A 170 kV COMPACT SWITCHGEAR MODULE APPLICATION AT KOMOTINI OPEN-AIR SUBSTATION IN NORTHEASTERN GREECE

摘要

The application of a compact switchgear module at arnsuburban open-air substation 150/20 kV, located in therncity of Komotini, in Thrace, Greece, due to spacernlimitations, is presented to this paper. The appliedrnmodule is an assembly of an SF6 circuit breaker, and arncurrent transformer 500-1000/1-1-1A, combined intornone apparatus, where the current transformer supportsrnthe breaking chamber, resembling the Greek letter Γrn(gamma). The draw-out of Γ apparatus is equivalent tornan ensemble comprised of a circuit breaker plus arncurrent transformer plus an up-stream (line) and arndown-stream (bus) disconnector. An earthing switch isrnprovided on the line disconnector, as well as thernnecessary interlocks. Further to the presentation of thernapplied technical solution, some issues like testing,rnincluding seismic withstand capabilities, clearances,rnland requirements, erection time, life cycle assessmentrnand economic comparison of the compact switchgearrnmodule versus that of a conventional bay arernconsidered.rnThe compact switchgear modules, besides their obviousrnadvantage of limited land requirements and minimumrnimpact on the environment, present a number ofrntechnical advantages in comparison to conventionalrnequipment (fewer foundations, clear cable routing,rnimmediately apparent switching status, flexibility inrnterms of the substation drawings and in relocation, shortrnerection, and commissioning times, etc.). However, inrncase that a failure is noted at a component of a compactrnswitchgear module, the whole module becomesrnunavailable and must be removed for repair.rnA comparative economic analysis was carried out tornestablish a relation between the investment, erection,rncommissioning and engineering costs of the compactrnswitchgear module and the corresponding costs of thernconventional bay equipment. From the comparison, it isrnobvious that the investment cost of the compactrnswitchgear module is about twenty (20%) percentrnhigher than that of the corresponding equipment of arnconventional bay, without taking into account the costrnof land. The erection and commissioning costs are thern1/3 and the engineering cost is the 2/3 of thernconventional, i.e. in favor of the compact, while thernspace reduction succeeded by the compact solution isrnabout 65%. Taking into consideration investment, fixedrnand variable costs and assuming an interest rate of 8%rnand an expected life of 30 years, the life cycle costrnanalysis was carried out.rnFrom the whole analysis presented in the paper, it isrnapparent that the use of the compact switchgear modulerncan not be justified only on the basis of investment cost,rneven though it is recognized that in some cases of urbanrnsubstations the cost of land coupled with the cost ofrnconventional air insulated bay equipment could be asrnhigh as to tip the scale in favor of the compactrnswitchgear module. From the analysis presented it canrnbe also concluded that the compact switchgear modulernhas higher availability than that of a conventional airrninsulated bay and it requires less maintenance.rnFurthermore, the compact switchgear module has lowerrnlife cycle cost, and therefore a justification for its userncan be provided, even in cases where space orrnenvironmental concerns are not an issue.