Claudius Freye

A Cooperative Multi-Area Optimization With Renewable Generation and Storage Devices

With the rising number of intermittent renewable energy sources and growing energy demand, transfer capabilities are very close to their limits. Consequently, redispatch events occur more frequently and flexibility of conventional generation and storage devices will become increasingly important. The cooperative multi-area optimization strategy presented here enables transmission system operators (TSOs) to dispatch/redispatch interconnected networks securely, while reducing dispatch/redispatch costs. Schedules for storage devices, conventional- and renewable generation are obtained considering network constraints and ramping rates. An optimal schedule for several control areas is attained, including storage operation to achieve congestion relief. The distributed approach preserves control area responsibilities. All participating control areas attain a schedule close to the global optimum. TSOs implement agreements to share resulting profits. The functionality was shown successfully using stressed 14- and 118-node systems. A cross border dispatch with use of storage devices is realized to maintain a high share of renewable energy source (RES) feed-in, while reducing overall dispatch costs.

Investigation on the electrical characterization of silicone rubber using DC conductivity measurement

Extruded cable systems and accessories are key components within the area of power transmission systems. Taking into account that the number of high voltage direct current (HVDC) transmission solutions is continuously increasing the role of its components and insulating materials becomes more and more important. In addition to transient and alternating current (AC) field stress the more important material characteristic for designing electrical equipment under DC stress is DC conductivity. For this reason, the purpose of this paper is to investigate the material characteristics of silicone-based insulation materials used in cable accessories in terms of temperature- and field-dependent conductivity. Although silicone rubber is a common application in cable accessories the knowledge about dc conductivity can be increased. Thin layers of LSR as representatives for insulation materials of cable joints are prepared. The variation of field strengths and temperatures are kept with regard to operating conditions. The electrical characterization is done based on ASTM D257-14 using guard ring electrodes. A variation of electrical contacting is carried out in compliance with this standard.

Investigation on DC conductivity of elastomeric insulating materials considering and reducing influences caused by DC test voltage generation

Materials successfully used for insulation purpose in AC transmission applications need to be investigated prior implementation in DC applications as material stresses change with transmission technology. The use of elastomeric insulating materials in HV applications has significantly increased over the last decades due to their valuable electrical and mechanical properties leading to a broad range of operational areas. Investigations on DC conductivity measurements of these materials are rare within scientific publications. Especially addressing a possible use of these materials for HVDC components makes knowledge of conductivity essential. For this reason DC conductivity measurements of three different elastomeric materials (LSR, RTV) are conducted at two different temperatures. Obtained results and the impact of sputtered metal as an electrode are presented and discussed. Besides this the issue of influences caused by residual voltage ripples due to the used DC voltage supply is broached, theoretically analysed and simulated in frequency and time domain.

Repeatability study for a DC conductivity measurement setup using different types of XLPE

Conductivity measurements are important within the area of insulating material characterization especially for HVDC transmission application. Within first investigations a derived novel test setup showed promising results regarding overall reproducibility with regard to the test specimen production and test configurations. Based on these first results, the setup is subjected to further enhancements and used for a repeatability study focusing on measurement repeatability and robustness. With a detailed knowledge about the repeatability of obtained results any impact to the test specimen production and preparation can be determined. After a brief description of the experimantal setup a repeatability study in which two different test specimens are measured repetitively a deviation analysis is carried out. Furthermore as used materials are commercially available XLPE for AC and DC application a comparison of these materials is done whilst results are presented and discussed.

Numerical air clearance calculation method for HVDC converter stations: Atmospheric, statistic and geometric input parameter variation study

This paper presents an iterative calculation method which enables the dimensioning of indoor air clearances for High Voltage Direct Current (HVDC) converter stations for the purpose of insulation co-ordination based on simulated or calculated impulse (withstand) voltages. For this aim mainly normative procedures mentioned within several AC or test standards are used and combined to promote method acceptability. After a description of the deployed normative procedures and the derived calculation method necessary air clearances are calculated under consideration of atmospheric influences, shape of impulse withstand voltage, statistical and geometrical parameters. Furthermore influences of input parameters on the resulting air clearances are compared and discussed in order to identify system boundaries.

DC conductivity measurements on XLPE specimens with layer thickness in the mm range

Cross-linked polyethylene (XLPE) is well known as an excellent insulating material. Within the area of extruded cables for high-voltage direct-current (HVDC) power transmission XLPE has become a widely used compound. The determination of accurate DC conductivity is important to classify material changes and their impact on the electrical behaviour. Methods for performing DC current measurements whilst preserving a constant material composition are in discussion. A recently published test setup focusing on layer thickness in the mm range states promising results regarding reproducibility of DC conductivity characterization. Based on this realization a novel measurement setup is derived with the purpose to describe this setup in detail, compare and discuss the advantages of this setup focusing on measurement robustness.