Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Questions raised on the basis of this work are, witch loads are there at the stations, how big are the loads, are there nonlinear loads, are there motor loads with high starting currents, how do the rectifiers interact with batteries? The diesel unit starts about 10 minutes after a regional or national interference in a transformer station. The station’s DC power system is then fed during that time from batteries. The question of how rectifiers interact with the batteries is of importance because rectifiers are large instantaneous loads after some discharge of the battery.
The loads that occur at the stations is heat in the control building, server room cooling, lighting inside and out, cooling the reactor, electrical engines, PTO, heating for high voltage circuit breakers etc. These loads will not be active simultaneously and each will not consume a maximum power all the time. This means that you must find the tools to handle these loads. The present report presents developed load factor of the various components involved.
A diesel generator model has been developed consisting of a diesel engine coupled to a synchronous generator in operation through two control systems to regulate voltage and rotor speed. Based on measurements at stations with diesel power, steering systems have been modified for the unit to conform to reality as much as possible. Based on the model, simulations have been done to see what the start-up currents from the motor loads have for effect of voltage and frequency with different sizes of diesel generators.
Calculations have been made to examine the size of short circuit currents in different levels of the station's electrical system. This is to analyse if the fuses can be broken if necessary.
Duration curves of station loads are presented from various measurements to get a better picture of how the total load actually behaves.
From there, appropriate diesel unit size is developed and also EENS and LOLP are calculated.
Duration curves are also simulated based on the load factors that have been worked out and the actual duration curves made. The idea is that the simulated duration curve should conform to reality for engineers to be able to examine the probability of power shortages in emergency use in a planned station.
The results of the report are guidelines and instructions for an easy way to make good diesel units dimensioning of a reserve and emergency operation.
It turned out that the rectifiers have to be started in sequence to avoid to large fast charge cycles. Also a safety factor is multiplied to the rectifier continuous operation to avoid harmonics in the system at emergency operations.
Start currents from reactors cooling system must be analyzed separately and the generator requirements for those is determined from calculations found in the guide. It also turned out to a certain station can get by with a diesel unit at 100kVA instead of the current 400kVA.
2009. , 73 p.