Optimizing total transformer costs

Optimizing total transformer costs

Vol. 4 Issue 4

Power transformers are among the most expensive equipment in any energy supply network. Given the high investment costs, it pays to calculate precisely before making a purchase decision. The largest German distribution network operator performed a comparison between two different options: a transformer with conventional outdoor connections, or with pluggable Connex connection technology by Pfisterer. The calculation reveals that while price is an important factor, there are many other costs to consider in the long term.

Looking at the full picture

One feature that profitable businesses have in common is that they always consider the total costs – especially when buying long-lasting, high-quality capital equipment. That includes power transformers. With a planned lifespan of at least 40 years, they continue to affect operating income long after their acquisition cost is accounted for. “The initial costs are like the tip of an iceberg. Most of it remains hidden below the water’s surface. In terms of a transformer, this invisible part is the operating costs that the energy supplier has to meet over the decades,” says Harald Cuber, Head of Global Sales PTS Cable at PFISTERER. This view is supported by the Total Cost of Ownership (TCO) concept, which includes long-term items such as maintenance and repair work, the cost of modifications, and also an evaluation of failure risks and downtimes.

The largest German distribution network operator wanted to buy a new transformer based on a transparent economic analysis. So the company compared the costs of two different options for the medium voltage connection: the standard design versus the Connex plug-connector system, where the socket is installed in the transformer and serves as a standardised connection for various components. The model calculation assumed that with a conventional connection via open-air bushings, the busbars are connected to the bushing via expansion strips. The transformer and cable structure are mechanically decoupled, and can accommodate expansion due to temperature changes. The dimensioning of the busbars is determined by various calculation parameters for the switchgear. Small animal protection is provided in the form of shrink-fitting insulating material or protective covers. This contrasts with the solid-insulated Connex plug-connector system, where the cables are connected directly via plug connectors into elbow bushings installed in the transformer – up to four cable systems per phase and socket, dimensioned for up to 52 kV and 3150 A, for cable cross-sections up to 630 mm² and for a MV star point connection via a cable and plug connector. Since the fully encapsulated Connex system is touch-proof, there is no need for additional small animal protection.

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