New methodology for on-site measurement of Voltage Transformer magnitude and phase ratio as a function of frequency

Inductive Voltage Transformers are commonplace in low and medium voltage power distribution networks and are important for network monitoring and protection. Their performance at frequencies above 50Hz, defined as maintaining transformer ratio and input/output phase relationship, is often completely unknown. It is also a challenge to remove VTs from existing installation points to test thoroughly for VT ratio and phase frequency response using the standard swept-sine variable frequency testing. To meet this challenge, the Power Networks Demonstration Centre (PNDC) has developed a technique which relies on a harmonic analysis of the relationship between the transformer input and output. In laboratory testing it has a speed and safety advantage over conventional techniques, while in the future it may allow comparison with known levels of harmonics distortion on the distribution network to calculate the performance at higher frequencies of VTs in-situ

An open platform for rapid-prototyping protection and control schemes with IEC 61850

Communications is becoming increasingly important to the operation of protection and control schemes. Although offering many benefits, using standards-based communications, particularly IEC 61850, in the course of the research and development of novel schemes can be complex. This paper describes an open-source platform which enables the rapid prototyping of communications-enhanced schemes. The platform automatically generates the data model and communications code required for an intelligent electronic device to implement a publisher-subscriber generic object-oriented substation event and sampled-value messaging. The generated code is tailored to a particular system configuration description (SCD) file, and is therefore extremely efficient at runtime. It is shown here how a model-centric tool, such as the open-source Eclipse Modeling Framework, can be used to manage the complexity of the IEC 61850 standard, by providing a framework for validating SCD files and by automating parts of the code generation process. The flexibility and convenience of the platform are demonstrated through a prototype of a real-time, fast-acting load-shedding scheme for a low-voltage microgrid network. The platform is the first open-source implementation of IEC 61850 which is suitable for real-time applications, such as protection, and is therefore readily available for research and education

The reliability and optimal data usage of BGAN satellite communications for remote outstations

Telecommunications are a crucial element of smart grid technologies. Utility communication systems need to combine cost effectiveness with the need for high reliability. Due to its wide geographic coverage, satellite communication can be an appropriate alternative for power system automation in order to reach remote substations. This paper presents the experimental testing of Broadband Global Area Networks (BGAN) M2M technology between the supervisory control and data acquisition (SCADA) system running a primary front end processor (FEP) and the reclosers. Hardware test results for a number of different scenarios are discussed, compared and validated. The challenges for keeping the polls reliability at highest levels are also discussed

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

Testing and validation of the ACCESS system

With the increasing penetration of distributed renewable generation being connected, a number of solutions have been developed to avoid network overloads. A number of the already implemented schemes are based on generation curtailment during times of high generation and low demand. The ACCESS (Assisting Communities to Connect to Electric Sustainable Sources) system implements a more sophisticated predictive based solution. In the ACCESS system the generation resource and electrical demand is predicted and the storage heating resource is managed, providing a demand side management instead of a generation curtailment solution. The ACCESS system was installed, tested and demonstrated in the Power Network Demonstration Centre (PNDC), a research facility that enables realistic testing of novel hardware and network operation schemes in a controlled environment, in 2015. Following the testing at the PNDC, the ACCESS system was deployed in the Isle of Mull, in 2016. This paper reports on the outcome of the testing of the demand response features of the ACCESS system at the PNDC prior to its deployment on the Isle of Mull. This paper reports on: the different components of the system in detail (i.e. what it is designed to do and why); the test regime undertaken at the PNDC; the results of the testing (i.e. how effectively it achieves its design objectives); and the updates to the ACCESS system based on the testing with regards to the solutions employed and the benefits achieved

A model-based analysis method for evaluating the grid impact of EV and high harmonic content sources

The impact on the distribution grid when Electric Vehicles are connected is an im-portant technical question in the development of new smart grids. This paper looks in detail at the predictive capability of a model, calculating harmonic voltage and current levels, in the situation where an electric vehicle is being charged by an in-ductive charging plate which acts as a substantial source of harmonic distortion. The method described in this paper models distortion at the LV side of the distribution grid by reconstructing the HV harmonic distortion levels seen at a typical LV sub-station. Additional LV connected harmonic-rich current sources can then be added, allowing a quantitative analysis of the impact of such sources on the distribution grid in terms of measurable harmonics magnitude and phase angle with respect to the fundamental

International White Book on DER Protection : Review and Testing Procedures

This white book provides an insight into the issues surrounding the impact of increasing levels of DER on the generator and network protection and the resulting necessary improvements in protection testing practices. Particular focus is placed on ever increasing inverter-interfaced DER installations and the challenges of utility network integration. This white book should also serve as a starting point for specifying DER protection testing requirements and procedures. A comprehensive review of international DER protection practices, standards and recommendations is presented. This is accompanied by the identifi cation of the main performance challenges related to these protection schemes under varied network operational conditions and the nature of DER generator and interface technologies. Emphasis is placed on the importance of dynamic testing that can only be delivered through laboratory-based platforms such as real-time simulators, integrated substation automation infrastructure and fl exible, inverter-equipped testing microgrids. To this end, the combination of fl exible network operation and new DER technologies underlines the importance of utilising the laboratory testing facilities available within the DERlab Network of Excellence. This not only informs the shaping of new protection testing and network integration practices by end users but also enables the process of de-risking new DER protection technologies. In order to support the issues discussed in the white paper, a comparative case study between UK and German DER protection and scheme testing practices is presented. This also highlights the level of complexity associated with standardisation and approval mechanisms adopted by different countries

Dynamic model of commercially available inverters with validation against hardware testing

The increasing penetration of photovoltaics (PV) in the bulk power system has led to the growing need for better understanding the behavior of PV inverters during grid disturbances. A configurable dynamic model is presented in this paper emulating the behavior of a Low Voltage (LV) connected off-the-shelf PV inverter during faults and voltage dips. The model has been developed and validated against the results acquired throughout the empirical characterization of the real inverter. The physical testing of the Device Under Test (DUT) was performed at the Power Networks Demonstration Centre (PNDC), where the required network conditions were applied at the output of the inverter using a Real Time Digital Simulator (RTDS). Further simulations, conducted with the aid of the developed model, aim to reflect a distribution network dominated by inverter connected generation under a number of imposed fault scenarios

Multi-layered simulation platform for future worlds distribution system scenarios

With the current Distribution System Operator (DSO) transition, DSOs are looking for novel cost-effective solutions to manage distribution networks. To avoid operational failures these solutions must be evaluated in a realistic end to end test environment prior to deployment. To meet this requirement PNDC is presently developing a platform that integrates solutions for power system analysis, market modelling, and real-time simulation. This multi-layered simulation platform will be used to investigate the impact of different DSO operational scenarios (e.g. flexibility procurement, communication interfaces, and vendor provided solutions). To develop the case study presented in this paper aspects of the Open Networks ‘Future Worlds’ were utilised. The ‘Future Worlds’ were developed by the UK Energy Networks Association and represent potential scenarios for the UK future electricity industry structure. This paper presents a case study using the PNDC platform. This case study reflects ‘Future World’ A and simulates an enforced power exchange profile at a grid supply point. In the case study a controllable demand is simulated in real-time and interfaces with power flow analysis and an optimal flexibility procurement algorithm. The case study demonstrates the capability of the multi-layered platform to manage network limitations by procuring flexibility services within a simulated distribution network

Assessment of low frequency demand disconnection impact on network operability

This paper presents an assessment of Low Frequency Demand Disconnection (LFDD) impact on network operability. One of the issues arising from LFDD relay operation is the disconnection of Distributed Generators (DGs) along with loads during disconnection of large numbers of Extra High Voltage (EHV) substations. This could compromise the effectiveness of LFDD schemes considering the increasing presence of DGs in distribution networks. Another issue is the loss of system earth (i.e. from 132/33 kV substations) from the point of view of connected DGs following LFDD operation that might occur in some areas within distribution grids due to back-feed current from 33/11 kV primary substations. A distribution network model experiencing the above issues has been used in the PowerFactory to simulate a number of operation and fault scenarios. Different types of DGs including Photovoltaic (PV), Battery Energy Storage System (BESS), Wind Generation (WG) and Synchronous Generation (SG) have been modelled. The results provide useful insights on the LFDD schemes impact on network operation with DGs interface protection based on ENA Engineering Recommendation G99 and how the LFDD schemes based on direction of current could influence the frequency response in the network. The results also show that the loss of system earth issue on the studied LFDD scenarios occurs when the network is operating in its minimum loading condition