Dangerous geomagnetically induced currents
Nobody knows exactly when they’ll occur. Nobody can exactly predict with what force they’ll strain power grids – and yet more and more grid operators are arming themselves against geomagnetically induced currents (GIC). The result of solar storms and other space weather phenomena that disturb the Earth’s magnetic field, GIC can potentially damage high-voltage power transformers.
Nordic regions like Scandinavia and countries like Canada or Russia know these disturbances as auroras or Northern Lights – nice to look at but with possible dangerous side effects. In 1859, the strongest-ever sun storm was recorded. Northern Lights could be seen all over the world, poles sprayed sparks and electrical systems shorted out completely. More recent incidents have shown that solar events can also jeopardize power supplies. In 1989, GIC paralyzed the entire power grid in and around Montreal and in 2003 left around 50,000 customers without electricity in southern Sweden. Other areas of the world aren’t immune to the effects of solar storms either, such as parts of the US, South Africa or England.
For their substation in Hofstad, the Norwegian transmission system operator Statnett needed a variable shunt reactor to compensate reactive power and control the voltage level – and they wanted that reactor to be tested for GIC.
Outwitting the weather in space
Siemens has been involved in the development of GIC-safe transformers since 1989, creating various calculation models, special algorithms and designs. Now, for Statnett, Siemens has been able to prove for the first time worldwide that GIC tests are also possible for variable shunt reactors (VSR).
In the Siemens high-voltage laboratory in Weiz, Austria, experts have thoroughly tested VSRs for a worst-case scenario. The reactors withstood the simulated GIC storms without complication, and the test measurements confirmed complete DC-stability, harmonic-free operation and uncritical temperature behavior.
In order to compensate for the daily reactive power fluctuations in the high-voltage grid, Statnett opted for a VSR from the Siemens plant in Weiz with a reactive power of 90 to 200 MVAr (megavolt ampere reactive) that can be adapted in stages without interruption. And this range of control allows Statnett to make fast, situation-specific adaptations of the momentary local reactive power demand. It also leaves them well prepared for future changes in grid requirements.
A worldwide showcase project
With the world’s first successfully GIC-tested reactor in operation at Hofstad, the substation will be a showcase model for other transmission system operators. The costs for tested GIC safety were extremely low, and when GIC requirements for VSRs are similar to the ones at Hofstad, they’re only marginally more expensive than units that have not been GIC-tested. This is true as well for large power transformers, where the costs for GIC-tested safety are equally low.
„State of the art transmission products have to be reliable and provide power resiliently at all times. As a part of our Pretact® concept, GIC-safe design is an important feature to protect assets from harm caused by extreme weather events – or even threats from cosmic events”, says Dr. Beatrix Natter, CEO of Siemens Transmission Products.
Siemens Transmission Products
Transmission products play a vital role in the energy value chain. Siemens Transmission Products offers all key elements including Power Transformers, Gas Insulated and / or Air Insulated Switchgear and components, individually or bundled, with related engineering. With our global factory network and leading innovations we provide the highest level of quality and reliability to support our customers in achieving their objectives.