Advanced Technologies, Expert Implementation 


RXPE Circuit

When an offshore wind developer decided to build a project in the Irish Sea, a robust solution was required to help the project comply with the UK Grid Code.

As one of the world’s most experienced developers of offshore wind projects, DONG Energy has extensive experience of integrating its projects into the host transmission grids in the countries where it operates.

In December 2014 DONG Energy made its Final Investment Decision to build the Burbo Bank Extension Offshore Wind Farm after receiving Final Investment Decision Enabling contracts (Contract for Difference) from the UK Government in April 2014.

The project uses 32 MHI Vestas Offshore Wind V164-8.0MW wind turbines with a total capacity of 258MW.


All forms of generation connected to the UK Electricity Transmission System must comply with the UK Grid Code. Specific requirements apply to renewable generation such as offshore wind turbines, specifically in relation to reactive power delivery and Low Voltage Ride Through.

Modern wind turbines are designed to address these requirements however in some cases their performance requires additional support from Dynamic Reactive Power Compensation equipment such as STATCOM technology.

In December 2014 DONG Energy contracted RXHK (then part of RXPE) to design, supply, install and commission a STATCOM technology based ±50Mvar dynamic reactive compensation system. The system consists of the STATCOM valve, built into pre-fabricated modules within the factory, cooling water system, phase arm reactors and MV switchgear through which the STATCOM connects to the tertiary windings of the two 220/400kV grid transformers. All equipment supplied by RXHK is located at the onshore substation near St Asaph in North Wales.


The STATCOM operates to provide any additional reactive capacity required over what is delivered by the turbines. As such it operates as a slave to the Vestas power park controller. The integrated performance of the Vestas power park controller and the RXHK STATCOM controller were tested prior to all equipment arriving at site to ensure that the required performance was achieved. The Maxivar™ STATCOM enabled this goal to be met cost-effectively as well as offering wider benefits.

The Maxivar™ STATCOM underwent extensive Factory Acceptance Testing witnessed and verified by DONG Energy representatives, including testing against RXHK’s in-house RTDS system. It met project requirements, providing dynamic reactive compensation support, voltage control and Low Voltage Ride Through.

The project was project managed and engineered from RXHK’s offices in the UK.


Current status

The Maxivar™ STATCOM has been in operation since November 2016 and has supported the commissioning and ongoing operation of the Burbo Bank Extension Offshore Wind Farm

The ongoing success of this project underlines the capability, reliability and benefits of RXHK’s voltage source converter STATCOMs.

Contact us for more detail about our Maxivar™ STATCOM solutions

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