Open Substation Research Articles

Planar Sensor for Noise Cancellation During Partial Discharge Detection in Open Substation

In compliance with next-generation high-voltage substations, ultra-high frequency (UHF) planar sensors are becoming more popular than ever for their online features in partial discharge (PD) diagnostics. However, PD signals mixing with different noises still exists as a major challenge for UHF sensors. Especially in open substations, telecommunication interferences become predominant noise sources to an external UHF sensor placed outside of the equipment chamber. Despite band-stop filters are additionally connected to UHF sensors for de-noising, the inherent noise cancellation mechanism is not yet found in any UHF sensor. With the best of our knowledge and survey, we are the first to introduce here a planar sensor that inherently eliminates telecommunication interferences during PD detection for open substations even without using any post-processing filters. To design our sensor, we have applied techniques of truncated partial ground plane for wideband characteristics and modified radiating patch for enhanced gain performance. A novel intermingled coupling resonator is designed to remove the GSM-900 band from within the sensor bandwidth. We have tested our prototype both for the free-space propagation and PD detection performances. The prototype has a compact physical size of 16×8 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and an operational bandwidth within 792-1414 MHz. For a surface discharge source, the prototype successfully detects the PD signals at the earliest stage. Our prototype minimizes the ambient noise-floor to 2.5 mV and improves the signal-to-noise ratio by more than 27.9 dB which is relatively higher than conventional UHF sensors. The proposed sensor also has potentials of classifying PD sources.

«Птицы и ЛЭП» в России: наследие СССР, современные достижения и вопросы

«Птицы и ЛЭП» в России: наследие СССР, современные достижения и вопросы

Design of Quadruped Inspection Robot for Substation

The intelligent inspection robots in substations mostly use wheeled chassis, which have good passability when running on flat roads, but it is difficult to effectively cross obstacles under terrain conditions such as steps and stairs. A quadruped inspection robot for substation is designed to improve the walking ability of the robot with a four-leg alternate walking mode to optimize the leg structure design for road conditions such as steps and stairs in the substation. The robot is equipped with pan-tilt detection components and inspection equipment such as multi-degree-of-freedom manipulators can complete intelligent inspection and lightweight maintenance tasks in open substations, and achieve full coverage of the inspection area.

Protein Ligand-Induced Amplification in the 1/f Noise of a Protein-Selective Nanopore.

Previous studies of transmembrane protein channels have employed noise analysis to examine their statistical current fluctuations. In general, these explorations determined a substrate-induced amplification in the Gaussian white noise of these systems at a low-frequency regime. This outcome implies a lack of slowly appearing fluctuations in the number and local mobility of diffusing charges in the presence of channel substrates. Such parameters are among the key factors in generating a low-frequency 1/f noise. Here, we show that a protein-selective biological nanopore exhibits a substrate-induced amplification in the 1/f noise. The modular composition of this biological nanopore includes a hydrophilic transmembrane protein pore fused to a water-soluble binding protein on its extramembranous side. In addition, this protein nanopore shows an open substate populated by a high-frequency current noise because of the flickering of an engineered polypeptide adaptor at the tip of the pore. However, the physical association of the protein ligand with the binding domain reversibly switches the protein nanopore from a high-frequency noise substate into a quiet substate. In the absence of the protein ligand, our nanopore shows a low-frequency white noise. Remarkably, in the presence of the protein ligand, an amplified low-frequency 1/f noise was detected in a ligand concentration-dependent fashion. This finding suggests slowly occurring equilibrium fluctuations in the density and local mobility of charge carriers under these conditions. Furthermore, we report that the excess in 1/f noise is generated by reversible switches between the noisy ligand-released substate and the quiet ligand-captured substate. Finally, quantitative aspects of the low-frequency 1/f noise are in accord with theoretical predictions of the current noise analysis of protein channel-ligand interactions.

Design of Grinding Tool for Isolating Switch with Multiple Operating Conditions in Substation

The isolating switch in the open substation is exposed to the outdoor environment for a long time, and it is easy to rust due to the erosion of the natural environment, resulting in contact heating and affecting the quality of power supply. The grinding tool with multi-working conditions consists of grinding section, cleaning section, clamping section, connection section, rotating section and control system. The grinding tool is used for isolation switch in the open-type substation with voltage level of 220kV and below. The operation mode of remote control is adopted to polish and clean the isolating switch under multiple working conditions to achieve the task of derusting.

Features of thermovision control of open substations equipment with wind load registration

The features of the thermovision control of open substations electrical equipment when exposed to air flow (wind loads) are considered. Wind loads have a significant impact on the change (decrease) of the surface temperature of electrical equipment, which is confirmed by the experimental data presented. Disregarding wind loads impact reduces the reliability of the results of thermovision tests and subsequent expert evaluation, including hidden defects in the structure. There is no method for assessing the effect of air flow on the surface temperature of the object under study. The lack of a technique is a cause of deterring the use of thermovision diagnostic methods for evaluating electrical equipment. In order to take into account the impact of wind loads, a method developed by the authors for considering the cumulative influence of numerous factors was proposed for estimating the density of heat fluxes in the volume of electrical and dielectric materials during operation. The collection of experimental data was carried out for objects from various materials: porcelain, aluminum, nichrome. The main factors influencing the surface cooling intensity are substantiated: excess of the surface temperature blown by the wind Δtв, external diameter D of the structure, air speed v, medium temperature T0, thermal conductivity coefficients of materials, surface emissivity coefficients, electrical resistance of conductors, and features of the shape of the analyzed node. As a result of the analysis of experimental data, it was found that with an increase in the speed of the air flow up to 5 m/s, the temperature decreases by 25-30 ° C. The sharpest decrease in temperature of the objects under study is observed with an increase in the speed of the air flow from 0 to 1 m/s.

Real-time measurement of protein-protein interactions at single-molecule resolution using a biological nanopore.

Editors summarySingle-molecule analyses of transient protein-protein interactions are enabled using an engineered biological nanopore.Protein-protein interactions (PPIs) are essential for many cellular processes. However, the transient nature of these PPIs is difficult to quantitate due to numerous limitations of available methods. We engineered a genetically-encoded sensor for real-time sampling of transient PPIs at single-molecule resolution. Our sensor comprises a truncated outer membrane protein pore, a flexible tether, a protein receptor and a peptide adapter. When a protein ligand present in solution binds to the receptor reversible capture and release events of the receptor can be measured as current transitions between two open substates of the pore. Importantly, the binding and release of the receptor by a protein ligand can be unambiguously discriminated in a complex sample containing fetal bovine serum. Our selective nanopore sensor could be applied for single-molecule protein detection, could form the basis for a nanoproteomics platform or might be adapted to build tools for protein profiling and biomarker discovery.

Kinetic and Energetic Insights into the Gating of a Single Protein Channel

Gating of a beta-barrel membrane protein is a fundamentally important and ubiquitous process in membrane biology. Here, we systematically examined details of the kinetics and energetics of the current fluctuations within the OccK1 protein, a family member of outer membrane carboxylate channels from Pseudomonsa Aeruginosa. Temperature-dependent, single-molecule electrophysiology analysis of the native and loop-deletion OccK1 proteins demonstrated the distinctive nature of two energetic barriers: an enthalpic barrier of the large-current amplitude, infrequent O1 to O2 transitions and an entropic barrier of the low-current amplitude, highly frequent O2 to O3 transitions. Changes in temperature produced asymmetric kinetic and energetic modifications that caused a switch of the most probable open sub-state, O2 to O3, at the lowest examined temperature of 4 0C. Our approach might be used in the future to obtain a semi-quantitative assessment of the discrete fluctuation dynamics in other beta-barrel protein channels of the outer membranes of Gram-negative bacteria, mitochondria and chloroplasts.Acknowledgments: This work is funded in part by grants from the US National Science Foundation (DMR-1006332, L.M.) and the National Institutes of Health (R01 GM088403, L.M. and R01 GM085785, B.v.d.).

An Outer Membrane Protein Undergoes Enthalpy- and Entropy-Driven Transitions

β-Barrel membrane proteins often fluctuate among various open substates, yet the nature of these transitions is not fully understood. Using temperature-dependent, single-molecule electrophysiology analysis, along with rational protein design, we show that OccK1, a member of the outer membrane carboxylate channel from Pseudomonas aeruginosa, features a discrete gating dynamics comprising both enthalpy-driven and entropy-driven current transitions. OccK1 was chosen for the analysis of these transitions, because it is a monomeric transmembrane β-barrel of a known high-resolution crystal structure and displays three distinguishable, time-resolvable open substates. Native and loop-deletion OccK1 proteins showed substantial changes in the activation enthalpies and entropies of the channel transitions, but modest alterations in the equilibrium free energies, confirming that the system never departs from equilibrium. Moreover, some current fluctuations of OccK1 indicated a counterintuitive, negative activation enthalpy, which was compensated by a significant decrease in the activation entropy. Temperature scanning of the single-channel properties of OccK1 exhibited a thermally induced switch of the energetically most favorable open substate at the lowest examined temperature of 4 °C. Therefore, such a semiquantitative assessment of the current fluctuation dynamics not only demonstrates the complexity of channel gating but also reveals distinct functional traits of a β-barrel outer membrane protein under different temperature circumstances.

Analysis of gating transitions among the three major open states of the OpdK channel.

OpdK is an outer membrane protein of the pathogenic bacterium Pseudomonas aeruginosa. The recent crystal structure of this protein revealed a monomeric, 18-stranded β-barrel with a kidney-shaped pore, whose constriction features a diameter of 8 Å. Using systematic single-channel electrical recordings of this protein pore reconstituted into planar lipid bilayers under a broad range of ion concentrations, we were able to probe its discrete gating kinetics involving three major and functionally distinct conformations, in which a dominant open substate O(2) is accompanied by less thermodynamically stable substates O(1) and O(3). Single-channel electrical data enabled us to determine the alterations in the energetics and kinetics of the OpdK protein when experimental conditions were changed. In the future, such a semiquantitative analysis might provide a better understanding on the dynamics of current fluctuations of other β-barrel membrane protein channels.

Enhanced resolution of molecular recognition to distinguish structurally similar molecules by different conformational responses of a protein upon ligand binding

MutT distinguishes substrate 8-oxo-dGTP from dGTP and also 8-oxo-dGMP from dGMP despite small differences of chemical structures between them. In this paper we show by the method of molecular dynamics simulation that the transition between conformational substates of MutT is a key mechanism for a high-resolution molecular recognition of the differences between the very similar chemical compounds. (1) The native state MutT has two conformational substates with similar free energies, each characterized by either open or closed of two loops surrounding the substrate binding active site. Between the two substates, the open substate is more stable in free MutT and in dGMP-MutT complex, and the closed substate is more stable in 8-oxo-dGMP-MutT complex. (2) Conformational fluctuation of the open substate is much larger than that of the closed substate. An estimate of associated entropy difference was found to be consistent with the experimentally found difference of entropy contribution to the binding free energies of the two molecules. (3) A hydrogen bond between H7 atom of 8-oxo-dGMP and the sidechain of Asn119 plays a crucial role for maintaining the closed substate in 8-oxo-dGMP-MutT complex. When this hydrogen bond is absent in the H7-deficient dGMP-MutT complex, the closed substate is no more maintained and transition to the more entropically-favored open substate is induced. (4) Thus, this mechanism of the hydrogen bond controlling the relative stabilities of the drastically different two conformational substates enhances the resolution to recognize the small difference of the chemical structures between the two molecules, dGMP and 8-oxo-dGMP.

Gating-associated conformational changes in the mechanosensitive channel MscL

Bacterial cells avoid lysis in response to hypoosmotic shock through the opening of the mechanosensitive channel MscL. Upon channel opening, MscL is thought to expand in the plane of the membrane and form a large pore with an estimated diameter of 3-4 nm. Here, we set out to analyze the closed and open structure of cell-free MscL. To this end, we characterized the function and structure of wild-type MscL and a mutant form of the protein (G22N MscL) that spontaneously adopts an open substate. Patch-clamp analysis of MscL that had been reconstituted into liposomes revealed that wild-type MscL was activated only by mechanical stimuli, whereas G22N MscL displayed spontaneous opening to the open substate. In accord with these results, Ca(2+) influx into G22N MscL-containing liposomes occurred in the absence of mechanical stimulation. The electrophoretic migration of chemically cross-linked G22N MscL was slower than that of cross-linked wild-type MscL, suggesting that G22N MscL is in an expanded form. Finally, electron microscopy using low-angle rotary shadowing revealed the presence of a pore at the center of G22N MscL. No pore could be detected in wild-type MscL. However, wild-type MscL possessed a protrusion at one end, which was absent in G22N MscL. The deletion of carboxyl-terminal 27 residues resulted in the loss of protrusion and proper multimerization. The structures of wild-type and G22N MscL reveal that the opening of MscL is accompanied by the dissociation of a carboxyl-terminal protrusion and pore formation.

Lateral diffusion and conductance properties of a fluorescein-labelled alamethicin in planar lipid bilayers

In order to follow alamethicin diffusion within membranes under conditions of pore-formation, a fluorescein isothiocyanate (FITC) analogue was synthesized. To test the influence of the fluorescent probe addition on the pore-forming activity of the new analogue, macroscopic and single-channel experiments into planar lipid bilayers were performed. Although the apparent mean number of monomers per conducting aggregate was equivalent, the voltage-dependence of the new analogue was slightly reduced and hysteresses were broader, in agreement with the much longer duration of the open single-channels. Thus, the conducting aggregates seem to be stabilized by the introduction of the probe, presumably through the interaction of the conjugated cycles with the lipid headgroups, while the added steric hindrance may account for the slightly higher conductances of the open substates. Lateral diffusion of the labelled peptide associated with the bilayer was then investigated by the fluorescence recovery after photobleaching technique. Under applied voltage, associated with high conductance, D, the lateral diffusion coefficient, was reduced by 50% when compared to peptide at rest. These results provide new independent experimental evidence for a voltage-driven insertion of the highly mobile surface-associated peptide into the bilayer as a prominent step in pore formation.

Ion channel classes in purified olfactory cilia membranes: planar lipid bilayer studies.

Ciliary membrane fragment fusion to planar lipid bilayers resulted in the insertion of four ion channel types. cAMP-activated, cation-selective channels could be detected only in the absence of Ca2+ and had a conductance of 23 pS. They exhibited an apparent dissociation constant (Kd) for the cyclic nucleotide of approximately 30 microM and an estimated permeability ratio (PNa/PK) of 2.4. The cAMP cation-selective channel coinserted with a K(+)-selective channel refractory to cAMP, Ca2+, and D-myo-inositol 1,4,5-trisphosphate. This K+ channel was voltage independent and exhibited open-conductance substates of 60 and 112 pS. cAMP was also found to modulate a novel K+ channel with a Kd = 140 microM. It displayed three nearly equally spaced open substates with conductances of 34, 80, and 130 pS. In the absence and in the presence of cAMP the probability of occurrence of the open substates was binomially distributed. A fourth channel type was a Ca(2+)-activated K+ channel with a conductance of 240 pS. It was blocked by charybdotoxin at nanomolar concentrations (Kd = 3 nM). These results add support to the idea that, besides cAMP-activated cation-selective channels, vertebrate chemosensory olfactory membranes possess an arrangement of ion channels.

Ion channels from the mouse sperm plasma membrane in planar lipid bilayers.

Fusion of purified mouse sperm plasma membranes to planar lipid bilayers resulted in the insertion of three ion channel types. They could be discerned on the basis of their selectivity, conductance, gating and voltage-dependent properties. The presence of a previously reported large, Ca2+ -selective channel was confirmed. Here, it is reported that the Ca2+ -selective channel from mouse sperm plasma membrane displayed a PNa+/PK+ = 1.6 +/- 0.2 (n = 4) and was blocked by micromolar concentrations of ruthenium red. Fusion yielded also a cation-selective channel (PNa+/PK+ = 2.5 +/- 0.3, n = 3) with a main open conductance substate of 103 pS and a smaller open substate of 51 pS (600 mM K+ cis/100 mM Na+ trans). The channel inserted into bilayers in two stable fashions: a high-activity mode (open probability = 0.57 +/- 0.02, n = 3), and a low activity mode (open probability < 1%, n = 4). In high mode, the channel displayed bursting kinetics and burst length was voltage independent. In addition, a perfectly anion-selective channel, with a slope conductance of 83 pS (600 KCl cis/100 KCl trans), was identified. It displayed a high, nearly constant open probability (approximately 0.90) in the 0 to -80 mV range.

Open states of nuclear envelope ion channels in cardiac myocytes.

Prevalent nucleocytoplasmic transport theory views flow of monoatomic ions as completely unrestricted, resulting from the presence of large diameter pore complexes (NPCs) that perforate, but hold together, the two separate membranes of the nuclear envelope (NE). However, three lines of investigations indicate that, at least in some cell types, monoatomic ion flow is restricted. (i) Patch clamp reveals quantized, ion channel-like activity in several NE preparations; activity thought to result from nuclear ion channels (NICs) connected to NPCs. (ii) Ratiometric fluorescence microscopy demonstrates that ions, as well as small molecules relevant to signal transduction, do distribute as if there is a NE barrier. (iii) Electron microscopy shows that NPCs contain material that behaves like a plug. NICs' large conductance (up to 1,000 pS) makes them a major determinant of nuclear ion concentrations which, in turn, influence nuclear processes. Therefore, NICs are an important modulating force of gene and transcriptional activities--two major determinants of gene expression. As nuclear processes may take from seconds (e.g., signaling) to minutes (e.g., transcription), the time the channels dwell in the ion-conducting open state is relevant to understanding NICs' role in nuclear function. Consequently, dwell-times and lifetimes of open NIC states were studied in 61 patch-clamped adult mouse cardiac myocyte nuclei. Upon voltage stimulation, NICs opened to main states of large conductance (281 +/- 198 pS, range = 120-490 pS, n = 55) and wide-range mean dwell-times (approximately 100 msec, 1-10 sec, and min). Closed states (0 pS) also had widely distributed mean dwell-times (approximately 100 msec, 1-10 sec, and min). Putative open substates (37 +/- 11 pS, range = 25-50, pS, n = 6) of high bursting frequency (< 1 msec) were observed without intervening main states (approximately 5% of patches). Fast (approximately 0.1 msec) and slow (approximately 10 msec) state-transitions were also detected. These observations suggest a role of NICs in mediating cytoplasmic signal control of cardiomyocyte gene expression.

The sodium channel activator Brevetoxin-3 uncovers a multiplicity of different open states of the cardiac sodium channel

The interaction of Brevetoxin 3 (Pbtx-3), a sodium channel activator, with the cardiac sodium channel was studied at the single channel level. It was found that Pbtx-3 (20 μM) shifted steady-state activation to negative potentials, without major effects on the time course of macroscopic activation or macroscopic currents decay, as calculated from averaged single-channel records. Single-channel open times were found to be prolonged. Under the influence of the toxin, sodium channel openings could be observed frequently even at maintained depolarisation. These openings occurred to at least nine different subconductance levels of the open state with smaller conductivities than the maximal one and differed in their open times. Current amplitudes of these open substates were found to cluster around certain amplitude values. Appearance of substates at maintained depolarization was dependent on the transmembrane potential ( E m): Substates with smaller conductivity appeared more frequently at lower E m values whereas at higher E m values substates with higher conductivity values dominated. Furthermore, it was demonstrated that appearance of substates did not result from incomplete recovery from inactivation. From these observations it was concluded that the open substates observed correspond to different conformational states of the channel's activation gates. Under physiological conditions, when the sodium channel opens directly from its closed state these ‘incomplete’-open states of the cardiac sodium channel are obscured by fast gating transitions between the corresponding, electrically silent, preopen states. Thus, Pbtx-3 acts mainly via stabilisation of the channel's preopen and different open states. A classification of sodium channel modifiers, based on their interaction with different conformational states of the channel is suggested.

Rapid kinetic analysis of the calcium-release channels of skeletal muscle sarcoplasmic reticulum: the effect of inhibitors

During excitation of skeletal muscle fibers, Ca ions stored in the cisternal compartments of the sarcoplasmic reticulum (SR) are released to the cytosol within milliseconds. In this study, the kinetics of the fast release of Ca were analyzed by means of a newly developed rapid filtration apparatus. Isolated SR vesicles of cisternal origin were preloaded with 1 mM 45CaCl2, and Ca efflux was studied (between 20 and 1000 ms) after dilution into media of various composition. The effect of extravesicular Ca on the gating of the Ca-release channels and its susceptibility to the influence of drugs were thoroughly investigated. In the presence of 1 mM MgCl2 and 3 mM ATP, highest rates of Ca release were observed at a free Ca concentration between 1 and 50 microM. In the lower micromolar Ca range, compounds such as neomycin and FLA 365 inhibited the release monophasically and with an IC50 of 0.37 and 3.4 microM, respectively. At Ca concentrations between 10 and 50 microM, the inhibitors could not block Ca release effectively. Close analysis of the dose-response curves revealed a biphasic pattern, indicative of the presence of two substrates of the Ca-release channel, displaying high- and low-affinity binding sites for the inhibitors. Interestingly, neomycin (or ruthenium red) and FLA 365 at low concentrations acted synergistically and blocked release completely. The results indicate the existence of various open substates of the Ca channels that can be distinguished pharmacologically. Effective blockade of rapid Ca release requires inhibition of all substates coexisting under a given condition.