Transpower was forced to move fast when 13-percent cost overruns and a five-month delay to a new control system threatened to leave it without proper protection from hackers.
Transpower operates New Zealand's nationwide transmission wires and monitors New Zealand's entire electricity system from a secure room in Wellington using a system known as SCADA.
The system allows remote monitoring of all aspects of New Zealand's electricity system, such as voltage, frequency, outages or total electricity consumption.
But technical support for the ageing system was due to end last July, leaving its security increasingly vulnerable.
Both the Electricity Authority and Transpower then agreed on an upgrade to the system with new technology named PRISM, but the work was nowhere near ready when support for the old scheme was about to end.
However, IT support for the old system was extended, and both organisations insist the New Zealand electricity system is secure.
The new scheme still needs an injection of cash and its commissioning date has been deferred to next month.
The development came as electricity systems overseas were breached by hackers.
In Ukraine, the government accused Russian agents of a cyber attack on its electricity system that left tens of thousands of customers in the dark.
A similar attack was thwarted in Israel.
There has been no similar danger in New Zealand but the Electricity Authority warned some time ago that Transpower could run an increased risk of a hacking attack.
The Electricity Authority noted in a new paper that the upgrade project was running behind schedule and was over budget. "This is affecting the costs and timing for other projects," it said.
But it praised Transpower for taking the danger seriously, and encouraged it to carry out a proper review when the immediate problems were overcome.
In a statement, Transpower said SCADA was a critical operating system both to run the national grid and to oversee the practicalities of the entire electricity system.
"The project has unfortunately been delayed by five months, due to the need to resolve some modelling and control software functionality and performance issues.
"Given the criticality of the SCADA system, this delay is prudent to ensure the new platform operates at its full functionality.
"The project is forecast to run 13 percent over budget. A full project review will be undertaken upon completion to ensure any lessons can be applied to future projects."
Transpower expected to get the new system working by next month.