Coastal Southeast Asia takes a beating from typhoons every year. In places like central Vietnam and Luzon in the Philippines, the hours before and after a typhoon makes landfall are the most dangerous. Substations and transformer bays are often the first to fail. Once the typhoon arrives, you're in emergency repair mode. What actually makes a difference is the window between the storm forming and making landfall - checking what needs checking, reinforcing what needs reinforcing, and stocking up what needs stocking up.
Start with the drainage system inside the substation. Cable trenches, cable basements, and stormwater manholes look fine most of the time, but once water collects during a typhoon, moisture rises fast. Switchgear bases end up sitting in water, and insulation on secondary cables drops in no time. Run the drainage pumps to make sure they start and stop properly, and switch over to the backup pump for a test run. Float switches and level alarms can't be allowed to fail. Clear the silt and junk out of the sump pits beforehand. Check the door seals on outdoor terminal boxes and mechanism boxes one by one. Shut the door and shine a light around the gap - if you can see light, replace the seal. Don't let the drain holes at the bottom of the box get blocked with mud; that's the only path for water to escape during a downpour.
On the transformer, a few spots need close attention. If the silica gel in the breather has already turned pink or clear, it's saturated with moisture. Replace it before the typhoon comes, otherwise humid air goes straight into the conservator and the winding insulation gets damp - not something to fool around with. Check the oil level against the temperature. Temperatures swing a lot before and after a typhoon, and an oil level that's too low or too high is a problem. Top up or drain as needed. If there's gas in the Buchholz relay, take a sample and check the color. No color usually means air, but if it has color, take it seriously. Wipe down the transformer bushings. Salt deposits plus rain make a ready-made creepage path. Turn on the heaters in the terminal boxes to keep the inside dry, and seal up any gaps with putty where the sealing isn't good.
Surge arresters and drop-out fuses are the easiest things for the wind to tear up during a typhoon. On pole-mounted arresters, the leads shouldn't be pulled tight, and they shouldn't hang so loose that the wind swings them wildly. Leave enough distance between the leads and the crossarm and guy wires. In strong wind, leads move a lot more than normal, and if the clearance isn't enough, they'll touch. Check the arrester's grounding down-lead from top to bottom. Rusted connectors and loose bolts need fixing - that's the only path for lightning current to discharge. Typhoons bring dense lightning, so an unreliable ground is like leaving the transformer directly exposed to a strike. For drop-out fuses, make sure the fuse tube is seated correctly and the latch isn't loose. If the tube is damp or peeling, replace it ahead of time. Don't wait for the wind to blow it off during the storm and drop a phase.
Wind-proofing around the substation also has to be done. Temporary shade nets, plastic sheets, and colored tarps around the yard must all be taken down before the typhoon. Once the wind gets going, they'll blow onto the busbars and cause a short circuit. Clean out bird nests and debris from the outdoor structures. Fix loose covers on the patrol walkways. Cut dead branches from trees near the gate and along the fence, and trim anything hanging too close to the conductors. Go through spare parts and emergency supplies too - fuse elements, insulation tape, cable sealing putty, emergency lights, charged radios. These seem small, but when you're in the middle of a repair, missing one thing costs time.
Finally, sort out the staffing. In the 24 hours before landfall, strengthen the duty roster and step up patrol records. For critical substations and transformer bays, arrange emergency generators in advance and check the fuel level. If there's online monitoring on the transformer, crank up the data refresh rate and keep a close eye on oil temperature, oil level, and partial discharge readings. Nobody can predict which part will fail first during a typhoon, but if you take care of drainage, sealing, wind-proofing, and grounding beforehand, most accidents can be avoided. A substation or transformer that rides out a typhoon doesn't survive on luck - it survives on the preparation work done in the days before the storm.