Flexible optical measurement system for grid monitoring

With the aim to analyse network failures, Swissgrid launched a monitoring project where CONDIS’ optical current transformers (OCTs) were chosen over conventional measurement systems.


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Supplying advanced optical monitoring solutions

As an early adopter of digital solutions, the Swiss TSO Swissgrid recently opted for CONDIS metering products to complete a monitoring system within their 380/220kV GIS substation at Châtelard/Valais, where one of Europe’s largest hydro power plant is connected to the transmission grid.
The main purpose of this system is to measure with high precision the network faults coming from generators in the hydro plant. The collected records are used to compare network failure simulations with real measurement and potentially as proof of failure towards third parties.


Close attention to short-circuit currents

The essential aspect of enhancing the monitoring features was to provide with accurate measurements of asymmetric short-circuits currents at the 380/220kV GIS substation Châtelard. Indeed, network simulations have shown that in case of near generator short circuits, DC components of several thousand amperes can occur.
Such significant DC components can take classical high-voltage switchgear such as installed at the GIS substation in Châtelard to their technical limits. Switching without a zero-crossing can lead to serious damage on the equipment itself or even harm substation personnel.
In response to these observations, CONDIS’ advised for the installation of three sets of flexible OCTs, connected to two 380kV and one 220kV cable-lines at the output of the GIS substation, where the substation itself is connected to the high-voltage overhead lines.
With the reduced footprint, the non-invasive installation of the flexible OCTs as well as the precision and performance for measuring both AC and DC currents, CONDIS’ OCTs have shown significant advantages compared to traditional CTs and competitive OCT solutions.

F-EFOCT installation at Swissgrid substation

Costs and resources optimization

As a reliable and close partner to Swissgrid, CONDIS SA has been able to deliver this project within only five months, reducing drastically the costs and resources for all participants. Indeed, on-site calibration and functional testing during site acceptance tests were conducted by CONDIS experts which reduced the number of external partners.
In addition, the successful factory acceptance testing (FAT) already showed functionality of CONDIS’ OCTs by measuring fault events before the installation of the system on site. As a result, the following site acceptance testing (SAT) could be reduced to a minimum of three days.
Within only four days of commissioning work, the three 3-phase cable lines were equipped with OCTs including wiring and functional testing.


Opening the way for other successes

The use of CONDIS’ OCTs for monitoring applications is a promising field of activity in addition to measurement & protection applications in the grid. Perfectly aligned with the company’s strategy, CONDIS’ OCT portfolio aims to offer a strong value proposition to the grid operators with best-fit products and outstanding customer experience.


We, at CONDIS, are looking forward to support Swiss and international companies willing to discover and experiment our cutting edge low-power instrument transformer (LPIT) products to securely initiate their digital transformation. Contact us at condis@condis.ch or +41 26 411 85 95.