Interconnectors

Why interconnectors matter

Interconnectors allow power to move from regions with surplus (and lower spot prices) to regions with higher demand (and higher prices). They can reduce the need for extra local generation and often narrow price differences between regions—but only when capacity is available. When an interconnector is constrained, additional flow is not possible even if prices differ, which drives regional price separation and volatility.

NEM interconnectors at a glance

The table below summarises the main interconnectors and their nominal capacities by direction. All values are in MW. Ranges indicate that capacity depends on network and generation conditions.

Terranora (N-Q-MNSP1)

Terranora is the flow across the two 110 kV lines from Mudgeeraba (Queensland) to Terranora (New South Wales). It connects to the NSW network via Directlink, a DC link commissioned in 2000 with three bipolar DC cable pairs (each 60 MW), forming the first transmission link between NSW and Queensland. Local load around Terranora means the nominal capacity differs from Directlink’s raw rating. Limits are often set by thermal constraints in northern NSW (e.g. N>N-NIL_LSDU) or by rate-of-change limits on Directlink (NQTE_ROC, QNTE_ROC).

Nominal capacity: NSW→QLD 107 MW; QLD→NSW 210 MW.

Queensland to New South Wales (NSW1-QLD1 / QNI)

QNI is defined as flows across the two 330 kV lines between Dumaresq (NSW) and Bulli Creek (Queensland). The AC link was commissioned in 2001 and includes double-circuit 330 kV and 275 kV lines (Armidale– Dumaresq–Bulli Creek–Braemar–Tarong), transformers at Braemar, and later connections for Millmerran, Braemar, Kogan Creek and Sapphire wind. A “QNI minor” upgrade (Transgrid and Powerlink, 2022) uprated Liddell–Muswellbrook–Tamworth 330 kV lines and added SVCs and shunt capacitors; when fully proven, it is expected to support higher transfers (e.g. up to ~1,450 MW NSW→QLD and ~950 MW QLD→NSW).

NSW→QLD flow is mainly limited by thermal overload on Bayswater– Liddell 330 kV (N>>NIL_33_34). QLD→NSW is limited by voltage collapse for loss of Sapphire–Armidale (8E) (Q^^N_NIL_SRAR) and thermal limits on Port Macquarie–Herron Creek, Tamworth–Liddell, Tamworth–Muswellbrook, Armidale–Tamworth and Uralla–Tamworth 330 kV lines. Historically, oscillatory stability and voltage collapse limits also applied; Phasorpoint availability can affect the oscillatory limit.

Nominal capacity: NSW→QLD 850 MW; QLD→NSW 1,400 MW.

Victoria to New South Wales (VIC1-NSW1)

VIC1-NSW1 is the flow across the 330 kV Murray–Upper Tumut (65), Murray–Lower Tumut (66), Jindera–Wodonga (060), the 220 kV Buronga– Red Cliffs (X1, X9), the 132 kV bus tie at Guthega (normally open), and the 330 kV Buronga–Bundey (6F) line. It replaced the former SNOWY1 and V-SN interconnectors from 1 July 2008. The VNI Minor upgrade (March 2023) added a second 500/330 kV transformer at South Morang, re-tensioned Dederang–South Morang 330 kV lines, and installed modular power flow controllers. Project Energy Connect (PEC) Stage 1 (late 2024) replaced the original Buronga–Red Cliffs line with X1 and X9 and added 6F to the VNI definition; 6F will move to a new NSW–SA interconnector with PEC Stage 2.

Nominal capacity depends strongly on Murray (NSW) and Tumut (NSW) generator output. VIC→NSW is limited by voltage collapse (e.g. 220 kV north-west Victoria, APD potlines), thermal limits on Murray–Upper Tumut and Yass transformers, and transient stability (Hazelwood–South Morang). NSW→VIC is limited by voltage collapse (e.g. loss of largest VIC generator or Basslink, north-west VIC generation) and thermal limits (e.g. Elaine–Moorabool 220 kV). Proposed augmentations include VNI West and HumeLink.

Nominal capacity: VIC→NSW 400–1,700 MW; NSW→VIC 400–1,900 MW.

Basslink (T-V-MNSP1)

Basslink is the DC cable between George Town (Tasmania) and Loy Yang (Victoria), commissioned in early 2006 when Tasmania joined the NEM. It includes the undersea DC cable, converter stations and control schemes in Tasmania. Unlike other NEM DC links, Basslink has a frequency controller and can transfer frequency control ancillary services (FCAS) between Victoria and Tasmania.

Limits in both directions are often set by FCAS constraint equations for mainland and Tasmanian contingencies; capacity can be reduced when load or generation available for the Tasmanian frequency control special protection scheme (FCSPS) is limited. TAS→VIC (594 MW at Loy Yang) is mainly limited by low fault level at George Town (T^V_NIL_9). VIC→TAS (478 MW at George Town) is mainly limited by transient stability for a fault and trip of a Hazelwood–South Morang line. For several years Basslink often ran below nominal capacity to manage undersea cable thermal loading; a Cable Loading Prediction System (CLPS) entered service in mid-2024, allowing operation up to nominal capacity subject to pre-loading conditions.

Nominal capacity: TAS→VIC 594 MW; VIC→TAS 478 MW.

Heywood (V-SA)

The Heywood interconnector is the flow across the 275 kV lines between Heywood (Victoria) and South East (South Australia). It was commissioned in 1989 from Victoria’s western 500 kV network at Heywood (near Portland) to Para in SA, with connections to the parallel 132 kV network in south-east SA. A 2015/16 upgrade added a third transformer at Heywood, series capacitors at Black Range and network changes; the design limit is up to 650 MW each way, but tested limits are 600 MW VIC→SA and 550 MW SA→VIC and remain in place pending further stability testing and review (including post–SA black system work). PEC Stage 1 extended the V-SA definition to include the Buronga–Bundey (6F) 330 kV line; 6F will be removed from V-SA with PEC Stage 2 when a new NSW–SA interconnector is registered. PEC Stage 1 testing aims to verify Heywood to 650 MW each way on the Heywood–South East lines.

VIC→SA (600 MW) can be limited by transient stability (loss of largest SA generator or South East–Tailem Bend 275 kV), rate of change of frequency (loss of both Heywood–South East lines), under-frequency load shedding, and Hazelwood–South Morang transient stability. SA→VIC (550 MW) can be limited by voltage collapse (e.g. Haunted Gully–Moorabool and APD potlines). The combined Heywood and Murraylink limit SA→VIC was increased to 580 MW (January 2011) based on oscillatory stability with Phasorpoint; when Phasorpoint is out of service the combined transfer is limited to 420 MW. During forecast destructive wind conditions, a 250 MW import (VIC→SA) limit on Heywood applies under the contingency reclassification framework (the former SA protected event was revoked in 2023).

Nominal capacity: VIC→SA 600 MW; SA→VIC 550 MW.

Murraylink (V-S-MNSP1)

Murraylink is the flow across the DC cable between Red Cliffs (Victoria) and Monash (South Australia). It is a 220 MW DC link commissioned in 2002, with runback schemes in SA and Victoria to manage thermal issues in the Riverland and western Victorian 220 kV network. ElectraNet increased thermal capacity of Robertstown– North West Bend and North West Bend–Monash 132 kV lines in 2016/17; dynamic line rating may further increase capability at times.

VIC→SA transfers are mainly limited by thermal overloads on Monash– North West Bend #2 and North West Bend–Robertstown #1 132 kV lines, and by voltage collapse for loss of Darlington Point–Buronga (X5) 220 kV when the NSW Murraylink runback is out. Prior to VNI Minor, SA→VIC was also limited by South Morang F2 transformer thermal limits.

Nominal capacity: VIC→SA 220 MW (at receiving end); SA→VIC 200 MW (at receiving end).

Planned and proposed links

Project Energy Connect (PEC) is a new link between NSW and South Australia. Stage 1 (completed late 2024, testing early 2025) includes double-circuit 275 kV Bundey–Robertstown, 330 kV Bundey–Buronga (one circuit energised), replacement 220 kV Buronga– Red Cliffs (X1, X9), phase-shifting transformers and synchronous condensers at Buronga. PEC Stage 1 nominal capacity is 150 MW in both directions (initially limited by Buronga phase-shifting transformer thermal until the remaining units were commissioned). Stage 2 (planned late 2026) adds 330 kV Buronga–Dinawan–Wagga Wagga and reactive plant; full PEC is expected to have 800 MW each way and to allow Heywood to reach 750 MW each way, with a new SA–NSW interconnector registered and Heywood/VNI returning to their pre-PEC definitions.

Marinus Link is a proposed second DC interconnector between Tasmania and Victoria (TasNetworks), in two stages of 750 MW each (e.g. Heybridge–Hazelwood HVDC and associated transmission), with Stage 1 targeting commissioning around 2030.

AEMO interconnector variables

supagrid uses AEMO dispatch interconnector data aligned to 5-minute settlement intervals. The table below describes the main variables available for interconnector analysis (e.g. in the Command Centre or data export). Positive flow is typically defined as flow into the “to” region; import/export limits follow AEMO’s SouthEast / NorthWest convention.

For current limits and constraint equations, see AEMO’s MMS Data Model (DispatchInterconnectorRes), Monthly Constraint Report, and Annual NEM Constraint Report. Nominal capability is described in AEMO’s Interconnector Capabilities publication.

Related

Regions & Interconnectors covers how regions and interconnectors affect pricing and constraints. For AEMO variable definitions across the platform, see AEMO variables.