A Comparison of Partial Discharge Sensors for Natural Gas Insulated High Voltage Equipment

This paper proposes two alternative methods for online partial discharge (PD) detection and localization of a 6.2/7 kV XLPE insulated medium voltage (MV) power cable. The artificial defect as surface discharge was made in the middle of the cable at the joint connecting between two of 10 m length cables with 50 sq.mm diameter. Therefore, the total length of the cable is 20 m. In addition, the corona discharge was also made at the end of cable termination. The PD measurement was performed under uncontrollable noises with limitations of cable characteristics. UHF and HFCT sensors together with their supplemented techniques as Trending method for UHF sensor as well as Time Domain Reflectometry (TDR) technique for HFCT sensor are applied in the experiment in order to identify and locate the PD types. The results for PD identification and localization of both UHF and HFCT sensors are satisfied.

The occurrence of surface release on high voltage equipment is the Partial Discharge (PD) phenomenon. Partial Discharge measurements are very important to determine the condition of electrical equipment. The cause of the partial discharge is not only old equipment but also from set-up errors and insulation problems. In high-voltage equipment such as cables, circuit breakers, bushings and transformers there are generally surface release phenomena due to aging insulation in high-voltage equipment, aging of insulation caused by heat, electricity, ambient and mechanical factors. Liquid insulation as a dielectric material used in high-voltage equipment functions as insulation and heat transfer or cooling. This study aims to determine the surface release characteristics around the surface edge of the Printed Circuit Board (PCB) with a plate electrode model in liquid insulation (mineral oil). PCBs that have epoxy insulating material (FR-4) are one of the basic ingredients used in the isolation of high voltage equipment but have disadvantages due to pollutants. The measurement of partial discharge is carried out using electric and non-electric methods. Electric methods use RC Detectors and HFCT sensors and nonelectric methods with Loop Antenna sensors. Measurement parameters taken include Partial Discharge Inception (PDIV), partial discharge extinction voltage (PDEV), Partial Discharge waveform, Partial Discharge phase pattern and breakdown voltage. This Partial Discharge phase pattern data is presented in the form of a φ-q-n pattern. In oil isolation testing measurements are carried out at voltage levels of 17 kV, 18, kV, 19 kV, and 20 kV for Partial Discharge waveform parameters and Partial Discharge phase patterns. The test results revealed that in the isolation of oil the PDIV value in surface release testing obtained using RC sensor detectors had a higher Vpp value than the air isolation test. Judging from the value of dielectric strength in PCB surface release testing in oil insulation has a higher value compared to air insulation.

Partial discharges result in cable line faults that can occur in defective insulation systems made of rubber, polyethylene, XLPE, and flexible PVC. Insulation defects may occur due to disruptions in their production process, cable installation, and operational conditions. Therefore, the diagnostic and monitoring of partial discharge occurrence in cable insulation help prevent emergencies in damaged cable line sections. Partial discharge registration is a non-destructive diagnostic method that helps assess the cable line condition and localize the detected defects. There are various methods of operational monitoring and partial discharge cause analysis based on operative partial discharge sensors. The assessment of cable line condition depends on the efficiency of signal detection and processing by the sensors used. This article reviews the problems of detecting and localizing partial discharges in cable lines and junction boxes using HFCT and UHF sensors. Having analyzed the capabilities of these sensors, we believe that the combined usage of HFCT and UHF sensors is the best method of detecting and localizing partial discharge within the entire cable system (lines and junction boxes).

Partial discharges (PD) are the most common and harmful threat to the health of electrical insulation of high voltage (HV) and high field (HF) equipment. The occurrence of PD activity in HV and MV equipment is at the same time a cause and a sign of insulation degradation that may eventually result in the breakdown of the HV power equipment. For the safe and reliable operation of HV power equipment, continuous PD monitoring needs to be conducted conveniently to prevent any unplanned power outages and damage to electrical power equipment. The ultra-high frequency (UHF) PD measurement method has been widely used as an effective technique to detect PD activity on HV power equipment due to its non-invasive principle. To enable PD detection accuracy, there is still a need for more sensitive PD sensors that can assist the UHF PD monitoring system by suppressing ambient background noise and low-frequency electromagnetic interferences from telecommunication such as GSM signals. To tackle the sensitivity issues, this article presents a new design of ultra-wideband (UWB) microstrip patch antenna that is capable of effective suppression of low-frequency interference signals. The proposed antenna, designed, simulated, and optimized using the CST Microwave Studio software, has a bandwidth of 3.3GHz, below -10dB, in the operating frequency range of 1.2GHz-4.5GHz. The prototype of this antenna, printed on an FR4 substrate of a thickness of 1.6mm and a dielectric constant of 4.4, featuring a compact size of 100mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times100$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.6$ </tex-math></inline-formula> mm, was implemented to detect PD through laboratory experiments. This paper shows that the designed UWB antenna has high sensitivity, good noise rejection and it is, therefore, a promising candidate sensor for PD detection on HV equipment.

Partial Discharge (PD) is a natural phenomenon that occurs inevitably in high voltage equipment mainly due to the degradation of insulation materials. PD emits high frequency signals above 40 kHz which can be easily detected by Acoustic Emission (AE) method. This paper presents the processes of designing a PD detection device using ultrasonic sensor. The finished design is known as Partial Discharge Detection (PDD) device and its function is to detect PD on a medium voltage cross-linked polyethylene (XLPE) cable. Outcomes of the design processes show the complete design of the PDD device, the fabricated PDD device, and the functionality of the PDD device. The end results show that the PDD device is capable to detect PD much like a HFCT sensor does. The prototype device will be very beneficial in the upcoming future as the physical dimension of the device itself is relatively small, portable and cost efficient to manufacture when compared to the commercial PD sensing devices. Further advancement of the PD device, such as to incorporate Artificial Intelligence (AI), can be an added feature to the device moving forward. In addition, the prototype can also be converted into Flexible Printed Circuit Board (FPCB) form factor for ease of implementation and robustness. Such finding will be of utmost help to the power industries in monitoring PD activities on high voltage equipments using an affordable and efficient device in an effort to reduce the repair and maintenance costs.

Electricity has a crucial function in contemporary civilization. The power grid must be stable to ensure the efficiency and dependability of electrical equipment. This implies that the high-voltage equipment at the substation must be reliably operated. As a result, the appropriate and dependable use of systems to monitor the operating status of high-voltage electrical equipment has recently gained attention. Partial discharge (PD) analysis is one of the most promising solutions for monitoring and diagnosing potential problems in insulation systems. Noise is a major challenge in diagnosing and detecting defects when using this measurement. This study aims to denoise PD signals using a data decomposition method, improved complete ensemble empirical mode decomposition with adaptive noise algorithm, combined with statistical significance test to increase noise reduction efficiency and to derive and visualize the Hilbert spectrum of the input signal in time-frequency domain after filtering the noise. In the PD signal analysis, both artificial and experimental signals were used as input signals in the decomposition method. For these signals, this study has yielded significant improvement in the denoising and the PD detecting process indicated by statistical measures. Thus, the signal decomposition by using the proposed method is proven to be a useful tool for diagnosing the PD on high voltage equipment.

Partial discharge (PD) activity in high-voltage power equipment is a warning sign of insulation degradation that subsequently leads to the aging and breakdown of the power equipment. For the reliable and safe operation of high voltage power equipment, a PD diagnostic technique needs to be performed to assess and monitor closely the insulation condition. This paper presents a new type of UHF microstrip patch antenna with ultra-wideband frequency that can assist the UHF PD monitoring system to detect PD on high voltage equipment such as power transformers. This antenna was designed and simulated using CST Microwave Studio software. After design and simulation, the antenna was fabricated on a printed circuit board with FR4-epoxy substrate having a thickness of 1.6mm and dielectric permittivity of 4.4. The radiating patch and ground plane of this antenna are made of copper whose thickness is 0.035. The designed microstrip patch antenna was implemented to detect partial discharge on the transformer tank model. Based on the measurement results of the antenna characteristic parameters by using the Vector Network Analyzer, it is seen that the designed antenna has an operating frequency range of 1.2GHz-4.5GHz, and a bandwidth of 3.3GHz. Based on PD measurement results, the new design of the microstrip patch antenna has a high sensitivity in detecting the PD signals caused by insulation defects inside the transformer tank. The ultra-wideband frequency response of this antenna makes it a suitable and promising sensor for PD detection and PD recognition on high voltage equipment such as power transformers.

Partial discharge (PD) measurements provide valuable information for assessing the condition of high voltage (HV) insulation systems, contributing to their quality assurance. Different PD measuring techniques have been developed in the last years specially designed to perform on-line measurements. Non-conventional PD methods operating in high frequency bands are usually used when this type of tests are carried out. In PD measurements the signal acquisition, the subsequent signal processing and the capability to obtain an accurate diagnosis are conditioned by the selection of a suitable detection technique and by the implementation of effective signal processing tools. This paper proposes an optimized electromagnetic detection method based on the combined use of wideband PD sensors for measurements performed in the HF and UHF frequency ranges, together with the implementation of powerful processing tools. The effectiveness of the measuring techniques proposed is demonstrated through an example, where several PD sources are measured simultaneously in a HV installation consisting of a cable system connected by a plug-in terminal to a gas insulated substation (GIS) compartment.

Partial discharge (PD) has been used as a reliable diagnostic technique for High voltage equipment. UHF methods have been widely applied for the detection of electromagnetic waves emitted from PD source in High Voltage equipment. EM wave propagation produced by PD can be detected by using UHF sensors. This paper discusses the new design of double layer bowtie antenna with modification of the wing edge of the antenna as a UHF sensor for PD detection in air insulation. The double layer bowtie antenna was designed by using FR4-epoxy substrate type and later on printed on PCB. The 3D-HFSS software was used to design the bowtie antenna. Based on simulation results of double layer bowtie antenna, the optimum design for PD measurement was obtained with a minimum return loss (RL) of -34.7 dB, the bandwidth of 560 MHz, and Voltage Standing Wave Ratio (VSWR) of 1.03. Based on the measurement results for the designed bowtie antenna by using the Vector Network Analyser (VNA), the bowtie antenna has a return loss of -14 dB, the bandwidth of 555 MHz, and VSWR of 1.05. The designed UHF double layer bowtie antenna is capable of detecting PD in UHF range since PD signal have a frequency range of 300 MHz - 3 GHz.

Partial discharge (PD) may cause the insulation deterioration in power equipment and impact the reliability. Therefore, the PD detection with pattern recognition is an important tool in insulation diagnosis of High Voltage (HV) equipment. This paper presents the application of Possibilistic fuzzy c-means (PFCM) clustering approach to recognize PD patterns of HV equipment. The PD patterns are measured by using a commercial PD detector. A set of features used as operators for each PD pattern is extracted through statistical schemes. The significant features of PD patterns are extracted by using the nonlinear principal component analysis (NLPCA) method. The proposed PFCM classifier has an advantage of high robustness and efficacy to ambiguous patterns and is useful in recognizing the PD patterns of the HV equipment. To verify the effectiveness of the proposed method, the classifier has been verified on various test samples. The test results show that the proposed approach may achieve quite satisfactory recognition of PD patterns and the number of features in the feature vector will influence the accuracy of pattern recognition.

Managing impure carbon dioxide produced by fossil fuel-based generation of electricity is required for successful implementation of carbon capture, utilization, and storage. Impurities in carbon dioxide, particularly [Formula: see text] and [Formula: see text], are geochemically more reactive than the carbon dioxide and may adversely impact a carbon dioxide storage reservoir by generating additional acidity. Hydrothermal experiments are performed to evaluate geochemical and mineralogic effects of injecting [Formula: see text]-[Formula: see text] fluid into a carbonate reservoir. The experimental design is based on a natural carbon dioxide reservoir, the Madison Limestone on the Moxa Arch of Southwest Wyoming, which serves as a natural analog for geologic cosequestration of sulfur dioxide and carbon dioxide. Idealized Madison Limestone ([Formula: see text]) and [Formula: see text] brine ([Formula: see text], initial [Formula: see text]) reacted at reservoir conditions (110°C and 25 MPa) for approximately 165 days (3960 h). Carbon dioxide fluid containing 500 ppmv sulfur dioxide was injected and the experiment continued for approximately 55 days (1326 h). Sulfur dioxide partitions out of the supercritical carbon dioxide phase and dissolves into coexisting brine on the time scale of the experiments (55 days). Injecting supercritical [Formula: see text]-[Formula: see text] or pure supercritical carbon dioxide into a brine-limestone system produces the same in situ pH (4.6) and ex situ pH (6.4–6.5), as measured 28 h after injection because dissolution of calcite buffers in situ pH. Precipitation of anhydrite sequesters injected sulfur and, coupled with dissolution of calcite, effectively buffers the amount of dissolved calcium to the same concentrations measured in limestone-brine experiments injected with pure carbon dioxide. Supercritical [Formula: see text]-[Formula: see text] does not enhance the sequestration potential of a carbonate reservoir relative to pure supercritical carbon dioxide. Our results substantiate predictions from natural analog studies of the Madison Limestone that anhydrite traps sulfur and carbonate minerals ultimately reprecipitate and mineralize carbon in carbonate reservoirs.

Partial discharge (PD) measurement is an established technique to detect local defects in the oil/paper insulation. They can be measured by electrical PD measurements according to IEC 60270 or by electromagnetic measurements in the ultra-high frequency range (UHF: 300 MHz – 3 GHz). The electromagnetic emissions of PD are recorded using an UHF sensor which is inserted into the transformer tank. The importance of PD measurements is reflected in the standard for charge-based electrical measurements (IEC 60270). Because of the standard, apparent charge, QIEC, became an essential factor for determining insulation quality in transformers. To be an accepted factor for both, quality testing in factory acceptance tests (FAT) or site acceptance tests (SAT) and continuous PD monitoring, the UHF technology must be as reliable and reproducible as the electrical method. To achieve this, a standardized calibration procedure is needed: It makes UHF measurement results from different systems comparable. Because this calibration procedure was lacking in the past, the UHF technology does not provide comparability between measurement systems and different sensors, yet. However, it shows advantages for on-site acceptance tests like SAT, continuous monitoring, and diagnostic purposes. E.g., regarding signal to noise ratios, the possibility for localization of PD sources and also for practical reasons like preparation times and accessibility on-site. This contribution presents a PD monitoring system which can be calibrated according to the calibration process described recently in Cigré TB 861 and two different types of UHF PD sensors for power transformers. One sensor type is for new transformers using dielectric windows and the other is for retrofitting transformers using their DN50/80 drain valves. A recommendation or strategy on where to place window-type UHF sensors at the tank of new power transformers is also provided in accordance with TB 861. Additionally, this contribution provides a description of the calibration process for UHF PD measurement systems consisting of two steps: 1) Calibration of the measurement instrument analogous to the calibration of the electrical PD measurement circuit using a defined reference signal. 2) Calibration of a UHF sensor using its characteristic antenna factor (AF). Furthermore, it shows three case studies from different power transformers equipped with UHF sensors and UHF PD monitoring systems.

Partial Discharge (PD) measurement is a very important tool for insulation diagnosis of High Voltage (HV) equipment. The interpretation of PD data is very challenging and has ability to diagnose incipient faults in HV equipment. PD measurement at normal operating power frequency (50/60 Hz) is being carried out for decades and the data interpretation is widely established. At present there is a need of PD measurement to be performed at different frequency of excitation voltage such as Very Low Frequency (0.01–0.1) Hz. But the data interpretation and diagnosis becomes challenging because of limited available studies. In this paper, an attempt is made to compare the corona characteristics, with and without insulation barrier, at Very Low Frequency (0.1Hz) and normal operating power frequency (50 Hz). The corona characteristics used for comparison include average charge magnitude, inception voltage and Phase Resolved Partial Discharge (PRPD) pattern.

Understanding PD (Partial Discharge) phenomena under impulse voltage is important knowledge for the improvement of reliability of HV (High Voltage) equipment. PD in HV equipment can cause severe insulation deterioration resulting in breakdown, production loss and high cost of repairs. HV equipment insulation can fail due to PD activities which are initiated by impulse voltages such as lightning and switching. The latter has been exacerbated by load shedding switching operations in South Africa. PD detection under AC (Alternating Current) frequency voltage conditions is well developed, however there is inadequate knowledge in PD detection and diagnosis under non-power frequencies. The challenge is to enable PD detection during impulse voltage, due to the overlaps between the impulse voltage and the PD frequencies. In the present work, balanced PD detection circuit is implemented to suppress impulse voltage interference for the purpose of detecting cavity PD under impulse voltage. The measurement results show that PD pulses occur on specific locations of the impulse test voltage waveform and is consistent with similar results in the literature.

The conditions for initial hydrate formation in systems containing carbon dioxide, propane and water were obtained over a wide concentration range for the hydrate-water-rich liquid-gas phase region. The locus of the four-phase equilibrium consisting of hydrate, water-rich liquid, gas and propane - carbon dioxide - rich liquid was determined. The maximum temperature at which hydrates would form in the three-component system was found to be 57.7 °F, compared to 50_3 DF for pure carbon dioxide and 42.3 °F for pure propane. An analysis of the data in terms of the solid-vapour K-factor concept indicated that the If-factors reported for propa.ne do not apply in systems containing carbon dioxide. INTRODUCTION A GAS HYDRATE is an inclusion compound in which water and at least one other component are associated through the enclosure of the hydrate-forming molecules in a crystalline lattice-like structure formed by the water molecules. The process of hydrate formation may be represented by: (Equation Available In Full Paper) where a hydrate-forming gas, R, combines with n molecules of water to form the solid crystalline hydrate. The forces stabilizing the structure are physical in nature, and the value of n may theoretically vary from 5.75 to over 17.0, depending on the hydrate-forming molecule and the structure of hydrate formed (1). Many of the organic and inorganic gases form stable hydrates. These include, for example, carbon dioxide, hydrogen sulphide, methane, ethane, propane and nitrogen, all of which are commonly found in naturally occurring gas reservoirs. For this reason, information on the hydrate-forming conditions of these gases and their mixtures is of importance to the natural gas handling and processing industries. Although extensive experimental work has been reported in the literature on hydrate formation for the pure components, far less information is available on mixtures. Some of the systems for which information is available include methane – hydrogen sulphide(2), methane – carbon dioxide(3). methane-nitrogen(4), methane-propane(5) and propane hydrogen sulphide(6). Initial hydrate formation in several natural gas mixtures is reported by Deaton and Frost(7,8). As an extension of the work reported above, it was decided to study initial hydrate formation in a system containing carbon dioxide and propane. Both of these components are commonly found in natural gas; furthermore, the system is of interest from a phase behaviour point of view, because pure carbon dioxide and pure propane form hydrates in different crystal structures. Hydrate Structure And Phase Behaviour The crystal structures in which hydrates are formed have been classified as Structure I and Structure II by Claussen(9) and von Stackelberg(10,11) and the theory pertaining to this is extensively reviewed by van der Waals and Platteeuw12. In this classification, carbon dioxide, a smaller molecule, forms in Structure I and propane, a somewhat larger molecule, forms in Structure II. The ternary system containing water, propane and carbon-dioxide exhibits two four-phase equilibrium consisting in one case of hydrate II (Hir), water-rich liquid (L1), gas (G) and propane – carbon dioxide – rich liquid (L2) and, in the other case, of hydrate I (Hr), water-rich liquid (L1), gas (G) and propane - carbon dioxide - rich liquid (L2).