Verification of the program PowerGrid and establishment of reference grid for calculations

Sammanfattning: Fortum Distribution AB uses a program called PowerGrid (PG) in its daily work. PG is a combined Network information system and grid calculation program. The development of this program is an ongoing process, so Fortum desired a reference program be set up as a means of controlling the continued accuracy of PG’s calculation results. Fortum is aware that PG has had difficulties in calculating some grid designs. An important goal, therefore, is to verify if these problems still exist so that Fortum if so can put increased pressure on their program developer to resolve them. This thesis includes work on 9 different grid set-ups that were known or thought to cause problems in PG. They are drawn up and calculated in PG and then modeled in Matlab where e.g. power flow and short-circuit calculations are carried out. Results are compared, the goal being to discover problems and deviations in PG and to understand more about how PG works. In short, a number of problems are discovered with PG’s calculations, and most grid set-ups that were suspected to be problematic are confirmed to be so. The largest problems occur when alternatives to the single 2-winded main-transformer set-up are tested. Otherwise, it is in the transitions between voltage levels that most of the problems arise. A related observation is that having more than one medium-voltage level or more than one low-voltage level is difficult for PG to handle. Finally, an Excel macro is introduced – a macro that can be used to compare results from different PG calculation engines and highlight any found differences. In short, it can be used as a quick-check before more thorough investigations are launched.