Monopolar Configuration Research Articles

Overvoltage characteristics in symmetrical monopolar HB MMC-HVDC configuration comprising long cable systems

This contribution focuses on high voltage direct current (HVDC) transmission systems comprising modular multilevel converters (MMC) equipped with half-bridge (HB) submodules and analyses cable voltage stresses during various station internal as well as dc side faults. In order to examine relevant overvoltage characteristics affecting HVDC cable systems, a systematic approach to evaluate overvoltage stresses is presented and an extensive set of time-domain simulations is analysed for schemes operating in symmetrical monopolar configuration. Obtained results are relevant for considerations on insulation co-ordination of HVDC cable systems and for a comprehensive definition of high voltage testing requirements.

The role of dye molecular weight on the decolorization performance of the electrocoagulation

Comparative results of color removal performances of Reactive Blue 198 (RB198), Reactive Yellow (RY145) and Reactive Blue 19 (RB19) by electrocoagulation process are presented. Our primary objective was to investigate whether the dye molecular weight affects color removal performance. Dye removal costs of each dye were calculated and compared. Experiments were performed at current densities of 1.04, 2.08, 4.17 and 10.42 A/m2 in electrocoagulation (EC) reactor with aluminum electrodes connected parallel monopolar configuration. Laboratory-scale experiments were run in batch mode with 0.5 L synthetic dye solution volume and 50 mg/L initial dye concentration. Results showed that the color removal efficiencies were directly influenced by the molecular weight of the dyes. The color removal efficiency of the dye with the greatest molecular weight (RB198) was the highest, whereas the color removal efficiency of the dye with the smallest molecular weight (RB19) was the lowest. Moreover, results indicated that the operating cost of RB198 was significantly lower (2.91 $ per kg dye removed) than RY145 (6.61 $ per kg dye removed) and RB19 ($6.72 per kg dye removed) at a current density of 4.17 A/m2.

PH-differential design and operation of electrochemical and photoelectrochemical systems with bipolar membrane

Electrochemical and photoelectrochemical systems for hydrogen production and CO2 reduction are regarded as prospective technologies to achieve carbon-free energy vision. Electrolytes in different pH environment is desirable for each half electrochemical reaction to optimize the electrode kinetics and reduce the cost of noble metal catalysts. The bipolar membrane provides excellent opportunities to enable pH-differential operation. However, the effect of the bipolar membrane on electrochemical performance is not clarified yet. Here, a numerical modeling framework for bipolar membrane-based cells for electrochemical and photoelectrochemical applications was presented to study the viability of using bipolar membrane in the aspect of energy loss. The model for the first time successfully integrates the water dissociation at the bipolar membrane with the rest electrode kinetics and mass transfer, by treating the interfacial layer as a virtual electrode. Based on the model, the activation loss involved in the bipolar membrane devices were identified and compared with the ones with conventional monopolar membranes. A critical current density was identified for bipolar membranes, which is determined by the water dissociation performance of the membrane. Based on the critical current, the viable operation regions of using the bipolar membrane can be clarified for the electrochemical device. It is found that the bipolar membrane-based photoelectrochemical reactor has higher energy conversion efficiency than monopolar membrane configurations. However, the advantage of bipolar membrane becomes vanishing with photocurrent rising.

Overcoming the Interfacial Limitations Imposed by the Solid-Solid Interface in Solid-State Batteries Using Ionic Liquid-Based Interlayers.

Li-garnets are promising inorganic ceramic solid electrolytes for lithium metal batteries, showing good electrochemical stability with Li anode. However, their brittle and stiff nature restricts their intimate contact with both the electrodes, hence presenting high interfacial resistance to the ionic mobility. To address this issue, a strategy employing ionic liquid electrolyte (ILE) thin interlayers at the electrodes/electrolyte interfaces is adopted, which helps overcome the barrier for ion transport. The chemically stable ILE improves the electrodes-solid electrolyte contact, significantly reducing the interfacial resistance at both the positive and negative electrodes interfaces. This results in the more homogeneous deposition of metallic lithium at the negative electrode, suppressing the dendrite growth across the solid electrolyte even at high current densities of 0.3 mA cm-2 . Further, the improved interface Li/electrolyte interface results in decreasing the overpotential of symmetric Li/Li cells from 1.35 to 0.35 V. The ILE modified Li/LLZO/LFP cells stacked either in monopolar or bipolar configurations show excellent electrochemical performance. In particular, the bipolar cell operates at a high voltage (≈8 V) and delivers specific capacity as high as 145 mAh g-1 with a coulombic efficiency greater than 99%.

Development of a solar electrocoagulation technology for decentralised water treatment

The goal of this research was to investigate the feasibility of using electrocoagulation (EC) as a primary surface water treatment process that could be used with solar panels in decentralised locations. In this study, the removal of turbidity, ultraviolet light at 254 nm (UV 254) and dissolved organic carbon (DOC) was studied. Operating parameters such as current density (0·91–10 mA/cm2) and charge loading (0·083–1·250 A h/l) in bipolar and monopolar configuration were studied using a direct current (DC) power supply. Experimental results showed that a current density of 4·55 mA/cm2 and a treatment time of 60 min in the bipolar configuration allowed the best removal of turbidity, UV 254 and DOC (97·0, 93·0 and 95·2%, respectively). For the second part of the study, the DC power supply was replaced by two photovoltaic panels without the use of a set of batteries and a charge controller. According to the results, the turbidity removal is directly proportional to the solar radiation intensity. This suggests that it is possible to control the charge loading by adjusting the treatment time as a function of solar intensity. Such outcomes suggest that solar-powered EC would be a suitable technology for areas not connected to centralised water treatment networks.

The Effect of Sub-Threshold Pre-Pulses on Neural Activation Depends on Electrode Configuration.

Published research on nerve stimulation with sub-threshold conditioning pre-pulses is contradictory. Like most early research on electrical stimulation (ES), the pioneer work on the use of pre-pulses was modelled and measured only for monopolar electrodes. However, many contemporary ES applications, including miniaturized neuromodulation implants, known as electroceuticals, operate in bipolar mode. We compared depolarizing (DPPs) and hyperpolarizing (HPPs) pre-pulses on neural excitability in rat nerve with monopolar and bipolar electrodes. The rat common peroneal nerve was stimulated with biphasic stimuli with and without ramp and square DPPs or HPPs of 1, 5 and 10ms duration and 10%-20% of the amplitude of the following pulse. The effects were opposite for the monopolar and bipolar configurations. With monopolar electrodes DPPs increased the amplitude required to activate 50% of the motoneuron pool (between 0.7% and 10.3%) and HPPs decreased the threshold (between 1.7% and 4.7%). With bipolar electrodes both pre-pulse types had the opposite effect: DPPs decreased thresholds (between 1.8% and 5.5%) whereas HPPs increased thresholds (between 0.5% and 4.1%). Electroneurograms from the stimulated nerve revealed spatial and temporal differences in action potential generation for monopolar and bipolar electrodes. In bipolar biphasic stimulation, excitation first occurred at the return electrode as a response to the transition between the cathodic and anodic phase. These data help to resolve the contradictions in the published data over two decades. They also show that fundamental research carried out in monopolar configuration is not directly applicable to contemporary bipolar ES applications.

Mineralization of cyanide originating from gold leaching effluent using electro-oxidation: multi-objective optimization and kinetic study

This study examines the electro-oxidation (EO) of cyanide originating from an industrial plant´s gold leaching effluent. Experiments were carried out in a laboratory-scale batch cell reactor. Monopolar configuration of electrodes consisting of graphite (anode) and aluminum (cathode) was employed, operating in galvanostatic mode. Response Surface Methodology (RSM), based on a Box–Behnken experimental Design (BBD), was used to optimize the EO operational conditions. Three independent process variables were considered: initial cyanide concentration ([CN−]0 = 1000–2000 mg L−1), current density (J =7–107 mA cm−2), and stirring velocity (η = 250–750 rpm). The cyanide conversion $$\left( {X_{{{\text{CN}}^{ - } }} } \right)$$, Chemical Oxygen Demand (COD) removal percentage (%RCOD), and specific Energy Consumption per unit mass of removed cyanide (EC) were analyzed as response variables. Multi-objective optimization let to establish the most effective EO conditions ([CN−]0 = 1000 mg L−1, J = 100 mA cm−2 and η = 750 rpm). The experimental data ($$X_{{{\text{CN}}^{ - } }}$$, %RCOD, and EC) were fitted to second-order polynomial models with adjusted correlation coefficients ($$R_{\text{adj}}^{2}$$) of ca. 98, 99 and 87%, respectively. The kinetic analysis, performed at optimal EO operational conditions, allowed determination of time required to meet Colombian permissible discharge limits. The predictive capacity of kinetic expressions was verified against experimental data obtained for gold leaching effluent. Total cyanide removal and 96% of COD reduction were obtained, requiring EC of 71.33 kWh kg−1 and 180 min. The BOD5 (biological oxygen demand)/COD ratio increased from 4.52 × 10−4 to 0.5573, confirming effluent biodegradability after EO treatment. The variation of cyanide (CN−), cyanate (CNO−) and ammonium (NH4+) ions concentrations vs. time at alkaline conditions. EO operational conditions: [CN−]0 = 1000 mg/L, J = 100 mA/cm2 , η = 750 rpm, [NaCl] = 0.15 M and pH 11.1.

The treatment of printing and packaging wastewater by electrocoagulation– flotation: the simultaneous efficacy of critical parameters and economics

In this work, electrocoagulation–flotation (ECF) following sedimentation was applied as a printing and packaging wastewater treatment using four Al electrodes with a parallel monopolar configuration. A sedimentation process was applied after the ECF as a post-treatment phase to remove large pollutants. The simultaneous efficacy of the operating parameters initial color content (1,843.44–12,156.56 ADMI), initial pH (3.56–10.44), current density (6.02–22.18 mA/cm2), and treatment time (5.62–74.38 min) on color and chemical oxygen demand (COD) removal efficiencies were evaluated alongside processing costs. Response surface methodology (RSM) and central composite design (CCD) optimized these key parameters to achieve the highest removal efficiencies and lowest operating costs. Based on the results analyzed by RSM-CCD, using initial color content of 5,576.38 ADMI, initial pH of 7.29, the current density of 18.49 mA/cm2, and treatment time of 59.76 min as optimum operational conditions can result in 97.8% and 92.1% for color and COD removal efficiencies, respectively. At these optimum conditions, operating costs (OPCs), including electrodes material and energy consumption, were 0.07 US$/(kg color removed) and 0.4 US$/(kg COD removed). The results confirm ECF-sedimentation as a promising and costeffective tool for the treatment of printing and packaging wastewater.

Analysis of Cable Overvoltages in Symmetrical Monopolar and Rigid Bipolar HVDC Configuration

The symmetrical monopolar configuration is the prevailing scheme configuration for high voltage direct current (HVDC) interconnectors utilizing the modular multilevel converter (MMC) topology. However, the rigid bipolar configuration is gaining significance, as first projects are currently in planning stage. The purpose of this paper is to analyse both HVDC scheme configurations with regard to cable voltage stresses originating from short-circuit faults. The study focuses on HVDC cables with extruded insulation connected to MMCs equipped with half-bridge (HB) submodules. Basic design aspects in rigid bipolar configuration such as the station grounding concept are discussed. Moreover, various station internal as well as dc faults are examined by means of electromagnetic transient (EMT) simulations. Occurring cable voltage stresses are analyzed with respect to voltage polarity, peak value and wave front-parameters and compared in symmetrical monopolar and rigid bipolar configuration. It is demonstrated that cable overvoltages with same polarity as the dc operating voltage are significantly reduced in schemes operating in rigid bipolar configuration. Voltage reversals caused by the discharge process during a cable fault are nearly independent of the selected scheme configuration. Obtained results are relevant with regard to upcoming projects in rigid bipolar configuration and provide insights to further refine insulation co-ordination aspects related to dc cable systems.

Performance comparison of mono-polar and bi-polar configurations of alkaline electrolysis stack through 3-D modelling and experimental fabrication

Generation of hydrogen using electrolysis process with integrated renewable energy sources is highly important especially in environmental aspects. In this paper, we demonstrate that the enhancement of electrolysis performance of alkaline electrolysis stacks by diminishing the distance between electrodes, while changing the properties of the Membrane Electrode Assembly (MEA). Prior to that, the performances of mono-polar and bi-polar configurations of alkaline electrolysis stack are compared through 3-D modelling and experimental fabrication. At first, two different single cell alkaline electrolysers are designed using SolidWorks as a design software and the designed cell has been fabricated using an in-house 3D printer, to avoid post machining processes. Thereafter, the best performing cell is selected by considering the performance of both designs through different experiments. Finally, the performance of the selected cell is enhanced by changing the distance between electrodes and properties of MEA. Thus, the best performing cell has been selected for the fabrication process of mono-polar and bi-polar electrolysis stacks. At last, both mono-polar and bi-polar configurations of alkaline electrolysis stacks are designed and implemented to compare the electrolysis performance of both configurations by maintaining minimum electrode distance. The results imply that the electrolysis performance of the cell can be enhanced by reducing the distance between electrodes, and the designed bi-polar stack has a better performance in terms of the efficiency, power and flow rates than the mono-polar equivalent.

TNEP of meshed HVDC grids: ‘AC’, ‘DC’ and convex formulations

With the increased utilisation of high-voltage direct current (HVDC) links in power systems, it is necessary to upgrade the traditional ac grid focused transmission network expansion planning (TNEP) problem to accommodate multiple HVDC links and even HVDC grids. This study proposes a non-linear formulation for the TNEP problem of dc grids and derives two relaxations of the problem: the linear approximation, the second-order cone convex relaxation as a branch flow model. The presented formulations allow both monopolar and bipolar configurations, and this as point-to-point connections and HVDC grids as expansion candidates. The three formulations are examined on various test cases and compared for their accuracy and computational speed.

The Magnetic Properties of Electrical Pulses Delivered by Deep-Brain Stimulation Systems

The aim of this article is to analyze the magnetic field properties for both the monopolar and bipolar electrode configurations of deep-brain stimulation electrodes using 3-D magnetic field measurements and to investigate if the magnetic measurements enable a localization of the electrode as a proof of concept. Therefore, a simplified head phantom with an integrated deep-brain stimulation electrode was created to measure the magnetic flux densities in all the three dimensions with a fluxgate magnetometer over a sensor trajectory of measuring points inside the magnetically shielded chamber. The magnitude of the magnetic flux density for monopolar stimulation and bipolar stimulation is in the nT and pT ranges for the frequency 160 Hz, depending on the stimulation amplitude and on the distance between the sensor and the electrode. The field distributions show a linear decline in the magnetic field for the monopolar and a quadratic decline for the bipolar stimulation. We were able to reconstruct the magnetic field using multiple recording sites. As the magnetic field of deep-brain stimulation can be measured and its field strength can be reconstructed, it is feasible to estimate the strength of the field within the limits of programmable stimulation parameters and distance between the sensor and the electrode. The presented results are intended as preliminary work for the further development of electrode localization methods using magnetic measurements. As an example of the feasibility of electrode localization, this article presents a bipolar measurement that creates a more focused spatial field distribution and results in an accurate localization.

AVALIAÇÃO DA TAXA DE REMOÇÃO E CUSTO DO TRATAMENTO DA ÁGUA RESIDUÁRIA DO CAFÉ POR UM SISTEMA ELETROLÍTICO

A Água Residuária do Café (ARC) pode causar sérios impactos ambientais se for lançada no meio sem tratamento prévio. Assim, o tratamento eletrolítico surge como uma técnica bastante promissora nesse procedimento. Por esse motivo, objetivou-se nesse estudo avaliar a taxa de remoção dos poluentes e o custo do tratamento por essa técnica com base nas variáveis turbidez, sólidos totais e Demanda Química de Oxigênio (DQO) e no comportamento do pH e da condutividade elétrica. Utilizou-se uma célula eletrolítica com as dimensões internas de 8,15 de largura, 13,8 cm de comprimento e 8,9 cm de profundidade, possuindo um volume de 1000 cm3. Placas de alumínio com área de 0,02054 m² foram empregadas em uma configuração monopolar em paralelo. Realizaram-se ensaios em batelada variando a distância de placas, densidade de corrente e intervalos de coleta do efluente do reator entre 60 a 1440 segundos para a água residuária com e sem reúso, respectivamente. Por fim, constatou-se que os poluentes apresentam taxas e custos de remoção específicos, estando relacionados à corrente aplicada, distância de placas, eficiência de remoção, tempo de detenção hidráulico e concentração de outros componentes.

Application of the response surface methodology (RSM) in heavy metal removal from real power plant wastewater using electrocoagulation

In this study, application and efficiency of electrocoagulation (EC) in the removal of nickel and iron from real powerplant wastewater was evaluated. Fe electrode (St 12) was used as anode and cathode, connected with parallel monopolar configuration. Tests were conducted in two phases. Phase I mainly focussed on changing the range of the parameters to attain the possible range in which the tests can be conducted and also reached the optimum efficiency. A stirred batch reactor was used to define the test parameters range, including initial pH, electrical current (A), electrode distance (cm) and electrolysis time (min). Then, phase II of this study was conducted using the response surface methodology to design and optimise operational parameters. Outcomes indicated that considering pH = 8.1, d = 1 cm, I = 1.5 A and t = 18 min as operational conditions can result in 99.9% removal efficiency. Remarkably, the high correlation between experimental and predicted values (R 2=99.5% and 99.6% for iron and nickel, respectively) demonstrated that the EC process is a promising method to remove heavy metals from power plant wastewater.

Electrochemical removal of phosphate from synthetic effluent: A comparative study between iron and aluminum by using experimental design methodology

In this work, the removal of orthophosphate from synthetic wastewaters is studied by the electrocoagulation (EC) process using respectively aluminum and iron electrodes connected in monopolar configuration. The effects of current intensity, initial phosphate concentration, initial solution pH, treatment time and electrode type were investigated by experimental design methodology (EDM). The factorial design (FD) used in the first time shows that the current intensity and the electrolysis time have a positive effect on the orthophosphate removal rate while the pH and the initial concentration have a negative effect on it. Using Aluminum electrode, phosphate removal rate were higher than those recorded with iron electrode. A central composite design (CCD) was then used to optimize the removal rate while minimizing the mass of sludge produced. The optimal conditions obtained are the following: for aluminum electrodes (intensity 1.09A, concentration 48.55mg / L, pH 4 and time 59.19min) and for iron electrodes (Intensity 0.85A, concentration 26.8mg/L, pH 3 and time 47.48min). Under these conditions, 99.33% (48.21mg/L) of phosphate was removed by using aluminum electrode with metallic residues of 2.1g. By comparison, 80.74% (21.63mg/L) of phosphate was removed using iron electrode with metallic sludge residues generated of 1.01g.

High-throughput production of magnetite nanoparticles prepared by the monopolar arrangement of iron electrodes in water

Magnetite nanoparticles have been successfully produced by the electro-oxidation of iron in water using a monopolar arrangement of iron electrodes. Two types of monopolar configurations were used: conventional monopolar (CM) and alternating monopolar (AM). The production rate of the magnetite nanoparticles could be increased significantly (∼30 times higher) by using the AM electrode arrangement compared to the production rate of one-pair of electrodes in the same system. The particle sizes ranged from 28 to 88 nm for the CM and from 20 to 25 nm for the AM arrangements. The performance of the AM arrangement was superior that of the CM arrangement in regard to production rate, particle size, and product purity. A numerical simulation showed distinguishable electric fields between the AM and CM arrangements. The magnetite particles produced using the CM arrangement contained impurities in the form of FeOOH and Fe2O3. On the other hand, only magnetite was identified in the particles prepared using the AM arrangement. In addition, particle morphologies other than spherical could also be produced using the AM arrangement by changing the operating condition. The magnetite nanoparticles exhibited ferromagnetic properties. They can be used as a promising catalyst for oxygen reduction reactions in alkaline media.

Enhancement of electrocoagulation-flotation process for urban wastewater treatment using Al and Fe electrodes: techno-economic study

The performance of batch electrocoagulation-flotation (ECF) process using aluminum (Al) and iron (Fe) electrodes with monopolar configuration was investigated.The effect of several operational parameters (initial pH, current density, initial NaCl concentration and operating time) on the removal efficiency of chemical oxygen demand (COD) from real urban wastewater was studied. At optimum conditions (initial pH of 5 and 7, current density of 20mA.cm-2, NaCl concentration of 2 g.L-1 and electrolysis time of 6 minutes), COD removal from urban wastewater containing 1000 mg.L-1was found to be 84% and 80% using Al and Fe electrodes, respectively. The operating cost at optimum conditions was calculated as 0.80 $.Kg-1 and 0.82 $.Kg-1 using Al and Fe electrodes, respectively. It can be concluded that COD removal using Al electrode is as effective and low cost as using Fe electrodes

Removal of Methylene Blue in aqueous solutions by Electrocoagulation process: Adsorption, Kinetics, studies

The purpose of this study is to understand the mechanism driving the removal of methylene blue through electrocoagulation process. Experiments were carried out using iron as anode and cathode in a batch electrochemical cell operated in a monopolar configuration. The effects of operating parameters (initial pH, current density, initial dye concentration and energy consumption) on the removal of methylene blue from solution were investigated. The results showed that the optimum removal efficiency of 93.2% was achieved for a current density of 9.66 mA/cm2, optimal pH of 8±0.01 with a specific energy consumption of 7.451 kWh/m3. Afterwards, first and second-order rate equations were successively applied to study adsorption kinetics models. On top of usual correlation coefficients (r2), statistical test Chi-square (χ2) were applied to evaluate goodness of fit and consequently find out the best kinetic model. Results showed that MB adsorption process onto iron hydroxides formed in aqueous solution during electrocoagulation treatment followed a second-order kinetic.

On the (Non-)equivalency of monopolar and bipolar settings for deep brain stimulation fMRI studies of Parkinson's disease patients.

The majority of Parkinson's disease patients with deep brain stimulation (DBS) use a monopolar configuration, which presents challenges for EEG and MRI studies. The literature reports algorithms to convert monopolar to bipolar settings. To assess brain responses of Parkinson's disease patients implanted with DBS during fMRI studies using their clinical and presumed equivalent settings using a published conversion recipe. Prospective. Thirteen DBS patients. 1.5T and 3T, fMRI using gradient echo-planar imaging. Patients underwent 30/30sec ON/OFF DBS fMRI scans using monopolar and bipolar settings. To convert to a bipolar setting, the negative contact used for the monopolar configuration remained constant and the adjacent dorsal contact was rendered positive, while increasing the voltage by 30%. fMRI activation/deactivation maps and motor Unified Parkinson's Disease Rating Scale (UPDRS-III) scores were compared for patients in both configurations. T-tests were used to compare UPDRS scores and volumes of tissue activated (VTA) diameters in monopolar and bipolar configurations. The patterns of fMRI activation in the monopolar and bipolar configurations were generally different. The thalamus, pallidum, and visual cortices exhibited higher activation using the patient's clinical settings than the presumed equivalent settings. VTA diameters were lower (7 mm vs. 6.3 mm, P = 0.047) and UPDRS scores were generally higher in the bipolar (33.2 ± 16) than in the monopolar configuration (28.3 ± 17.4), without reaching statistical significance (P > 0.05). Monopolar and bipolar configurations result in different patterns of brain activation while using a previously published monopolar-bipolar conversion algorithm. Clinical benefits may be achieved with varying patterns of brain responses. Blind conversion from one to the other should be avoided for purposes of understanding the mechanisms of DBS. 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018.

Pulse-rate discrimination deficit in cochlear implant users: is the upper limit of pitch peripheral or central?

Cochlear implant (CI) users do not reliably associate an increase in pulse rate above 300 pulses per second (pps) with an increase in pitch. The locus of this upper limit of pitch remains unknown. The present study tested the hypothesis that this deficit resides at least initially at the auditory nerve. The hypothesis was tested by comparing pulse rate discrimination in different neural excitation patterns, in which a large versus small population of auditory nerve fibers was activated. If poorer pulse rate discrimination was found under conditions where narrower spread of neural excitation (SOE) was anticipated where a relatively small neural population was activated, then it would support the hypothesis that the rate processing deficit found in CI users is related to peripheral neural degeneration. Nine listeners (12 ears) implanted with the Cochlear Americas Nucleus® devices participated in the study. Different SOE conditions were created by (1) selecting electrodes that showed narrow versus broad forward-masked psychophysical spatial tuning curves, and (2) by measuring these electrodes in monopolar (MP) and narrow bipolar (BP0) electrode configurations. Rate discrimination difference limen (DL) was measured at the selected electrodes in two electrode configurations at three base rates (200, 300 and 500 pps). Consistent with the prediction, group mean DL was better (1) at stimulation sites measured with broader tuning, and (2) in MP relative to BP stimulation. These effects were more salient at the more challenging base rates. There was a weak relationship between rate discrimination (above thresholds) and the effect of rate on detection thresholds. Finally, rate discrimination at rates above the known upper limit (i.e., 500 pps) was correlated with duration of deafness and highly predicted the subjects’ speech recognition performance in noise. These findings support that pulse rate discrimination depends, at least partially, on neural conditions at the auditory periphery and this peripheral limit predicts speech recognition outcomes with a CI.