We propose an objective formulation of the impulse analysis problem from a signal analysis viewpoint. The winding response is quintessentially that of a deterministic network to a finite energy signal, with breakdown and partial discharge being inherently nonlinear events. A significant improvement to the acquisition of waveforms is demonstrated by a virtual instrument approach. It retains the advantages of the time- and frequency-domain methods. The drawbacks of the transfer function method are highlighted and a new piecewise linear approach is proposed for analysis. Experiments on a discrete lumped parameter model of the winding are used to validate the PXI based instrument. © 2007 IEEE.

A. Palani

V. Jayashankar

DIGITAL INSTRUMENTS

Discharge (fluid mechanics)

Distributed power generation

Electric transformers

Frequency domain analysis

LIGHTNING

Partial discharges

Piecewise linear techniques

Signal analysis

signal processing

Winding

ANALYSIS PROBLEMS

Breakdown

DOMAIN METHODS

FINITE ENERGIES

LIGHTNING IMPULSE TESTS

LUMPED PARAMETER MODELS

Piecewise linear

TRANSFER FUNCTION METHODS

VIRTUAL INSTRUMENT

VIRTUAL INSTRUMENTS

Time domain analysis

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Virtual Instrument for Lightning Impulse Tests

IEEE Transactions on Power Delivery

The ability of a transformer to withstand the dynamic effects of a short circuit test is conventionally evaluated by a measurement of short circuit reactance before and after the test. We propose new techniques for fault detection based on continual assessment during the test. The methods are based on the comparative null method for accuracy measurement in instrument transformers. They include voltage comparison, current comparison and real/reactive power measurements. High resolution sampling based acquisition systems are used to compute changes on a cycle-to-cycle basis. The proposed methods are validated on a number of models including a voltage transformer and a distribution transformer winding. They would be useful for designers in assessing events leading to failure in a more transparent manner. © 2008 IEEE.

Real-time techniques to measure winding displacement in transformers during short-circuit tests

A method is proposed for recognizing PD events within a winding during impulse tests using a lock-in amplifier technique. The resonant frequencies of the winding serve as the basis of selection of the lock-in amplifier reference frequencies. It is implemented with a virtual instrument and validated with an independent stand-alone lock-in amplifier. A physical model of a winding with discrete elements is used to demonstrate the results. A theoretical basis for the instrument is established using an 'abc' model of PD along with a linear discrete winding model. The influence of location of PD is also addressed. The method will provide online recognition of PD during the impulse test and can be adapted for onsite measurements. © 2007 IEEE.

IEEE Transactions on Dielectrics and Electrical Insulation

A lock-in technique for PD measurement during impulse tests

A correlation method is proposed for the location of partial discharge within a winding. Theoretical simulations and experimental results on a lumped parameter model of a winding are shown to prove the feasibility of the method. © 2006 IEEE.

A correlation method for detection of partial discharges in transformers

Several phenomena in transformers are best analyzed In the frequency domain when energized by broadband excitation. These include dielectric behavior to lightning impulse, winding deformation during transport and structural failure during short circuit tests. We propose an adaptive architecture that characterizes all these events in an unifying manner. The developed instrument is based on the PXI hardware with necessary software developed under LABVIEW environment. Experimental results using the developed instrument are reported to demonstrate its versatility.

IEEE Region 10 Annual International Conference, Proceedings/TENCON

An adaptive high resolution measuring system for characterizing transformers subjected to broadband excitation

Experimental results on fault simulations during impulse tests across windings and other specifically designed networks are reported. Both breakdown and partial discharge studies are conducted with digital acquisition of fault records. © 2005 IEEE.

Simulation of faults during impulse tests

A fusion of hard and soft computing is proposed for the impulse analysis problem. An optimal hardware platform for the data acquisition and a minimal set of simulations form the hard computing element. As the number of simulations can become unbounded to cater to all types of faults, a soft computing approach based on fuzzy logic is proposed. This can lead to automation of impulse analysis function.

SMCia/05 - Proceedings of the 2005 IEEE Mid-Summer Workshop on Soft Computing in Industrial Applications

Fuzzy logic based Impulse test analysis

An objective classification of faults that can occur during impulse tests on power transformers is proposed. It includes nonlinear elements, breakdown, and partial discharge events. An analysis of a layer winding in the time and frequency domains with these faults shows that current assessment methods must be used with caution. A model reference approach is proposed to distinctly improve recognition in such cases. The method is immune to changes of wave shape and the instant of fault is available by observation.

IEE Proceedings: Science, Measurement and Technology

Impulse testing of power transformers - A model reference approach

Virtual instrument for lightning impulse tests

Journal	IEEE Transactions on Power Delivery
ISSN	08858977
Open Access	No