Managing the Risks of Power System Balancing Considering f-P Control as a Service of the Balancing Market and the Influence of Renewable Energy Sources

The safety of managing the electric power system (EPS) in free, deregulated electricity market solves the problem of techno-economic risks related to operative balancing of the system by taking into consideration one of the ancillary services, that is frequency control and exchange active power (f-P), and contribution of renewable energy sources in a specific surrounding. It is well known that the electricity market derives significant risks for all participants, especially for the transmission system operator (TSO) which is responsible for balancing electricity generation and consumption regardless of their probability, which means they have stochastic nature. Therefore, the main idea is to provide the safety of the system\u27s drive by analysing certain risks related to the problem of balancing the process of electricity generation with the goal: \u27\u27maximum safety and minimum risk\u27\u27. The power trading and ancillary services provision comprise technical and financial risks and therefore require a structured risk management. Focus of this paper is on financial risk management that is important for the system operator faces when providing and using ancillary services for balancing of power system

The influence of magnetic field shape on dielectric characteristics of vacuum switches

Cilj ovog rada je ispitivanje uticaja oblika magnetnog polja u međukontaktnom prostoru u smislu degradacije kontakata tokom sklopnih operacija isklopa pod opterećenjem. U tom smislu statistički su analizirani rezultati merenja naizmeničnog probojnog napona i impulsnog probojnog napona. Eksperimenti su sprovedeni na komercijalnim prekidačima sa CuCr kontaktima. Parametri u eksperimentu bili su vrednost napona prilikom prekidanja struje i međukontaktno rastojanje. Ustanovljeno je da prekidači sa radijalnim magnetnim poljem u međukontaktnom prostoru trpe manje ireverzibilne promene tokom prekidanja nominalne struje i nominalne struje kratkog spoja.The aim of this paper is to examine the influence of the magnetic field shape in the inter-contact space in the context of contact degradation during the switching operation of circuit-breaking with current. The results of measuring the AC breakdown voltage and pulse breakdown voltage are statistically analyzed for that purpose. The experiments are carried out on the commercial switching elements with CuCr contact. The experiment parameters are the current breaking voltage value and inter-electrode distance. Results showed that switches with radial magnetic field suffer less irreversible changes during the breaking operation such as circuit-breaking with nominal current and circuit-breaking with short-circuit current

Correlation and regression between the breakdown voltage and pre-breakdown parameters of vacuum switching elements

This paper considers the influence of switching operations on the characteristics of vacuum switching elements. The following operations, all with circuit-making without current, have been taken into account: circuit-breaking without current, circuit-breaking with nominal current and circuit-breaking with short-circuit current. The influence of switching operations is examined for the random variables breakdown voltage (ac and pulse) and the pre-breakdown parameters V-4, V-5, and V-6. Parameters V-4, V-5, and V-6 represent the dc voltage at which the pre-breakdown current takes values of 10(-4), 10(-5), and 10(-6) A, respectively. Switching element characteristics after the switching operations are compared with the corresponding results obtained for switching element with conditioned contacts. The main result is an examination of the correlation and regression between the experimentally obtained breakdown voltage (ac and pulse) random variable and its corresponding pre-breakdown parameters V-4, V-5, and V-6, respectively. Statistical samples created by using this method do not require the repetition of switching operations and therefore the dielectric strength of the vacuum insulation is kept in its initial state. The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts

Correlation and regression between the breakdown voltage and pre-breakdown parameters of vacuum switching elements

This paper considers the influence of switching operations on the characteristics of vacuum switching elements. The following operations, all with circuit-making without current, have been taken into account: circuit-breaking without current, circuit-breaking with nominal current and circuit-breaking with short-circuit current. The influence of switching operations is examined for the random variables breakdown voltage (ac and pulse) and the pre-breakdown parameters V-4, V-5, and V-6. Parameters V-4, V-5, and V-6 represent the dc voltage at which the pre-breakdown current takes values of 10(-4), 10(-5), and 10(-6) A, respectively. Switching element characteristics after the switching operations are compared with the corresponding results obtained for switching element with conditioned contacts. The main result is an examination of the correlation and regression between the experimentally obtained breakdown voltage (ac and pulse) random variable and its corresponding pre-breakdown parameters V-4, V-5, and V-6, respectively. Statistical samples created by using this method do not require the repetition of switching operations and therefore the dielectric strength of the vacuum insulation is kept in its initial state. The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts

The construction of capacitive voltage divide for measuring ultrafast pulse voltage

The problem of pulse voltage measurements in the nanoseconds range has become of great importance with ongoing problems related to the construction of pulse fusion generators as well as with simulations of electromagnetic pulses related to the atmospheric nuclear explosion. Ultrafast pulses in the nanoseconds range can be measured by the capacitive voltage divider. The problem that arises with ultrafast voltage occurrence is inductivity. Under conditions of the nanoseconds pulse increaserate, conductors of about few centimeters should be regarded as inductivity. Therefore, capacitive divider can be treated as an equivalent RLC circuit. The ohmic resistance R in that equivalent circuit originates from the characteristic impedance (either 50 Ω or 75 Ω) and, depending on its design, it can introduce an additional parasite inductivity. The aim of this paper is to consider and analyze the constructive solutions of capacitive voltage divider for measuring ultrafast voltage occurrence. Three types of capacitive divider will be constructed for that purpose. The high-voltage capacitor of each divider will be gas capacitor (in order to avoid both electrostatic and electrodynamic influence on measurement accuracy). The variations between divider types will be made for low-voltage capacitor. The designed low-voltage capacitors will be: 1-in the shape of 10 mica capacitors connected in a parallel with a discrete ending resistor of 50 Ω 2-in the form of gas trimmer capacitor with a discrete ending resistor of 50 Ω, and 3-the continual mica capacitor with waveguide resistor of 50 Ω (L=0). Ultrafast pulse response will be measured with dividers constructed in such manner, and will be compared with the corresponding response obtained from the numerical simulations

The construction of capacitive voltage divide for measuring ultrafast pulse voltage

The problem of pulse voltage measurements in the nanoseconds range has become of great importance with ongoing problems related to the construction of pulse fusion generators as well as with simulations of electromagnetic pulses related to the atmospheric nuclear explosion. Ultrafast pulses in the nanoseconds range can be measured by the capacitive voltage divider. The problem that arises with ultrafast voltage occurrence is inductivity. Under conditions of the nanoseconds pulse increaserate, conductors of about few centimeters should be regarded as inductivity. Therefore, capacitive divider can be treated as an equivalent RLC circuit. The ohmic resistance R in that equivalent circuit originates from the characteristic impedance (either 50 Ω or 75 Ω) and, depending on its design, it can introduce an additional parasite inductivity. The aim of this paper is to consider and analyze the constructive solutions of capacitive voltage divider for measuring ultrafast voltage occurrence. Three types of capacitive divider will be constructed for that purpose. The high-voltage capacitor of each divider will be gas capacitor (in order to avoid both electrostatic and electrodynamic influence on measurement accuracy). The variations between divider types will be made for low-voltage capacitor. The designed low-voltage capacitors will be: 1-in the shape of 10 mica capacitors connected in a parallel with a discrete ending resistor of 50 Ω 2-in the form of gas trimmer capacitor with a discrete ending resistor of 50 Ω, and 3-the continual mica capacitor with waveguide resistor of 50 Ω (L=0). Ultrafast pulse response will be measured with dividers constructed in such manner, and will be compared with the corresponding response obtained from the numerical simulations

Irreversible changes of vacuum circuit breakers' dielectric strength as a result of current breaking operation

In the vacuum switching element, current breaking operations cause the changes of the electrodes' surface by means of the following mechanism: 1 - cathode erosion (during the movement of electric arc's cathode spot); 2 - the explosion of the conducting metal bridge during the arc stretching; 3 - condensation of neutral metal vapor on the contacts, and 4 - the emission of micro-particles of the melted electrode surface regions the first three mechanisms are dominant in the case of diffuse arc (there are more parallel arcs of the small current, up to 100 A, which do not have consolidated the cathode spot) the fourth mechanism is dominant for the constricted arc (cathode spot is consolidated) the diffusion arc has the arc voltage typical value of 30 V, while in case of the consolidated arc, the arc voltage may increase more than 100 V the transition between the diffusion arc and consolidated arc does not occur instantaneously, but rather, there are some transitional shapes the mentioned contact topography changes of the vacuum circuit breakers lead to irreversible changes of vacuum insulation through the braking operations the aim of this paper is to determine the irreversibility rate of the vacuum insulation caused by circuit braking operations thereby evaluating the possible number of these switching operations in the course of the life cycle of one such element the results of measuring the AC breakdown voltage, pulse breakdown voltage and the voltage whose corresponding prebreaking current equals 10-4 A and 10-5 A will be statistically analyzed for that purpose the experiments will be carried out on the commercial switching elements with CuCr and CuBi contacts the experiment parameters will be the current breaking value and interelectrode distance, respectively

Synergy of radioactive 241Am and the effect of hollow cathode in optimizing gas-insulated surge arresters characteristics

The paper discusses the possibility of improving the character of gas surge arresters. Examined were: the magnetic field effect, the effect of the hollow cathode, and the effect of the alpha radiation source 241Am. Numerical and real experiments conducted are presented together with theoretical interpretations of the obtained results. Real experiments were carried out on a model of a gas surge arrester spatially constructed for experiments presented in this paper. The model was designed in such a way that it was possible to change all the relevant parameters of the gas surge arrester model. Experiments were conducted under well-controlled laboratory conditions. The tests were performed with d. c. and impulse voltage. The results obtained by experiments were processed by sophisticated statistical methods. The expressed measurement uncertainty of the experimental procedure showed a high statistical reliability of the obtained results. Based on the results of the research, the model of a gas surge arrester, in which the effect of the hollow cathode and the radioactive source 241Am were combined, unambiguously proved to have the best characteristics

Low frequency electric field radiation level around high-voltage transmission lines and impact of increased voltage values on the corona onset voltage gradient

In this article the summary of measurement and calculation values of low frequency electric field radiation around the high-voltage transmission lines and impact of the increased voltage values on the AC corona onset voltage gradient are presented. The measurements of the low frequency electric field radiation level were performed under the 400 kV transmission lines of horizontal configuration with standard and compact dimensions. In all cases analyzed in this article, the measurements are performed in the middle of the span, because at this point the conductors are closest to the ground. The analysis in this article has been initiated by the increased voltage values of long duration that have been registered in nodes of the 400 kV network in Bosnia and Herzegovina and the neighbouring countries during the last years. The calculation of the low frequency electric field radiation of the different configuration of the high-voltage transmission lines will be useful for determining the non-ionization radiation exposure levels of the general public in the future as well as to determine their impact on the AC corona onset voltage gradient