IEEE Power & Energy Magazine - November/December 2020 - 26

450

216 V (Nominal -6%)

V99% ≤253 V

V01%
V50% (Median)
V99%

400
350

87.7% of
V50% ≤244 V

300

250

200

150

4.4% of
V01% ≤216 V

100

260

258

256

254

252

250

248

246

244

242

240

238

236

234

232

230

228

226

224

0
222

0
220

10
216

50
218

Number of Sites

100
253 V (Nominal +
+10%)
90
98% of

230 V (Nominal)

Cumulative Percentage of Sites

500

Voltage

figure 7. Voltage measurements for the LV monitoring of Energex networks during the summer peak week in February 2020. The data are from ~4,000 LV monitors (out of approximately 150,000 LV networks in Queensland). For further
details, please refer to "Distribution Annual Planning Report" in the "For Further Reading" section.

ieee power & energy magazine

225

210

195

180

p.
30

p.
4:

m
.
3:

p.
30

12
:

m
.
a.

m
10
:

m
00
9:

Voltage (V)

240

m
.

255

m
.

270

Average Power (kW)

The curtailment of distributed PV generation due to high
voltages in the distribution system has received considerable
interest due to the potential lost revenue for consumers with
PV equipment. In addition, overvoltage curtailment may limit
opportunities for DER participation in the broader power system, for instance, through VPPs. Typically, curtailment occurs
when local network voltages exceed inverter overvoltage set
points, causing the inverter to "trip" and curtail to zero power
output, even when there is a behind-the-meter load (Figure 8).
During recent years, Australian DNSPs have moved to mandate that volt-var and volt-watt response modes are enabled
for new D-PVs, which facilitates a more progressive reduction
in the inverter output as the voltage rises, rather than relying
on overvoltage trip settings. Legacy D-PVs installed under the
previous inverter interconnection standard tend to have higher
overvoltage set points. Regions with high penetrations of
legacy D-PVs can therefore produce higher voltages and trigger greater levels of curtailment than areas with significant

Estimating PV Curtailment

numbers of nonlegacy D-PVs. The same standard also applies
to BESSs and can prevent the systems from operating, even
when they are attempting to charge, which would otherwise
assist with alleviating overvoltage conditions.
An analysis of more than 1,300 South Australian sites
observed by a solar-monitoring company, Solar Analytics,

Customers at the ends of LV circuits are exposed only to
the lowest voltages on a few days each year, when peak loads
happen. DNSPs are responsible for maintaining voltage
compliance during peak periods, when maximum demand
occurs, just as they must maintain compliance during the
spring and autumn months, when loads are modest and the
reasonable solar irradiance results in minimum demand,
events that are likely to be observed significantly more frequently. Figure 7 indicates that during the weeks when maximum demand occurs, there is very limited room for further
widescale reductions in voltage levels.

PV Generation
Lost Self-Consumption
Lost Export
Behind-the-Meter Load
Voltage (at the Meter Board)

figure 8. An example of PV curtailment and the loss of
self-consumption at a single site in South Australia on
5 March 2017.
november/december 2020

IEEE Power & Energy Magazine - November/December 2020

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - November/December 2020