Current–time characteristics of resistive superconducting fault current limiters

Superconducting fault current limiters (SFCLs) may play an important role in power-dense electrical systems. Therefore, it is important to understand the dynamic characteristics of SFCLs. This will allow the behavior of multiple SFCLs in a system to be fully understood during faults and other transient conditions, which will consequently permit the coordination of the SFCL devices to ensure that only the device(s) closest to the fault location will operate. It will also allow SFCL behavior and impact to be taken into account when coordinating network protection systems. This paper demonstrates that resistive SFCLs have an inverse current-time characteristic: They will quench (become resistive) in a time that inversely depends upon the initial fault current magnitude. The timescales are shown to be much shorter than those typical of inverse overcurrent protection. A generic equation has been derived, which allows the quench time to be estimated for a given prospective fault current magnitude and initial superconductor temperature and for various superconducting device and material properties. This information will be of value to system designers in understanding the impact of SFCLs on network protection systems during faults and in planning the relative positions of multiple SFCLs

Application of multiple resistive superconducting fault-current limiters for fast fault detection in highly interconnected distribution systems

Superconducting fault-current limiters (SFCLs) offer several benefits for electrical distribution systems, especially with increasing distributed generation and the requirements for better network reliability and efficiency. This paper examines the use of multiple SFCLs in a protection scheme to locate faulted circuits, using an approach which is radically different from typical proposed applications of fault current limitation, and also which does not require communications. The technique, referred to as “current division discrimination” (CDD), is based upon the intrinsic inverse current-time characteristics of resistive SFCLs, which ensures that only the SFCLs closest to a fault operate. CDD is especially suited to meshed networks and particularly when the network topology may change over time. Meshed networks are expensive and complex to protect using conventional methods. Simulation results with multiple SFCLs, using a thermal-electric superconductor model, confirm that CDD operates as expected. Nevertheless, CDD has limitations, which are examined in this paper. The SFCLs must be appropriately rated for the maximum system fault level, although some variation in actual fault level can be tolerated. For correct coordination between SFCLs, each bus must have at least three circuits that can supply fault current, and the SFCLs should have identical current-time characteristics

Analysis and quantification of the benefits of interconnected distribution system operation

In the UK, the Capacity to Customers (C2C) project is underway to determine the potential benefits of increased interconnection in distribution systems, combined with demand side response technology. Managed contracts with customers, i.e., the agreement that certain loads are interruptible following system faults, allows distribution circuits to be loaded beyond the limits presently required for security of supply. This potentially permits load growth but avoids the cost and environmental impact of conventional network reinforcement. This paper provides the results of electrical system modelling to quantify the benefits of the C2C operation, using actual circuit data and typical load distributions. Based upon simulations of these circuits, it is shown that increased interconnection generally leads to minor improvements in electrical losses and system voltage. By connecting managed (i.e., interruptible) loads, circuits typically can be loaded significantly further than the present practice in the UK—an average increase of 66% for radial operation and 74% for interconnected systems

Beckhoff and TwinCAT 3 System Development Guide

This document is a guide for setting up a Beckhoff hardware controller and a development PC. It is assumed that the development PC runs Windows 7 or Window 8/8.1, although other versions of Windows (including 32-bit and 64-bit) should also work. In particular, guidance is given on using C++ modules and integrating MATLAB Simulink models within TwinCAT 3

Effects of Milk Replacer and Multivitamin-mineral Supplementation on Performance of Heat Stressed Dairy Calves

Seventy-one Holstein calves were used to evaluate the effects of milk replacer (MR) feeding management alone or in combination with a multivitamin-electrolyte supplement on growth and mitigation of heat stress. Milk replacer treatments consisted of Land O’Lakes Herdmaker Supreme (20% CP, 20% fat) and Land O’Lakes Warm Front (27% CP, 10% fat). Calves received either 0 or 20 ml Palamountains Calf Boost® in MR once daily. Calves were offered treatments beginning on day 4. Calves on 27% CP : 10% fat MR were fed 2.72kg MR twice daily for the first three weeks of life, and 3.86kg twice daily until weaning. Beginning on day 42, MR feeding was reduced to 1 time per day to decrease MR intake by 50%. On day 49 calves were weaned. Water and calf starter (20% CP) were offered ad libitum beginning on day 4. Body weight, hip height, wither height, hip width, and body length were recorded weekly, and grain and water intakes were measured twice daily. Blood was collected on days 14, 28, 42, and 56 for analysis of plasma urea nitrogen (PUN), glucose, and â-hydroxybutyrate (BHBA), as well as rumen fluid for analysis of volatile fatty acids (VFA) and pH. There was a main effect of MR, with calves fed 27% CP: 10% fat MR showing greater body weights and increased hip height, wither height, and body length (P\u3c0.05). Calves fed 27% CP: 10% fat MR consumed less grain than 20% CP: 20% fat MR calves (P\u3c0.05) until the end of week 7, but showed no difference at week 8). Calves fed 27% CP: 10% fat MR had greater PUN concentrations (P \u3c 0.05) than 20% CP: 20% fat. Glucose concentrations decreased (P \u3c 0.05) as calves aged. There was no treatment effect (P \u3e 0.05) on plasma BHBA or VFA concentrations; however, concentrations increased (P \u3c 0.05) as calves aged. No effects of treatment or time were observed (P \u3e 0.05) for rumen pH. These data indicate that MR feeding management may improve growth performance in neonatal dairy calves, but multivitamin mineral supplements may not provide any additional benefit

A Workshop on the Spiritual Disciplines: Teaching Church Members How to Listen to God Through Prayer, Meditation, Solitude and Journaling Developed For the Members of Eau Claire Baptist Church Columbia, South Carolina

Listening to God is so vitally important. This project includes five 75-minute teaching sessions where participants learn how to listen to God through use of the spiritual disciplines of prayer, meditation, solitude, and journaling. Participants take part in various home assignments to practice these spiritual disciplines in their personal lives throughout the week. Participants respond to surveys rating their progress weekly in practicing each of the disciplines mentioned above. Results indicated increased awareness of hearing God speak following the intentional use of the spiritual disciplines and the increased practice of these disciplines by participants

Analysis of the Technical Performance of C2C Operation for HV Networks

This report evaluates the technical benefits of the Capacity to Customers (C2C) project, an Ofgem Low Carbon Network Fund project led by Electr icity North West Limited (ENWL) in conjunction with several industrial and academic partners. The objective of the C2C project is to test a combination of new automation technology, non - conventional network operational practices (i.e., increased network interconnection), and commercial demand - side response (DSR) contracts. These changes will allow ENWL to increase interruptible demand and generation connections on a selection of trial circuits without resorting to conventional reinforcement measures. The project will thereby “release” inherent spare capacity in the high voltage (HV) system in order to accommodate the future forecast increases in demand and DG, and will therefore assist in meeting the UK’s ambitious CO2 emission targets