Electrovaya (Canada)

This report documents the results of analysis performed to investigate the impact of inverter-based resource (IBR) response to unbalanced faults on transmission system protective relay dependability and security. Electromagnetic transient (EMT) simulations were performed to simulate IBR response to these faults using existing manufacturer-developed EMT models for four separate IBRs. The study team was composed of IBR manufacturers, relay manufacturers, transmission providers, reliability coordinators and industry consultants with experience in EMT simulation and system protection. The results indicate that under certain conditions, IBR response can result in protective relay misoperations if current protection practices, which were developed based on conventional power sources, are not adapted to the characteristics of IBRs.

Introduction: Recently, the balance between sodium and potassium intake, i.e. sodium-to-potassium (Na/K) ratio, has received a lot of attention for prevention of hypertension. Previous studies reported that the positive association between 24-hour urinary Na/K (uNa/K) ratio and hypertension. However, no studies have evaluated the relationship between uNa/K ratio measured by casual urine measurement and home hypertension in large populations. We aimed to clarify whether casual uNa/K ratio using the self-monitoring device was associated with home hypertension in general population. In addition, we assessed whether multiple days measurement of uNa/K ratio by casual urine increase the accuracy of the prediction of home hypertension compared with casual urine collected in a single day. Hypothesis: We assessed the hypothesis that multiple measurement of uNa/K ratio was positively associated with home hypertension, and increase the prediction of home hypertension compared with a single measurement. Methods: The subjects were over 20 years old who participated in The Tohoku Medical Megabank Project Cohort Study. Of these participants, we targeted 2,551 subjects who borrowed home blood pressure monitors (HEM-7080IC) and uNa/K ratio monitors (HEU-001F) for continuous 10 days. To assess the relationship between casual uNa/K ratio and home hypertension, we performed multiple logistic regression analyses and calculated aOR with 95% CI. We included covariate factors as age, sex, BMI and drinking status. In addition, to compare the prediction of home hypertension in multiple measurement with that in a single measurement, we calculated area under the ROC curve (AUROC) of uNa/K ratio. Home hypertension was defined as a SBP ≥ 135 mmHg and/or a DBP ≥ 85 mmHg. Results: Among 849 subjects had home hypertension (33.3%). Although uNa/K ratio was even positively associated with home hypertension by a single day (P for trend <0.01, aOR of home hypertension increase per quartile =1.11), the relationship between uNa/K ratio of multiple measurement and home hypertension was more robust (aOR of more than 5 days: 1.23 to 1.25). Similarly, AUROC of uNa/K ratio measurement for home hypertension in 5 days was larger than that in a single day. Conclusions: In conclusion, even single measurement of uNa/K ratio was positively associated with hypertension, the multiple measurement of uNa/K ratio strongly related with home hypertension. We suggested that multiple measurement of uNa/K ratio is desirable for assessing home hypertension because long term measurement of uNa/K ratio might reflect participants’ dietary balance of Na/K ratio.

Introduction: Mechanisms of formation, enlargement, and rupture of cerebral aneurysm (CA) are not fully understood. Unveiling the mechanisms lead to the prevention of a life-threatening subarachnoid hemorrhage. Although several CA models in rats have been reported, most of CAs in the models are immature and insufficient for the close investigation into the mechanisms of enlargement and rupture. The establishment of a large CA model is required for full disclosure of the mechanisms. Methods: A new CA model in rats was designed by modifying the Hashimoto model in that high-dose β-aminopropionitril fumarate (BAPN-F) was administrated intraperitoneally. Seven-week-old male Sprague-Dawley rats were deeply anesthetized, the left common carotid artery was dissected and the bilateral posterior branches of the renal artery were ligated. After the operation, rats were fed food with 8% sodium chloride and divided into 4 groups according to the weekly dose amount of BAPN-F as well as the breeding periods (group 1: n=31, 400mg/kg for 4weeks, group 2: n=31, 400mg/kg for 8weeks, group 3: n=27, 2800mg/kg for 8weeks, group 4: n=13, 2800mg/kg for 12weeks). We then investigated aneurysmal development pathologically along with calculating CA induction rate and mortality rate in each group. Results: Continuous hypertension were induced in all groups. CA induction rate was 19.4%, 29%, 85.2%, and 84.6% while mortality was 12.9%, 16.1%, 7.4% and 30.1% in the group 1, 2, 3, and 4, respectively. Group 3 has statistically significant differences in both the induction rate (p=0.018) and mortality (p=0.027). Among 4 groups, CAs were located at anterior cerebral artery - ophthalmic artery bifurcation, anterior communicating artery (Acom A), and posterior communication artery (Pcom A). We defined the large CA as over one and a half times the size of its parent artery. Large CAs were predominantly detected at Acom A and Pcom A in the group 3 (22.2%) and 4 (23.1%). In addition, all large CAs were morphologically and histologically similar to that of human. Conclusions: Intraperitoneal administration of 2800mg/kg BAPN-F enabled us to induce large CAs with 20% induction rate and low mortality. A further investigation of this model should be promising for full disclosure of the CAs mechanisms.

Summary form only given. Different HVDC grid types and the respective protection options are discussed. An earthed bi-pole HVDC grid was modeled in PSCAD, and using simulation results, the necessity of di/dt limiting inductors to contain the rise of fault currents within the capacity of current hybrid DC breakers is demonstrated. The impact of different inductor sizes on current rise was studied. A fault detection and localization scheme using the rate of change of voltage (ROCOV) measured at the line side of the di/dt limiting reactors is proposed. The protection system was modeled and tested under different fault types and locations. The results show that the proposed method of HVDC grid protection is feasible using the current hybrid DC breaker technology. A systematic procedure for setting the necessary protection threshold values is also demonstrated.

Background and Purpose: We previously presented the robust neuroprotective effects of post-ischemic trans-arterial regional hypothermia therapy in I/R injury model rats (ISC 2014, San Diego). This treatment showed a significant suppression of infarct volume and inflammatory reaction at 24hrs after reperfusion. To characterize the neuroprotective effects in terms of microvascular integrity, we investigated microvascular morphological changes and inflammatory reactions by a time course analysis within 24hrs. Methods: At reperfusion onset, 2hr-MCAO rats were divided into cold saline group (10°C, 20ml/kg of trans-arterial infusion from the recanalized artery for 15mins), warm saline group (37°C, in the same manner as cold saline group), and control group (recanalization only). Microvascular morphological changes were examined by vWF Immunohistochemistry (IHC) and transmission electron microscopy (TEM), and inflammatory reactions were examined by Western blotting and IHC at the time point of 0hr, 2hrs, 6hrs, and 24hrs of reperfusion. Results: IHC analysis and TEM observation revealed that astrocyte end-feet swelling occurred at 2hrs and progressed to 6hrs, and microvascular narrowing due to the swelling occurred at 6hrs in control group. This microvascular morphological change was attenuated in cold saline group. While endothelial ICAM1 overexpression started at 6hrs in control group, MPO, MMP9, and Iba-1 overexpression occurred only at 24hrs in the same group. These inflammatory reactions were also inhibited in cold saline group. Conclusions: Post-ischemic trans-arterial regional hypothermia therapy attenuated astrocyte end-feet swelling from 2hrs and the swelling induced microvascular narrowing at 6hrs. The treatment also inhibited endothelial ICAM-1 overexpression at 6hrs, and subsequently inhibited inflammatory reactions at 24hrs. The maintenance of microvascular morphological and functional integrity may be the primary cause of the neuroprotective effects by the regional hypothermia.

The advent of VSC-based overhead dc transmission allows reversal of power direction by reversing current flow rather than voltage polarity. This, in turn, allows the poles of HVdc line to be designed independently, taking advantage of polarity-based differences in insulation strength, radio and audible noise generation, and ground-level electric field perception. Doing so will generally allow a negative voltage from 10% to 20% higher than the positive voltage, resulting in an increase in MW rating of approximately 5% and 10% respectively. The economic value of that gain is shown to be substantially greater than the incremental cost of tower and converter terminal asymmetry.

Background Postoperative cerebral hyperperfusion is known to occur after superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis and indirect synangiosis in moyamoya disease. However, the clinical features and pathophysiology still remain to be elucidated. Objective To clarify the incidence and pathogenesis of postoperative hyperperfusion after surgical revascularization for moyamoya disease. Methods This study included 41 consecutive patients (58 surgeries) who underwent STA-MCA anastomosis and indirect synangiosis for moyamoya disease. Their medical records were evaluated to identify clinical features of postoperative hyperperfusion. Using 15O-gas positron emission tomography (PET), cerebral hemodynamics and metabolism were determined before surgery in all patients. Using 123I-IMP single photon emission computed tomography (SPECT), cerebral blood flow was qualitatively measured on Day 0, 2, and 7 after surgery in all patients. A multivariate logistic regression analysis was conducted to identify the predictors for postoperative hyperperfusion. Results Postoperative hyperperfusion was observed in 29 (50.0%) of 58 operated sides. In pediatric patients, it was quite rare. Thus, symptomatic and asymptomatic hyperperfusion occurred in 1 (5%) and 3 (15%) of 20 sides, respectively. In adult cases, however, symptomatic and asymptomatic hyperperfusion were significantly more often (P=0.0037 and P=0.026, respectively) and were noted in 12 (31.5%) and 13 (34.2%) of 38 sides, respectively. A logistic regression analysis revealed that cerebral blood volume (CBV) increase before surgery was a significant predictors for symptomatic hyperperfusion in adults (P=0.036). Furthermore, hyperperfusion immediately after surgery was at significantly higher risk to be symptomatic (7/9=77.7%, P=0.033). Conclusions Postoperative hyperperfusion after STA-MCA anastomosis in adult moyamoya disease is not rare. Preoperative CBV increase was closely related to the occurrence of symptomatic hyperperfusion in adult cases. Hyperperfusion immediately after surgery may easily cause neurological deficits or other symptoms. Precise evaluation of cerebral hemodynamics and metabolism before and after surgery would be valuable to predict postoperative hyperperfusion and prevent perioperative complications.

This chapter contains sections titled: Introduction Simulation Optimization Sensitivity Analysis Physical Modeling Economic Modeling References Glossary