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If a generator is generating 20MW and only 5MW is used where does the other 15MW goes?
1- Goes to auxiliary of all electrical equipments that ensure the properly working electrical system.
2- Goes to loss( permanent and variable loss) in all electrical equipments such as transformers, conductors, mortors, compensators that we cannot disconnect from the voltage of line.
But if your question is real, I thing your generator surly will tripped due to over frequency relay is working. If is not real, I thing is the …… question.
Parrallel working of power transformer having advantage as:
1- To minimized the load loss in transformer during pike time (according to load graphic)
2- Increasing the reliability and effeciency of power system
3- keep the permissible temperature rise in top oil & winding under safety margin
4- low investement capital by comparing with one transformer (in same capacity of two)
in contrary also having:
1- Increasing the no load loss in transformer during off- pike time
2- Increasing the short circuit current, becuase the total impedence is divided by two
Thus the parrallel operation of power transformer need the flexible monitoring by operators that working in Dispatching Control Center according two the load graphic of local load.
Hi, manh-hoa09,
There are many applications in steel plants. They range from simple conveyor and pumping applications to more complex rolling mills to very complex arc furnaces. Without knowing the specific equipment involved and the nature of the problem it is impossible to state that any one solution works.
You might contact the local Schneider Electric power quality specialist in your country.
Regards,
Rated power of a lamp is in watts -> Careful – if it's halogen / fluorescent / LED / metal Halide then there will also be additional losses in the transformer / ballast / driver / ballast respectively.
Electrical Supply Utilities charge in KiloWattHours – if you are a large utility, you may also be charged for apparent power, which is power drawn out of phase with the voltage. This happens extensively with old magnetic ballasts and magnetic transformers.
In addition, most electrical utilities will also charge more for on-peak power, and less for off-peak power.
Simply though, without taking into account control gears & out of phase power …..
A 600 watt load (incandescent lamp or mains voltage halogen only) turned on for 1 hour is equal to 600 / 1000 (kW) x 1 (h) = 0.6kWh.
A quick look at the Building code of Australia section J6 says upto 2 lights on a motion detector saves you about 45%, upto 6 lights will save you 30% and upto 200square metres controlled by a single detector will save a measly 10% – the figures are probably pretty conservative though.
, and more than 6 lights
GTOs and IGBTs do block the negative. They are semicondutor devices and must be forward biased to work. The difference is that they are not line commutated like a thyristor or diode which turns off under its own volition when it becomes reverse biased. A thyrsitor cannot be turned off once ignited unless the supply across it goes negative (or current is otherwise interrupted). A GTO can be turned on by a pulse to one gate and off by a pulse to a second gate. This allows it to be turned off before the supply across it goes negative. Thus it can be turned on and off a number of times in any half cycle rather than once only as for the traditional thyristor. This is what allows it to be used for pulse width modulation.
The IGBT is a transistor and will only turn on when base current flows. Thus it can be turned on and off by turning on and off the base current. Through this it can also be turned on and off many times in a half cycle and thus be used for PWM applications.
GTOs and IGBTs are the building blocks of PWM controls. It is also worth noting that they are not only used for AC to DC conversion but also DC to AC conversion such as in VVVF drives and DC transmission links.
Whether you produce DC from AC or AC from DC depends on how you connect the IGBTs and what patterns of pulse witdth modulation you use.
Try getting hold of a manual of a VVVF drive from say Siemens or ABB and this will explain it all very well.
Not sure whether you are looking at traditional overcurrent/short circuit protection on a busbar or busbar zone protection. They are two different things.
If you are talking about detecting internal and external faults you are talking about zone protection. This works on a principle the principal of differential protection. Here you monitor the current coming in at the switchboard incomer and the current going out at each feeder. The relay sums all of these and the resultant should be zero when all is healthy. If a fault occurs outside the board the currents passing will be very high but the sum will still be zero and the relay will ignore it. If the sum is not zero it will indicate that there is some form of fault in the board and trip. You will need to take some care as to the time delay settings to take care of allowable transients.
If you are looking at traditional overcurrent/short circuit protection there is a bit more to consider.
The relay is a universal device and effectively has hundreds of algorithms to choose from. You will need to choose exactly the right one for your application. The right algoritm is selected through the relay settings which select particular current/time curves and time delay setings from the many that are available.
To determine discrimination with upstream circuit breakers or protection relays you must know what the settings in those are.
You then need to set the characteristics of your relay such that they are underneath those of the upstream relay/breaker. This means that your relay will be set to a lower trip current for any given time trip time. On the charateristic current/time tripping curves, this will mean that you relay curve must lie to the left of the upstream relay curve in the vertical or near vertical part of the curve (this is the inverse time part of the curve) and below the horizontal part of the upstream relay curve (this is the instantaneous trip part of the curve).
The next check will be that the continuous current setting you have chosen will be above the rated current of the device you are protecting. This means that the vertical part if the current/time characteristic of your relay (this is the continuous current area where your relay will not trip if that current passes) must lay to the right of the current that the load will draw.
A final check if you are starting an induction motor which will have a high staring current for a short time after which it falls back to the rated current, will be that the starting current value will lay to the laft or below the curve of the relay for the starting time of the motor.
Once you have done this the algoritm will monitor the passing currents and trip when necessary.
Whether it trips correctly or not will depend on youy skills in setting it correctly. It will no magically do the job for you straight out of the box.
Hope that this helps
Add the vectors (magnitude and phase angle) of the current in each phase and the resultant will be the current that flows in the neutral which is the unbalance current.
vivek_radhakrishnan said:
What is the role of the copper braid that is present in the MCB's. Can a MCB be used as a normal switch.
Will a MCB be able to take-up cyclic load as a normal switch. In case I use a MCB as a normal switch and conduct 40,000 operations will there be any distortion in the braid present in the MCB ?
The copper braid connects the moving element with the static element.
MCBs are designed as protection devices and expected to operate on an infrequent basis.
If you have an application that requires frequent operation, use the correct equipment such as a load break switch, operated manually, or a contactor operated electrically.
Most manufacturers who make MCBs also make switches and contactors that fit to DIN rails and in the same distribution board enclosures.
Hello,
Here is a typical diagram explaining the operation of a PWM rectifier, as used in the Power supply of your PC.
Best regards,
Jacques Schonek
0.6kWh is the answer in the above example,power units are often confused for energy units the difference being used over time hence the prefix 'h' on the end, also there's the usual use of capitals were lower case should be used.
erickench said:
I would suggest using the KVA method in performing a short circuit calculation. You wouldn't have to use per units or complex numbers.
i m studying in electrical engg. will u plz help me in basic concepts?
Being employed by a major switchboard manufacturer for the last eight years, I have been privy to a number of short circuits, which were caused by equipment failure and errors in either manufacture or modifications.
Depending on the nature of the fault, the damage of equipment can be extensive.
Unfortunately, I have been involved with one short circuit which has caused personnel injury and this occurred when modifications were performed to an existing switchboard. The works being conducted were straight forward and similar works had been performed by all personnel involved on multiple occassions.
The build of the switchboard meant that the main isolation point was behind a cover, which needed to be removed to return power. The cover was removed without any issue. However, once the switching took place there was a short circuit between a phase and earth (reasons still unknown). The subsequent arc gave severe burns to the person conducting the switching, who in turn required extensive plastic surgery and physiotherapy to recover. The fact that this person did not manage to close the switch completely and it sprung back to the isolated position, probably saved his and other peoples lives.
After assessment, it is thought that a small piece of conductive material landed across the cunducter and earth when the door was removed from the switchboard to access the isolation point.
Considering this incident was a minor one when compared to what could have happened if the isolating switch closed, it just enforces how dangerous a short circuit can be.
I hope this is the sort of information which you are after and don't hesitate to contact me should you feel the need.
Thanks,
Leigh
