Megavars
Megavars
(OP)
Can someone please give a basic summary on megavars and what they do?Thanks in advance.
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RE: Megavars
non-zero vars indicates reactive current flow is taking place, and represents current flow that is performing no useful work, but which increase the voltage drops in you feeders
Watts (real power) := Volt-Amps * Cosine (phase angle)
Vars (reactive power):= Volt-Amps * Sine (phase angle)
while the Power Factor is defined as:
PF:=Cosine (phase angle between the voltage and the current)
RE: Megavars
negative megavars too.
Positive megavars can result in very high system voltage and over-excitation.
negative megavars can result in low system voltage, and going below the under-excitation limit which is very dangerous because the generator can fall out of synchronism and get mechanically damaged... badly. not a pretty sight.
cheers.
a.
RE: Megavars
RE: Megavars
One other real aspect of reactive power is that it is a necessary component of power transmission, and there is a real tug of war right now with independent power producers in the USA because no one gets paid for "shipping" reactive power, and none of the independents want to do it, where as the regulated utilities recognized it as a fact of life, and accomodated it by the way they operated certain units to generate the reactive power a system needed. That is about all I can comprehend about the matter as an "iron piler".
RMW
RE: Megavars
We get paid for producing Mvars by the grid company and can be instructed to produce leading or lagging Mvars inside the capability curve of the generators and transformer.
RE: Megavars
RE: Megavars
week We had a bad experience with Generator, quicly the
automatic excitation was zero, mvars too and after this
we saw that mvars changed to negative value.
At the next day, we worked out(out service) the generator,
for inspection and this one, done equal failure.
What's your aswers to these experiences ?
RE: Megavars
javi1972 - I understood you to say you lost excitation and now your generator is damaged. My guess is that possibly there was a pole slip since real power wasn't reduced and effective power transmission capability was diminished by reduced generator voltage (P ~ |V1||V2|/|X|). Obviously protection should function to protect generator from damage under these circumstances.
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RE: Megavars
Because the system is AC (cyclic), the rate of energy exchange between the generator and induction motor (to provide the buildup and decay of the field) is the reactive power.
RE: Megavars
Been out for a few weeks so forgive the delay. I understand all about VARs but was wondering if your generating plant bills for VAR's? None of ours do (we are federal though so our superiors are not real business savvy). I always wondered why they did not since the utilities do bill the end-users for this.
RE: Megavars
the wear and tear on the equipment far out weighs any percieved benefit. at a minimum you experience a lot of undervoltage trips (increased voltage drop due to the vars being shoved around), etc.
the best bet is to run as close to unity pF as possible and perform the pF correction in other ways.
RE: Megavars
Can't leading loads cause generator problems, problems with voltage regulators and oscillations and voltage instability? Wouldn't we like a bigger cushion than running at unity?
RE: Megavars
RE: Megavars
RE: Megavars
RE: Megavars