Clarification regarding small embedded generation requirements
This Industry News confirms recently advised changes to inverter installations and clarification of related matters, including export limit of 5kW for single phase, two-phase arrangements, single phase upgrades, addition of battery storage, and application of voltage control in inverters.
Background
South Australian customers are continuing to install solar photovoltaics (PV) with nearly one in three households in South Australia now having solar panels on their roofs.
PV by nature provides maximum power output during the middle of the day when there is typically low load on the network but provides minimal or no generation during peak consumption periods (5pm – 8pm).
High penetrations of such systems can impact power quality for neighbouring customers as well as reducing the effectiveness of the customer’s PV system itself. With the significant increase in the number of PV installations in South Australia, there is need to manage this more closely to minimise power quality issues for customers.
Changes to the Australian Standard, AS/NZS4777, including the reduction of the maximum singlephase inverter system from 10kW to 5kW, have been introduced in South Australia to help manage these issues. As of the 1 December 2017, SA Power Networks requires customers to meet the requirements of AS/NZS4777:2015 for inverter energy systems installed after this time.
The Service & Installation Rules and Technical Standard TS129 -Small Inverter Energy Systems (IES) – Capacity not exceeding 30kW have been updated to reflect this, and should be referenced when designing or commissioning systems.
New single-phase installations
As previously advised, SA Power Networks has adopted the updated AS/NZS4777 requirements to allow a maximum total inverter system size of 5kW for a single-phase system. A system up to 10kW of inverter capacity may be installed, provided it is export limited to 5kW as shown in the tables for the different scenarios.
| Inverter size | Export to grid | |
|---|---|---|
| ≤ 5kW | ≤ 5kW | Permitted |
| > 5kW and ≤ 10kW | ≤ 5kW | Permitted |
| > 5kW and ≤ 10kW | > 5kW | Not Permitted for single phase* |
| > 10kW | ≤ 5kW | Not Permitted for single phase* |
*three-phase supply conversion may be required.
For a two-phase system (ie two single phase inverters connected to different phases), each inverter must be similarly limited to 5kW export as shown in scenario 1 in the gallery below.
| Hybrid inverter size | Export to grid | |
|---|---|---|
| ≤ 5kW | ≤ 5kW | Permitted |
| > 5kW and ≤ 10kW | ≤ 5kW | Permitted |
| > 5kW and ≤ 10kW | > 5kW | Not Permitted for single phase* |
| > 10kW | ≤ 5kW | Not Permitted for single phase* |
*three-phase supply conversion may be required
Upgrade of an existing single-phase installation
Adaption of the new Australian Standard AS/NZS4777:2015 may introduce limitations for a customer with an existing PV inverter who wishes to add a battery storage system. Following a review, SA Power Networks has further clarified its requirements for upgraded systems.
A battery storage system can be added to an existing PV installation, provided the total size of all inverter systems is 10kW or less, and exports must be limited to no more than 5kW for a singlephase. If the required hybrid system is larger, a three-phase system will generally need to be installed.
However, if the existing approved PV inverter allows the export to the grid in excess of 5kW, the existing PV export capability may remain (ie if the current approved PV system is 6kW then the allowable limit will remain at 6kW). To assist in managing the export requirements, a battery storage system with zero export capabilities must be installed (refer to Scenario 3 in the gallery below).
| Existing PV inverter size | New battery inverter size | PV export to grid | Battery export to grid | |
|---|---|---|---|---|
| ≤ 5kW | Up to total inverter capacity of 10kW | As per existing approved export limit | Combined PV and battery export ≤5kW | Permitted |
| > 5kW and ≤ 10kW | Up to total inverter capacity of 10kW | As per existing approved export limit | 0kW | Permitted |
Three-phase systems
For three-phase systems, the inverter energy system must have a balanced output with the imbalance between phases being no greater than 5kW. For small embedded generating systems, the maximum capacity of a three-phase system is 30kW.
Inverter voltage response modes
SA Power Networks’ customers have experienced an increase in the number of PV related power quality issues. In the past three months, reports have more than tripled the historic average. This increase can be attributed to the increased number of PV systems connected to the grid and to the new inverters implementing AS/NZS4777.2:2015 which specifies greater sensitivity and management of over-voltage conditions.
Inverters that are AS/NZS4777.2:2015 compliant have the capability to self-manage over-voltage conditions before they occur, minimising the likelihood of the inverter cutting out. This capability is referred to as Voltage Response Modes. As of the 1 December 2017, SA Power Networks will require all new PV installations to switch on this capability as part of the embedded generating system approval.
The electrical contractor/installer must ensure the South Australian power quality response mode has been set in the inverter(s) and must not be changed without written approval from SA Power Networks. These settings must be validated and tested by the electrical contractor/SEG installer.
The South Australian power quality response modes are shown in TS129 -Small Inverter Energy Systems (IES) – Capacity not exceeding 30kW.
The changes highlighted in this ‘Industry News’ will be included in the Service & Installation Rules and TS129 -Small Inverter Energy Systems (IES) – Capacity not exceeding 30kW which will be the reference documents for these changes.
For any further inquiries regarding the connection of small embedded generation to our network email seg@sapowernetworks.com.au