Wiremu Rangi was eighteen and in week three of a two-year cadetship, and by Friday in July he had worked out that the only part of the job he was allowed to touch was a pencil and a log book, which was correct, and which he resented correctly too. He sat at the third console of the North Island desk in the regional control centre, in his orange hi-vis vest with his name printed on the back over a grey work shirt with the sleeves turned up, and at five o'clock four thousand people came home and switched on the lights.
The grid they switch them on with is not a supply in the ordinary sense. It is a set of machines turning at exactly fifty times a second, all of them locked to each other, and it works because there is one number every machine in the country agrees about. On the wall in front of him, on a black dial with a white needle, was that number. If generation and demand match, the needle stands at 50.00. If demand is short by a hundred megawatts, the machines that have not yet picked up the slack each take a little of it and everything slows down together, and the difference between that number and fifty is the closest thing the country has to a heartbeat.
Denise Halliday, fifty-one, his shift supervisor, put her tea down and said, “You have got four hours of pretending to be a piece of furniture and then I will teach you the interesting part.” At six minutes to six she was on the phone to a line crew in the Bay of Plenty and Wiremu was watching the mimic panel, which is the whole North Island drawn in lines and boxes and coloured by what is flowing where, with one wide line under the Cook Strait and an arrow pointing north. At 17:52:11 the double-circuit line from Whakamaru to Motukorea came out of the board, and a second box four seconds later. His hand was on the phone before he had decided to put it there. “Whakamaru to Motukorea, both circuits, on a relay operation.” Denise said, “Both circuits?” “Both circuits,” he said, and then, because the panel had put a red rectangle on the line crew's job card and he was told to read them out, “Four-nineteen on the fall of the other. That will be a conductor down onto the other one.”
Five hundred megawatts, and he had the arithmetic out before his heart had finished. In his first year at the institute they had given him one number to carry for the rest of his life: every hundred megawatts that disappears off this system takes eight hundredths of a hertz with it. Five hundred was two fifths of a hertz, and fifty minus two fifths is forty-nine and six tenths, and that is what the dial did, and the peak-hold marker held at 49.61 while he was still saying it out loud. It came back. The batteries at Merino hold two hundred megawatts of reserve on contract and answer inside a second, so the needle stopped dropping in about a second and a half and came up. Then the governors all over the country woke up and pushed, and the needle sat at 49.79. Two tenths low, and he did not need to be told what that meant, because two tenths times the eight hundredths rule was two hundred and fifty megawatts. Something had put two hundred and fifty back in, and there were still two hundred and forty to find.
“Write it down,” Denise said, and he wrote it down, and he wrote the wrong thing down, which was the first thing that went wrong that night and the only one nobody noticed. He wrote 490. The number that belonged in the box was 240, because five hundred had gone out and two hundred and fifty had come straight back, and a log that says five hundred is a log that says the grid lost five hundred and got nothing back.
The grid does not work like that, and the arithmetic of it is the whole job. Reserve is not generation. Reserve is a promise that generation will turn up on demand, and the difference between the two is the difference between a tap and a tap with water in it. The batteries had given him fifteen seconds and were now an ordinary power station with an empty tank, and needed a quarter of an hour before the men at Merino could have them back where the contract says they must be. So there was two hundred and forty megawatts of hole in the North Island at six on a Friday evening in winter, and it had to be filled by hand, from a desk, in minutes. Where the hole gets filled is a list, and he knew it in the order Denise had taught him. Hydro first, because the water is already in the pipe. Then gas, which is running and only needs its governors opened up. Then the link. And last, and never, asking somebody to turn something off.
“Waipori first,” Denise said, “then Karapiro, then Mangawe. Leave Arapuni out, Arapuni is on the lake and the lake decides.” That last was the sentence that mattered and he did not understand it until eight o'clock. Clyde, Karapiro and Mangawe all draw from the Waipori River, and the Waipori comes out of Lake Taupō through the gates at Waikato, and the gates cannot go further than the lake allows, because the lake is a flood problem before it is a power problem. On a wet night you can take 350 megawatts off that scheme in twenty minutes. On a dry night in July the gates are already as far as they go and the whole scheme is worth 60. “Tell me what the generators are doing,” Denise said. Huntly one and two, a thousand each, up to their limits. McKees Glen, 360, up to its limit. Pukekura, Glenbrook, Te Rapa, Raglan, all at their limits, all of them pushed up against the fifty the needle wanted. And the Waipori, and 240 needed. “Link is at one thousand and sixty north,” he said. “Link's rated one thousand two hundred.”
“There you go,” Denise said. “You have just been wrong and did not know it, which is the good kind of wrong. That one thousand two hundred is megavolt-amperes. You only get megawatts out of it if the power factor holds, and we are at zero point nine three because there is a fault out there that our equipment does not much like. So the transformers are the limit, not the megawatts. Work out what we can actually take.” He worked it out on the back of the log, the way they had taught him, because the relationship is the same one you use for everything. Power equals apparent power times the power factor, so apparent power is power divided by the power factor. One thousand and sixty divided by zero point nine three is one thousand one hundred and forty, against a nameplate of one thousand two hundred. So there were sixty megavolt-amperes of room in the transformers, and the power factor turns those into fifty-six megawatts. “Fifty-six,” he said.
“Fifty-six. And we need two hundred and forty. The island has to find one hundred and eighty-four on its own, and you have until half past six.” He found it in eleven minutes, in the only place it existed, which was in the machines that had not started yet. Rankine, 88 megawatts, spinning up but not connected, four minutes from being there. Haranui, 44, twelve minutes away. A synchronous condenser at Bunnythorpe, 65 megawatts of nothing at all, which does no work and only holds the voltage up, and which he counted for a second before he knew to leave it out.
Then Denise made him do the part he hated, which was the ring. The North Island is not fed from one place. It is fed around a loop, from Auckland down the central plateau to Wellington and back up the west coast, on purpose, so that when a piece of it breaks the power goes the other way round and nothing stops. Except that going the other way round means the pieces on the far side suddenly have the whole island's traffic to carry, and that is where a line stops being a route and becomes a temperature. The mimic panel showed it in colour. Baring Head to Huia was pale yellow at four minutes past six, eighty-two per cent of the way to its limit. Denise told him to read the numbers, not the colours, because a colour is a hint. Seventy-eight per cent, then eighty-four, then ninety. The conductor temperature at Taupo came from a weather station, from a man who had not seen the conductor. The short-term rating, which is what you may push through a line for a quarter of an hour when nothing else will do, was one hundred and five per cent.
“Do we take it?” Wiremu said. “We take it, and we write down that we took it,” Denise said, “because it is the fourth time in a fortnight and the fifth time is the one where the conductor comes off the clamp.” A short-term rating is not free. Run a conductor above its continuous rating and it runs hot and the sag comes down, and the sag is what the people on the ground work under, and if the conductor comes down in the wrong place while somebody is under it then the whole exercise stops being a number on paper. The rating comes with a clock on it, and once the clock has run you do not get it back. He wrote 18:06 in the margin and did not know he had spent what would have mattered at twenty to seven.
At twenty past six the link was at 1,116 megawatts, which is every megavolt-ampere the converter transformers have, and Rankine had come in and taken its 88, and the needle was back at 49.98, and the two hundred and forty megawatts of the country's evening was being carried by the fact that four hundred thousand people had not yet come home. The line crew called at twenty-five to seven. They had found the conductor at the gantry, down and lying across the other circuit's phase conductor, and they wanted an earth so that they could cut it off and go home. “Earthing it,” Denise said. “Both of them.” Wiremu said, “Both circuits are already out.” Denise said, “They are out from the system. To put an earth on the conductor that came down I have to be certain there is nothing at either end of it and that nobody can energise it while my crew is under it, and the only way to be certain of that is to have both circuits open at both ends and earthed at the work site. So yes, both of them.”
That is a piece of arithmetic with nothing to do with electricity. A job that had already paid for itself was about to cost the system a hundred and ninety megawatts, because the safe way to work on one circuit of a double-circuit line takes the whole line out of service. Nobody said it out loud, because that does not make it smaller.
The last circuit went at 18:34:07. A hundred and ninety megawatts this time, which by the rule in his head is about fifteen hundredths of a hertz, so 49.98 went to 49.83, and the batteries came in again and it came back to 49.84 and stayed. The needle had a red dot drawn on the scale at 49.5 and it was nowhere near it, and there was no emergency, and it was the worst half hour of his year.
Because the needle was not the problem, the deficit was, and for the first time in his life Wiremu went down the list and found it empty. The batteries had fifteen seconds and then a quarter of an hour of being a power station with a flat battery. The gas machines were at their limits and had been since six, and none of them goes past its limit without a designer in the room. The ring lines were back on their continuous ratings. The link was at every megavolt-ampere it had. The Waipori was at the gates. And in Christchurch it was the winter evening peak too, and they had given him fifty-six and were not giving one more. “There is nothing on the list,” he said. “Then it comes off the end of the list,” Denise said. “You are going to have to ask somebody to stop.”
The end of the list is a telephone call to a district controller, who has a contract, and the contract is with the people who own cold stores and a freezing works and a very large number of cold rooms in a very small number of buildings. A hundred and seventy megawatts of it. He read the numbers off the screen, and they were the same numbers he had been reading all night, meat and milk and power, except that now each of them was a shift at a place on the coast that somebody does not get to do. He made the call. He said the number and then, as he had been taught, “This is an instruction under the emergency arrangements and it is not a request.” He listened to a woman with an extremely calm voice ask him to repeat the number, and he did, and she repeated it back, and she said it would take eight minutes to get the doors closed, and he said take them, and she took them. He had never in his life given an instruction to a stranger that he could not take back.
The frequency came back into the band at 18:53 and sat at 49.96, and by half past seven the whole arrangement was back to doing what it does, which is nothing, which is fifty exactly, and the room was very quiet, and there were about four hundred people in an unknown number of places who had lost the last of their shift on a Friday evening and would not be paid for it. Denise made him write it up, and that was the part she had promised him at five o'clock. You cannot run a grid out of your head, she said, because the next person has to know what you did and why, and the one after that, and in ten years a man who has never met either of you, and the log is the only thing all of them will have.
So he wrote it. 17:52, Whakamaru to Motukorea, both circuits, 490 megawatts, conductor down. 17:54, batteries, 200 megawatts. 18:06, ring lines on short-term rating, Baring Head to Huia to one hundred and five per cent, fifteen minutes. 18:34, line earthed for repair, 190 megawatts. 18:45, shed 170 megawatts, freezing works and cold stores. 18:53, frequency restored to band. Then the last line, which was the one he went back to four times, because a shed is an instruction and an instruction is not a measurement. He had asked for a hundred and seventy. The district controller could prove a hundred and sixty-three from the half-hourly data, and the freezer's engineer later quoted a hundred and fifty-eight off the chart on the wall of the plant, which nobody had calibrated for the purpose. Three numbers, and only one had been measured.
The company wrote in March, saying the interruption had been a hundred and fifty-eight megawatts, seven minutes shorter than it had been, and wanting the difference paid for. The log still said a hundred and seventy, because a log says what was instructed. His name was on it because he had written it, and it was still there in the spring.
What he wanted instead, on the Friday night bus with his vest still on because he had not thought about it, was to be left alone with the fact that the system had not failed anywhere. A conductor came down on another conductor, two circuits came out, and everything that answered did so inside the time it had been built to answer in. Three hundred million watts ran for half an hour down the country's only road to the South Island without anyone having to be brave about it. And at the end of it, when the lot had run out, about four hundred people in cold rooms had lost a shift, and there was no name at all attached to any of it.
The woman from the night shift at the freezing works, whose shift it had actually been, sent him a message on the Monday. She said the floor had stood at the windows in the rain waiting for the thunder, and that it had stopped at about twenty to seven, and that the men had gone back in and finished the shift and been paid the overtime. She said it had been the quietest night they had had all season, and that everybody had stood in the yard a bit anyway before going home, because the sky was doing something enormous over the ranges and nobody wanted a normal Friday. He read it twice, then wrote it on the back of the log sheet, which is not a place for that kind of thing, and then tore it off and put it in his pocket, because he was not going to be the man who put that on an operational record, and because the log had a number in it that was five megawatts out and there was no page on that form for any of this.
On the Monday Denise gave him the ten minutes she had promised, and she did not say that he had run anything at all. She said the only two numbers that came out of his own head were the two hundred and fifty megawatts in the first eight seconds and the fifty-six at the link, and that both had been right, and that he was to learn the second one without a calculator, because at three in the morning in winter there would not be one. Then she sent him down to the induction bay, and he read the instruction sheet for the plants he had talked about all night, one of which was his cousin's workplace, which he had not known until he had to look it up.
