Planning for New Zealand’s Inter-Island HVDC Pole 1 ... · PDF filePlanning for New Zealand’s Inter-Island HVDC Pole 1 ... 220 kV HAYWARDS ... -350 kV 2 kA HVDC LINK SINGLE LINE

Planning for New Zealand’sInter-Island HVDC Pole 1

Replacement

Peter GriffithsMohamed Zavahir

EEA Conference 2007 : Engineering – Our Future

Inter-Island HVDC Pole 1

• A brief history• Benefits• Why replace?• Earliest date for replacement• Retirement planning• Selecting the preferred replacement option• Planning and engineering for replacement• The way forward


Inter-Island HVDC Link

Benmore

Haywards

DC Line - 570 km

DC Cables - 40 km


Original Inter-Island HVDC Link (1965)

– Mercury arc valves– World’s 4th HVDC scheme; 3rd to include submarine cables– 600MW bipolar +/-250kV link– DC line - 570km; DC cables (x3) – 40km


Hybrid Upgrade (1993)

– DC line upgraded; new DC cables (x3) – 350kV– Original MAV link upgraded to 270kV and paralleled to form

Pole 1 - 540MW 270kV – New thyristor valve Pole 2 – 700MW 350kV– New control systems– 1240MW bipolar scheme reduced to 1040MW following

decommissioning of the last original cable in 1997


HVDC Configuration as at present - Total 1040 MW

Pole 1

Pole 2


Wilton

Bunnythorpe

Linton

220 kV HAYWARDS

110 kV HAYWARDS(8 110 kV Circuits)

216/200/80 MVAT2

C2

60 MvarT5

35 Mvar 35 Mvar

C4 C3

40 Mvar

C1

40 Mvar60 Mvar

47.5Mvar

Filters(5, 7, 11, 13 + HP)

47.5Mvar

T1

y/y

C8

65 Mvar

C9

65 Mvar

y/

VG4

POLE1B

C10

65 Mvar

C7

65 Mvar

y/y150/172/66 Mvar

98.5 kV

VG2

High Speed Switch

POLE1A

0.8 H

0.8 H

0.8 H

0.8 H-270 kV

2 kA

Rated at 1.43 kA

Rated at 1.43 kA

Rated at 1.43 kA

Rated at 1.43 kA

46.3Mvar(24th)

60Mvar(12th)

Filters

46.3MVAr(24th)

60Mvar(12th)

Filters

Filters,(5, 7, 11, 13 + HP)

y

652.6/326.1/326.1 MVA815.4/407.7/407.7 MVA overload220/143.9/143.9 kV3 3

350 kV1.6/2.0 kA

0.16 H

POLE 2

y

y

y

652.6/326.1/326.1 MVA815.4/407.7/407.7 MVA overload220/143.9/143.9 kV

3 3

350 kV1.6/2.0 kA

0.16 H

POLE 2

Neutral Switch

VG3

Te Hikowhenua

Neutral Switch

VG3

Commutating Breaker25 km

Commutating Breaker25 km

Bog Roy

110 kVVG1 135 kV

1200 AVG1135 kV

1200 A

y/

y/

VG2

VG4POLE

1A

POLE1B

187.5 MVA

79.3Mvar

(11/13th)

Filters

79.3Mvar(24th)

Filters

/

/

220 kV BENMORE16 kV BENMORE

G1

G3

G2

G4

G5

G6

y/

Filters(5, 7, 9, 11, 13 + HP)

y/

50.5Mvar

y/

50.5Mvar

200/200/60 MVA

y

y

Filters(5, 7, 9, 11, 13 + HP)

6 x 112.5 MVAHydro Generators

Aviemore 1

Twizel

Ohau C

Ohau B

-350 kV2 kA

HVDC LINK SINGLE LINE DIAGRAM NORTH TRANSFER

Aviemore 2

Haywards Benmore


Benefits of HVDC link

• Certainty to Energy Market – Linking both island markets– Widening the market base

• Energy security between the two islands• Ramp up and self cover – reduce reserve

requirement• Power system stability

– Modulation functions (voltage, and frequency stabilisation)• Spinning reserve sharing between the islands• Increased choice of locating generation• Balancing renewable and intermittent generation


Why Replace MAV Pole 1?

• One of only two mercury arc valve (MAV) based HVDC systems still in service– Vancouver Island MAV pole

• Younger• Intermittent operation• Operates in parallel with an AC cable link

• Primary equipment now over 42 years old– 45 years old in 2010– Spares are the same age– Additional spares can’t be source for some key components

• No other HVDC plant using similar technology has reached 40 years of service before replacement or removal


Why Replace MAV Pole 1?

• Combination of risks factors– Technical obsolescence– Seismic– Fire– Environmental– Main circuit equipment performance– Control system equipment performance

• Higher level of maintenance required for Pole 1• Pole 2 availability and reliability is consistently

superior to Pole 1• Unlock existing infrastructure capacity• Improve functionality


Earliest Date for Replacement

• If a replacement option is economic - earliest approval would be mid-2008– Economic investment– Expected net market benefit must be > 0

• At least 4 to 5 years from approval to implement (2012)– longer for options with new transmission lines


MAV Pole 1 Retirement

• Gap between planned retirement (2010) and earliest possible replacement (2012)

• Transpower reviewing strategies for extending operation beyond 2010 through to 2012– Retirement plan under review– Primary equipment will be over 47 years old by 2012– No plan to carry out major life extension works for operation

past 2012


Level of detail

Long list of options

Long-short list of options

Short list of options

Preferred option

OPTIONS SCREENING

OPTIONS RANKING

GRID INVESTMENT TEST

OPTIONS IDENTIFICATION

Number of options

Exp

lora

tion

Red

uctio

n

Identifying the Preferred Option


HVDC Preparatory Work

Identifying HVDC Environmental issues, setting up process for approval and resource Consents

Environmental Investigations

Engineering studies relevant to overload rating of Pole 2, synchronous condensers at Haywards, noise assessments, seismic issues, civil work requirements, AC switchyard layouts, submarine cables, and improved cost estimates.

Engineering Investigations

Load flow, dynamic and harmonic analysis, initial design studies, and production of performance specifications.

System Investigations

Scope of WorkActivity


System Studies

• HVDC power system analysis to identify possible AC/DC system interaction issues

• Enable preparation robust performance specifications including desired control system functionality.


Identify potential substation configurations, transfer capacity requirements and preliminary design considerations including system strength and reactive support requirements.

Planning Studies


Determine distortion limits, harmonic levels, harmonic impedances and parameters for inclusion in performance specifications for the harmonic filters and control system.

Planning Studies

Harmonic Analysis


Planning Studies

Harmonic Analysis

Reliability Assessment

Determine the optimal configuration and converter rating for Pole 1 taking into account the spares requirement and Pole 2 ratings


Planning Studies

Harmonic Analysis


Initial Design Studies

- Consolidate findings from preceding activities -Identify the preferred system configuration for detailed analysis, and- Provide input into Engineering Investigations.


Planning Studies

Harmonic Analysis



Transient Analysis

- Verify operation of the HVDC system at possible operating conditions, - Assess dynamic interaction - Identify the need for any special dynamic control or special protection.


Planning Studies

Harmonic Analysis



Transient Analysis

Control System Analysis

Verify steady state and transient performance and special control functionality for enhancing system performance.


Planning Studies

Harmonic Analysis



Transient Analysis


Performance Specifications

Produce performance specifications for all major systems including the converter poles, and control and protection systems for Pole 1, Pole 2 and Bipole.


Planning Studies

Harmonic Analysis



Transient Analysis


Performance Specifications


Planning criteria

• Economic investment– Energy transfer benefits– Assessment of dynamic benefits difficult– Dry year security is not a determining criteria

• Equivalent short circuit ratio of 2.5– Short circuit ratio, SCR = Short circuit capacity/HVDC_Capacity– ESCR = (Fault Level – Filter MVA)/HVDC_capacity

• N vs N-1 criteria– Application of runbacks

• North vs South flow benefits• Natural transfer limits

– North Flow determines HVDC equipment and augmentation requirement

– Resulting South Flow limits


Engineering investigations

• Pole 2 Overload Investigation– Pole 1 equipment rating and reserve requirement– Critical equipment being analysed by Supplier

• Submarine Cable Survey and Route Investigation

– Need additional cable for 1400 MW rating– Spare consideration (practicality and economics)– Desktop study of route in Cable Protection Zone– Treatment of disused cables

• Engineering Feasibility Studies…


..Engineering Feasibility Studies• Synchronous condensers

– Condition assessment– Preferred configurations to connect synchronous

condensers via 110kV or 220kV• Substation

– Detailed noise assessments, particularly Haywards– Seismic design issues at the converter stations and cable

terminal stations– Switchyard layouts and transition staging plans– Civil work investigations for location of additional equipment– Conceptual civil design for high level cost estimates– AC equipment assessment to confirm suitable ratings of

existing equipment– Functional specifications


Environmental Investigations

• Approvals concerning work – At Benmore and Haywards substations– At Oteranga Bay and Fighting Bay cable terminals– Additional Cook Strait cables

• Ultimately to include – Status confirmation with regional plans; – Confirming suitable approaches with Councils;– Consultation with affected parties; – Preparation of applications for resource consents– Assessments of effects on the environment.


Way Forward

ShortList

To E

lect

ricity

Com

mis

sion

8 June 2007

Consultation/Workshops

31 July 2007

GIT

October 2007

Long/ShortList GUP

December 2007

GIT Data Book Published

22 May to 22 June


www.gridnewzealand.co.nz/n278.html#


Questions?

Documents

Planning for New Zealand’s Inter-Island HVDC Pole 1 ... · PDF filePlanning for New Zealand’s Inter-Island HVDC Pole 1 ... 220 kV HAYWARDS ... -350 kV 2 kA HVDC LINK SINGLE LINE