Abstract
This study examines the results of thermal tests on a 6(10) kV digital combined current and voltage transformer conducted in an environmental chamber. This measuring instrument consists of current and voltage transformers, featuring a resistive divider, and is used for commercial and technical electric power accounting. Ambient temperatures and levels of insolation on the transformer surface were set for the environmental chamber, with simulation of voltage transformer functioning in normal and emergency modes. We determined the time needed for the thermodynamic system to move to steady heat exchange mode, and also the final temperatures in the lower resistors and on the surface of the voltage transformer insulation cover. The results of our study have been used in developing algorithms for self-diagnostics of the thermal state of a digital combined transformer.
Highlights
An important task in the functioning of digital combined current and voltage transformers in commercial and technical electric power accounting in summer conditions with high ambient temperatures and levels of insolation and the possibility of grid voltage exceeding rated values is to examine the exchange of heat between a transformer and its environment
The environmental chamber comprises a closed, isolated structure consisting of two compartments: a warm compartment and one for a step-up voltage transformer
The warm compartment is shielded by means of PVC sheeting, and features a heating element used to maintain constant ambient temperature, creating the necessary temperature conditions corresponding to the worst transformer operating conditions, taking into account the environmental version and placement category
Summary
An important task in the functioning of digital combined current and voltage transformers in commercial and technical electric power accounting in summer conditions with high ambient temperatures and levels of insolation and the possibility of grid voltage exceeding rated values is to examine the exchange of heat between a transformer and its environment. Developing new systems of self-diagnostics checks for the thermal state of digital instrument transformers that determine temperature according to the most heated up electrical equipment part in real time is an important task, especially in the development of “smart” power grids. We conducted a series of experiments in the high voltage laboratory of our High Voltage Equipment Department to study the influence of voltage, high ambient temperatures and insolation on the operating temperature of a digital combined transformer. Electrical processes occurring in resistive voltage dividers comprising groups of resistors are related to heat emission.
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