4 research outputs found
Low power radiometric partial discharge sensor using composite transistor-reset integrator
The measurement of partial discharge provides a means of monitoring insulation health in high-voltage equipment. Traditional partial discharge measurements require separate installation for each item of plant to physically connect sensors with specific items. Wireless measurement methods provide an attractive and scalable alternative. Existing wireless monitoring technologies which use time-difference-of-arrival of a partial discharge signal at multiple, spatially separated, sensors place high demands on power consumption and cost due to a requirement for rapid sampling. A recently proposed partial discharge monitoring system using a wireless sensor network and measuring received signal strength only, has potential cost and scalability advantages. An incoherent wireless sensor incorporating a transistor-reset integrator has been developed that reduces the measurement bandwidth of the PD events and alleviates the need for high-speed sampling. It is based on composite amplifier techniques to reduce the power requirements by a factor of approximately four without compromising precision. The accuracy of the proposed sensor is compared to that obtained using a high-speed digital sampling oscilloscope. Received energies were measured over a 10 m distance in 1 m increments and produced an error within 1 dB beyond 4 m and 3.2 dB at shorter distances, resulting in a measurement accuracy within 1 m
Gated pipelined folding ADC based low power sensor for large-scale radiometric partial discharge monitoring
Partial discharge is a well-established metric for condition assessment of high-voltage plant equipment. Traditional techniques for partial discharge detection involve physical connection of sensors to the device under observation, limiting sensors to monitoring of individual apparatus, and therefore, limiting coverage. Wireless measurement provides an attractive low-cost alternative. The measurement of the radiometric signal propagated from a partial discharge source allows for multiple plant items to be observed by a single sensor, without any physical connection to the plant. Moreover, the implementation of a large-scale wireless sensor network for radiometric monitoring facilitates a simple approach to high voltage fault diagnostics. However, accurate measurement typically requires fast data conversion rates to ensure accurate measurement of faults. The use of high-speed conversion requires continuous high-power dissipation, degrading sensor efficiency and increasing cost and complexity. Thus, we propose a radiometric sensor which utilizes a gated, pipelined, sample-and-hold based folding analogue-todigital converter structure that only samples when a signal is received, reducing the power consumption and increasing the efficiency of the sensor. A proof of concept circuit has been developed using discrete components to evaluate the performance and power consumption of the system
An Envelope Detector as a Trading Cost Technique for Radiometric Partial Discharge Detection
Partial discharge (PD) measurement is an established high voltage insulation monitoring technique used to facilitate the detection of incipient faults in high voltage apparatus. Based on the great importance of the power system, is constant the research about the nature and characteristics of PD sources. A low-cost, free-standing, radiometric, partial discharge wireless sensor network (PD WSN) is described for application to real-time condition monitoring, asset management and operations optimization in the future smart grid. The proposed PD WSN is based on a novel approach to PD location which obviates the need for synchronization between sensors thereby improving scalability. In this paper, the progress in the development of a PD WSN prototype is described. For the proposed evaluation of PD signals, several measurements were performed using a diskcone antenna and a commercial system based on the IEC 60270 standard. Early progress in the development of components for a PD detection system using a network of free-standing radiometers for monitoring of electricity substations has been also presented
Absolute calibration of radiometric partial discharge sensors for insulation condition monitoring in electrical substations
Measurement of partial discharge (PD) is an important tool in the monitoring of insulation
integrity in high voltage (HV) equipment. Partial discharge is measured traditionally using
galvanic contact techniques based on IEC 60270 standard or near field coupling [1]. Freespace
radiometric (FSR) detection of PD is a relatively new technique. This work advances
calibration method for FSR measurements and proposer a methodology for FSR
measurement of absolute PD intensity. Until now, it has been believed that absolute
measurement of partial discharge intensity using radiometric method is not possible. In this
thesis it is demonstrated that such measurement is possible and the first ever such absolute
measurements are presented. Partial discharge sources have been specially constructed.
These included a floating electrode PD emulator, an acrylic cylinder internal PD emulator
and an epoxy dielectric internal PD emulator. Radiated signals are captured using a
wideband biconical antenna [1]. Free-space radiometric and galvanic contact measurement
techniques are compared. Discharge pulse shape and PD characteristics under high voltage
DC and AC conditions are obtained. A comparison shows greater similarity between the
two measurements than was expected. It is inferred that the dominant mechanism in
shaping the spectrum is the band-limiting effect of the radiating structure rather than band
limiting by the receiving antenna. The cumulative energies of PD pulses in both time and
frequency domains are also considered [2]. The frequency spectrum is obtained by FFT
analysis of time-domain pulses. The relative spectral densities in the frequency bands 50
MHz – 290 MHz, 290 MHz – 470 MHz and 470 MHz – 800 MHz are determined. The
calibration of the PD sources for used in the development of Wireless Sensor Network
(WSN) is presented. A method of estimating absolute PD activity level from a radiometric
measurement by relating effective radiated power (ERP) to PD intensity using a PD
calibration device is proposed and demonstrated. The PD sources have been simulated
using CST Microwave Studio. The simulations are used to establish a relationship between
radiated PD signals and PD intensity as defined by apparent charge transfer. To this end,
the radiated fields predicted in the simulations are compared with measurements. There is
sufficient agreement between simulations and measurements to suggest the simulations
could be used to investigate the relationship between PD intensity and the field strength of
radiated signals [3]