Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

Abstract

The paper presents a method for the frequency characterization of voltage transformers (VTs) for medium voltage (MV) grids which involves only sine waves. It is called extended SINDICOMP, since it is an extended version of the previously developed technique SINDICOMP. It requires, in the first step, an evaluation and a compensation of the non-linearity introduced by the VT when it is supplied with a 50 Hz sinusoidal input at rated value. Then, the VT is characterized with a low voltage sinusoidal frequency sweep from the second harmonic frequency up to the first resonance frequency. Some rules to build the approximated frequency response, starting from these two sets of data, are given in the paper. The proposed approach is applied to three commercial MV VTs. Significant improvement of the VT performance is obtained, compared to the use of a frequency response obtained from the low voltage characterization.

How Instrument Transformers Influence Power Quality Measurements: A Proposal of Accuracy Verification Tests

“…At present, there are few papers in the literature dealing with metrological performances of ITs used for PQ measurement. Some authors of this paper have already shown that the metrological performances of ITs in the presence of PQ phenomena can drastically change [ 30 , 32 , 33 , 34 , 35 , 36 ].…”

“… The test waveform should be complex because the error of ITs can be drastically increased when more PQ phenomena are superimposed to fundamental waveform. The simple and consolidated compensation techniques [ 33 , 34 , 35 ] present in the literature are ineffective when several PQ phenomena are superimposed to fundamental waveform. …”

Instrument Transformers for Power Quality Measurements: a Review of Literature and Standards

“…In fact, [4]- [7] propose techniques to measure and compensate the IT non-linearity, leading to a strong reduction of the IT errors contribution in harmonic measurement. In particular, in [4] and [5], the nonlinearities are measured and compensated by measuring the spurious phasors at the IT secondary side when it is supplied with a sinusoidal signal at rated voltage and frequency. In [6] and [7], the compensating phasors are measured suppling a VT with dual-tone and multitone signals, respectively.…”

Transformation of Transient Overvoltages by Inductive Voltage Transformers

“…In this paper the determined characteristic of voltage ratio error at harmonics with frequency for a given medium voltage inductive instrument transformer is used to predict the value of the slow-front overvoltage in its secondary circuit. The nonlinearity of the magnetization characteristics of the magnetic core of the inductive VTs causes the need for accurate evaluation of the values of ratio error and phase displacement at harmonics of the rated primary voltage; this is required during the test [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. There are many methods and measuring systems that enable evaluation of the values of ratio error at harmonics of inductive VT.…”

“…There are many methods and measuring systems that enable evaluation of the values of ratio error at harmonics of inductive VT. The most recent solutions from a given group of authors are referenced as [ 17 , 18 , 25 ]. However, the resonance frequencies and the measured values of ratio error and phase displacement do not change with the value of the applied voltage.…”