NESO has been pushing the need for retrospective EMT models as part of the GC 0168 code modification. This requirement is being requested by NESO as part of its overall plan to build a full EMT-level model of the UK system, in order to allow it to undertake more detailed studies and understand the risks of moving to a Net Zero fully renewable grid.
How Aurora can help
If you are likely to be caught up in this work, please get in touch. We have serious expertise in PSCAD and have spent the last six months investing heavily in AI tooling and MCP servers that connect directly to PSCAD, allowing us to build models quickly and efficiently. Using our agentic workflow, we can also construct OEM control system models directly from paper or PDF drawings, including creating the sub-modules and writing the FORTRAN code.
Technical Requirements
The technical requirements are not unreasonable, and section 1 of the NESO requirements align with typical NESO engineering approach to EMT models, so are fairly well understood within the industry. The requirement is for a working PSCAD v5.0.2 model that is compatible with both 32-bit and 64-bit version and the Intel compiler and Visual Studio.
There are a few requirements in the NESO guidance that are challenging and will be difficult to meet in reality. These include issues such as:
- Compatible with both 32–bit and 64- bit versions of Intel Fortran Complier. The challenge here is that older models were often designed and tested by OEMS against one or the other – not usually both, and this will require OEM engagement.
- Being rigorously tested against factory acceptance tests and/or site-specific compliance tests for the corresponding version of Plant. The obvious issue here is that historical plants will not have been tested in the same way and aligned with current EMT models.
- The model should initialize and reach steady state to any user defined and valid operating conditions within 4 to 6 seconds of simulation time. This may work for simple IBR plant, but is decidedly more challenging for large CCGT generation.
- Include the transformer magnetising curves. This will almost certainly be problematic, as they are often not available
- Have no unexpected or uncharacteristic responses. The model must not show characteristics that are not present in the Plant response, both in terms of the electrical response and modelling numerical artefacts. While this is fine in theory, it is rather vague!
- The model should represent all installed protection systems in detail for both balanced and unbalanced fault conditions. This is too vague, what level of accuracy is acceptable. It would be easy to spend 6+ months modelling an advance relay in detail.
The problems arise really on historical sites. Whilst NESO acknowledges this – the problem of getting data on historical plant with busy and uncooperative OEMSs will be difficult and in many cases may no longer exist. This is not some simple data hunting exercise but may turn into a substantial amount of reverse engineering.
Timescales
The problem is that the timescales being suggested are very ‘optimistic’, to put it charitably – to expect the development and deployment of full EMT models in 3–9 months is challenging, to say the least. There are a number of issues, such as finding and obtaining information, engaging with OEMs, agreeing NDAs and disclosure and then there is the availability of suitable engineering staff with the consultancy.
- EU Code User (IBR): 3 Months
- EU Code User (Synchronous Machine): 3 months
- Non-EU Code User with EMT requirement in BCA: 3-6 months
- Non-EU Code User of Synchronous Machines: 6 months
- Non-EU Code User of IBR: 9 months
NESO’s Priority Regions
Pages 16 and 17 of the NESO document give a priority list based on area / ETYS zones:
- Northeast and Northwest Scotland (T1, T2, T3, T4, T5, T6)
- North Central Scotland (S5)
- East England, East Midlands & Humber (D4, D5, J1, J2, J3, J4, J5, J6, J7, K1, K2, K4, K5, K6, L8, P7, P8)
- Southeast England & London (A1, A3, A4, A6, A7, A8, A9, B1, B2, C1, C2, C3, C4, C5, C6, C7, C8, C9, J8)
- South Central Scotland (S6)
- South Central and Southwest England (B3, B4, D6, E1, E7, E8, F6)
- North Wales, South Wales and West Midlands (G1, G5, G6, G7, H1, H2, H6, L1, L2, L3, L5, L7, M4, M5, M6, M7, M8)
- Mersey, Northwest England, North and South Yorks (N1, N2, N3, N4, N5, N6, N7, N8, P1, P2, P3, P4, P5, P6, Q2, Q4, Q5, Q6, Q7, Q8, R4, R5, R6)
Within each priority region, NESO (‘The Company’) will consider the following order when issuing notifications for EMT model submissions:
- Generators/Interconnectors that are EU code Users will be notified first, since these Users might have developed EMT models previously.
- The size of the Plant will be considered to prioritise the request, working from large to small Plant.
- If any new connection compliance study requires retrospective EMT models in that study region, those Generators will be notified.
- To investigate any system events that have occurred, EMT models from the relevant Users will be prioritised.
