Return of Experience from Installation, Commissioning and Operation of the World's First Modern SF6-free 420 kV Dead Tank Circuit Breaker

United States. Return of experience is of key importance to share know-how and to facilitate the exchange in the T&D community on the new technology.

In the present paper, the user of the first installation of the 420 kV SF6-free dead tank circuit breaker, a transmission system operator, and the breaker’s manufacturer share their experience in four areas:

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• Motivation for the deployment of the SF6-free 420 kV DTB in the grid

Installation and commissioning experience

Operational experience • Trends from monitoring The first two years of operation in the grid can be summarized as follows:

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• The circuit breaker behaves very similar to an SF6 based counterpart regarding production, gas handling, commissioning, and operation. There is some difference regarding the gas handling and analysis equipment.

The SF6 free circuit breaker successfully cleared a fault that occurred in the grid.

The monitoring of gas quality and main circuit resistance has shown stable and expected values.

Concerning humidity of the gas, seasonal changes are visible in line with the expectations for SF6 and SF6 free equipment documented in CIGRE Technical brochures