Studying the figure which presents the single line diagram of the 66/11 KV substation that feeds the residential area in this project shows that the substation consists of a sectionalized double bus bar system fed by eight 66 KV cables, two incoming from the preceding substation in the 66KV ring and two are outgoing to the next substation in the ring and the remaining four 66 KV feeder cells as reserve.
The busbar sections are coupled by a bus coupler consisting of a circuit breaker and two isolating switches; together with the four isolating switches dividing the bus bars into four sections.
Three 66/11 KV, 35 MVA transformers are fed from the bus bars, and are connected in parallel groups or each to a separate section of the bus bars. The transformer connection circuit to the bus bar, as well as the feeder connection circuit, consists of a 66 KV circuit breaker with two isolating switches towards the bus bars. Current and potential transformers are connected in the circuits for the objectives of protection, control and measuring.
The transformers are connected via circuit breakers to the 11 KV sectionalized busbar. This is cut into three sections coupled with three bus couplers. Outgoing 11 KV feeders come out of the 11 KV bus bar sections, running outside the substation to feed the distribution points as well as some big consumers directly.
Studying the figure of the indoor substation shows the layout of the substation on a plan at the ground level indicating the substation arrangement. Three rooms for the three main transformers in addition to a fourth room for a spare transformer are shown on one side of the 66 KV switchgear hall.
Meanwhile the 11KV switchgear hall, the control room, the auxiliary transformers room, as well as other service areas and the stairs are shown on the other side. Above this, several offices are arranged as well as the rest of services rooms, which could be shown on another plan at the level of the first floor. The 66KV bus bars could be shown on a third plan at a higher level.
The Studying the figure of the outdoor substation shows the elevation and the side view of the substation together with its simplified single line diagram. The side view describes clearly the circuit connections of the 66KV feeder and the 66/11 KV transformers to the 66 KV busbars. It also shows clearly the arrangement of the various equipment in the circuit including the circuit breakers, the isolating switches and the potential and current transformers.
Further, the single line diagram as well as the substation elevation show the lightning arrestors used to protect the substation from lightning surges in case of overhead transmission lines feeding the substation.