Existing electricity distribution management systems (DMS) have been designed using operational and algorithmic procedures that are highly centralised. As more of the distribution network becomes active, accurately estimating the state of the system becomes essential and therefore DMS must include functions to achieve the required near to real-time state estimation. The objective of this paper is to evaluate and to compare the performances obtained with two different solutions developed by EDF R&D for the Distribution State Estimator (DSE) algorithm for MV networks: classical optimization resolution approach using a Newton resolution algorithm on one side and a Particle Swarm Optimization algorithm on the other side. The performances of these solutions are evaluated in terms of precisions obtained for the estimates related to the primary and secondary variables and of computation times.

SUMMARY The penetration of distributed generation (DG) in t he French electric system has widely increased in the last years, with PV panels and wind farms conne ctions to the Medium and Low voltage networks, either on dedicated MV feeders or to the existing n etwork (MV and LV feeders with a mix of both load and generation). In the latter case, the volta ge profiles along feeders are impacted leading to voltage rise issues, mainly in rural networks domin ated by long overhead lines with a low consumption level. To be able to face these impacts , ERDF (French Distribution Network Operator) envisages to implement a centralized Voltage Control Function (VCF) which adjusts the voltage profiles in real-time. As described in the paper, t he experimentation of such control function in a zo ne of ERDF’s network is a first step before its deploy ment. The centralized control function requires a cost ef ficient instrumentation of the MV network which enables an assessment in near to real time of the v oltage profiles along MV feeders. The accuracy of instrumentation is critical for the efficiency of t he voltage control algorithms, while synchronizatio n of the measurements retrieval is compulsory for the “n ear to real time” state estimation on which the voltage algorithms rely. The distribution network s tate estimation function and the voltage control functions will be implemented in the control center tools of ERDF. The voltage management approach determines a voltage control set point at the MV busbar of HV/MV substations in order to keep all voltages in the MV and LV networks within statutory limits: such control signal is sent from the SCADA system to HV/MV substation RTUs. This control can be considered as a secondary voltage control. The auto matic mode of HV/MV transformers’ on-load tap changers will then keep the MV busbar voltage near this voltage reference: this local control can be considered as a primary voltage control. This paper describes centralized voltage control solution which will be experimented in ERDF’s MV network. The different equipments’ requirements for the implementation of this centralized control function are discussed: • Sensor’s number and position in the network, sensor s’ accuracy • RTUs’ functionalities • Communication requirements Then, the paper illustrates how the function is pla nned to be integrated with the existing SCADA system of ERDF distribution control centers. Such a rchitecture shall be flexible enough to enable efficient functional evolutions management on both sides (SCADA & VCF). Moreover the VCF design shall allow its operation in different Contr ol system modes (real time operation, simulation, etc).

Today, neutral compensation based on Petersen coils is being applied in many MV electrical networks.The main reasons for this are : -an important expansion of the underground network in rural environment.This leads to high phase-to-ground capacities of the outgoing feeders, which increases fault currents in networks using impedant grounding, -an increased sensitivity of the customers to the quality of supply, -changes in international standards (insulation coordination).The introduction of arc suppression Petersen coils allows both to reduce the current in single phase-toground faults and to improve the quality of supply by reducing short supply disconnection.Adapting this solution to the existing networks made it necessary to change the protection system, by using zero sequence wattmetric relays.The feedbacks of the zero sequence wattmetric relays operating today show the need of an evolution of this protection equipment specifications.To address this need, EDF R&D has investigated the use of Modelica language for the electrical system modeling.At first the relevance of Modelica language for electrical systems modeling has been studied.This work was made from a comparison of simulation results with those traditionally obtained with EMTP software, normally used by EDF R&D.This paper details this approach and underlines the interest of Modelica for the electrical network fields.The next step will be the use of the ModelicaML profile in order to establish a new version of the protection system specification.

A new type of network namely “Active Network” is foreseen as a relevant evolution of the current passive distribution networks and might be a technically and economically feasible solution to facilitate Decentralized Energy Resources (DERs) interconnections in a deregulated energy market. But one of the difficulties of related studies consists in the small size of Distributed Generator (DGs) and the quantities of algebraic and differential equations resulting from the large number of buses and state variables attached with their control systems. These factors, added to the limited state estimation in distribution networks make it difficult for the Distribution System Operator (DSO) to have online security assessment. This paper presents a hybrid reduction method, which enables the DSO to decrease the number of computed elements and, consequently, the simulation time for distribution network. This reduction should enable also DSOs to facilitate the real time critical and emergency analysis of distribution network in presence of DGs.

Distribution networks are facing significant technical constraints that must be resolved at minimum cost: regulatory and customer pressures to improve reliability of supply, reduction of losses and the technical challenges related to the connection of an increasing amount of distributed generation. The use of new approaches is therefore being encouraged to develop cost-effective solutions often leading to the concept of Active Management. However, the lack of monitoring in present distribution networks is a barrier to the implementation of the corresponding automation functions. On the other hand a full monitoring of the distribution network is not economically realistic. Therefore, there is a need for intermediate solutions such as the one presented in this paper: EDF R&D has developed a distribution state estimator (DSE) based on voltage state variables. Such algorithm is expected to provide quasi-real time system supervision of voltages and power flows which are required as inputs of Distribution Management System (DMS) functions. Even if based on techniques applied to transmission networks, the requirements and performances of DSE are different and adapted to distribution needs. The paper discusses the limits of such approach and proposes thumbed rules for sensors placement as well as research perspectives to overcome these limits.

In the future, with the high penetration level of the distributed generation, their decoupling from network during the fault will eventually cause critical consequences. In order to avoid such situation, it is necessary to perform the transient stability analysis. The paper investigates the hybrid methods for fast transient stability assessment which are able to detect quickly the loss of stability of distributed generation. These methods are based on the transient energy function and SIME methods. Then the hybrid-based preventive control for generation redispatch will be proposed to help the distributed generators withstand disturbance in distribution network. The methods described in this paper using detail model of generator allow a very high precision in the application for the small synchronous generators installed in the distribution network.

The major change in the last decade concerning distribution network is related to the penetration of distributed generation (DG). The current practice in France concerning the connection of DG was to fit the network to the worse case of use of DG to avoid any problem. This approach will reach his limits and many developments will be necessary to optimize the network operation, taking the presence of DG into account. In this document, we introduce some research topics going on in our team as voltage control, management of load and generation, stability analysis of networks with DG, optimization of use of fault indicator, choice of optimal configuration and automatic post fault restoration, distribution system availability assessment. We also stress on the problem of interdependency between power and ICT infrastructures.

Automation offers new margins to improve the performance of distribution operation and control. Additional distribution automation is particularly beneficial when it allows the network operators to use the dispersed generation and enhanced load control capabilities and in some case postpone new network upgrades. Such improved flexibility and control of the distribution network is only possible if the Control Centre operator has a more accurate real-time picture of the network. This paper explains how a Situation Awareness tool fed by a distribution state estimator would improve operators performance, facilitate grid operation and enhance network performance. Situation Awareness allows operators to anticipate and prepare for the next network operations in real time. This paper presents different scenarios of use of the situation awareness functions as well as a the architecture of these functions. (4 pages)

As the penetration level of the distributed generations on distribution network will increase, they must take their share of responsibility in the system security and provide flexibility and controllability necessary to support secure system operation. However, following the occurrence of large disturbances on the network (short-circuits, line outage, voltage dips...) the protective disconnection of large amount of DG (Distributed Generation) plants results in loss of generation and of support to the network that may lead to significant load shedding or in the worse case even a blackout. This paper presents an investigation about the transient stability and the capacity of DG to withstand disturbances of distributed synchronous generators and wind turbine generators on the distribution network. Two proposed control solutions to avoid the loss of generation are presented.

A high penetration of distributed generation (DG) may influence the operation and control of the distribution system and the transmission system, leading to technical issues that must be identified and analyzed. The distributed generators are small or medium scale units connected to the low or medium voltage networks (LV or MV). Due to their low inertia for small rotating machines, these distributed generators are very sensitive to network disturbances and can cause many technical and operating issues regarding the DG stability. This paper focuses on these stability aspects taking into account the location and the clearing time of the short circuits. Various assumptions about DG coupling mode on LV and MV networks, DG regulation systems, DG rated power and interaction between DG are investigated. Influences of DG with power electronic interface on the stability are discussed. For a large distribution network with a high penetration of DG, a dynamic equivalent reduction technique is used for the study

A complete framework dealing with power line communication in medium voltage network is proposed. Based on path loss measurements, a complete characterisation of inductive couplers is performed. After a brief recall of inductive coupling techniques, we address the issue of power switching influence on inductive coupler performances. Finally, we show the key role of the medium voltage to low voltage transformer for a phase to ground propagation mode.

A few years ago, the study and simulation of fast phenomena in real-time, was the private ground of analog simulators, But the limitation in modeling, the complexity and the costly maintenance of these simulators was a brake upon their development and made their profitability uncertain.The test of power system equipment such as controls, relays or power electronic devices needed a new type of simulator, much more versatile and cost-efficient than their predecessors: the real-time Digital Transient Network Analysers (DTNA), Until a few months ago, the design of DTNA's was based on dedicated technologies, Today, the ever increasing calculation power has now reached a level that allows realtime simulations of fast phenomena to be carried on standard computers.We present in this paper a new and fully digital TNA that relies on a standard computer.

In this paper, a new method to initialise the simulation code of an electromagnetic transient program and its application in the simulator ARENE [1], the EDF's Digital Transient Network Analyser (DTNA), is presented.Its principle is based on a load-flow calculation that gives the initial steady-state conditions of the simulation. The block diagrams which define the simulated control Functions are initialised automatically with a graphical method presented in this paper. The determination of initial conditions of complex apparatus such as non-linear elements is discussed and the incorporation of the corresponding procedures in the load-how is investigated.Finally, the capabilities of the developed methods are demonstrated and the correct performance is verified by means of case studies.

This paper presents a new and powerful Graphical User Interface (GUI) for Power System simulation tools and its application to the simulator ARENE, the EDF's Real Time Digital Transient Network Analyzer (DTNA).Its principle is based on the concept of Meta-Development (MD) which permits to introduce the electrotechnical information from the software simulation tool. The main characteristic of the independent MD tool is to offer the possibility to add new electrical and automatic components without modifying the GUI or the kernel of the calculation parts. The MD concept insures the upgradability and the modularity of the simulator and reduces the cost of development and maintenance.Moreover the use of an integrated GUI and, in the GUI, the use of palettes, Hierarchical Blocks and sets of parameters simplify and improve the work and the results of the user. These friendly and efficient concepts, decrease drastically the testing sessions specially in the use of DTNA where batch testing is commonly used.

The need for testing power system equipment (e.g. protective relays and controllers) is well kno\\n to the industry. These tests are required for testing both the equipment itself and its interaction with the power system. Different solutions have been developed over the years to perform these itests, from off-real time numerical simulation to real time analog and hybrid laboratories. Onlly recently, fully digital, real-time simulators have been developed, capable of representing electromagnetic transients. We present in this paper a new fuilly digital real-time transients siimulator which runs on a standard, multipurpose parallel computer. With a time step of 50 / /s, the Digital Transient Network Analyzer (DTNA) can test a itle variety of equipment: protective relays, controllers, as n ~ l l ,as FAC'1'S and HVDC prototypes. The first prototype of the DTNA is scheduled at the end of 1095 and will model a power system of some 10 generators and 50 busses. KeywordsPower S y s teni sim u la t ion, Rea I 'li ni e I> i g i t a I 'I" A, Test of equipment, pairallel computer.