Determination of Cumulative Distribution Function of the Crest Value of the Lightning Current Circulating Through Line Surge Arresters

For the selection and design of line surge arresters (LSA), it is essential to know the characteristics of the lightning current circulating through LSA. When lightning strikes a transmission line, only a part of the lightning current circulates through LSA. This part mostly depends on the point of impact, and the characteristic of the lightning strike current. The determination of the cumulative distribution function of the lightning current circulating through arresters is presented in first part of the paper. It can be applied on transmission lines where LSAs will be installed to protect the line against the effect of atmospheric discharges. Second part of paper presents the calculation results of the cumulative distribution function of the lightning current circulating through arresters for particular 110 kV transmission line located in an area with high lightning activity

Influence of Cables on Power Transmission Network Frequency Response

Harmonic resonance is an important factor to be considered in a power transmission networks during connection of remote generation units with high-voltage cables (e.g. wind or solar power plants etc.). It is known that cable characteristics differ from characteristics of conventional overhead lines. Cable capacitance is far higher than capacitance of an equivalent overhead line, what can potentially lead to the low resonant frequencies which may be triggered by various switching events, such as transformer or shunt reactor energization etc. In this paper, possible consequences of power plant connection to transmission network with long HVAC cable are analysed, with regard to harmonic resonance and frequency response of the network. The research has been conducted on developed model of the power transmission network in the software for calculation of electro-magnetic transients EMTP-RV

Integral Approach for Overvoltage Management Based on Field Data and Modelling

The requirements for the power network to be flexible and to be able to transmit more power are becoming more important as a consequence of high share of the renewables. Therefore, to maintain the level of reliability of the power network, it is necessary to monitor more and more data as well as to better understand the phenomena that might exist in the power system, such as transients. One of the points that are of interest are interaction between power transformer and the other components in the network. A failure of such component may lead to power network unavailability and high economic cost. According to the CIGRE WG A2.37, high portion of the transformer failure may have been caused by the overvoltage. Therefore, it is important to handle overvoltage in the power network with high care. In this paper, an integral approach for power transformer overvoltages management based on field measurements and advanced electromagnetic transients (EMT) modelling is presented. It consists of simulating overvoltages using detailed power network models, including the high frequency transformer models and continuous monitoring of overvoltage events at the places of interest in the power network. This work gives a framework for dealing with overvoltages in the power network that could be implemented by power utilities

Fleet Asset Management Opportunities Arising from Transient Monitoring of Power Transformers and Shunt Reactors

Power transformers and shunt reactors are strategic assets for every system operator and their downtime should be kept as low and controlled as possible. During their multi-decade service life, they are regularly exposed to transient overvoltages. These situations stress their insulation systems and can cause accelerated deterioration and aging. Since the shapes of these overvoltages are usually unknown, an additional approach to assessing the health index can be realized using monitoring systems with transient recorders. Analyzing the transient overvoltages using frequency domain severity factor, a quantification of additional stress on the transformer’s/shunt reactor’s insula

Model za određivanje frekvencijskoga odziva prijenosne elektroenergetske mreže

In this work a custom mathematical model of three-phase transmission network for calculations in the frequency-domain in EMTP-type software is developed. With the possibility of analysis of resonant frequencies and power transmission network frequency response, it can be used as well for steady-state and time-domain calculations. Developed model in EMTP-RV is validated by comparison of load-flow results with the model which primary focus is load-flow calculations, e.g. PSS/E. Frequency dependent network equivalent seen from the certain point of the network can be very useful in cases of new power plant connection, because they can be transmitted by TSOs to power plant owners or manufacturers to perform certain type of calculations. Model of frequency dependent network equivalent obtained using the Vector Fitting method is validated through comparison of time-domain results with full-network model and with on-site measurements. A case scenario of power plant connection with long HVAC cable is analyzed on developed model to show its influence on network’s frequency response and resonant frequencies. Also, a procedure for identification of areas sensitive to the change of network topology is established. In order to determine the most influential parameters of the power transmission network on frequency response, a procedure for sensitivity analysis which consists of defining an input parameters and output signals and their parameterizing with EMTP-type module for parametric studies is established. Sensitivity analysis is performed graphically and using Moriss Method.U radu je opisan postupak za razvoj modela prijenosne elektroenergetske mreže za izvođenje proračuna u frekvencijskoj domeni u EMTP-tipu računalnog alata. Uz mogućnost modela za analizu rezonantnih frekvencija i frekvencijskoga odziva prijenosne elektroenergetske mreže, može se koristiti i za proračune u ustaljenom stanju i vremenskoj domeni. Razvijeni model u EMTP-tipu računalnog alata je validiran usporedbom tokova snaga s modelom čiji je primarni fokus na proračune tokova snaga, primjerice PSS/E. Frekvencijsko ovisni ekvivalent u određenom čvorištu mreže može biti vrlo koristan u slučajevima priključenja novih elektrana, zato jer ih operatori prijenosnih sustava mogu dati na korištenje trećim stranama za potrebe izvođenja određenih proračuna. Model frekvencijsko ovisnog ekvivalenta dobivenog korištenjem Vector Fitting metode je validiran usporedbom proračuna u vremenskoj domeni sa detaljnim modelom mreže i sa rezultatima mjerenja. Na razvijenom modelu je analiziran slučaj priključenja elektrane s dugim VN kabelom kako bi se utvrdio utjecaj na frekvencijski odziv i rezonantne frekvencije. Također, uspostavljen je postupak za određivanje osjetljivih područja s obzirom na promjenu topologije mreže. Sa svrhom određivanja najutjecajnijih parametara prijenosne mreže na frekvencijski odziv, uspostavljena je procedura za provođenje analize osjetljivosti koja se sastoji od definiranja ulaznih parametara i izlaznih signala, te njihovog parametriziranja sa EMTP-tipom modula za parametarske analize. Analiza osjetljivosti je provedena grafički i korištenjem Morissove metode

Model za određivanje frekvencijskoga odziva prijenosne elektroenergetske mreže

In this work a custom mathematical model of three-phase transmission network for calculations in the frequency-domain in EMTP-type software is developed. With the possibility of analysis of resonant frequencies and power transmission network frequency response, it can be used as well for steady-state and time-domain calculations. Developed model in EMTP-RV is validated by comparison of load-flow results with the model which primary focus is load-flow calculations, e.g. PSS/E. Frequency dependent network equivalent seen from the certain point of the network can be very useful in cases of new power plant connection, because they can be transmitted by TSOs to power plant owners or manufacturers to perform certain type of calculations. Model of frequency dependent network equivalent obtained using the Vector Fitting method is validated through comparison of time-domain results with full-network model and with on-site measurements. A case scenario of power plant connection with long HVAC cable is analyzed on developed model to show its influence on network’s frequency response and resonant frequencies. Also, a procedure for identification of areas sensitive to the change of network topology is established. In order to determine the most influential parameters of the power transmission network on frequency response, a procedure for sensitivity analysis which consists of defining an input parameters and output signals and their parameterizing with EMTP-type module for parametric studies is established. Sensitivity analysis is performed graphically and using Moriss Method.U radu je opisan postupak za razvoj modela prijenosne elektroenergetske mreže za izvođenje proračuna u frekvencijskoj domeni u EMTP-tipu računalnog alata. Uz mogućnost modela za analizu rezonantnih frekvencija i frekvencijskoga odziva prijenosne elektroenergetske mreže, može se koristiti i za proračune u ustaljenom stanju i vremenskoj domeni. Razvijeni model u EMTP-tipu računalnog alata je validiran usporedbom tokova snaga s modelom čiji je primarni fokus na proračune tokova snaga, primjerice PSS/E. Frekvencijsko ovisni ekvivalent u određenom čvorištu mreže može biti vrlo koristan u slučajevima priključenja novih elektrana, zato jer ih operatori prijenosnih sustava mogu dati na korištenje trećim stranama za potrebe izvođenja određenih proračuna. Model frekvencijsko ovisnog ekvivalenta dobivenog korištenjem Vector Fitting metode je validiran usporedbom proračuna u vremenskoj domeni sa detaljnim modelom mreže i sa rezultatima mjerenja. Na razvijenom modelu je analiziran slučaj priključenja elektrane s dugim VN kabelom kako bi se utvrdio utjecaj na frekvencijski odziv i rezonantne frekvencije. Također, uspostavljen je postupak za određivanje osjetljivih područja s obzirom na promjenu topologije mreže. Sa svrhom određivanja najutjecajnijih parametara prijenosne mreže na frekvencijski odziv, uspostavljena je procedura za provođenje analize osjetljivosti koja se sastoji od definiranja ulaznih parametara i izlaznih signala, te njihovog parametriziranja sa EMTP-tipom modula za parametarske analize. Analiza osjetljivosti je provedena grafički i korištenjem Morissove metode

Model za određivanje frekvencijskoga odziva prijenosne elektroenergetske mreže

In this work a custom mathematical model of three-phase transmission network for calculations in the frequency-domain in EMTP-type software is developed. With the possibility of analysis of resonant frequencies and power transmission network frequency response, it can be used as well for steady-state and time-domain calculations. Developed model in EMTP-RV is validated by comparison of load-flow results with the model which primary focus is load-flow calculations, e.g. PSS/E. Frequency dependent network equivalent seen from the certain point of the network can be very useful in cases of new power plant connection, because they can be transmitted by TSOs to power plant owners or manufacturers to perform certain type of calculations. Model of frequency dependent network equivalent obtained using the Vector Fitting method is validated through comparison of time-domain results with full-network model and with on-site measurements. A case scenario of power plant connection with long HVAC cable is analyzed on developed model to show its influence on network’s frequency response and resonant frequencies. Also, a procedure for identification of areas sensitive to the change of network topology is established. In order to determine the most influential parameters of the power transmission network on frequency response, a procedure for sensitivity analysis which consists of defining an input parameters and output signals and their parameterizing with EMTP-type module for parametric studies is established. Sensitivity analysis is performed graphically and using Moriss Method.U radu je opisan postupak za razvoj modela prijenosne elektroenergetske mreže za izvođenje proračuna u frekvencijskoj domeni u EMTP-tipu računalnog alata. Uz mogućnost modela za analizu rezonantnih frekvencija i frekvencijskoga odziva prijenosne elektroenergetske mreže, može se koristiti i za proračune u ustaljenom stanju i vremenskoj domeni. Razvijeni model u EMTP-tipu računalnog alata je validiran usporedbom tokova snaga s modelom čiji je primarni fokus na proračune tokova snaga, primjerice PSS/E. Frekvencijsko ovisni ekvivalent u određenom čvorištu mreže može biti vrlo koristan u slučajevima priključenja novih elektrana, zato jer ih operatori prijenosnih sustava mogu dati na korištenje trećim stranama za potrebe izvođenja određenih proračuna. Model frekvencijsko ovisnog ekvivalenta dobivenog korištenjem Vector Fitting metode je validiran usporedbom proračuna u vremenskoj domeni sa detaljnim modelom mreže i sa rezultatima mjerenja. Na razvijenom modelu je analiziran slučaj priključenja elektrane s dugim VN kabelom kako bi se utvrdio utjecaj na frekvencijski odziv i rezonantne frekvencije. Također, uspostavljen je postupak za određivanje osjetljivih područja s obzirom na promjenu topologije mreže. Sa svrhom određivanja najutjecajnijih parametara prijenosne mreže na frekvencijski odziv, uspostavljena je procedura za provođenje analize osjetljivosti koja se sastoji od definiranja ulaznih parametara i izlaznih signala, te njihovog parametriziranja sa EMTP-tipom modula za parametarske analize. Analiza osjetljivosti je provedena grafički i korištenjem Morissove metode