Scheduling and Dispatch

Published Schedules

The system operator publishes a number of schedules on WITS to provide market participants an overview of what the inputs to the power system are leading up to real time. All the schedules produced in the Market System are listed in the summary document, with the inputs to each schedule and what information is published.

Constraint information is included in the schedules. The Constraint Overview document provides a summary of all the types of constraints used in the Market System, why and where they are used and also provides examples of their use.

GL-OC-208 SPD Constraint Overview [ pdf 206.69 KB ]
GL-OC-209 SPD Schedule Inputs [ pdf 113.38 KB ]

Reserve Adjustment Factors

Reserve Adjustment Factors (RAFS) will normally be 1. RAFs will be set to 0 following an Interruptible Load (IL) event as the dispatched reserves are no longer available (they have been converted to energy). Once the situation is stabilised and the IL is restored, the RAFs will be reset back to 1.

RAFs are no longer reduced for a shortage of offers. To cover a Contingent Event (CE), where there are insufficient offers and/or reserve offers in the current trading period, SPD will break one or more of the reserve constraints. This will result in a dispatchable solution that clears all available reserves and an amount of deficit reserve. If this situation also occurs in final pricing it will be treated as an infeasibility situation. This will normally be resolved by increasing the Net Free Reserve (NFR) variable to obtain a feasible final pricing solution.

CAN Winter Initiatives - Changes to Variable Reserves [ pdf 59.97 KB ]

Standby Residual Check

The Standby Residual Check (SRC) determines:

  • whether there are enough energy offers to meet demand after the loss of the largest risk (energy shortfall)
  • whether there are enough energy and reserve offers to meet demand after the loss of the largest risk and schedule reserves to cover the new risk (capacity shortfall).

The SRC information is available to registered Market Participants on WITS.  WITS displays a graph indicating when there is a shortfall situation. The data from the graph is also available.

SRC Training Presentation [ pdf 384.8 KB ]

SPD Model

The New Zealand power system is modelled for the purposes of Scheduling, Pricing, and Dispatch as a national set of nodes and branches connecting those nodes.

The  SPD diagram [ pdf 333.53 KB ] represents those nodes and branches, but does not provide any information on injection (generation) off-take (demand) on those nodes, or the power flow on the branches.

The Node names are defined by a seven-character alphanumeric code that links to the standard three-letter substation abbreviation and the node voltage (in kV) and bus number. For full names and geographic area, refer to the abbreviation list.

​For further information on dispatch services or the SPD model contact us at system.operator@transpower.co.nz

NIPS and SIPS

The New Zealand power system consists of the North Island Power System and the South Island Power system connected by a 1040 MW HVDC link between the two islands.

NIPS and SIPS are an electrical representation (single line diagrams) of the New Zealand Power system. These diagrams are intended to give an overview of the New Zealand power system and therefore show only the electrical connections on the system. 

Substation and Power Station names are shown by three letter codes. For full names and geographic area, refer to the Standard Site Abbreviation list.

Site Abbreviation List [ xlsx 390.8 KB ]
North Island - NIPS [ pdf 165.24 KB ]
South Island - SIPS [ pdf 111.11 KB ]

Substation Map

The Substation Locator Map shows the geographical location of the substations, power stations and transmission lines.

Substation Locator Map [ pdf 1.42 MB ]

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