2012 IEEE I2MTC - International Instrumentation and Measurement Technology Conference, Proceedings
About: This article is published in The Journal of Thoracic and Cardiovascular Surgery.The article was published on 2012-08-06 and is currently open access. It has received 7 citation(s) till now. The article focuses on the topic(s): Instrumentation (computer programming).
Summary (2 min read)
- Partial Discharge (PD) is a clear ageing agent in electrical insulation of power systems.
- The measurement procedure is always done in industrial environments, where low Signal-to-Noise Ratio (SNR) signals are obtained or several microscopic sites are usually discharging simultaneously.
- This is the reason to add new measurement techniques where PD pulse waveform analysis is a fruitful methodology for noise rejection and PD source separation  .
- In order to solve this, acoustic and UHF PD detection techniques are recently being applied to these systems, since these are non-contact measurements that can help in on-line PD monitoring and location  -  .
- It is not fully understood the relationship between conventional HF or VHF signals and UHF signals  .
A. Partial Discharge generation
- A constant and predictable partial discharges activity is necessary to ensure the repeatability of results.
- It has been found, that using new and dry transformer paper sheets, the partial discharges activity (internal PDs in microscopic air voids between papers) starts around 2 kV and is stable during at least three hours which is enough to acquire proper signals in VHF with the HFCT and in UHF with the antennas.
- Hence, the high voltage source is slowly set slightly above the inception voltage and the measuring campaign starts.
B. Antennas deployment
- The distances between the test object and the antennas are not critical parameters at this stage because the experiment is focused on studying the frequency response of the signals and not the pulses in the time domain; nevertheless, distances were of a similar range, as can be seen in Fig. 2 .
- Since PD source location is not the focus of this paper, the lengths of the coaxial cables are random too.
- PDs activity is a stochastic phenomenon that depends on several factors such as applied voltage level, insulation ageing status, environmental conditions, etc.
- During the experiments in laboratory, most factors were controlled to assure uniformity in Figure 3 .
III. SIGNAL ACQUISITION AND PROCESSING
- Prior to starting the acquisition of partial discharge pulses, the background noise is characterized to be compared with the FFT in the presence of pulses.
- The importance of these results lays on the FFT content that appears in the range from 1300 to 1900 MHz and that is directly related to the UHF emission of the partial discharge pulse, compare Fig. 6 and Fig. 4 .
- The column on the right represents the ratio between the power content in squared volts in those ranges with PD and without PD.
- This study opens a research trend to characterize the behavior of monopole antennas with different lengths and shapes.
- Their significant components above 1.3 GHz are an interesting characteristic for PDs location, where the geometric sensitivity is determined by the bandwidth of the antennas.
- The 10 cm monopole and zig-zag antennas show an overall better performance in the two frequency bands of study after comparing the behaviour of the four antennas.
- The 5 cm monopole antenna is the best detecting PDs emitting in UHF from 1300 to 1900 MHz band.
- Monopoles and zig-zag antennas are strong candidates for further studies because these antennas are inexpensive, simpler, smaller, easier to manufacture and can be tuned to a frequency band of interest by changing their lengths.
- The paper also gives practical indications about PDs detection with different antennas.
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Q1. What contributions have the authors mentioned in the paper "Antenna selection and frequency response study for uhf detection of partial discharges" ?
In this paper, four antennas will be tested in order to compare their response to this physical phenomenon.