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 1st Harmonic Information Note – Covers basic theory and background information on the topic

– 2nd 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 Screening

15m 12m Technical

Studies Resolve issues

connect

Customer Provides

Wind Farm Model

Possibly long Lead times

for solutions

EirGrid provides

Harmonic Limits & Loci

Wind turbine, reactive power or

cable mods

EirGrid Reminder for

PED

Model updated with PQ

recorder data Compliance

with Harmonic

Limits

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

190 MW

Wind Farm 100 MW

100 MW

95 MW

95 MW

190 MW

N-1 Criteria Limit steady-state (pre-fault) flows to prevent N-1 overloads Increased Constraints

Bulk Supply Point

100 MW 190 MW

Wind Farm 100 MW

100 MW

50 MW

50 MW

Simplest SPS Allow increased pre-fault flows on the assumption that automatic control action will Prevent an overload

Bulk Supply Point

190 MW

Wind Farm 100 MW

100 MW

95 MW

95 MW

190 MW 0 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]

187 MVA

187 MVA

15 MW

200 MW

70 MW

80 MW 35 MW

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

187 MVA

187 MVA

Wind

15 MW

200 MW

70 MW

80 MW 35 MW

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

187 MVA

187 MVA

Wind

15 MW

200 MW

70 MW

80 MW 35 MW

SPS Example

Integrated Option: – Largest WF was selected as the most feasible location for the SPS

– All communications and actions could be incorporated within the same station

– Overload Relays would monitor flows on the Bally circuits

– In the event that overload was detected the 200 MW WF is tripped

– This scheme is Simple, Reliable, Fast and trips a single block of generation

187 MVA

187 MVA

Wind

15 MW

200 MW

70 MW

80 MW 35 MW

SPS Example

Integrated Option: – Works for trips at both ends

187 MVA

187 MVA

Wind 200 MW

70 MW

80 MW 35 MW

SPS Example

– Estimated 15 seconds between circuit trip and wind farm trip

– Circuits would not be damaged within this time

– Power flow needs to remain stable for 15 second period while max power flows

– Significant Power Flow issues with the extreme power shifts associated with the SPS scheme

– Angle difference and Vars absorbed by such large flows make the Power Flow scenario physically impossible

187 MVA

187 MVA

Wind 200 MW

70 MW

80 MW 35 MW

Summary of SPS Principles

SPS can be viable for local constraint issues Scheme should be binary Different schemes should not interact Schemes should not require Control Centre action post operation Schemes requiring 4-5 actions and tripping large amounts of generation are not ideal Level of generation tripped could be close to the largest infeed

Needs to be considered in terms of technical impact on the power system

SPS should not impact system security