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Security Management

The System Operator implements security policies as defined in Transpower’s connection contract.

The Policy Statement and Procurement Plan provide further information on security policies and the reasons for adopting them.

Specific security studies and co-ordination activities may occur on request to address anticipated security situations, up to about a year in advance. Current forums on short-term security issues can be found in our Consultation section.

The System Operator prepares a System Security Forecast (SSF) to identify potential longer term security and quality requirements.

Outage Planning

Outage Co-ordination is an essential part of managing the operation of the power system in a secure and efficient manner. The Planned Outage Co-ordination Process (POCP) was agreed by the Planned Outage Forum in Oct 2002, and presented to the Grid Security Committee in Nov 2002.

A review of the POCP is currently underway. 

• Planned Outage Co-ordination Process Review

A POCP website has been established to host the prototype outage database and a detailed User Guide to the POCP. 

• http://pocp.redspider.co.nz/

Security Constraints

SPD will normally dispatch the lowest-cost generation to meet demand (allowing for co-optimisation of energy and reserves).

When unconstrained dispatch does not allow the System Operator’s security policies to be met - e.g. if transmission assets are expected to be operated beyond rated short-term capability after any defined contingent event - then a security constraint is applied in SPD.

Security constraints may be applied as:

• a temporary constraint - to deal with an outage situation when some assets are not available
• a permanent constraint - when the normal integrated power system capability and expected generation offers and demand may not result in secure operation.

The Excel spreadsheet below provides a current list of both permanent and temporary security constraints. This file is published by close of business every Monday.

Procedures for Managing Security Constraints

The System Operator uses a number of procedures to manage the creation and maintenance of security constraints.  We have published a combination of procedures and summary flow charts that may be of interest to market participants:

System Operator Constraint Audit

At a settlement meeting in July 2005 the System Operator agreed to commission an audit of its processes for designing, developing, testing and applying constraints and the process of removing constraints.  The audit was included in the System Operator's 2005/6 internal audit plan and was completed by Elliston Power Consultants Limited.

The audit report and a summary of the recommendations and resulting actions are below:

Manual Load Shedding

Manual Load Shedding is the final step in a process that begins, where possible, with the System Operator communicating with the distributors regarding an impending or current Grid Emergency and the likely demand reductions required.

The Electricity Governance Rules require each distributor to maintain an up to date process for the disconnection of demand for points of connection, which has agreement of both the Grid Owner and System Operator.

A template of the Distributor Manual Demand Disconnection Process is available for use by distributors.

If our template is used by the distributor for manual load shedding, the EGRs requirements are met and the distributor is only required to submit the information as requested in the Distributor Demand Shedding Data Sheet available below.

If the distributor chooses to use a different process for manual load shedding then the System Operator will need to:

• assess the documents for suitability and accuracy
• request Grid Owner Approval for the MLS and process
• confirm approval of both Grid Owner and System Operator by letter to the distributor.

If distributors do not have a letter confirming agreement to Manual Load Shedding Schedules at their points of connection, they are requested to submit their MLS details in the format above.

All manual load shedding data is to be sent to system.operator@transpower.co.nz