Online Monitoring

The need for sophisticated irrigation strategies in fruit tree orchards has led to an increasing interest in reliable and robust sensor technology that allows automatic and continuous recording of the water stress of trees under field conditions. In this work we have evaluated the potential of the leaf patch clamp pressure (LPCP) probe for monitoring water stress in a 4-year-old 'Arbequina' hedgerow olive orchard with 1667 trees ha −1 . The leaf patch output pressure (P p ) measured by the LPCP probe is inversely correlated with the leaf turgor pressure (>50 kPa). Measurements of P p were made over the entire irrigation season of 2010 (April to November) on control trees, irrigated up to 100% of the crop water needs (ET c ), and on trees under two regulated deficit irrigation (RDI) strategies. The 60RDI trees received 59.2% of ET c and the 30RDI trees received 29.4% of ET c . In the case of the RDI trees the irrigation amounts were particularly low during July and August, when the trees are less sensitive to water stress. At severe water stress levels (values of stem water potential dropped below ca. −1.70 MPa; turgor pressure < 50 kPa) half-inversed or completely inversed diurnal P p curves were observed. Reason for these phenomena is the accumulation of air in the leaves. These phenomena were reversible. Normal diurnal P p profiles were recorded within a few days after rewatering, the number depending on the level of water stress previously reached. This indicates re-establishment of turgescence of the leaf cells. Crucial information about severe water stress was derived from the inversed diurnal P p curves. In addition P p values measured on representative trees of all treatments were compared with balancing pressure (P b ) values recorded with a pressure chamber on leaves taken from the same trees or neighbored trees exposed to the same irrigation strategies. Concomitant diurnal P b measurements were performed in June and September, i.e. before and after the period of great water stress subjected to RDI trees. Results showed close relationships between P p and P b , suggesting that the pressure chamber measures relative turgor pressure changes as the LPCP probe. Therefore the probe seems to be an advantageous alternative to the pressure chamber for monitoring tree water status in hedgerow olive tree orchards.

Cutting tool wear is known to affect tool life, surface quality and production time. Because of this an online tool wear measurement and monitoring system has been developed, using a low-cost sensor. The system is able to detect and analyze signals relating to the deflection of the tool holder from the cutting force, and the corresponding estimation of wear is displayed on the computer screen. New statistical analysis is used to identify and characterise the changes in signals from the sensors. A two-channel strain gauge is mounted at the tool holder to measure the deflection in both tangential direction and feed direction. The signal is transmitted to the signal conditioning device, then to data acquisition, and finally to the computer system. MATLAB software is used as the platform software to develop a user-friendly graphical user interface (GUI) for online monitoring purposes. Results show that this developed online monitoring system, using the strain gauge signal, is an effective method of detecting the progression of flank wear width during machining. This is an efficient and low-cost method which can be used in the real machining industry to predict the level of wear in the cutting tool.

Interturn faults are a significant problem in power transformers that can eventually burgeon into catastrophic faults and likely result in an overall network failure. The main problem with SFRA as one of the well-recognized diagnostic tools for detecting winding faults is its restriction to the domain of offline testing since the method requires injection of a test signal into the transformer windings through the high-voltage bushings. To address the difficulties arising from this issue, in this contribution, a new technique for online transfer function monitoring of the power transformers windings through a quite simple, economic, and noninvasive capacitive sensor installed on the surface of the transformer bushing is presented. Interturn faults with various levels of severity were imposed on the winding of a 35-kV/400-V, 100-kVA oil-immersed distribution transformer to evaluate the feasibility and sensitivity of the method. The experimental results proved that the newly developed online monitoring system is feasible and sensitive to detect unambiguously interturn faults even down to 0.2% shorted turns along the winding. As such, the proposed approach in this paper enables timely warning of a rising failure and serves a better purpose in assessing the health of a faulty transformer.

Power transformer monitoring as a reliable tool for maintaining purposes of this valuable asset of power systems has always comprised partial discharge offline measurements and online monitoring. The reason lies in non-destructive feature of PD monitoring. Partial discharge monitoring helps to detect incipient insulation faults and prevent insulation failure of power transformers. This paper introduces a software package developed based on structural data of power transformer and discusses the results of the simulation on Abetti winding, which might be considered as a basic layer winding. A hybrid model is used to model the transformer winding, which has been developed by first author. Firstly, winding is modeled by ladder network method to determine model parameters and then multiconductor transmission line model is utilized to work out voltage and current vectors and study partial discharge propagation as well as its localization. Utilized method of modeling makes it possible to simulate a transformer winding over a frequency range from a few hundred kHz to a few tens of MHz. The results take advantage of accurate modeling method and provide a reasonable interpretation as to PD propagation and location studies.

Membrane fouling is the most serious problem affecting membrane bioreactors (MBR). It decreases membrane permeability and consequently increases energy consumption. Various methods and techniques to measure fouling rates (FR) can be found in the literature, but few provide online data, and most are expensive or too invasive. The aim of this short communication is to present a new online method for monitoring and estimating the fouling in an MBR, based on the use of the derivative of the transmembrane pressure (TMP) per cycle, for which hourly and daily mean values can be obtained. This online method (FR per cycle) was experimentally evaluated at a lab-scale MBR plant, where fouling conditions were induced by the addition of a protein (albumin) and a polysaccharide (glucose). Finally, we compared the new method to standard methods, such as the flux-step method. Similar results for fouling rates were found, but the new method showed increased sensitivity. At the same time, the method seems to be useful in characterizing the nature of fouling.

The Light Water Reactor Sustainability (LWRS) Program is a research and development (R&D) program sponsored by the U.S. Department of Energy (DOE). The program is operated in close collaboration with industry R&D programs to provide the technical foundations for licensing and managing the long-term, safe, and economical operation of Nuclear Power Plants that are currently in operation. The LWRS Program focus is on longer-term and higher-risk/reward research that contributes to the national policy objectives of energy and environmental security.

Wide area monitoring, protection and control for power network systems are one of the fundamental components of the smart grid concept. Synchronized measurement technology such as the Phasor Measurement Units (PMUs) will play a major role in implementing these components and they have the potential to provide reliable and secure full system observability. The problem of Optimal Placement of PMUs (OPP) consists of locating a minimal set of power buses where the PMUs must be placed in order to provide full system observability. In this paper a novel solution to the OPP problem using a Memetic Algorithm (MA) is proposed. The implemented MA combines the global optimization power of genetic algorithms with local solution tuning using the hill-climbing method. The performance of the proposed approach was demonstrated on IEEE benchmark power networks as well as on a segment of the Idaho region power network. It was shown that the proposed solution using a MA features significantly faster convergence rate towards the optimum solution.