The context
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Homes and businesses get power through low voltage networks
1. Most homes and businesses connect to the electricity system through low voltage distribution networks. The power supplied from a low voltage network is sometimes called ‘mains supply’.
2. Electricity typically flows from generators to consumers through progressively lower voltage lines (transmission, sub-transmission, and distribution). The voltage is transformed at each point by a transformer.
3. Most electricity is generated by large power stations connected to Transpower’s high voltage transmission network. High voltages in Transpower’s national transmission network allow large amounts of electricity to be transported over long distances with minimal losses. Lower voltages in sub-transmission and distribution networks allow electricity to be safely transported to homes and businesses, and at each point of supply, the low supply voltage enables electricity to be used by a wide variety of electrical appliances.
Standard low voltage can currently only vary by ±6%
4. In New Zealand (NZ), regulation 28 of the Electricity (Safety) Regulations 2010 requires single phase low voltage electricity to be supplied at a nominal voltage of 230 Volts (V) alternating current (AC), and except for momentary fluctuations must be kept within 6% of that nominal voltage.[1]
5. NZ regulations allow the standard low voltage to vary by ±6% because voltage cannot easily be maintained at 230 volts at every supply point due to constantly varying demand and generation in the low voltage network. The voltage at a point of supply typically falls when demand in the vicinity increases and rises when generation increases.
6. Regulation 23 of the Electricity (Safety) Regulations 2010 requires electrical appliances sold in NZ must comply with regulated standards to ensure they operate safely and efficiently with low voltage mains supply. The relevant standards for appliances and fittings in New Zealand are either shared standards with Australia or standards from the European-based International Electrotechnical Commission (IEC).[2]
The demands on low voltage networks are changing
7. The demands on low voltage networks are evolving as homes and businesses change the way they use interact with the electricity system. More homes and businesses are investing in rooftop solar photovoltaic (solar PV) generation and in electric vehicles (EVs)[3]. This is expected to accelerate in the years ahead as the costs of these resources fall and their performance improves. Electricity consumption may also increase as homes and business switch from using natural gas to electricity to heat their properties and hot water.
8. The increasing use of distributed generation (particularly rooftop solar panels) is expected to change the pattern of power flows in low voltage networks. During the day, a large amount of solar PV generation flowing into the network (often refer to as exporting) coinciding with relatively low household demand could result in overvoltage (voltage exceeding the regulated upper limit) if no mitigating actions are taken.
9. Similarly, the advent of electric vehicles (EVs) that are charged at home (or stationary in-home battery systems) could significantly change the scale and pattern of demand. In particular, a large number of EVs charging at home around 6pm could exacerbate the high demand typical at that time in winter. This could potentially result in undervoltage (voltage falling below the regulated lower limit) if no mitigation is taken.
We are proposing to modernise our voltage range
10. We are proposing changing NZ’s regulated voltage range from 230 Volts ±6% to 230 Volts +10% and -6%. This proposal would bring NZ closer to alignment with Australia[4] and is expected to be the least cost option for mitigating potential constraints on low voltage networks. The evidence you provide in your submission will help inform analysis of the benefits and risks of changing voltage regulations.
11. Alternatively moving to ±10% would align NZ with other countries that have a nominal voltage of 230 Volts, including the United Kingdom (UK) and countries in Europe. This range would also bring NZ’s supply voltage range into alignment with the voltage range that has been reflected in NZ’s regulated appliance standards for many years.
12. The Electricity (Safety) Regulations 2010 are made under section 169(1)(7) of the Electricity Act 1992. The proposal would change the prescribed requirements for standardisation of systems of supply and the preservation of the quality of electricity supplied in NZ. The proposal is consistent with the purposes in section 1A of the Electricity Act 2010 to provide for the regulation, supply, and use of electricity in NZ, to protect the health and safety of members of the public in connection with the supply of electricity in NZ, and to promote the prevention of damage to property in connection with the supply and use of electricity in NZ. This discussion document focuses on whether expanding the voltage range is likely to impact those purposes.
Footnotes
[1] A higher nominal voltage of 400 volts applies to multiple-phase supplies, which are used in some industrial or larger commercial environments – but must also remain within 6%.
[2] Relevant standards are listed in Schedule 4 of the Electricity (Safety) Regulations 2010.
[3] Information about investment in solar PV can be found on the Electricity Authority’s EMI website:
Electricity market information dashboard – Installed distributed generation(external link) — Electricity Authority
[4] Australian states and territories, except Western Australia, have harmonised their supply voltage at 230 Volts with a range of +10% to -6%. Western Australia remains at 240 Volts ±6%. In practice, this means the upper voltage limit in Western Australia is 254 Volts, compared to 253 in the rest of Australia.