# Western Power Upgrades 330 kV GIS Substations and Deploys 100 Mvar Variable Reactors to Counter Critical Low Daytime Demand

> To manage unprecedented voltage rise driven by 3 GW of rooftop solar backfeeding during sunny mild weekends, Western Australia’s Western Power has completed 330 kV Gas-Insulated Substation (GIS) renewals and installed four 100 Mvar Variable Shunt Reactors across the South West Interconnected System.

- **Publish Date:** 2026-09-20
- **Category:** transformers-grid
- **Reading Time:** 4 min
- **Original Source Citation:** [Western Power Network Operations](https://www.westernpower.com.au/about/news-media/330kv-gis-substations-minimum-operational-demand-upgrades-september-2026)
- **Tags:** Western Power, SWIS, 330 kV, GIS, Shunt Reactors, Australia, Voltage Control
- **Canonical URL:** https://voltformer.com/news/western-power-swis-upgrades-330kv-gis-substations-minimum-demand
- **Markdown Source:** https://voltformer.com/news/western-power-swis-upgrades-330kv-gis-substations-minimum-demand.md

## Countering Severe Voltage Rise During Minimum Operational Demand

Operational demand on the isolated South West Interconnected System (SWIS) has dropped to historic lows below 400 MW at midday due to residential solar generation. With long lightly loaded 330 kV transmission circuits acting as giant capacitors, line capacitive charging generated severe overvoltage conditions exceeding statutory limits.

Western Power installed four new 100 Mvar 330 kV oil-immersed Variable Shunt Reactors (VSRs) equipped with on-load tap changers, dynamically regulating reactive absorption between 20 Mvar and 100 Mvar.

## Compact 330 kV GIS Upgrades in Urban Substation Footprints

At the terminal Neerabup and Muja switching stations, older air-insulated bays were replaced with compact 330 kV SF6-sealed GIS equipment, reducing physical substation footprints by 70% and upgrading interrupting duty to 50 kA.

Automated voltage control algorithms integrate real-time SCADA telemetry to throttle reactor tap positions automatically, maintaining regional transmission voltage within a strict ±2% regulatory band.

---
Related: [Power & Energy News Hub](https://voltformer.com/news.md) · [Voltformer Substation & Transformer Catalog](https://voltformer.com/catalog.md)