TOTEM: Transmission Owner Tools for EMT Modelling

TOTEM is a NIA (Network Innovation Allowance) project led by Scottish Hydro Electric Transmission along with Scottish Power Energy Networks (SPEN), National Grid Electricity Transmission and National Grid Electricity System Operator. The National HVDC Centre has been supporting this project by providing technical support, model review and verification- and will be hosting IT infrastructure to run the extensive off-line Electromagnetic Transient (EMT) models in a large-scale simulation environment focussing on the Scottish areas of GB but with the capability of covering the whole of GB.

Project Background:

The increased integration of renewable sources and HVDC transmission links is significantly changing the characteristics of the GB network. These changes, resulting in reduced system inertia and lower short circuit levels give rise to the potential for new control interactions and interactions between the devices across the network to occur which conventional Route Mean Squared planning tools such as DIgSILENT PowerFactory and PSSE  may not capture, or be capable of highlighting adequately. Historically for most planning analysis an AC network is modelled in the  RMS domain has been sufficient- where electrical quantities are presented in the phasor domain which essentially averaged over a fundamental frequency period. In this domain, the network elements are expressed in impedances characterised by constant reactance rather than constant inductance/capacitance. This has been computationally efficient for large scale system-level studies to date, as these networks have been dominated by synchronous generation resources which define strong phasor and electro-mechanical behaviours on a power system, which in general may be approximated within RMS analyisis.  For renewable and HVDC resources power convertors are actively measuring and tracking the voltage waveform, and their responses to that and the range of phenomena that can result cannot be adequately captured within the RMS domain.

A new form of EMT model optimised to capture and illustrate the range of phenomena accurately across the network yet remaining computationally efficient to support planning study, is needed. PSCAD has been selected given the variety of models provided by projects in this format today and to be further required within Grid code change (GC0141) currently being progressed towards consultation.  This project will develop the whole GB reference model for such analysis, together with the associated software and hardware enabling its use. If successful it will further de-risk the transition towards Net Zero technologies, complementing other de-risking methods used.

Project objectives:

  1. Build and validate a PSCAD model of the GB transmission network and from that derive separate models for each of the three TO licence areas;
  2. Deliver tools for PSCAD model manipulation and analysis that will support the TOs in their use of the GB model;
  3. Provide the GB TOs with the knowledge and understanding required to adopt the models and put them into use; and
  4. Establish shared computing resources for running the most complex models.

Further details are available in the following link: