Joint Grid Code Review Panel

POR Working Group

Meeting 2 27th March 2015

Chairperson : Michael Preston

Terms of Reference :Scope of Working Group It is proposed that a working group of the Joint Grid Code Review Panel be established to: • Develop an assessment methodology, to be used by the SOs, when deciding

whether a Generation Unit has complied with its required POR response, under its HAS contract and relevant Grid Code.

• The assessment methodology should take account of the inertia effect.

• The assessment methodology will be proposed to the JGCRP for approval.

• If necessary modifications will be proposed to the relevant Grid Codes in Ireland and Northern Ireland, as a result of this revised assessment methodology.

Terms of Reference :Scope of Working Group It is proposed that a working group of the Joint Grid Code Review Panel be established to:

• Review Modification Proposal MPID 252 to the Ireland Grid Code, regarding the definition of POR, and make a recommendation to the JGCRP regarding this modification, or a revised version of this modification. Also review consistency of this modification MPID 252, with the Northern Ireland Grid Code and the ENTSO-E Network Codes, and make a recommendation to the JGCRP on whether the Northern Ireland Grid Code requires any similar modification with regard to the definition of POR.

Terms of Reference :Scope of Working Group • Review the declaration process for POR (currently EDIL) and comment on

whether this should be changed to more accurately reflect POR capability of Generation Units, and if so investigate feasibility of implementing this (at a high level) and associated benefits.

Action from GCRP :In relation to MPID 265 Reactive Power : MP will assess the EDIL issue as part of the Scope of POR Working Group.

Deliverables :• Assessment methodology, to be used by the SOs, when deciding whether

a Generation Unit has complied with its required POR response, with supporting documentation, technical justification, and worked examples.

Grid Code Modifications required, if any, in Ireland and Northern Ireland to enable and/or support implementation of this assessment methodology.

• Recommendation regarding MPID 252 to the Ireland Grid Code: whether this modification (or a specific revised version of MPID 252 should be made to the Ireland Grid Code; whether a similar modification is required to the Northern Ireland Grid Code.

• Recommendation on whether declaration process (EDIL) change should be implemented for POR reserve and MVAr characteristics and if so include high level feasibility, benefit analysis.

Frequency RH scale Unit delta output 0MW = average -60 to -30 sec pre-event LH scale

Inertia only response from a non -governed steam turbine7/1/15 event

Primary Operating Reserve time period 5 to 15 seconds

Event start T=0 sec @ 49.8 Hz

Nadir ≈3 secPOR assessment @ 5 sec

Inertia only response from a non -governed steam turbine7/1/15 event

≈ 4 MW being absorbed from the system due to +ve ROCOF

Inertia only response from a non -governed steam turbine7/1/15 event

• Only events with the nadir before 5 sec require inertia adjustment

• Events with the nadir within 5 to 15 sec – normal assessment

Inertia output 0 at nadir where RoCoF = 0

Review of analysis

Limitations of methodology

• The calculation method does not account for the generator and power system interactions that occur immediately after a generation trip

• The analysis initiates that the calculated inertia MW value is reasonably accurate at 5 secs which is shortly after the frequency nadir with lower RoCoF values

• The application of the calculation will require a tolerance for the MW value

Review of analysis

134119

Review of analysis

Review of analysis

Review of analysis

Review of analysis

PMU analysis

PMU analysis

PMU analysis event 157 GI trip

PMU analysis event 164GI trip

Proposed assessment method

• The issue arose from the current assessment method which requires the POR assessment to be carried out at the lowest frequency during the POR period (5-15 secs)

• For events with the nadir before 5 secs the assessment was therefore carried out at 5 secs

• The proposed change to the assessment method is to calculate the inertial response of the synchronous generators as they react to the rising system frequency at 5 secs and take the calculated power value into account when determining POR performance

Existing assessment method

POR assessed at lowest frequency during 5 – 15 sec period

Unit output limit with available capacity Unit capacity limit

Unit output limit by sustained load capability

Unit output corresponding to governor droop

POR sustained load curve referenced at pre event unit output

Pre event frequency minus Nadir frequency ( = frequency delta)Frequency delta with governor droop to calculate droop lift requirement at frequency nadir time

POR requirement POR achieved

POR tolerance 1 MW

POR tolerance 10% of POR requirement max

Time of minimum frequency within 5 -15 secs periodNadir time within 5 -15 secs determined

minimum

minus

At NADIR time Unit output – pre event output

Fail if negative (reserve deficit after tolerance applied)

Proposed assessment method

• Inertia MW value at 5 sec calculated from RoCoF and generator H value

• RoCoF required from at least 100mS sampling rate source

• Use Tandragee event recorder frequency source initially for all Island

• Apply an error tolerance value to the inertia MW calculated value to increase the calculated value

• Tolerance value to be a % of the K value ?

• Either reduce POR requirement with inertia value Or • Increase POR achieved with inertia value

EDIL Reserve and Reactive

MVAr lagging MVAr leading

MW

EDIL declaration for Leading and Lagging at Max output

Reactive Capability Curves

P

Q

SR

T

U

MVAr lagging MVAr leading

MW

EDIL declaration for range of points Reactive Capability Curves

MW output

MW Reserve

Reserve Curves

EDIL declaration Maximum

MW output

MW Reserve

EDIL declaration for range of points

Reserve Curves

MW output

MW Reserve

EDIL declaration for range of points

Reserve Curves