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Aliass posted:Im talking from complete cold start. That was the figure i was told but most of ours are pretty old. We normally use gas turbines to deal with the excess demand and only use coal fired power stations to provide the baseload power. How fast a plant can start up is usually determined by how fast you can heat up the system. A boiler is started up very slowly over several days to prevent the refractory from cracking. Depending on how the plant is built there might be an extensive process to bring the whole plant on line. For a steam plant, start-up will put the most stress on your equipment usually. Because of the long start up times companies will generally be reluctant to take a coal plant offline. Three-Phase posted:That sounds similar to US large customers, but the stuff I'm more familiar with is a lot larger than 100kW+, more like 10MW-250MW range. But yeah, there's complicated billing based on peak watts/VARs (I think it's in a sliding 15-minute range) along with total consumption and making sure you don't lag more than, say, 0.95 power factor at any time unless you want to be fined extra. I worked doing O&M for a gold mining company that built a power plant when their long term power contract expired and the power company wanted to renegotiate higher. We had around 118 MW of capacity that was just about enough to cover the companies mines in the state (should have been more than enough but they kept adding more load to the contract). During winter and spring it was easy for our broker to supply cheap power and reduce the plant to minimum generation (the company did not negotiate prices for parasitic load so we had to have 2 engines, 16MW, running at all times to keep from being charged peak rate). During peak season we ran at 100% capacity for as long as possible. Even if the broker was able to find decent spot prices the PowCo frequently cut our imports and made us generate due to a lack of transmission. Each week the mines would predict their generation and send it to the broker who would look for power on the market to cover with a combo of long term contracts and spot prices. If the mines had equipment go down or the PowCo had a problem there was a direct line to their control room on our desk we used to discuss issues with them. They would call every now and then begging for any spare capacity we had as we had start up times of 5 minutes or less usually. They also asked us to adjust our PF once but there was nothing in the contract for that so screw them. Also, the gold mining company had never had a power plant before and did not know how to negotiate a contract leading to things like the PowCo being able to charge peak power prices for any parasitic load we might draw even at off peak times. We could also never go down without spinning reserve for even a minute without the PowCo being able to charge something like peak price for the whole month. On the one time we tripped two of our transformers offline for less than 10 minutes we would have been on the hook for $500k or so (the PowCo engineers told the accountants to gently caress off and not charge us since we gave them any help we could with generation when they called).
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Sep 22, 2011 18:45
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Three-Phase posted:
I was working at a power plant that had just finished commissioning and was still under warranty when we started getting an undervoltage relay trip on one of the generators when we tried to put it online. Both the plant electrician and warranty engineer insisted it had to be the protection and nothing could possibly be wrong with the generator as it had meggered at infinity on the way out of the factory and it was barely a year old. After changing the LVR's around for several days they finally meggered the generator and found two phases had dead grounds on them. Watching them take it out and put a new one in was pretty cool since they had to lift it over two engines on rails. Cost the OEM over $1 mil on a project they were already millions in the hole on. Im just glad the protection was new and worked exactly as it was supposed to, it was a good lesson. It could have been very messy.
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Oct 9, 2012 04:36
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