Harmonics Progress John Ging Transmission Access Planning
What has happened since the last LG meeting? • Background harmonic data was recorded at various stations for model building and verification • Publication of 1 st Harmonic Information Note – Covers basic theory and background information on the topic – 2 nd Information Note on Harmonics Policy due imminently • Studies of some South West clusters completed – Harmonic Voltage Limits and Impedance loci were communicated with the relevant customers
Current work on Harmonics • Organising a harmonics workshop for stakeholders – Expected Mid October • Reviewing Charging Policy for harmonics issues – Information note expected to issue in the coming weeks • Evaluating suitability of harmonics clause in the Grid Code – Discussion at GCRP • Further Studies for select nodes with significant cable build are underway – South West, North West – More studies will be prioritised after offer acceptance and modifications received
Next Steps • Exchange disturbance recorder data with the DSO – 38kV recording data on MV side and 110kV data on HV side of transformers will aid mutual model validation • Identify “ Designated Study Areas ” – Priority regions due to high existing background distortion • Communication with all applicants in problem regions – Explore issues on a cluster basis • Complex analysis is required for any application in the proximity of Designated Study Areas or if a harmonic problem has been identified – The processing of associated offers will necessitate bespoke timelines
Timeline – Harmonics Data Annual Technical Resolve 15m 12m connect Screening Studies issues Wind turbine, EirGrid reactive power or Reminder for Possibly long cable mods PED Lead times for solutions Customer Model updated Provides with PQ Wind Farm recorder data Model Compliance with EirGrid Harmonic provides Limits Harmonic Limits & Loci
What must customers do? Prior to receipt of Harmonic Injection Limits and Impedance loci Contact the System Operator well in advance of any potential cable request modifications Notify the System Operator of turbine types or reactive power devices on site as early as possible After obtaining Harmonic Injection Limits and Impedance loci from the System Operator, some or all of the following may be required Purchase/Install turbines that have limited harmonic injections at the specified frequencies Install harmonic mitigation plant such as filters to reduce harmonic injections below acceptable levels at the specified frequencies Communicate the parameters of the solution devices with the System Operator
More details can be found on our Harmonics Information page http://www.eirgrid.com/customers/gridconnections/harmonics/
Liaison Group – 3 September 2013 Marie Hayden Charging for Harmonics
What is Connection Charging • Recovery of “shallow” asset capital costs associated with customer connections. • Focused on transmission assets required up to the meshed system. • Governed by a number of policy documents which set out high level principles for the assigning of costs.
Connection Charging: basics • Focused on determining causation and drivers of specific works. • Charging is applied on a Least Cost Chargeable (LCC) basis – charge may not correspond to the actual build. • Assets which are not driven exclusively by a given customer/subgroup are considered “deep” and are recovered via TUoS tariffs. • Rebates are payable where customers connect to assets which were funded by pre-connected parties.
Harmonics issues in a charging context • Difficult to assign causation to specific customers – suggests “deep” from a charging perspective. • Harmonic issues often driven by customer requests (cable), policy permits charging for deeps in such circumstances. • If harmonic solutions are optimised on a geographic basis, are deep in the system and mitigate harmonics for a number of applicants, how do we assign costs. • First mover – pay for harmonic solution, free rider issue. Impossible to allocate rebates for deep assets, how do you quantify system benefits and account for these?
Considerations • The charging approach needs to: – Be fair and proportional. – Send a signal about the cost that cable requests impose on the system. – Be relatively simple to apply, not requiring a suite of “charging” power quality studies. – Work in general, not just solve issues with current Offer Process modifications.
Options being considered
Option 1: Charge for the technical solution identified Pros: • Entirely cost reflective. Cons: • Extremely complex from a charging perspective. • Would require additional “charging” power quality studies to determine “drivers” and the extent to which individual subgroups/applicants are contributing to optimised solutions. • Rebating issues: first mover disadvantage.
Option 2: Apply a Least Cost approach • Apply an LCC type approach – e.g. charge for a filter bank at the point of connection to the meshed system where the connection exceeds harmonics limits. Pros: • Consistent with the LCC principle, pay for the lowest cost solution to the problem, regardless of what is ultimately installed. • Clear and transparent approach. Cons: • Rebating issues – we charge and rebate on actual build, free rider issue. (include filter bank in cable charge?)
Option 3: Apply a harmonics levy • Harmonics levy: apply a levy on all requests for cable on a “polluter pays” principle. Pros: • Reflects that harmonics issues are cumulative • Clear & transparent, avoids rebating complexity Cons: • Customers that request cable in an area of low underlying harmonics would pay the same as in high areas • Not consistent with charging to date which has been the application of a standardised capital charge on clearly identified assets
Next steps • We would like to receive comments on each of the options presented here • We will consider these comments and finalise the policy approach • We will communicate the policy approach to industry and then capture in the next revision of charging policy papers • Timeline – Linked to overall Harmonics Action Plan • Should be completed before next LG meeting
Special Protection Schemes Tom Gallery Transmission Access Planning
Overview of Presentation – Introduction to Special Protection Schemes (SPS) – EirGrid Special Protection Scheme (SPS) Policy – Examples of SPS schemes – Future Work
Introduction A special Protection Scheme is defined as: An automatic protection system designed to detect abnormal or predetermined system conditions, and take corrective action other than and/or in addition to the isolation of faulted components to maintain system reliability. Such action may only include opening circuit breakers, changes in demand or generation (MW and MVAr) to maintain system stability, acceptable voltage or power flows
N-1 Criteria Bulk Supply Point 100 MW Wind Farm 95 MW 190 MW 190 MW 100 MW 95 MW
N-1 Criteria Limit steady-state (pre-fault) flows to prevent N-1 overloads Increased Constraints Bulk Supply Point 100 MW Wind Farm 50 MW 100 MW 190 MW 100 MW 50 MW
Simplest SPS Allow increased pre-fault flows on the assumption that automatic control action will Prevent an overload Bulk Supply Point 100 MW Wind Farm 95 MW 190 MW 0 MW 190 MW 100 MW 95 MW
SPS Policy The EirGrid SPS policy is intended to balance the benefits of the scheme against the impact the scheme will have on: – Other system users; – The dispatch of other plant on the system; – The additional overhead of maintaining such schemes; – Increased complexity of operating the power system; – Impact on system security The SPS policy gives guidelines on how the scheme could be implemented and covers: – Operation; – Redundancy; – Maintenance; – Failure; – Communications; – Control; – Modelling and – SPS Approval Process
SPS Example During intact network, in theory, the 400 MW could be accommodated (assuming some power consumed by local loads and flows are relatively balanced) [187 x 2 = 374] > [400 – loads] 200 MW 15 MW 80 MW 35 MW 187 70 MW MVA 187 MVA
SPS Example Local Generation would not be dispatched to 385 MW due to risk of N-1 overloads Output from area would be limited to less than 200 MW Wind 200 MW 15 MW 80 MW 35 MW 187 70 MW MVA 187 MVA
SPS Example A Special Protection Scheme could allow generation be dispatched beyond 200 MW by: – Monitoring the flows on the circuits – Trip/Reduce generation output in the event of an overload – Thus increasing the MW export from the area by eliminating risk of N-1 overloads – EirGrid SPS Policy used to inform possible SPS options – Range of options considered – Most schemes require extensive communications and wind farm interactions Wind 200 MW 15 MW 80 MW 35 MW 187 70 MW MVA 187 MVA
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