Due to the rising number of electric vehicles in operation the handling of charging stations concerning testing and personal safety has been becoming more and more a focus of interest in practice.Currently there are still open questions concerning safe installation, inspection and operation of such charging stations.This paper focuses on protective measures for safety and initial as well as periodic testing of DC charging stations.At the beginning of the work an overview of legal regulations and technical standards for charging stations is compiled.Further on different DC charging processes (of charging stations from different manufacturers in normal operation and in cases of faults) are measured as well as analysed.It shows that DC charging stations of different manufacturers react differently with regard to switch-off behaviour or switch-off times to various fault scenarios.

For the reliable and safe operation of electrical installations, the dissipation of natural and human-made electrical currents into the earth is of great importance. In order to safely dissipate such currents into the earth in a well-controlled manner, blank electrical conductors are specifically inserted into the earth and galvanically connected to the electrical installation. The construct of earth-sensitive conductors (earth electrodes) forms the earthing arrangement. Due to the present conductivity of the earth, galvanically separated earth electrodes interfere electrically through mutual transiting currents. This paper shows geometric arrangements of earth electrodes inserted vertically into the earth, including the effects of the electrical interference on the currents dissipated into the earth, (partial) fault voltages, as well as the resistance to earth by means of calculations. The soil layering and the varying electrical conductivity of the layers are also taken into account. In order to verify the calculations, measurements of the resistances to earth of the vertical earth rods were carried out in a substation in construction.

Due to the increasing number of electric vehicles, the necessary charging infrastructure is extending. For fast charging of electric vehicle batteries and for integration of the charging stations into the electrical infrastructure (e.g. vehicle-to-grid - v2g, grid-friendly behaviour), more and more direct current electric vehicle charging stations (DC-EVCS) are installed. These have to be verified periodically in order to ensure long-term safe operation for users and operators. This contribution focuses on the periodic verification of such DC-EVCSs. Currently, there is a lack of directly applicable international and national normative documents as well as standards for reproducible verification. Existing standards in this context are summarized and a proposal for a suitable scope for verification guidelines is presented. Furthermore, the basic concept of a testing device demonstrator for the grid-independent verification of DC-EVCSs is shown.

The nominal power of electric vehicle charging stations or charging parks is constantly increasing. Most of the users are ordinary persons and handle such equipment with a rated power of several 100 kW. Until now, equipment with such power ratings was only common in electrical operating facilities such as industrial plants where the users are at least instructed and protective measures are specified. If ordinary persons handle equipment with such power ratings in the field, the question arises as to whether the conventional safety goals are met in the event of an electrical fault. The consideration is: If the power increases so much, it can be assumed that the short-circuit power and thus the fault current increase and so does the risk of a dangerous electric shock. In this contribution, calculations of line-to-earth short-circuits on the low-voltage AC side of the three-phase system and their effects in typical configurations of charging stations are carried out. Considering the electromagnetic interference, the calculations provide the fault current and its distribution to determine the electrical potentials during the fault. From this, the (partial) fault voltages and active fault voltages are calculated. Based on the active fault voltage, the expected body impedance and consequently, the body current can be determined. With the body current and the break time of the protection device the risk of electric shock using international standards as guidelines is evaluated. As a result, recommendations for the planning, installation and safe operation of charging stations are given. It turns out that considering certain aspects like the conductor cross-sections or the electromagnetic interference, the risk of electric shock can be reduced to a conventional level. Periodic testing of the electrical system is necessary for safe and reliable operation. For example, follow-on faults due to unintended, improper use by ordinary persons can be prevented. Also, regular inspection of the electrical system is necessary for safe and reliable operation to prevent hazards due to aging or wear. However, it seems challenging to define an installation guideline that applies to all configurations as the boundary conditions vary depending on the type of system, installations in the area of interference and environmental influences.

In a previous contribution [1], vertical earthing rods were used to show how they dissipate currents to the earth and what influence the geometrical arrangement, the installation depth, the length and the earth resistance have on the resistance to earth and partial fault voltages. Results show, depending on the geometry of the rods' arrangement, individual earthing rods interfere with each other over the in the earth propagating electrical flow field. The difference between the measurement results of the resistance to earth of different rod arrangements in a substation in construction and the calculation results was small. This proves that for power frequency currents a steady-state calculation method is sufficiently accurate for designing earthing systems for usual power frequencies. It was also established that vertical rods are disadvantageous regarding to high partial fault voltages in their immediate area of influence and, with them only, it is difficult to realise a modern, safe and integrated earthing system. Based on the knowledge gained from [1], in this contribution horizontal electrodes are added and their electrotechnical characteristics, which differ from those of the vertical rods, are discussed. Despite the differences, it is shown how the advantages of both types can be used through appropriate arrangement and galvanic connection.

For the periodic verification of DC electric vehicle charging stations (EVCSs) currently no standardised verification and test procedures or associating methods and protocols have been established. This belongs to the incomplete standardisation work as well as the ongoing developments of EVCS. In the course of this paper, first important approaches for possible procedures for the periodic verification of DC-EVCSs, which are already installed in the field, are presented. On the one hand, appropriately applicable sequences from existing AC test routines will be used, and on the other hand, new test procedures required in addition for DC charging stations are presented. Furthermore, a mobile high performance test device demonstrator including its functional scope is shown. Still existing questions and challenges with regard to the mentioned topic round off the article.

Current trends, such as the increasing spread of electric vehicle charging stations (EVCSs) with and without battery storage combined with heat pumps (HPs) and air conditioning systems, replacing classical heat supply, are challenging the operation of low-voltage (LV) grids. This can result in noteworthy load flow and short circuit problems in traditional existing power LV grids. A crucial example is the overloading of line segments by loads with significant simultaneity (e.g. EVCSs, HPs, air conditioning systems). Moreover, high local infeed caused by decentralised power generators (e.g. photovoltaic (PV) systems, small hydropower plants, battery energy storage systems (BESSs)) can lead to power quality problems (e.g. voltage limit violations, voltage drop, very short interruption). The project ‘Power System Cognification’ (PoSyCo) defines six Use Cases (UCs) to tackle these challenges. It aims to implement a ‘SOFTprotection’ system, which contributes to fault prevention and serves as an add-on for the conventional ‘HARDprotection’ (fuses, circuit breakers (CBs)). This paper presents an overview of PoSyCo's UCs but is focusing on algorithm for UC4: overload prevention by temporary meshing.

ZusammenfassungAktuelle Trends, wie die zunehmende Verbreitung von Ladestationen für Elektrofahrzeuge (EVCSs) mit und ohne Batteriespeicher in Kombination mit Wärmepumpen (WP) und Klimaanlagen, stellen Niederspannungsnetze (NS-Netze) bzw. deren Betrieb vor neuartige Herausforderungen. Diese können beispielsweise in Form von nennenswerten Lastfluss- sowie Kurzschlussproblemen in deren traditionellen, meist radialen Strukturen bzw. Topologien auftreten. Ein wesentliches Beispiel dafür ist die Überlastung von Leitungssegmenten durch Lasten mit erheblicher Gleichzeitigkeit (EVCSs, WPs, Klimaanlagen etc.). Darüber hinaus können hohe lokale Einspeisungen durch dezentrale Stromerzeuger (z. B. Photovoltaikanlagen, Kleinwasserkraftwerke, Batterie-Energiespeichersysteme) zu Problemen der Spannungsqualität (bspw. Verletzung der Spannungsgrenzen, Spannungsabfall, schnelle Spannungsänderungen) führen. Das Projekt ,,Power System Cognification“ (PoSyCo) entwickelt Lösungsansätze, um diese eben genannten Herausforderungen zu bewältigen. Es zielt darauf ab, ein ,,SOFTprotection“-System zu implementieren, das zur Vermeidung von systemkritischen Zuständen des Niederspannungsnetzes bzw. von Fehlern beiträgt und als Ergänzung zur herkömmlichen ,,HARDprotection“ (u. a. Sicherungen, Leistungsschalter) dienen soll. Im Zuge dieses Beitrags wird einer der dafür entwickelten Methoden in Form eines Algorithmus zur automatisierten Netzrekonfiguration auf Ebene der Niederspannung (NS) näher beschrieben.

In the near future, electrical power transmission with high-voltage direct current cable systems with a length exceeding several 100 km will become more important. Such HVDC systems must be reliable and safe, as they make a significant contribution to security of supply with the planned transmission capacities in the gigawatt range. Due to the high rated voltage, currents in normal and faulty situations and long transmission distances, high demands are required on the earthing and equipotential bonding system. Its task is to protect persons and material goods from impermissibly high step and touch voltages during a fault and to protect the electrical system components from disturbances and damages. A particular challenge is the handling of the shield earthing of HVDC cables – the manufacturers of such cables specify a maximum value for the shield-to earth voltage (shield voltage). In order to minimize the shield voltages during normal operation and in case of a fault, the cable shields are connected and earthed along the cable route in so-called link boxes. The aim of operators of HVDC transmission lines is to minimize the number of link boxes, as these generate costs both in investment and in operation (e.g. through maintenance). Often so-called earth continuity conductors (ECCs), which are usually made up of bare copper and are attached to improve the earthing conditions. For monitoring of the cable route, the shields are led into measurement boxes near the surface, in which the shields are accessible but not directly earthed. In order to show the transient processes during an earth fault between an inner conductor and the earth and to define the requirements for the earthing system for both the measurement boxes and the link boxes, a 400 km long HVDC transmission cable route has been simulated with EMTP-RV1. The feasibility of an ECC is also discussed with regard to the required number of link boxes, where the cable shield earthed. The criterion here is the occurring shield voltage.

Electrical earthing (grounding) is necessary for the proper operation of electrical systems, machines and electronic equipment in the event of a fault, for protection against lightning and personal injury, and for reasons of electromagnetic compatibility. Earthing is understood as ”making an electrical connection between a given point in a system or in an installation or in equipment and a local earth“. Electrical grounding systems are designed according to national and international standards, with some of these standards occupying a significant place in the legal hierarchy in Austria and being binding. Simple structures are designed using approximate formulas given in the literature and standards; more complex arrangements use programs with analytical or numerical models for the calculation and design of grounding systems. Underground infrastructure projects require additional considerations. Starting with the technical and legal requirements, the typical process steps for the design of electrical grounding systems are shown.

With the steadily increasing number of electric vehicles on the market and the associated, ever-growing charging infrastructure, more and more questions regarding the measures against electric shock as well as the verification of charging stations for electric vehicles arise. The installation, the operation as well as the electrical safety especially of DC charging stations is not yet fully standardized respectively regulated. The focus of this paper is on the protective measures against electric shock or in detail on the initial and periodic verification of DC charging stations for electric vehicles. As a first step, the most important legal regulations as well as international standards applicable to charging stations are summarized. Based on this, measurement results including corresponding analyses of various DC charging processes of charging stations of two manufacturers in normal operation and during an event of a fault are compared and documented. In summary, it can be seen that the analyzed DC charging stations do not always react identically with regard to their switch-off behavior or their switch-off times to different fault scenarios.

AbstractElectrical earthing (grounding) is necessary for the proper operation of electrical systems, machines and electronic equipment in the event of a fault, for protection against lightning and personal injury, and for reasons of electromagnetic compatibility. Earthing is understood as ”making an electrical connection between a given point in a system or in an installation or in equipment and a local earth“. Electrical grounding systems are designed according to national and international standards, with some of these standards occupying a significant place in the legal hierarchy in Austria and being binding. Simple structures are designed using approximate formulas given in the literature and standards; more complex arrangements use programs with analytical or numerical models for the calculation and design of grounding systems. Underground infrastructure projects require additional considerations. Starting with the technical and legal requirements, the typical process steps for the design of electrical grounding systems are shown.