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The increased power and voltage capability of semi conductive devices enable the usage of Medium Voltage Direct Current (MVDC) grids. One component of the MVDC system is the transformer inside the DC/DC converter. A reduced size and increased efficiency of the converter is expected, when the switching frequency is in the range between 1 and 10 kHz [1, 2]. The Medium voltage transformers of the converter...
A control system model of a virtual power plant with reactive power supply is proposed for small signal stability analysis of voltage control in medium voltage distribution grids. The model is linearized at different operating points and the damping factor is assessed. Depending on the virtual power plant's control parameters, oscillating system reactions can be observed. A parameter variation is...
The parallel routing of high voltage AC and DC systems on the same transmission tower is one new option for a timely integration of HVDC technology into existing AC power grids, enhancing the latter's flexibility. However, the rare event of an intersystem fault is a new fault type which might occur in these configurations. Previous studies indicate that existing protection concepts are necessary but...
In high voltage direct current (HVDC) transmission systems, based on voltage source converters (VSC) with overhead line (OHL) segments, DC line faults have a strong impact on the converter's power electronic devices. Fault tolerant multilevel converters are able to limit and control these fault currents after their detection. Especially for low impedance and AC/DC intersystem faults the detection...
Due to recent political developments in Germany new High Voltage Direct Current (HVDC) transmission right-of-ways will have to be realised preferably as cable systems, especially near densely populated areas. Hence, overhead line (OHL) systems in combination with underground cable sections near urban areas — so-called partial underground cabling systems — become a viable option. This however leads...
Depending on the operating current and the ambient conditions, the operating temperature of vacuum interrupters (VIs) may vary. An increase in VI temperature can result from heat loss at electrical contact resistance points, whereas a significant decrease in temperature will especially occur if VIs are used in future applications in a liquid nitrogen (LN2) environment (e.g. in combination with high-temperature...
Due to the impact of arcing on the high purity surfaces and bound residual gases, current interruption operations may influence the internal pressure in vacuum interrupters (VIs). In this paper, we investigate the temporal development of internal pressure in VIs immediately after a current interruption operation, non-intrusively using the magnetron method. By means of an experimental test setup that...
Circuit breakers are important components in the electrical power supply grid. The maintenance of high voltage gas circuit breakers requires high personnel as well as monetary efforts for the asset operator. Furthermore, a faulty reassembly of the circuit breaker during maintenance can lead to a circuit breaker failure during operation. For this reason the maintenance strategy changed from a periodic...
State of the art of insulation systems for superconducting power components are based on liquid nitrogen. One disadvantage of these insulation systems is their significantly reduced dielectric strength, if gas bubbles occur due to heat losses during operation of the component. In previous research work, syntactic foam has been found to be a promising solid alternative insulation system, i.e., regarding...
Decentral generators in distribution grids lead to new challenges regarding voltage quality. Voltage control utilizing innovative equipment, such as voltage-regulated distribution transformers (VRDT), is being discussed as a method to avoid cost intensive grid expansion. In this paper, a method using measurement data in the low voltage level is developed to evaluate voltage and power quality and to...
Inverter interfaced distributed generators (IIDG) play increasingly important role in German low voltage grids. Today IIDG in German low voltage grids disconnect in case of a grid faults following the valid guidelines (AR-N4105). It is discussed to change the guidelines towards a delivery of reactive current in case of grid faults similar to the present German guidelines for the medium voltage (BDEW,...
In the coming years an increasing quantity of vacuum interrupters (VI) is expected to reach the end of its service life. Leading manufacturers can provide a service life of up to 30 years due to high quality standards and sophisticated production processes. However, their operating performance observed so far indicates the possibility to extend this service life, in case of non-intrusive diagnosis...
The magnetron method is well established for the internal pressure measurement of vacuum interrupters. Its application during the manufacturing process is essential for the determination of the vacuum quality. The evaluation of the magnetron measurement requires precise knowledge of the residual gas composition and the influence of the metallic surfaces in the vacuum interrupter due to gas binding...
The maintenance of high voltage gas circuit breakers requires high personal as well as monetary efforts for the asset operator. Furthermore, a faulty reassembly of a circuit breaker during maintenance can lead to a circuit breaker failure during operation. One possibility to reduce those efforts as well as the failure risk is the application of non-invasive diagnostic techniques. This research work...
The search for alternatives for the strong greenhouse gas SF6 (sulphur hexafluoride) in high voltage gas insulated switchgear (GIS) and circuit breakers lead to the identification of CO2 (carbon dioxide) as possible substitute for use as quenching gas. Nevertheless the first prototypes of circuit breakers filled with CO2 up to rated voltages of Ur = 145 kV show that an optimization of the CO2 technology...
This paper deals with theoretical and experimental investigations on an innovative insulation material called syntactic foam. Syntactic foam is a composite dielectric consisting of a polymeric matrix with embedded hollow microspheres. The main focus of the present study is on the electrical breakdown process of syntactic foam under electrical dc field stress. Furthermore, the study deals with the...
Insulation materials of the future are confronted with a wide range of requirements such as lower weight and higher operating temperatures. Syntactic foam represents an alternative to conventional insulation materials. It consists of a polymer matrix as epoxy resin or silicone (called binder) and hollow spherical particles with a diameter in the range of 30–100 μm (microspheres) which are mixed into...
The ongoing debate on climate change and emission restrictions for greenhouse gases also forces the search for SF6 alternatives (sulphur hexafluoride) in the energy transmission and distribution sector. Hence several challenges for the asset manufactures result as changing the insulating medium implies a redesign of the switchgear and its components. Here one effect in gas insulated switchgear is...
In standard high voltage gas circuit breakers -important safety elements in today's power grids-, a small surface layer of polytetrafluoroethylene (PTFE) vaporizes at the high temperatures occurring in the arcing zone during the high current phase of the interruption process. This ablation continues even some hundred microseconds after the arc has been quenched and it actually changes the total gas...
The Grid 4 Vehicles project (G4V) has analyzed the effects of a mass integration of electric and plug-in hybrid electric vehicles (EV and PHEV) into some distribution grids in Europe. A consortium consisting of six European research institutions and six European utilities has developed a methodology to investigate the effects of EV and PHEV in distribution grids and has proposed different options...
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