IEEE Power & Energy Magazine - November/December 2020 - 30

to accommodate all additional DERs. This could be
achieved through a combination of network augmentation (such as investment in voltage regulators) and
non-network solutions, such as demand management.
2) It could start applying static connection limits to new
DERs, which might result in "zero-export limits" for
DERs in parts of the network that are at their technical
capacity (i.e., no exporting is allowed).
3) It could apply dynamic export limits ("flexible export
connections"), meaning that DER export limits could
vary depending on actual conditions when there are
periods of export below the current 5-kW limit and
potentially during periods when the export exceeds
this threshold.
A techno-economic analysis indicated that enabling
dynamic export limits would provide the greatest net economic benefit to all consumers, and hence this is SAPN's
proposed approach. The application is currently under
review by the Australian Energy Regulator as part of the
revenue determination process conducted every five years (it
is also referred to as a general rate case in some regions). If
dynamic export limits are approved, SAPN plans to implement flexible export connections for all small and medium
DERs by 2023.
A key component of this solution lies in the establishment
of a standard web interface to communicate dynamic export
limits to smart inverters, aggregators, and VPPs. SAPN is
already undertaking preliminary trials in this area in conjunction with VPP operators in South Australia and planning a

larger pilot to extend this capability to smart solar inverters in
2021. This will be undertaken in collaboration with another
DNSP, leading inverter manufacturers, and a gateway vendor.
SAPN is planning to adopt Standard for Smart Energy Profile
Application Protocol, IEEE Standard 2030.5, which is also
being applied in California as part of Rule 21. SAPN has leveraged the work undertaken by the standard-setting organization SunSpec Alliance and is identifying which aspects of
IEEE Standard 2030.5 should be applied in the South Australian context. A 24-h forecast series of export limits is expected
to be communicated to solar inverters, VPPs, and aggregators
every 5 min on a rolling basis, with the technical architecture
appearing in Figure 14.

System Security
Challenges
A growing body of evidence indicates that D-PV generation
poses significant system security challenges in NEM, due
to the response of inverters en masse during major power
system disturbances and the continued "hollowing out" of
the daytime system load. This section focuses on the D-PV
disturbance response. However, it is important to note that
reduced system load profiles have begun to impact operations
in South Australia due to the region's high share of D-PV
generation relative to the local underlying demand and weak
transmission interconnection with neighboring regions, making the state more susceptible to islanding from NEM. For
further details, please refer to "Renewable Integration Study

2018, Actual

Rural, Single Customer (2%)

2025 Forecast
(Neutral Uptake)

Old Underground (2%)

Current 5-kW
Export Limit

Small Overhead (2%)
Rural Township, Small (3%)

Voltage Limit
PV Penetration
Thermal Limit

Rural, Two to Four Customers (6%)
Rural Township, Large (7%)
Large Overhead (11%)
Rural Township, Medium (15%)
New Underground (24%)
Medium Overhead (26%)
0

3
4
5
6
7
D-PV Capacity per Customer (kWp)

figure 13. The modeling outputs for the SAPN hosting capacity. The orange bars indicate the D-PV capacity per customer that networks of each type can accommodate before voltage limits are exceeded. The length of the bar reflects the statistical variability between individual networks of a given type. The purple bars represent the amount of D-PV generation
per customer before thermal limits are reached due to a reverse current flow. The green bars show 1) the average level of
D-PV penetration in 2018 and 2) the forecast level of penetration in 2025. For further details, please refer to "Low-Voltage
Management Business Case" in the "For Further Reading" section. kWp: kilowatts peak.
30

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IEEE Power & Energy Magazine - November/December 2020

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