Ensuring reliability during electrical substation upgrade

When the time comes for electricity distributors to upgrade medium-voltage switchgear and substations, safety, reliability and environmental sustainability are key concerns.

These were the primary considerations for an electricity distributor in New Zealand upgrading one of its 33 kV substations — it required a solution that met both safety and environmental goals. It was also focused on the sustainable use of resources, minimisation of waste and wise use of energy.

Ageing outdoor equipment meant the switchgear in one of the substations was at the end of its life. The decision to replace the outdoor 33 kV switchgear with indoor switchgear would make working conditions safer for employees and allow the electricity distributor to explore more environmentally sustainable equipment options.

The distributor chose to work with Eaton’s partner and utilities specialist AD Riley to implement the Eaton Power Xpert UX 36 indoor switchgear solution.

This switchgear is free of sulfur hexafluoride (SF₆) greenhouse gas and oil, allowing the distributor to eliminate SF₆ recording and refilling, as well as minimising end-of-life disposal costs.

During the design process, the Eaton team faced a challenge as the 33 kV switch room design had a physical wall for fire mitigation separating the switchboard main busbar sections.

Eaton’s specialist engineers assessed the switch room design and within a couple of weeks had designed a busbar transition to enable the busbars to easily pass through the switch room wall.

The distributor specifically requested that air insulated switchgear be fitted with circuit breakers using vacuum interrupters. The combination of vacuum interrupters for switching and the SF₆-free feature ensured the design was environmentally sustainable and that performance could be maintained throughout the product lifecycle.

Safety first

While many organisations internationally require switchgear to be type tested to the ‘moderate’ qualification under the IEEE693 standard, this particular distributor required the Power Xpert UX36 switchgear to be seismically tested and recertified to an increased standard.

Working closely with the customer, Eaton successfully recertified the product to the IEEE693 standard for ‘high’ qualification and ensured all other technical requirements were met.

When undertaking testing of the switchgear and primary cables, safety was also a key consideration for the distributor. Eaton worked closely with its team to ensure a safer level of operation, designing a test truck it could use for commissioning and maintenance.

Investing for the future

The switchgear was installed by an experienced team of fitters and technicians. The well-engineered mechanical design of the Power Xpert UX 36 switchgear and busbar system enabled the installation team to erect the switchboard in a short period of time.

With no SF₆ gas or oil, the distributor has simplified switchboard maintenance and operation, avoided costs associated with gas and oil management and reduced end-of-life disposal costs.

The New Zealand-based electricity distributor has successfully enhanced the safety procedures for its employees and has since ordered a second UX36 to strengthen its ability to provide safe and reliable power to its customers.

Image credit: ©stock.adobe.com/au/yelantsevv