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Network Equilibrium

Funding mechanismLCN Fund Tier 2
DurationMar 2015 - Jun 2019
Project expenditure13 million
Research areaLow Carbon Generation and Connections
Region
  • South West

Project description

Network Equilibrium was awarded £13m Low Carbon Networks Funding in November 2014. The focus of the project is to balance voltages and power flows across the distribution system, using three methods to better configure the network, helping to integrate additional distributed generation within electricity networks more efficiently and deliver major benefits to distribution customers. The project will develop solutions that will be demonstrated across Somerset and Devon in the trial area.

Network Equilibrium Trial area across Somerset and Devon.

Problem(s)

UK electricity distribution network infrastructure has been designed and developed for passive power distribution requirements.  Voltage profiles and power flows are planned for the worst credible scenarios. As a result, the integration of significant levels of low carbon technologies (LCTs) within our present electricity networks can cause voltage management and thermal issues if networks are not reinforced or operated actively.

Conventional network reinforcement can increase network capacity. However in an increasing number of cases the reinforcement options are either prohibitively expensive or it takes multiple years to plan and construct, delaying new connections until the work is carried out.

Innovative solutions have shown how additional network capacity can be unlocked. For a business as usual (BAU) roll-out DNOs need to develop solutions, which are robust, take a strategic engineering approach, considering the whole system and not solving constraints on a piecemeal basis.  Network Equilibrium is expected to result in solutions that can be subsequently rolled out as BAU techniques.
 

Solution

The Equilibrium Solution provides DNOs with novel voltage and power flow management approaches to improve the utilisation of electricity networks. Significant additional capacity will be unlocked within electricity networks to accommodate increased levels of low carbon technologies, during normal operation and outage conditions.

The granularity of voltage and power flow assessments will be increased and, if proven successful, Equilibrium could result in amendments to ENA Engineering Recommendations and statutory voltage limits, in 33kV and 11kV networks. This will unlock capacity for increased levels of low carbon technologies, such as DG.

DNOs will be able to plan, more effectively, for outage conditions thereby keeping more generation and demand customers connected to the network when, for example, faults occur. This will become increasingly important as networks become more complex, with intermittent generation and demand profiles, and there is an increased dependence on communication and control systems.

Policies, guidelines and tools will be ready for adoption by other GB DNOs, to optimise voltage profiles across multiple circuits and wide areas of their networks.

The resilience of electricity network will be improved through FPL technologies, which will allow DNOs to control 33kV voltage profiles and allow power to be transferred between two, previously distinct, distribution systems including between DNOs.

Equilibrium will deliver a solution to increase the firm capacity of substations, which means that the security of supply to distribution customers can be improved during outage conditions, leading to a reduction in customer interruptions and customer minutes lost.
 

Method(s)

Method 1:  Enhanced Voltage Assessment (EVA)


EVA - Part 1, Method One - Advanced Planning Tool


Network Equilibrium will work with a supplier to deliver a scripted power system analysis tool, using historical demand and generation profile data for steady state evaluation of the 132kV, 33kV and truncated 11kV networks.  

The tool will create a number of profiles for substation loads and generator exports using available historical data, weather corrected forecast profiles for demand and generators using available historical data or historical profiles.  Historical and forecast profiles created by the tool will be stored in a TSDS (Time Series Data Store).  

The tool will be used by Primary System Design Engineers, Operations Support Engineers and Control Engineers for proactive and reactive network modelling using profile data.  This will give better information on the expected power flows and voltage profiles under both normal and abnormal network operations.  

The tool will incorporate the South West 132kV network, the associated 33kV and truncated 11kV network in the trial area. The tool will also be used to evaluate and configure smart solutions including SVO, FPL, Statcoms and generation operating in reactive power control modes. The tool will quantify the available headroom, on their 11kV and 33kV networks under normal and abnormal conditions with and without the smart solutions being applied.

EVA - Part 2, Analytical Study - Voltage Limits Assessment


The project will conduct a theoretical investigation into whether steady state statutory voltage limits (±6%) and step change limits for the 11kV and 33kV networks could and should be amended.  The study will assess the rationale for the current standards, assess if the validity of the original assumptions remains, assess if any DNO or customer equipment could limit the future amendments to voltage limits, if there is any commercial, safety or customer reasons which could limit future amendments to limits and based on the analysis, create a recommendation for future amendments to voltage limits.

It is expected that this project will create a definitive recommendation stating how the ESQCR statutory limits could be amended, how the P28 step change limits could be amended and if there any limitations which could prevent voltage limits from being changed, the further actions that would need to be taken.  This is expected to be disseminated both in a report and presentation format.
 

Method 2:  System Voltage Optimisation (SVO)

 

Network Equilibrium will work with a supplier to create an analysis and a control system and integrate this with WPD’s existing centralised DMS (Distribution Network Management system) PowerOn, this has been called System Voltage Optimisation (SVO).  SVO will assess the voltage impact of DG (Distributed Generation) and network demands on selected 11kV and 33kV networks, evaluate the real time and forecasted power flows available from a TSDS and the subsequent voltage profiles across the SVO substations taking into account current and plausible abnormal network running arrangements.  Using this information, if a more optimum target voltage setting can be applied, it will be sent to modern microprocessor AVC (Automatic Voltage Control) relays through the existing DMS using the existing SCADA network, optimising the network voltage profiles over the substations that SVO is applied. 
 
The SVO system must be able to compute more optimal voltage set-points for the AVC relays, on a number of substations in the trials area.  The method must be robust, accounting for failures of communications channels, SVO algorithms and the DMS systems.
 

Method 3: Flexible Power Links (FPL)


Network Equilibrium requires a supplier to provide and install a back to back power electronic convertor (AC-DC-AC) which will allow power transfers across two different 33kV networks which cannot currently be connected due to a number of issues including circulating currents, protection grading or fault level constraints.  This has been called a Flexible Power Link.

The project will install and trial one 20MVA link between two 33kV networks, ideally between two different grid groups that cannot be paralleled due to circulating current issues.  The FPL will allow controlled transfers of both real and reactive power flows between the two networks.  The FPL will be used in conjunction with the SVO to influence the local voltage profiles, it will also control power flows between the two different BSP networks, unlocking additional capacity under both normal and abnormal network conditions.