Research on residual current detection system of substation alternating current power supply

Residual current monitoring of substation is essential to prevent electrical fire and plays an important role in the safety of substation. This paper studied residual current detection technology of substation AC power supply, and proposed a residual current detection system composed of three devices: sensing terminal, management terminal and monitoring terminal. The design could solve some difficult problems such as the secondary line caused by equipment installation, fault wave recording, fault location analysis, and early warning based on analysis of big data. The study could improve the intelligent level and maintenance efficiency of residual current monitoring in substation.

Cuffless Blood Pressure Measurement Using a Smartphone-Case Based ECG Monitor with Photoplethysmography in Hypertensive Patients

The availability of simple, accurate, and affordable cuffless blood pressure (BP) devices has the potential to greatly increase the compliance with measurement recommendations and the utilization of BP measurements for BP telemonitoring. The aim of this study is to evaluate the correlation between findings from routine BP measurements using a conventional sphygmomanometer with the results from a portable ECG monitor combined with photoplethysmography (PPG) for pulse wave registration in patients with arterial hypertension. Methods: The study included 500 patients aged 32–88 years (mean 64 ± 7.9 years). Mean values from three routine BP measurements by a sphygmomanometer with cuff were selected for comparison; within one minute after the last measurement, an electrocardiogram (ECG) was recorded for 3 min in the standard lead I using a smartphone-case based single-channel ECG monitor (CardioQVARK®-limited responsibility company “L-CARD”, Moscow, Russia) simultaneously with a PPG pulse wave recording. Using a combination of the heart signal with the PPG, levels of systolic and diastolic BP were determined based on machine learning using a previously developed and validated algorithm and were compared with sphygmomanometer results. Results: According to the Bland–Altman analysis, SD for systolic BP was 3.63, and bias was 0.32 for systolic BP. SD was 2.95 and bias was 0.61 for diastolic BP. The correlation between the results from the sphygmomanometer and the cuffless method was 0.89 (p = 0.001) for systolic and 0.87 (p = 0.002) for diastolic BP. Conclusion: Blood pressure measurements on a smartphone-case without a cuff are encouraging. However, further research is needed to improve the accuracy and reliability of clinical use in the majority of patients.

Evaluation of the usefulness of smartphone-directed applications for measuring heart rate and arrhythmia detection

Introduction: There are many available applications for smartphones to measure heart rate (HR) based on a finger pulse wave, without any additional devices. An important feature of the application should be the possibility to detect arrhythmia, especially atrial fibrillation (AF). The purpose of this study was to evaluate the utility of HR measurement applications, available for smartphones, in terms of the reliability of the measurements and the possibilities for arrhythmia detection. Material/Methods: From the free applications available on smartphones with the iOS operating system we selected all (N=16), which offer HR measurement and a simultaneous graphical pulse wave recording. The HR was examined in 15 healthy volunteers with a sinus rhythm confirmed in ECG. The next step was to evaluate the reliability of HR measurement in 15 patients with AF. Results: The average difference in the HR was 6% (0.6%-33%), while a difference below 5% was observed in 11 applications. According to our study, the most reliable applications to measure HR in patients with sinus rhythm was Instant Heart Rate by Azumio company. Five most reliable applications have been selected to test in patients with AF. We have chosen this application according to the most reliable HR measurement (<5%), best graphic pulse wave recording and the ability to view the recording at the end of the measurement. Only 1 of 5 applications - Heart Rate from Bump company - had >95% HR compatibility with ECG (the measurement difference was 0.88 %). Conclusions: The majority of the free applications, available for smartphones, are able to measure HR precisely in patients with sinus rhythm, while in patients with AF, the exact measurement is significantly impeded by HR deficits. Only one out of 16 applications was able to measure HR in a patient with AF. None of the available applications could detect AF.