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        • Aurora works across a wide range of traditional power generation systems, from small CHP units up to large industrial power generation facilities. We have extensive experience in considering synchronous generators fault contribution into the network, as well as considering issues such as dynamic response and transient stability of synchronous generators.

        • Renewables & Energy Storage
        • Aurora provides a range of services to the Renewables and Battery Energy Storage Systems industries, and can provide advice on analysis on greenfield developments or integration into existing brownfield industrial facilities. We specialise in providing grid simulation and G99 compliance studies to support renewable connections to the UK network, and other European networks.

        • Transmission & Distribution
        • Aurora has extensive experience in the transmission and distribution sector, dealing with private 11kV and 33kV networks, iDNOs and DNOs and National Grid, for a variety of different design and analysis applications.

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        • Aurora has extensive experience in the Oil & Gas industry, and has undertaken a wide range of design activities, concept studies and simulation studies to support many large international EPC companies and service companies.

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        • Aurora works in light and heavy industry providing a range of services to help plant owners analyse and understand their networks, identify weak spots, providing guidance on system loadings, fault levels, earthing, protection coordination and arc flash.

        • Data Centres
        • Aurora has worked on a number of large data centres, providing a range of services to support existing specialist companies in this area, such as system analysis for fault levels, harmonic analysis, protection coordination and arc flash analysis.

        • Building Services
        • Aurora works in Building Services industry to support multiple M&E contractors in development of the HV aspects of their design, or integration of renewable technologies like roof top solar. ¬†Services include system analysis for fault levels, harmonic analysis, protection coordination and arc flash analysis.

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        • Aurora has extensive experience in the water industry and has worked fs, identify weak spots, providing guidance on system loadings, fault levels, protection coordination, motor starting earthing and arc flash. We also have extensive experience in helping water companies integrating renewalbe power and battery storge technologies into their sites.

        • Power System Analysis
        • Load flow, fault analysis, P28/2 voltage disturbance including flicker and transformer inrush, G5.5 Harmonics, G99 Grid studies, protection coordination, arc flash, dynamic and transient studies and electromagnetic transients.

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        • Concept selection, contingency analysis, switchgear and transformer specification, SLD preparation, cable sizing, UPS sizing, substation layouts, protection scheme design, wiring modifications for EPC and M&E companies.

        • Power System Earthing
        • Earth potential rise (EPR) calculations and touch and step voltage calculations with either CDEGS or XGSLab, earthing layouts, soil resistivity testing, fall of potential tests, earthing inspections and resistance testing.

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        • Concept development and decarbonisation strategies, preparations of G99 and National Grid connection applications, review of ICP and vendor proposals, due diligence checks and client representative and failure investigations.

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G5.5 Harmonics – Making Life Easier or Harder?

G5.5 Harmonic studies are applicable to any plant that contains sources of harmonics, typically associated with Solar PV, Wind, Battery Storage and large industrial sites. The studies are primarily carried out to determine the level of harmonic emissions from a site and to identify any potential resonances and the need for mitigation strategies like harmonic filters. The new G5.5 standard requires assessment up to the 100th harmonic and is increasingly identifying problems with many sites and increasing the need for low harmonic emissions and harmonic filters. The new standard is now very closely aligned with the IEC 61000-3-6 standard, and has more generous harmonic limits, but they are based on apportionment, rather than absolute values.

Harmonic studies are split into two main areas. Stage 2 studies for systems connected at 6.6kV and 11kV – these are very similar in difficult and content to the old G5.4 process. Unless your a studies / harmonics nerd the process will be very similar to the whole approach you are probably familiar with.

Stage 3 studies are required for sites connected at 33kV and above (or for failed Stage 2 studies). As the method is now aligned with IEC 61000-3-6, which means there is much less exporting data and summating in Excel spreadsheets, but it is where things get difficult (or interesting depending on your perspective). They key difference is that the background DNO / TSO network is now represented by a series of frequency impedance data – this is either in the form of harmonic frequency dependent impedance tables or the more complex harmonic impedance loci. From a studies this is both good and bad – its good because it saves the huge amount of time needed for modelling the DNO network, as we had to do in G5.4 – but the bad news (particularly if using impedance loci), is that it involves using a lot of scripts to run multiple harmonic loadflow cases and it is much harder to spot what specific cases are causing the problems are and find solutions if the system doesn’t meet the emissions limit.

There are a couple of interesting things that have come out of G5.5. Firstly a lot of the DNOs are finding it tough (time consuming and expensive) to produce full harmonic impedance loci and specifications needed for a Stage 3 connection. Secondly we are seeing a lot more non-compliance issues, this is for a mixture of reasons – sometimes its because there is less headroom, but often it is in the higher orders and the switching frequency of the inverters causes exceedances around the usual suspect frequencies of 2.9kHz, 3.1kHz or 5.9kHz

  • Stage 2A/2B/2C
  • Stage 3
  • Harmonic Loadflows
  • Harmonic Frequency Sweeps
  • Harmonic Filter Design
  • Renewable Power
  • EV Charging Stations
  • Industrial Plants

If your interested in how Aurora can help – please get in touch!