We were pleased to contribute a paper to CIDER 17, Cigre’s “Conference on the Integration of Distributed Energy Resources”  for the Asia Pacific region held in Sydney, 15 and 16 August 2017. The analysis approach for harmonic emission compliance studies in distributed generation systems is shaped by a regulatory framework that requires a priori resolution of several performance requirements. This approach is steeped in risk avoidance and, like most risk avoidance, results in conservative outcomes that are not necessarily in the best interest of the market. Our article describes this analysis approach and demonstrates how the regulation and associated analysis result in increased rather than decreased risk to the stakeholders. A suggestion is made for a pragmatic approach that will result in better outcomes for network owners as well as generation proponents. The recommended approach provides for an initial risk assessment followed by field measurements that quantify the extent of compliance and assist in the design of mitigation systems.

Medium and high voltage capacitor banks require protection against faults in the capacitor units and in the associated equipment such as feeder cables, series reactors, overhead structures and conductors connecting the various parts of the capacitor bank.

Faults inside capacitor units are generally cleared by internal fuses. The operation of these fuses must be monitored to allow for appropriate alarm and trip instructions to be issued based on voltage stress levels in the capacitor units. The same applies for unfused units with unbalance current providing an indication of the number of shorted elements. Such protection depends on very sensitive detection of relatively small currents in the star points of capacitor banks. External faults are either phase to ground or phase to phase and require more conventional over current and earth fault detection.

Both of these types of protection require current transformers to provide the necessary detection of current in the primary circuit. Appropriate selection of protection current transformers is therefore essential for safe operation of capacitor banks. This selection must be done to assure correct operation of protection while minimising cost and avoiding any false operation of protection, i.e. ensuring continuity of operation wherever possible.

ONE has prepared a brief application note describing this selection process to assist our clients in this process. Please contact us if more information is required.

In early December 2013 we presented a training course on harmonic filters to specialist engineers from Vestas in Singapore. The intention of the course was to extend the knowledge of engineers on practical and theoretical aspects of harmonic analysis, filter design, and component ratings. The course was attended by a truly international audience, with Singapore, Australia, New Zealand, China, India, Venezuela and Vietnam represented. The training lasted three days and included real world examples of filter design for wind farm connections.

We are passionate about our field of expertise and welcome any opportunity to share our knowledge with customers and their consultants. Contact us if you would like to know more.

Having the right tools for the job is essential, and when the job is to carry out complex harmonic filter design studies then the choice of the best power system analysis tools is critical. At Optimised Network Equipment we make extensive use of DIgSILENT PowerFactory for network analysis, allowing us to offer services ranging from compliance studies, conceptual design of solutions, and all the way to detailed engineering design covering aspects of harmonic filter component rating, switching transient analysis and stability analysis. Our infinite bus license enables us to tackle any problem, no matter how complex.

As a demonstration of our commitment to this aspect of our business and to share our experience with other users of the software we recently presented a paper on harmonic filter design to the bi-annual user group meeting in Sydney.

The paper can also be found in the Download section of the site. We would welcome any comment to this contribution.

Optimised Network Equipment is conducting a series of courses on reactive power compensation covering shunt capacitor banks, series and shunt reactors.

We will start the series with a specialised course in the design and application of harmonic filter on 19–20 November 2012, and we invite you to join us for training in this highly specialised but commonly used technology.