Pre-registration commissioning under an exemption is a way for a new generating system to energise and export a small amount of power before it is registered with AEMO, so that inverters, the plant controller, SCADA and protection can be proven early. The export is capped below the level that would require registration, and the testing is controlled by a temporary operating protocol agreed with the network service provider (NSP) and AEMO.
It is not a shortcut around the hold point program. It is a way of finding problems while the consequences are small. The terms are set case by case, so treat everything below as typical practice rather than a rule.
Why Projects Do It
Hold point testing under the GPS commissioning program starts once registration and the relevant approvals are in place. By then the program is under pressure and every problem found costs time with the whole plant waiting. Exporting a few megawatts earlier lets the team:
- prove the first inverters, their settings and their communications with the plant controller
- check SCADA points end to end, including the data the NSP and AEMO will monitor
- record power quality with the plant actually generating
- confirm protection operates as designed under load
- fix firmware and configuration issues before they affect the whole plant
Our article on why commissioning runs late explains why finding these issues early is worth the effort.
How It Is Typically Structured
| Element | Typical arrangement | Purpose |
|---|---|---|
| Export cap | A small export limit, below the registration threshold, enforced in the plant controller with margin | Keeps the plant within the exemption |
| Units in service | One inverter at a time, or a small group | Limits impact and isolates problems |
| Control mode | Fixed active and reactive power setpoints; voltage droop not used | Predictable behaviour while controls are unproven |
| Test steps | Active power in small increments with dwell times; reactive steps towards the inverter's limit; ramp to zero between blocks | Builds confidence progressively |
| Monitoring | Continuous power quality recording at the connection point; SCADA visibility for the NSP | Evidence and early warning |
| Exceedance handling | A flag in the NSP's SCADA if the cap is exceeded, with defined consequences | Enforces the cap |
| Contacts | A named daily contact for the control room | Clear communication |
The export cap
The cap is enforced by the plant controller, set below the exemption limit to leave margin for measurement error and transients. The NSP will usually want visibility of the plant's export in its own SCADA, and an alarm if the cap is exceeded. Repeated exceedance is typically grounds for disconnection, so the controller configuration should be audited before the first megawatt is exported.
One inverter at a time
Energising and loading inverters individually keeps the plant's impact on the network small and makes it easy to attribute behaviour to a specific unit. Inverters not under test are isolated, often with their low-voltage breakers locked out, so none can connect inadvertently. The lockout arrangement belongs in the temporary operating protocol.
Fixed control modes
Voltage droop and other closed-loop plant-level controls are normally not used at this stage, because they have not been tested and because a single inverter cannot represent the plant's full response. Fixed active and reactive power setpoints give predictable behaviour.
Evidence the NSP and AEMO May Ask For
Even at a few megawatts, the NSP and AEMO may ask for evidence that the commissioning activity cannot affect system security. A simple approach that has been accepted is a single-machine infinite-bus study at the minimum fault level, showing that one inverter moving between its full reactive limits changes the connection point voltage by a small fraction of a percent. A change that small cannot have a material stability impact.
Other evidence commonly requested:
Pre-Registration Commissioning Pack
- Temporary operating protocol: scope, export cap, units in service, control modes, contacts, lockouts
- Settings audit of every inverter to be energised, against the approved parameter list
- Plant controller export limit configuration and test
- Point-to-point SCADA checks for the signals the NSP will monitor
- Power quality recording to the relevant IEC measurement standards for the duration of testing
- Protection settings applied and tested on the connection point equipment
- Stability evidence for the commissioning configuration
- Test schedule with daily notification to the control room
Power Quality Recording
Continuous power quality recording at the connection point throughout pre-registration commissioning serves two purposes. It confirms the plant's emissions are within expectations as inverters are added, and it builds a record that can be compared with the background measurements taken before energisation. That comparison is far easier to interpret with one or two inverters running than with the whole plant. Our article on AEMO hold point testing covers the background measurement stage.
Common Problems Found Early
The value of exemption testing lies in what it finds. Typical issues that surface in the first days of generating include:
- inverter parameters that differ from the approved parameter list, often because a unit was shipped with a default or older configuration
- firmware versions that differ between inverters, or from the version the models were built on
- plant controller export limits configured on the wrong base or in the wrong units
- SCADA points mapped to the wrong signal, scaled incorrectly or missing from the NSP's display
- metering and protection CT or VT ratios entered incorrectly
- communication dropouts between the plant controller and inverters under real operating conditions
Each of these is quick to fix with one inverter running and a small export cap. With the whole plant at a hold point, each one becomes a stop, an investigation and a re-test. Record every finding and its resolution, because the NSP will want to know the same issue cannot recur on the remaining units.
Handing Over to Hold Points
Pre-registration commissioning ends when the plant is registered and the first GPS hold point begins. A clean handover needs:
- the settings audited during exemption testing carried forward unchanged, or changes documented
- the temporary operating protocol withdrawn and the permanent operating arrangements in place
- the power quality records and test results packaged for the NSP
- any issues found during exemption testing closed, with evidence
The hold point program then proceeds through increasing capacity with GPS compliance tests at each stage. Problems already found and fixed during exemption testing are problems that will not stop a hold point.
Is It Worth Doing?
For a large solar farm or battery, usually yes, provided the exemption can be agreed in time to be useful. It needs a well-prepared protocol, a disciplined site team and a cooperative NSP. The effort is small compared with discovering a firmware or SCADA problem with the whole plant waiting at a hold point.
Get Commissioning Planned Early
ElectraGlobe prepares commissioning plans, temporary operating protocols and test procedures for solar and BESS projects, and supports testing on site. See our construction management service, our article on commissioning a 5 MW solar farm, or contact us.
Frequently Asked Questions
Can a solar farm export before it is registered with AEMO?
In some cases, under an exemption that caps export below the registration threshold. The terms are agreed case by case with AEMO and the NSP and are controlled by a temporary operating protocol.
Why test one inverter at a time?
It keeps the plant's impact on the network small, makes it easy to attribute any behaviour to a specific unit, and allows problems to be fixed before more equipment is energised.
Is voltage control tested during exemption commissioning?
Usually not. Inverters are typically run with fixed active and reactive power setpoints, and plant-level closed-loop controls such as voltage droop are tested later during the hold point program.
Does pre-registration commissioning replace hold point testing?
No. It is additional early testing. The GPS hold point program still has to be completed after registration.