May 10, 20233 yr 55 minutes ago, Antonio de Sa said: Yes, indeed there are protection relays connected to the Gen breaker, there are there to do exactly that, the question is? are they operational? I worked for many years installing, commissioning and optimizing boiler/turbine control systems, I know of all the protection system there are installed in both boilers and turbines, any protection system can be bypassed. And that is exactly of what I'm afraid it can happen, Many, many years ago I saw a 60 Mw turbine going thru the roof at Taibos PS, the vibration protection system was faulty and by the time the operator realized was to late. True, any protection system can be by-passed. In my experience working for power plants, the protection that gets by-passed most of the times are ones that causes nuisance trips i.e at starting up of the generating units, smoke and fire after maintenance or overhaul, gas detection after maintenance of gas pipes etc. Generator reverse power, overload/shortcircuit, current imbalance etc we do not mess with those
May 10, 20233 yr 13 minutes ago, hoohloc said: True, any protection system can be by-passed. In my experience working for power plants, the protection that gets by-passed most of the times are ones that causes nuisance trips i.e at starting up of the generating units, smoke and fire after maintenance or overhaul, gas detection after maintenance of gas pipes etc. Generator reverse power, overload/shortcircuit, current imbalance etc we do not mess with those Generator reverse power, overload/shortcircuit, current imbalance etc we do not mess with those Agree with you, but that was before cANCer cadres were employed by Eskom. No so long ago they blew up a turbine/generator at Matla because they by-passed the Hydrogen detecting system, the hydrogen is used for cooling on the gen stator windings.
May 10, 20233 yr 4 minutes ago, Antonio de Sa said: Generator reverse power, overload/shortcircuit, current imbalance etc we do not mess with those Agree with you, but that was before cANCer cadres were employed by Eskom. No so long ago they blew up a turbine/generator at Matla because they by-passed the Hydrogen detecting system, the hydrogen is used for cooling on the gen stator windings. I remember the incident 😂
May 10, 20233 yr My goodness, when protection is bypassed on these large plants, this is insane. Not only for reliability of the grid, but for safety sake, as workers lives are then in danger. 😲
May 10, 20233 yr 36 minutes ago, TimCam said: My goodness, when protection is bypassed on these large plants, this is insane. Not only for reliability of the grid, but for safety sake, as workers lives are then in danger. 😲 @TimCam Believe you me a boiler/turbine set is basically a bomb under control. There are so many protections system attached to its control that is behind the average person's comprehension. For insurance purposes some of the more critical systems are what we call a 3 out 1 voting system, in other words there will be three instruments measuring one critical part of the plant if any one of the three fails the system will trip the boiler or turbine, those system cannot be by-passed, but there are many other not so critical systems that the Instrumentation technician can and will probably do it. In one condition, that part of the plant remains on manual control.
May 13, 20233 yr Some wise words from our President. South Africans will be ‘first to know’ when power grid collapses, says Ramaphosa (ewn.co.za)
May 13, 20233 yr 13 minutes ago, Don said: Some wise words from our President. South Africans will be ‘first to know’ when power grid collapses, says Ramaphosa (ewn.co.za) Yeah, these guys are bordering on genius 🤣
May 13, 20233 yr 34 minutes ago, Superfly said: LOL... they will declare a State of Disaster and ban alcohol, flip-flops etc... that's about it... unless they come up with even more stupid stuff... But... But... They have already... They want us to save eskom and the grid by using even less power... Not quite sure how they going to sustain all the free power they give out by making the people who actually pay use less...
May 13, 20233 yr Eskom is the only company in the world I know of that begs their customers on National TV not to use their product. Those adverts with the dial showing the grid usage and pleading that you switch off swimming pool pumps and everything else except your TV. Edited May 13, 20233 yr by Don
May 13, 20233 yr On 2023/05/12 at 3:24 PM, root said: Here we go again.... Your readings all seem in order for me. For sure no problem getting 219V or a 49.78Hz frequency.
May 19, 20233 yr If there is a cascade event where we have a two power stations dropping offline at the same time the remainder will disconnect themselves from the grid frequency < 50Hz without operator intervention (a trip) - as long as coal is fed to the boilers the generator will be operating and there will need to be synchronization to be done between the power stations again to get the grid up and running. A black start means everything is down - we have emergency reserve at all times at the various pumped storage schemes around the country to boot up a coal fired power station and that one can supply the next one etc ... and also the open cycle gas turbines - they start within a minute and operate independently from external power. There is also Koeberg - one unit is supposed to be operating at any given time, Maybe an electrical engineer can comment ???
May 19, 20233 yr 3 minutes ago, Garth Arendse said: If there is a cascade event where we have a two power stations dropping offline at the same time the remainder will disconnect themselves from the grid frequency < 50Hz without operator intervention (a trip) - as long as coal is fed to the boilers the generator will be operating and there will need to be synchronization to be done between the power stations again to get the grid up and running. A black start means everything is down - we have emergency reserve at all times at the various pumped storage schemes around the country to boot up a coal fired power station and that one can supply the next one etc ... and also the open cycle gas turbines - they start within a minute and operate independently from external power. There is also Koeberg - one unit is supposed to be operating at any given time, Maybe an electrical engineer can comment ??? Not that simple, in the case you describe once the generators breaker disconnects itself from the grid due to low frequency, there will be a sequence of events that will follow such an incident, the boilers steam pressure will go sky high, boiler pressure safety valves will open to vent the extra pressure. The generator will go in to barring mode, boiler will go on to what is called minimum stop limits, all primary fans( these fans are the ones that feed pulverized fuel to the burners) will reduce speed to its minimum, the coal feed to the milling plant will be reduced, possibly one or more of the coal mills will be stopped by the boiler operator in order to keep the boiler running within its minimum safety limits. boiler feed pumps speed will also be reduced (no more steam going to the turbine) so no need to feed water to the boiler there are many boiler protection systems that will take action, such as burner and flame management system can trip the boiler, so many things can happen.
May 19, 20233 yr 23 minutes ago, Antonio de Sa said: Not that simple, in the case you describe once the generators breaker disconnects itself from the grid due to low frequency, there will be a sequence of events that will follow such an incident, the boilers steam pressure will go sky high, boiler pressure safety valves will open to vent the extra pressure. The generator will go in to barring mode, boiler will go on to what is called minimum stop limits, all primary fans( these fans are the ones that feed pulverized fuel to the burners) will reduce speed to its minimum, the coal feed to the milling plant will be reduced, possibly one or more of the coal mills will be stopped by the boiler operator in order to keep the boiler running within its minimum safety limits. boiler feed pumps speed will also be reduced (no more steam going to the turbine) so no need to feed water to the boiler there are many boiler protection systems that will take action, such as burner and flame management system can trip the boiler, so many things can happen. Thanks for the info - so a steam turbine cannot just idle along as I had thought for an extended period. A few questions if you don't mind. a) How long does it take a boiler to start up from cold to it is able to produce steam to a generator ???. b) How long does it take for a generator to synchronize to the grid once it has steam ???. Amazing we still need to use glorified kettles for power :). Edited May 19, 20233 yr by Garth Arendse
May 19, 20233 yr 2 hours ago, Garth Arendse said: Thanks for the info - so a steam turbine cannot just idle along as I had thought for an extended period. A few questions if you don't mind. a) How long does it take a boiler to start up from cold to it is able to produce steam to a generator ???. b) How long does it take for a generator to synchronize to the grid once it has steam ???. Amazing we still need to use glorified kettles for power :). Yes, the turbine will be kept turning for a while, ( no load ) there will still be a bit of steam in the boiler to keep it for a while, that depends on the steam temperature, the steam has to be at +- 350 degrees C (saturated or dry steam) anything bellow can be dangerous as it may contain water droplets thus causing vibrations on the turbine and the turbine vibration protection will then trip the turbine, The big 600 MW units from cold start to full load could take up to 8 to 10 hours, once the boiler starts to produce steam at a set temperature that steam is feed to the piping feeding the turbine to slowly bring up to running temperature, but within about 4 hours it will be able to feed the turbine at +_ 10 to 30% of the load, Once the generator starts to produce any power can be synchronized to the grid. usually about 10% of its design capacity.
May 19, 20233 yr 12 minutes ago, Antonio de Sa said: Yes, the turbine will be kept turning for a while, ( no load ) there will still be a bit of steam in the boiler to keep it for a while, that depends on the steam temperature, the steam has to be at +- 350 degrees C (saturated or dry steam) anything bellow can be dangerous as it may contain water droplets thus causing vibrations on the turbine and the turbine vibration protection will then trip the turbine, The big 600 MW units from cold start to full load could take up to 8 to 10 hours, once the boiler starts to produce steam at a set temperature that steam is feed to the piping feeding the turbine to slowly bring up to running temperature, but within about 4 hours it will be able to feed the turbine at +_ 10 to 30% of the load, Once the generator starts to produce any power can be synchronized to the grid. usually about 10% of its design capacity. Thanks for the info. May be you can share more light on the bending of the generator shaft when stationary and to get it straight again.
May 19, 20233 yr 10 minutes ago, Scorp007 said: Thanks for the info. May be you can share more light on the bending of the generator shaft when stationary and to get it straight again. @Scorp007 That is why I said above the generator goes in to barring state (the turbine/generator) set is kept turning using the barring gear, until is cooled down to avoid bending the shaft
August 8, 20232 yr 11 hours ago, PowerUser said: Major power outages across Gauteng right now: @PowerUser I see in my are the frequency is quite low. see dashboard.
August 8, 20232 yr 33 minutes ago, Antonio de Sa said: @PowerUser I see in my are the frequency is quite low. see dashboard. I see it is lower and unstable but at least within the set limits of 47hz-52hz
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