Evaluation of the Accuracy and Frequency Response of Medium-Voltage Instrument Transformers under the Combined Influence Factors of Temperature and Vibration

Abstract

Instrument transformers are largely used to measure voltages and currents in public electricity networks. Their performance is essential for Power Quality measurements. Tests and procedures to estimate the effect of single influence factors are performed according to current standards. However, the instrument transformers are exposed simultaneously to more than one factor. The standardized procedures for their characterization with combined influence factors are under construction in Europe. The work in this paper is focused on the development of a new set-up for the determination of the accuracy and frequency response of medium-voltage transformers within the combined influence factors of temperatures and vibrations. The test set-up includes a platform for the combination of temperature and vibrations, a generating system for harmonics up to 9 kHz superposed with 35 kV, 50 Hz voltage and a reference measuring system. The results of several tests carried out on a 35 kV/100 V/50 Hz voltage transformer in the presence of these influence factors are discussed in this paper. They show that the accuracy and frequency response of the voltage transformers are more influenced by temperature than by vibrations.

Characterization of Instrument Transformers under Realistic Conditions: Impact of Single and Combined Influence Quantities on Their Wideband Behavior

“…The change in the temperature shifts the resonance frequencies as the winding geometry changes: with rising temperature, the resonance frequency decreases. Therefore, in the region close to the resonances, the ratio error for a given frequency can change in the range of 100% [ 31 ].…”

“…Similar observations were made when measuring the frequency response of the VT. However, at low temperatures, the deviations were more noticeable, regardless of the presence of vibration [ 31 , 40 ].…”

“…The Laboratoire National de Métrologie et d’Essais (LNE) has developed a comprehensive setup for the accurate characterization of the frequency responses of VTs under the influence of both temperature and vibration [ 31 ]. The test circuit of this setup is illustrated in Figure 2 .…”

“…As regards the scientific literature, a number of papers dealing with the assessment of the influence quantities on ITs’ wideband responses can be found. However, these published papers only refer to certain influence quantities and investigate specific types of ITs [ 30 , 31 ].…”

Measurement of High-Frequency Voltage Harmonics above 2 kHz in High-Voltage Networks

“…The impact of external factors on instrument voltage transformer frequency response behavior is covered in [111][112][113]. These factors do not include certain issues, such as transducer design aspects and inherent errors due to manufacturing processes, since they are considered as internal factors.…”