Detta examensarbete har utförts hos Vattenfall Eldistribution på avdelningen Kontroll och Skydd med målsättningen att utforma och utvärdera en nätmodell avsedd för jordslutningssimuleringar i PSCAD. Ombyggnationen från luftledningar till markkablar har medfört att kapacitansen i distributionsnätet ökat, vilket ställer högre krav på jordfelsutrustning och på nätanalyser för att kunna försäkra att en säkerställd frånkoppling kan ske enligt de myndighetskrav som föreligger. Syftet med arbetet har varit att undersöka hur en nätmodell bör utformas för analys av stationära in-svängningsförlopp och utvärdera hur stor noggrannhet som kan förväntas gentemot verkliga jordfelsprov vid felresistanser på främst 3 k? och 5 k?. Nätmodellen har ut-formats efter ett verkligt impedansjordat mellanspänningsnät med ?-länkar i PSCAD och utifrån de nätuppgifter som förekommer i Vattenfalls näthanteringsprogram Netbas.

This report describes a synchronous machine model with magnetic saturation in d-axis, neutralconnection and electrical exciter interface for the transient simulator PSCAD/EMTDC. It hasbeen designed and verified in comparison to the regular machine model in EMTDC.The performance of the model is very good when incorporating a linear as well as a saturatedmagnetising inductance. The dynamic deviation is only thousandths to ten thousandths perunit. By using a cubic interpolation of the saturation curve, the model gives a good representationof the saturation effect. The open source code implementation of the synchronousmachine model gives the possibility to easily adapt the model to specific requirements.The derived model makes it possible to simulate a synchronous machine with its excitationsystems, e.g.

This report describes a synchronous machine model with magnetic saturation in d-axis, neutralconnection and electrical exciter interface for the transient simulator PSCAD/EMTDC. It hasbeen designed and verified in comparison to the regular machine model in EMTDC.The performance of the model is very good when incorporating a linear as well as a saturatedmagnetising inductance. The dynamic deviation is only thousandths to ten thousandths perunit. By using a cubic interpolation of the saturation curve, the model gives a good representationof the saturation effect. The open source code implementation of the synchronousmachine model gives the possibility to easily adapt the model to specific requirements.The derived model makes it possible to simulate a synchronous machine with its excitationsystems, e.g.

This master thesis has been performed at Vattenfall Power Consultant in Gothenburg and Trollhättan for Vattenfall Vattenkraft. In this report vacuum circuit breaker in small-scale hydropower stations with the rated power 4 MVA and below has been studied. Models of the stations are modeled and analyzed in PSCAD/EMTDC to study the high voltage transients that are created after current chopping with vacuum circuit breaker. Vacuum circuit breaker may chop the current before it reaches zero value, which means that high voltage transients can be created. The equipment of the stations can be destroyed by high voltage transients.The purpose of this thesis is to examine the use of vacuum circuit breaker in small-scale hydropower stations and the risk for high voltage transients from current chopping.According to the results there is a risk of high voltage transients after current chopping with small synchronous generators in stations with the operating voltages 0.4 kV and 3.6 kV.