2021 ◽

Vol 69 (2) ◽

pp. 31-44

Author(s):

Petru NOTINGHER ◽

Cristina STANCU ◽

Ionuț DRĂGAN ◽

Maaya ISSEDOU BEI

Keyword(s):

Environmental Factors ◽

Solar Radiation ◽

Ambient Temperature ◽

Hot Spot ◽

Power Transformers ◽

Distribution Transformers ◽

Climatic Characteristics ◽

Spot Temperature ◽

Environment Influence

This paper presents a study on the influence of the environmental factors (respectively, ambient temperature and solar radiation) on hot spot temperatures and the consumed and remaining lifetimes of power transformers. In this regard, 15 identical 105 MVA distribution transformers are considered, loaded with the same load, and operating in 15 areas of Romania (with different climatic characteristics). Using the equations recommended by IEC 60076-7 (modified in the case of the presence of solar radiation) the values of oil temperature, hot spot temperatures and consumed and remaining lifetimes in two days from July 2020 are calculated, both in the presence and in the absence of solar radiation. It is shown that the values of the hot spot temperature and of the consumed lifetimes differ from one locality to another and that they increase with the increase of the ambient temperature and the intensities of the solar radiation. Finally, it is shown that the results obtained can be used to develop more efficient maintenance programs for distribution power transformers.

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