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

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

Analysis of energy dissipation in resistive superconducting fault-current limiters for optimal power system performance

Fault levels in electrical distribution systems are rising due to the increasing presence of distributed generation, and this rising trend is expected to continue in the future. Superconducting fault-current limiters (SFCLs) are a promising solution to this problem. This paper describes the factors that govern the selection of optimal SFCL resistance. The total energy dissipated in an SFCL during a fault is particularly important for estimating the recovery time of the SFCL; the recovery time affects the design, planning, and operation of electrical systems using SFCLs to manage fault levels. Generic equations for energy dissipation are established in terms of fault duration, SFCL resistance, source impedance, source voltage, and fault inception angles. Furthermore, using an analysis that is independent of superconductor material, it is shown that the minimum required volume of superconductors linearly varies with SFCL resistance but, for a given level of fault-current limitation and power rating, is independent of system voltage and superconductor resistivity. Hence, there is a compromise between a shorter recovery time, which is desirable, and the cost of the volume of superconducting material needed for the resistance required to achieve the shorter recovery time

Demonstration of adaptive overcurrent protection using IEC 61850 communications

This paper contains a description of an adaptive protection scheme that has been implemented and demonstrated in a hardware in the loop simulation environment using commercially available protection hardware and IEC 61850 communications.The implementation is based on an actual 11kV system which includes distributed generation and network automation. IEC 61850 communications offers several benefits for the implementation of adaptive protection, but also presents some limitations which are discussed in the paper. An alternative approach to overcome a number of the limitations is also presented

The Analysis and Application of Resistive Superconducting Fault Current Limiters in Present and Future Power Systems

Fault current levels in electrical systems are rising due to natural growth in demand, the increasing presence of distributed generation (DG), and increased network interconnection. This rising trend is expected to continue in the future. Marine vessel power systems are highly power-dense and are often safety-critical. Power system protection is increasingly challenging in these systems. Superconducting fault current limiters (SFCLs) offer an attractive solution to many of the issues faced. This thesis establishes and reviews the state of the art in resistive SFCL technology and application knowledge, and provides crucial research-based guidance for the adoption of resistive SFCLs in future power systems. The issues associated with the application of resistive SFCLs---including location, resistance rating, the recovery period, and interaction with protection systems---are demonstrated. The relationship between several resistive SFCL design parameters is established using a generic analytical approach, hence providing a framework for validating SFCL designs. In particular, it is shown that a particular SFCL resistance rating leads to a peak in the superconductor energy dissipation, which generally should be avoided. It is proven that resistive SFCLs have an inverse current-time characteristic, i.e., they will operate in a time that inversely depends upon the initial fault current magnitude. This knowledge is critical for underpinning the operation of a novel protection scheme using multiple resistive SFCLs. The scheme offers several advantages: very fast-acting operation in response to faults anywhere on the system under study; maximum prospective fault currents are prevented from occurring, reducing the duty on circuit breakers; inherent, fast-acting backup; and communications is not required. It is shown that the scheme is suited to highly-interconnected systems with a high presence of DG. The scheme is readily applicable to the design of future utility and marine vessel power systems

Translating proprietary protection setting data into standardized IEC 61850 format for protection setting validation

For smart grid development, one of the key expectations is that the data should be accessible to and readily interpreted by different applications. Presently, protection settings are represented using proprietary parameters and stored in various file formats. This makes it very difficult for computer applications to manipulate such data directly. This paper introduces a process that translates the proprietary protection setting data into IEC 61850 standardised format and saves the data as System Configuration description Language (SCL) files. A code generation process that allows rapid implementation of the translation process is proposed. Among various applications, the paper demonstrates how such a translation process and generated SCL files can facilitate the development of an intelligent system for protection setting error detection and validation

Standardization of power system protection settings using IEC 61850 for improved interoperability

One of the potential benefits of smart grid development is that data becomes more open and available for use by multiple applications. Many existing protection relays use proprietary formats for storing protection settings. This paper proposes to apply the IEC 61850 data model and System Configuration description Language (SCL), which are formally defined, to represent protection settings. Protection setting files in proprietary formats are parsed using rule-based reasoning, mapped to the IEC 61850 data model, and exported as SCL files. An important application of using SCL-based protection setting files is to achieve protection setting interoperability, which could bring multiple compelling benefits, such as significantly streamlining the IED configuration process and releasing utilities from being “locked in” to one particular vendor. For this purpose, this paper proposes a uniform configuration process for future IEDs. The challenges involved in the implementation of the proposed approach are discussed and possible solutions are presented

Superconducting fault current limiter application in a power-dense marine electrical system

Power-dense, low-voltage marine electrical systems have the potential for extremely high fault currents. Superconducting fault current limiters (SFCLs) have been of interest for many years and offer an effective method for reducing fault currents. This is very attractive in a marine vessel in terms of the benefits arising from reductions in switchgear rating (and consequently size, weight and cost) and damage at the point of fault. However, there are a number of issues that must be considered prior to installation of any SFCL device(s), particularly in the context of marine applications. Accordingly, this study analyses several such issues, including: location and resistance sizing of SFCLs; the potential effects of an SFCL on system voltage, power and frequency; and practical application issues such as the potential impact of transients such as transformer inrush. Simulations based upon an actual vessel are used to illustrate discussions and support assertions. It is shown that SFCLs, even with relatively small impedances, are highly effective at reducing prospective fault currents; the impact that higher resistance values has on fault current reduction and maintaining the system voltage for other non-faulted elements of the system is also presented and it is shown that higher resistance values are desirable in many cases. It is demonstrated that the exact nature of the SFCL application will depend significantly on the vessel’s electrical topology, the fault current contribution of each of the generators, and the properties of the SFCL device, such as size, weight, critical current value and recovery time