I work for a company that uses hundreds of megawatts of electricity. The company has been planning to curtail it's production prior to 1/1/2000 to prevent the destruction of equipment in the event of a power failure. It's power provider is trying to persuade them stay running by "almost guaranteeing" them that they will have power. I was wondering if the reason the provider was doing this was because if some generators were to trip off line they could load shed this customer and stabilize their portion of the grid. We are probably their biggest eletric load.

Ken

-- Anonymous, June 27, 1999

Answers

Ken,

Distribution networks are stable only between certain parameters. My national Generator/distributor has a Max capacity of 29Gw and normal loads at around 16Gw. However the network becomes unstable, and difficult to manage at loads below 7Gw and at 4Gw it 'blacks out'. (Falls over!) Needs a complete restart at that time. They are considering reducing tariffs at the year end to encourage the load to be constant.

Hope this helps you to decide NOT to shed load at the year end.

James Prosser

-- Anonymous, July 29, 1999

Ken,

Here in New Zealand we also have one large customer (an aluminium smelter) that uses hundreds of MW of electricity. Its actual demand is around 10% - 15% of the total demand for our country, and over the low usage period of Xmas/new year, that rises to 25% of our total load.

Part of our Y2K contingency planning involves maintaining supply to this company. It is normally connected to the national grid, and in the event of a lossof supply it it requires power to be back within two hours to avoid major damage to the smelting equipment. One large hydro station (NZ's largest) is kept generating to exactly match the smelter's demand. The group of stations that I am production controller for is the next most able to meet the required demand, and we have the contract with the grid to supply black-start capability.

The contingencies that we are looking at are: The grid goes down completely; or There is a partial collapse of the grid; or (worst case) the grid stays up, but the smelter goes down.

So Ken, I would agree with James and urge your company to just maintain a normal profile and try to ensure that your own company is Y2K ready at least.

James,

South Africa and New Zealand have a similar demand profile, but we do differ in the scale of the demand. We have 8GW connected capacity, and a peak demand of around 6GW. Average demand is more like 4GW, and over the very lowest period (Xmas day) its around 2GW. However there is no low figure at which our grid will go completely black. At various low loads we do require plant to be connected as sychronous condensors rather than as generators in order to keep the voltage down to acceptable levels, and at extremely low loads there is the real possibility of loss of stability which could require localised islanding, but we would still be able to maintain supply.

What is the issue in SA that would cause a black-out at 4GW?

Malcolm.

-- Anonymous, July 29, 1999