​Working with the Transmission System Operator

Working with the TSO

Safe operation of the electricity network in Ireland means that the distribution system and transmission system work together in a co-ordinated way so that the needs of all customers are met. The two systems will host over 8GW of renewable intermittent generation by 2030 which will require even stronger coordination between the Distribution System Operator (DSO) and the Transmission System Operator (TSO). Part of this will be the use of sophisticated ICT platforms and flexibility to deliver secure, sustainable and cost effective energy to all our customers. To do this the TSO, EirGrid, requires support services from generation customers and from demand customers most of whom are connected to the distribution system. 

Delivering a Secure Sustainable Electricity System (DS3)

ESB Networks is already facilitating our customers to provide these services in DS3. The number of service providers on the distribution network is currently low but the requirements for flexibility, in the form of flexible generation, DSR and energy storage, will see an increase in the amount of these service providers on the distribution network. In addition to active power management we are also working to facilitate provision of reactive power from the distribution system to the transmission system in response to network, customer and TSO requirements. This is being achieved by installing sophisticated control systems in existing HV substations and managing these systems from our Distribution Control Centres.

These challenges and opportunities will require us to work ever more closely with our flexibility and TSO partners to deliver appropriate solutions.

Real-time control and supervision play a crucial role in grid management and grid operation on all voltage levels. Distributed renewables based generation is becoming commonplace and is already beginning to displace large-scale fossil fuel based generators. This is resulting in bi-directional and more volatile power flows across the electrical system and particularly across the boundaries between the distribution and transmission networks. To enable all system operators to operate their system in the most efficient and prudent manner possible an increase in the volume and frequency of data exchange and information provision between the DSO and TSO is needed. However, the exchange of all data from all parties to all parties is costly and needs to be managed to prevent duplication and to be as secure and reliable as possible.

This project will focus on the development of a pilot information exchange platform that will be used to inform the development of a final platform that could be deployed across our system. This is being implemented in line with the requirements set out in the European Network Code – System Operation Guidelines. Key capabilities and requirements of the real-time information exchange platform are:    

 

  • Collecting all relevant real-time data from our SCADA system, generators and DSU resulting from the current operation of the electrical network / energy system to visualise the state of the network        
  • Aggregated generation per primary energy source in areas of our network and forecasts of generation       
  • Aggregated demand and forecasts of aggregated demand        
  • Forecasts of available flexibility capacity       
  • Capturing decisions about actions to be performed on the transmission and distribution networks. Intelligence to exchange appropriate information about decisions       
  • Capturing forecast service requirements e.g. DS3 system services or local distribution network services as appropriate

Future iterations of this platform could have the capability to integrate smart meter data and other metering data for smaller units. 

Among the consequences arising from the displacement of large synchronous generators with renewable non-synchronous forms of generation like wind, is a reduction in system inertia. This in turn, means that for a given disturbance on the power system, the frequency will vary more and at a faster rate than previously. 

This has a particular relevance for distribution connected generation since ESB Networks, like most utilities, has traditionally used Rate of Change of Frequency (ROCOF) as a means to detect the occurrence of local islanding, for which the generator needs to disconnect. To cater for these variations in frequency, in a renewables dominated grid, a new threshold of 1 Hz/s for ROCOF has been mandated.  The issue now is for a system wide event of up to 1 Hz/s, most distribution connected generators, set to disconnect at 0.4-0.6 Hz/s, would also disconnect and exacerbate the issue, which could ultimately lead to a black out. 

This project entails the implementation of settings changes to generator protection on generators across the distribution network to 1Hz/s, so that generators will stay connected to support the grid during system wide frequency events and are still able to detect local islanding events. These changes are a matter of compliance with the Distribution Code and must be complied with by the generator owners. This programme will ensure that we increase system frequency stability, maximise the benefits from renewable generation and deliver on Ireland’s targets for Renewable Energy Supply – Electricity (RES-E) for 2020.

It is a shared goal of the TSO and DSO to where possible utilise the existing connected capability of the Distribution system, particularly the reactive power capability of windfarms and other distributed generation, to deliver support to the operation of the transmission system. This is a large resource given half of the MW of connected generation is connected to the Distribution system. 

To facilitate the transfer of Reactive power to the Transmission system ESB Networks has developed a sophisticated control system called a Nodal Controller. 

The Nodal Controller is a new concept and seeks, for larger DSO connected windfarms, to use centralised and automated intelligence, to allow as much reactive power support as possible to be delivered to the TSO-DSO interface whilst at the same time, respecting voltage and thermal capabilities of the distribution network. To test this concept we are developing a pilot of this technology at the Cauteen wind cluster in Co. Tipperary. It is anticipated that once the concept has been proven, it will be rolled out to further wind clusters throughout the system. This will have the impact of providing valuable reactive power support to the transmission network and in some cases, obviating or deferring investment in transmission infrastructure such as STATCOMs and capacitor banks.

The wider rollout of the Nodal Controller will initially be limited to Distribution Code Type B connections. 

There is a further cohort of wind connection classifications, which are technically similar to the Type B where the connection is made to a separate 110kV transformer in an existing demand 110kV station. It is intended to install this control system in these networks in phase 2 of the Nodal Controller rollout. This will require additional development of the Nodal Controller system.  Further studies will determine the value of further implementation. The next category of generation connection is Type C connections. These connections also have demand customers connected and will require more trialling to optimise the control algorithms. 

ESB Networks is running a number of projects which seek to manage real or reactive power flows to support the operation of the transmission system (SERVO, Nodal Controller) which are already being procured through Eirgrid’s DS3 programme. However, the provision of real and reactive power flow services in separation can lead to conflicts and unintended results, therefore an integrated approach to distribution network management is required. This will maximise the capabilities of Distributed Energy Resources (DER) such as energy storage, distributed generation, EVs with vehicle-to-grid (V2G) capability and DSUs to contribute to the operation of the entire electrical energy system. This ambitious project will bring these two technologies together to control real and reactive power flows to support transmission system needs while still operating within acceptable limits on the distribution system. The efficient provision of this flexibility from distribution connected DER also enables decommissioning of fossil fuel plant which traditionally has supplied this flexibility. 

However, a technical solution alone in isolation will not be capable of delivering this and a complimentary workstream will investigate the most cost effective commercial and regulatory framework for the delivery of these services to the TSO and provide maximum value for money for the electrical energy system. One possible framework, would be where ESB Networks will offer reactive and active power services to the TSO, thus developing a new local balancing mechanism. In this scenario, we would act as the ‘aggregator of aggregators’ (i.e. a service aggregator). 

The project entails the development of ESB Networks’ SERVO platform that will permit effective and timely interaction with all market participants and the development of new commercial arrangements for the provision of the new services likely to be offered extensive market. The project also requires customer engagement to understand the potential for impediments to wider roll-out and the establishment of a framework for secure grid operations which will deliver efficient coordination across SO and DNO investment planning, operational planning and real-time horizons.

In Europe, there are four main DSO representative organisations. These are:

  • CEDEC        
  • Eurelectric        
  • EDSO for Smartgrids       
  • GEODE

A cross organisational committee has been established to form a common position on how best to progress the use of flexibility by distribution connected resources and meet customer expectations in this regard, whilst at the same time preserve the security and integrity of the Distribution System. 

As a member of Eurelectric, we are participating in the work of the committee. 

Sub-groups have been established to examine the following specific issues;    

  • TSO-DSO co-ordination        
  • Problem Definition      
  • Solution Space       
  • Modes of Service acquisition

It is intended to present the outcome to the European Commission by end of 2017. This will take the form of a report outlining how the committee sees how best to progress the use of flexibility in future distribution networks. The report will form part of the background to future EU energy packages.