A 138 kV Substation Swaps Air for Gas in Two Phases

CHINT has completed its first smart substation EPC project for the National Grid Corporation of the Philippines, at the Panitan 138 kV substation in Capiz, in the Visayas. The engineering interest is less in the equipment than in the sequencing, which is the problem every brownfield substation upgrade actually has to solve.

Phase I replaced the existing power transformer with a 138/69 kV, 100 MVA unit while keeping the existing secondary equipment — protection, control, metering — in service. That is the awkward middle state of any staged upgrade: new primary plant answering to old secondary systems, with the compatibility burden falling on settings, CT ratios and wiring that were specified for different equipment.

Phase II then did the harder half: a full conversion from air-insulated switchgear to gas-insulated switchgear, adding twelve new 138 kV and 69 kV GIS bays housed in a purpose-built five-storey GIS building. The secondary system was replaced in this phase, with CHINT supplying intelligent protection, control and communication platforms and a station-wide intelligent secondary system. Additional scope covered shunt reactors, current and voltage transformers, surge arresters and the AC and DC auxiliary supplies.

As EPC contractor CHINT carried civil works, equipment supply, protection and telecommunications, commissioning and HSE oversight — which in a live substation means executing all of it around outage windows negotiated with a transmission operator who would rather not have any.

The AIS-to-GIS conversion is the part with the widest relevance. Gas-insulated switchgear collapses the footprint of a switchyard dramatically, which is why it wins on constrained or urban sites, and moving the equipment indoors changes the maintenance and monitoring regime as much as the electrical design — SF6 density monitoring, partial discharge monitoring and a building's worth of auxiliary systems arrive with it. For anyone facing the same conversion, the phase split and the bay count here make the scope unusually legible, and the project doubles as a validation of CHINT's 138 kV and 69 kV GIS equipment with a national transmission operator.