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Electrical Protection of Synchronous Condenser
9

Electrical Protection of Synchronous Condenser

Electrical Protection of Synchronous Condenser

(OP)
Hello,
Our company is interested to change a synchronous generator 464 MVA to a synchronous condenser.
Do we need to change the generator electrical protections?
Thank you

RE: Electrical Protection of Synchronous Condenser

Yes, I suppose. As Synchronous condenser, the generator will be drawing Watts (active power) from the grid and supplying VArs to the grid.
If yes, the reverse power and Low forward power protections have to be reviewed.
I don't think other protections will be affected.

RE: Electrical Protection of Synchronous Condenser

How will you start it? Starting may require additional protection consideration. You are basically changing a generator to a motor.

RE: Electrical Protection of Synchronous Condenser

Hydro generator? Turbo generator? How do you plan to start it and bring it up to synch speed?

This is a big project which can't be done via internet forums. Take professional services.

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

(OP)
Thank you for your reference to the subject.
It's about GE turbo generator 40 years old . We plan to start it with a pony motor.
We have 2 REG216*4 that protect the generator.
RRaghunath :"...the reverse power and Low forward power protections have to be reviewed. I don't think other protections will be affected..." - O.K.
dpc :"...Starting may require additional protection consideration. You are basically changing a generator to a motor..." - additional protection what did you mean (the pony motor will come with his protection)?
edison123:"...This is a big project which can't be done via internet forums. Take professional services..." - You are absolutely right, we will definitely take it.

RE: Electrical Protection of Synchronous Condenser

Pony motor . . . hmmm . . . why?

If the required electrical equipment is already a/v considerable cost savings can be realized by going this route.

If not, there may well be more cost-effective ways of running up the machine, using one of several different solid-state devices.

A number of years ago I repeatedly had the delightful job of running up and synchronizing a pair of 160 MX synchronous condensers; these were 1960s vintage decoupled generators, formerly connected to steam-driven dual shaft cross-compounded turbines. Run-up used a six-pole-set wound rotor induction motor with salt-water liquid starting resistor driving a five-pole-set generator so full synchronous speed could be obtained.
With this background I can well visualize what it is you hope to do, hence the question.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

Is it a mothballed 2 pole TG set? If you plan to use a pony motor, then the generator settings should not need much change for condenser operation since it is mostly going to provide VAR load. Hydro generators are run often as condensers with the same generator settings.

Out of curiosity, what is the design HP of the pony motor? Will it be VFD driven or with a fluid coupling?

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

I suppose the pony motor will be to reduce the start up current/voltage dip. This works well verses a very large VFD, and preserves the fault current contribution of the condenser. As in some places the amount of inverter based generation has so reduced the amount of fault current, that a source needs to be inserted in the system.

We thought of that, but public view of a coal plant is seen as better to tear it down. But with a hydro unit, it needs to be investigated if the auxiliaries need the water for cooling.

RE: Electrical Protection of Synchronous Condenser

Pony motor will work, need to engineer the mechanical drive side. Low slip, oversized motor will be good.

Make sure you have field failure / pole slipping / field failure protection enabled.

Lots of GE Frame V sets were SYNCON enabled with a clutch in the gearbox, so nothing new here. Very often we shut down the GT and let the generator run on in case it was needed for compensation, since the losses were relatively low.

RE: Electrical Protection of Synchronous Condenser

sori: A synchronous condenser is essentially an synchronous motor operating at no (mechanical) load, with a very large power factor to allow generation of significant reactive power.

Your original generator rating has some power factor associated with the MVA rating. In effect, it already operates with a combination of active and reactive power (most likely). As a condenser, the intent is to presumably operate at a different power factor which shifts the balance to more reactive power than currently available. That (generally) means FAR more field current to the synchronous rotor winding - and your protection should account for this scenario. As Rragunath mentioned, be aware of power flow (direction) and adjust protective settings appropriately.

Converting energy to motion for more than half a century

RE: Electrical Protection of Synchronous Condenser

CR

Quote (Run-up used a six-pole-set wound rotor induction motor with salt-water liquid starting resistor driving a five-pole-set generator so full synchronous speed could be obtained.)


Interesting way to use slow speed machines to run up the generator. Quick questions.

1. Wouldn't six pole set motor driving five pole set generator produce only 5/6th frequency? It should be six pole set generator?

2. Once the main generator reaches synch frequency, how do you transfer to the mains from the pony MG set?

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

Quote (Cr shears)

Pony motor . . . hmmm . . . why?

I imagine it might be that having been built as a generator that would be connected to a prime mover, the amortisseur winding is not capable of accelerating it as an induction motor perhaps?


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

RE: Electrical Protection of Synchronous Condenser

Quote:

the amortisseur winding is not capable of accelerating it as an induction motor perhaps?

That would certainly be my assumption without some evidence to the contrary, jraef.

RE: Electrical Protection of Synchronous Condenser

2
Sorry all, I wrote that from memory on a busy day shift and got the pole numbers reversed; edison is correct, it was a five pole induction motor @ 60 Hz that only needed to run up to 600 rpm [five-sixths of its synchronous speed] so the six-pole generator could make 60 Hz.

High [steam] pressure generator [3600 rpm] and low [steam] pressure generator [1800 rpm] were not originally intended to ever start as motors and therefore had no amortisseur windings that I ever heard of - then again, they may well have been there only for system stability purposes, but nobody mentioned their existence or absence.

HP and LP generator output windings [~18 kV] were connected in common via "isolated phase bus" to two transformers, one being the Main 0utput Transformer [step-up to 115 kV] and the other being the unit station service transformer [step down to 4160V]. Run-up was via backfeed into the unit station service transformer.

Decoupled HP and LP machines were placed on turning gear for 24 hours prior to run-up to mitigate rotor sagging/eccentricity.

Required lube oil pressures and flows and bearing and lube oil cooling water flows were established.

Motor driven exciters were started, field breakers closed, and HP and LP excitation slowly applied until the HP and LP machines locked into synchronism. Since the sub-synchronous speed on turning gear were slightly different, one turning gear [usually the HP] would trip off and the other [usually the LP] would then drive both machines.

Pony generator output breaker was closed; IIRC it had amortisseur windings that pulled it up close to lock-in speed, excitation was then applied to it so it locked into synchronism with the HP/LP combo.

With liquid resistor at maximum, pony run-up motor was energized from 4 kV station service and run-up began.

As run-up progressed, pony motor current would drop, and liquid resistor prongs were lowered into the solute to decrease wound rotor path resistance and increase stator current back to maximum. Also excitation on the HP and LP machines and the pony set generator would be increased to maintain the V/Hz ratio within an acceptable range.

When the aggregate speed was near synchronous, the condenser would be synchronized to the system by closing the 115 kV breaker between the station buswork and the high side of the unit's MOT, and the run-up gear disconnected from the isolated phase bus. The condenser was then available for VAR dispatch.

RE: Electrical Protection of Synchronous Condenser

CR - Thanks for an excellent explanation of the process, which I could totally visualize. Using barring/turning gears for break away torque, which is the most pita, is brilliant. As is using slow speed MG set as a sorta VFD.

I know the cylindrical rotors do have embedded damper windings for speed swings correction but didn't know they are start duty rated. Thanks.

By any chance, do you still remember the nameplate ratings of the pony motor and the generator?

I wish I could h/t both of your posts. Silly ET rules.

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

Hi Muthu,

I don't have to remember; I kept a paper copy of the SLD for the scheme, along with a set of the start-up and shutdown procedures, and have fetched same from my locker.

I can therefore not only correct my earlier mis-remembrances but supply additional information.

Original units full load output when steam driven was 200 MW; unit rating as a synchronous condenser was from 40 MX in to 168 MX out.

There were actually two unit station service transformers connected to the isolated phase bus; the latter operated @ 13.8 kV, not 18 kV.

Run-up set pony motor was rated @ 3300 IHP; pony generator was rated @ 2400 kVA. The pony set was equipped with an overspeed trip set at 660 rpm.

Addition via edit: The pony generator had a squirrel cage winding so that when its output breaker was closed it would spin up slowly from rest to whatever sub-synchronous speed was for a prevailing isolated phase bus frequency < 1 Hz. Field excitation would then slowly be applied to it until it locked into synchronism with the HP and LP machines. Both the pony motor and generator had jacking [oil lift] pumps, [virtually?] eliminating any sticktion at spin-up from rest.

The external liquid resistor for the wound rotor induction pony motor contained washing soda dissolved in distilled water. Today of course one would use regenerative circuitry to recoup the energy formerly lost in heating up the liquid resistor by instead converting it back into an AC output and returning the power to the system.

Maximum allowable start-up sequence time was thirty minutes, but it could normally be completed in under twenty-five.

Using movable plug-in pin contacts, the run-up set could be configured to start C5, C6, C7 and C8, although only C6 and C7 were ever fully commissioned.

Question for the OP: was your protection concern only for the unit when on line and deployed as a VAR resource, or were you also looking at a protection package for the run-up gear?




CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

Thanks, CR.

2.4 MVA pony generator to start up 200 MW generators is pretty neat.

Is there a reason why the start-up sequence should not exceed 30 minutes?

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

edison123 Probable reason for 30 minute limit was heat generation in the squirrel cage winding of the pony motor, particularly at the bar-to-ring joint. (Note that this is the usual reason for line-start timing for any AC machine (induction or synchronous) spinning up under induction to line frequency. The limit does NOT exist for operation with a variable frequency source, provided the source can ramp up from < 1 HZ.)

Converting energy to motion for more than half a century

RE: Electrical Protection of Synchronous Condenser

What Gr8blu wrote sounds about right; if I find the stated answer I'll provide it. - addition via edit: went through the entire document; no reason for time limit given, only additional item is that operator would receive an "approaching maximum start time" annunciation one minute before actual trip would occur.

Somebody sure did some careful calculations to size the pony set properly; I remember the initial acceleration rate seemed almost breathtaking, but as the windage of the hydrogen blowers built with the square of speed, near synchronous the acceleration rate fell off significantly. Indeed if one kept an eagle eye and had the unit's terminal voltage close one could synch the units on the fly, meaning catching the wave just as the units accelerated through synchronous speed.

RE: Electrical Protection of Synchronous Condenser

edison123 wrote:

Quote:

I wish I could h/t both of your posts.

That sounds very complimentary, Muthu . . . but what does it mean?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

Gr8blu - CR said it's a slipring motor with external resistance used as a sort of speed control. In today's world, a cage motor with VFD would do it, as you say.

CR - It means that I could not give more stars for all your posts. ET's silly rule restricts it to only one star in a thread. These synch condensers were hydrogen cooled? That would explain such low levels of pony MG set since I expect windage loss with air to be much higher.

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

Hello sori, I realize I'm going beyond the scope of your OP, but more information would help.

For example, you state:

Quote:

We plan to start it with a pony motor.

This does not in any way say how you plan to go about this . . .

Would a retired prime mover be partially dismantled to make room for the pony motor needed to be permanently mechanically coupled to the prospective condenser it would drive to synchronous speed?

What kind of pony motor? What rating?

Or would your pony motor be driving a run-up generator similar to what I used to operate?

Or some other approach?

Depending what's already on site, a far cheaper approach could be to segregate a portion of the station's high voltage switchgear so that a two-shaft gas turbine generator rated at, say, 10 to 20 MVA could be electrically coupled to the prospective condenser and used to run it up to synchronous speed.

Alternatively a hydraulic unit at some other site could be segregated onto one circuit or feeder and electrically coupled to the machine for the same purpose.

One electrical area I am aware of found itself in need of a frequency changer between 25 and 60 Hz, and a very innovative approach was developed to address this need, to wit:

Since a great deal more water had been made available to this plant, it was twinned [although its twin had more than double the capacity]. There was therefore now more generating capacity available within the pair of plants than there was water to run them.

So one unit was decommissioned as a generator; the 25 Hz alternator on top was lifted out of the way, the turbine cavity was gutted, and the scroll case inlet and draft tube outlet sealed off with concrete. A new air-cooled 60 Hz alternator small enough to fit into the cavity was then installed, cooling water piped to its bearings and stator cooling rads [to reject the heat from the recirculated cooling air, while eliminating the requirement for a great deal of jack-hammering of structural concrete], and appropriate electrical connections made. The 25 Hz machine was then re-installed atop it and mechanically coupled up.

Starting was accomplished by separating the adjacent hydraulic unit and one outgoing circuit onto their own little synchronizing bus, starting the jacking oil pumps, getting the hydraulic unit creeping, applyiong excitation to both units until the two locked into synchronism, then running them up as a pair, maintaining the appropriate V/Hz ratio on the way to synchronous speed.

It worked beautifully.

Going one step further, the system design engineers did not want to be limited to starting only from the 25 Hz side, thus the ability to perform starts was specified for the 60 Hz machine as well so the unit could be started from the adjacent 60 Hz plant.

Addition via edit: since the frequency changer was kept i/s 24/7 and very rarely shut down, there was little additional burden imposed by system reconfiguration for these infrequent starts, and therefore very little financial incentive to develop a different starting means such as adding really beefy amortisseur windings to either of the machines so as to enable DOL starts.

Bottom line is, there may be any number of ways to not needlessly spend money and still accomplish your desired objective . . . more information yields better answers!

RE: Electrical Protection of Synchronous Condenser

edison 123 wrote;

Quote:

CR - It means that I could not give more stars for all your posts. ET's silly rule restricts it to only one star in a thread.

Then I guess all you can do is to try and talk others into giving me more LPSs !!! [ written tongue in cheek while displaying soot-eating grin ]

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

May or may not apply, but some GT sets are started by using a sort of VFD on the generator windings to bring it up to a speed where the GT can ignite. This scheme could be used to start a synchronous condenser to a speed, then attempt to catch it.
Just a thought.

RE: Electrical Protection of Synchronous Condenser

replying to edison123 post from 20 AUG Even a wound rotor induction (actual rotor winding connected to slip ring and from there to external resistance, usually supplied by liquid rheostat and mechanical movement of electrodes) still starts up "direct-on-line", just like any other squirrel cage induction or synchronous machine not operating on a drive. That means there is a thermal limit on the conductors of the windings and the connections between them, just like the other AC machines. All the external resistance does is limit the current being applied during the acceleration - thereby limiting the available torque through the rotor shaft.

The reasoning behind that magic 30 minute window still applies to a wound rotor motor design.

Converting energy to motion for more than half a century

RE: Electrical Protection of Synchronous Condenser

gr8blu - A slipring rotor starting on line rarely sees two times the rated current as LRA. Since 30 minutes is already continuous duty, this may have been a special purpose motor designed to handle that current continuously. Anyway, my post you referred was to point out it wasn't a cage motor.

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

Cranky108 wrote:

Quote:

May or may not apply, but some GT sets are started by using a sort of VFD on the generator windings to bring it up to a speed where the GT can ignite. This scheme could be used to start a synchronous condenser to a speed, then attempt to catch it.

Hi cranky, that was what I generalized about when I referenced "several different solid-state devices"; LCI was one of the approaches I had in mind, I just didn't want to get into the nitty-gritty details and possibilities too early into the thread.

Also, edison asked:

Quote:

These synch condensers were hydrogen cooled? That would explain such low levels of pony MG set since I expect windage loss with air to be much higher.

Yup, hydrogen cooled, with rotor-mounted blowers/fans to circulate the H2 through coolers with raw water flowing through them. I remember early on in my working life when I was an auxiliary plant operator in a similar coal-fire generating station operating these cooling systems, the seal oil system that kept the hydrogen inside the generator where it belonged, maintaining the internal casing pressure at ~30 psig, purging out hydrogen with CO2 and then purging that out with air when overhauls were about to commence, and on the way back from overhaul displacing the air with CO2 then top-filling with H2, operating the associated desiccant systems, and so on and so forth; fun times.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

One of the problems we saw with using a sort of VFD on the generator to start the GT, was that the unusual frequency caused the PT fuses to degrade, and blow for normal loading. But for the life of me I don't know why we need current limiting fuses when the high impedance neutral would limit the fault current to a very low value.
Anyway, different types of fuses, and now they are saying fuse orientation is an issue.
Looks like a bad design by GE, but we keep paying to fix it.

I was told that GE means 'Good Enough'.

RE: Electrical Protection of Synchronous Condenser

I was told that GE means 'Good Enough'.

I used to work for GE and we said the same thing. :)

RE: Electrical Protection of Synchronous Condenser

This link

https://www.google.com/search?rlz=1C1CHBD_enCA820C...

is to pictures of what the control room became for just a short while almost thirty years after I used to run up and control synchronous condensers there . . .

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

cranky - What was the rating of that VFD/LCI?

CR - Was hydrogen cooling used in condenser mode too? Those restaurant pictures are so dystopian.

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

Edison123 asked:

Quote:

CR - Was hydrogen cooling used in condenser mode too?

Yes, it was; units at full rotative speed could not have handled a gas of any greater density withut blower and other modifications, plus a fairly healthy current would be flowing in both the rotor and stator windings at 80 MX per generator @ ~14 kV [ unfortunately I have no documented information about whether these units also had stator winding cooling with demineralized water / raw water heat exchanger, and my memory isn't THAT good . . . ].

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

Thanks, CR. Your memory is damn good.

Muthu
www.edison.co.in

RE: Electrical Protection of Synchronous Condenser

cranky - What was the rating of that VFD/LCI?

I never thought it important to look into it. Should I?

I try to keep my nose out of things I don't need to be involved with. I.E. irritate other engineers that don't need the disruption.

RE: Electrical Protection of Synchronous Condenser

I have been away for awhile. crshears just brought this thread to my attention and asked for my comments.
First, my thoughts on motors and generators.
For most industrial machines, there is only a few RPM or Volts difference between a motor and a generator.
A an induction motor, synchronous motor, or a DC motor, a fairly minor increase in RPM and the motor is now a generator.
An induction motor rated for 1760 RPM becomes an induction generator when driven over synchronous speed. It will be pushing close to full rated current into the grid if over-driven at 1840 RPM. (Think; 1800 - 40 RPM, 100% loaded motor, 1800 + 40 RPM, 100% loaded induction generator.
A synchronous motor, needs only a few electrical degrees advance to become a generator.
A DC motor is similar to the induction motor in that if it is over-driven a few RPM it becomes a generator.
These motors generate back EMFs that are close to the applied voltage.
If the field is increased so that the back EMF of a synchronous motor rises above the line voltage the motor becomes a VAR generator.
I haven't seen it dome for many years but once upon a time and long long ago, plants would drive a large load with a synchronous motor that was two or more times the HP that was needed.
Then when in operation, it would be run over excited so as to both drive a load as a motor and function as a VAR generator to help the plant PF.

Consider a DC motor coupled to a drive of fixed speed. (This is a class-room demonstration of DC machine characteristics, and not intended to be a practical field application.)
Neglecting the field current and windage and friction, (shunt connected motor) if the field is adjusted so that the back EMF is equal to the applied voltage, the motor will idle and draw no armature current. With any increase in field strength, the motor will become a generator and export power to the source.
If the field is decreased, the back EMF will drop below the applied voltage and the machine will start to export mechanical power.
Now, if the field is held constant, so that the back EMF equals the applied voltage, and then the speed is reduced, the back EMF will drop and the machine will become a motor.
Likewise, if the speed of the drive is increased, the back EMF will rise above the applied voltage and the machine will become a generator.

To sum up.it can be said that there may be only a few RPM or a few volts difference between a generator and a motor.

Back on topic:
I have not seen mention of a synchro-scope in the above posts. If I missed it, I am sorry and I tender my regrets.
You may have two choices here;
1. You may use a synchro-scope and synchronize the machine as if it were a power generator.
2. You may be able to use a polarized field frequency relay and sync the machine on line similar to starting a synchronous motor.
If I saw someone about to close the breaker without any kind of sync check, despite friendly warnings, I may just move back and start recording. There is a fairly good chance of excitement with an out of phase closure.

The other point that I would mention is that heat is your enemy. I would not be running either the field or the armature above rated current. Motor or generator, I^2R doesn't care. Current is current and heat is heat.
If the field must be run at higher than rated current, then consider de-rating or reducing the armature current.
How much? It depends. A rule of thumb may be to calculate the heat developed (I^2R) in both the field and the armature windngs at rated currents and then again at the new proposed currents. Reduce the calculated maximum armature current somewhat to allow for hot spots and unforeseen consequences. You may consider that as the ultimate maximum. (If you find someone with proven experience in this matter, listen to him, and forget what I say.)

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Electrical Protection of Synchronous Condenser

Hi again, Bill, and thanks for weighing in.

I readily admit that I only mentioned synchroscopes in passing, almost tangentially if you will, when I wrote:

Quote:

Indeed if one kept an eagle eye and had the unit's terminal voltage close one could synch the units on the fly, meaning catching the wave just as the units accelerated through synchronous speed.

So just to be clear, yes, in the application I mentioned we synchronized the condenser to the grid using the then-conventional fully manual, perhaps now dated, synchroscope and voltmeters to match voltages, minimize slip frequency, and close the unit breaker just as the needle on the 'scope was approaching zero degrees [ 0° ] / twelve o'clock, meaning giving the breaker close impulse sufficiently in advance that by the time the 115 kV oil circuit breaker contacts actually closed zero degrees phase angle difference across them had been reached.

I was sometimes criticized for taking too long at this task, but as you allude to, I was not and am still not a fan of that kind of "excitement".

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

Sori ,
I am interested in the price of the taken reactive energy for your factory and positive results of converting a synchronous motor into condenser .
Often the price of reactive energy is low in relation to the active power you have to use to idle the synchronous motor and there is no economic interest in engaging in such activities

RE: Electrical Protection of Synchronous Condenser

Vars have no value, until your utility imposes a Power Factor penalty on your bill.
But Vars do consume transformer and lead capacity, and can cause over heating.
That extra current can cause voltage drop, which can lead to motors over heating, and starting problems.

So reactive power is important, but likely not to those who over simplify their plant electrical systems.

RE: Electrical Protection of Synchronous Condenser

Unfortunately explaining this to the bean counters can be problematic; you need to find one who has

[1] the willingness and vision to look beyond the limitations of, and information provided on, their spreadsheets so as to see the bigger picture, and

[2] the authority to direct others to incorporate these end facts into their thinking, fiscal structures, and financial decisions.


This is not always an easy task.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Electrical Protection of Synchronous Condenser

The value of a VAR:
Buying or selling?
It is common for consumers to be forced to buy VARS, to compensate for a poor power factor.
Rather than a direct, fixed cost per VAR, it is common to be charged a penalty for excess VAR consumption.
The worst case that I am aware of was an installation being charged a 90% penalty for VAR consumption.
That is, the penalty was 90% of the KWHr charges.
Think: Significant negative value.

On the other hand, I know of an instance where the main transmission line feeding a large city was being loaded beyond its capacity.
Note: On some transmission lines, the capacity is not limited by conductor ampacity but rather be the ability of the On Load Tap Changers to compensate for line loss.
In this instance, the line capacity was increased by mitigating the line losses to some extent by injecting VARs at the load end of the line.
This was done by taking an old diesel generating plant out of moth balls and putting it back online, over excited and under powered.
Running over excited, the sets injected VARs into the system.
Running at a low power setting resulted in little kW generation and low fuel costs.
I was never aware of the billing formula, but those VARs surely had value.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Electrical Protection of Synchronous Condenser

With the increase in non-synchronous generation in networks there has been more interest in provision of 'system strength' services, where having the machine spinning but not necessarily importing or exporting a nominated quantity of VArs can be desirable. This is probably more applicable to a Generator that directly participates in an energy market rather than conversion of a synchronous motor to a condensor for what is normally only a consumer.

Such an arrangement is likely to assist both in terms of provision of fault current as well as frequency support through spinning mass.

I'm not really across the financial arrangements as to how the Owner gets compensated for the power losses involved or makes money from having the machine spinning, but I do expect it'll become more common with a larger mix of inverter driven wind and solar.

EDMS Australia

RE: Electrical Protection of Synchronous Condenser

Synchronous compensation with added inertia becoming more common in Europe as some renewables wind, battery etc have virtually no inertia to help recover from load swings

https://www.siemens-energy.com/global/en/offerings...

RE: Electrical Protection of Synchronous Condenser

I was thinking we might get to a point of installing one because of decreasing fault currents.

RE: Electrical Protection of Synchronous Condenser

Our uk grid people tried a few years ago to get the small scale generation - cogeneration, CHP etc to increase their inertia ... at zero price increase ...

RE: Electrical Protection of Synchronous Condenser

Quote (Freddy)

With the increase in non-synchronous generation
I suspect that you mean "Low Inertia Generation".
As far as I know, most commercial wind and solar installations are synchronous, but low inertia.

Capacitor banks, whether static or rotational, have been common for decades, possibly a century.
Utilities use capacitors to improve power factors and thus free up equipment capacity and to mitigate line voltage drop on long lines, both distribution and transmission.
One of the more interesting projects that I worked on many years ago was installing capacitors in series with a transmission line.
The power source (Hudson Hope) was a long way from the utilization area (Vancouver and the Lower Mainland).
There were two transmission lines and each line had two capacitor stations.
In this case, the series capacitance offset the series inductive reactance that is a characteristic of long transmission lines.
The lines in question were rated to carry 2000 Amps as I recall.
The transmission voltage is 500,000 Volts.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Electrical Protection of Synchronous Condenser

I think that would be synchronous, as in synchronous machines, vs. synchronized, as in any connected generation.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Electrical Protection of Synchronous Condenser

My Ontario, Canada utility has a pair of 500 kV circuits that run Sudbury to Woodbridge, with one set of series capacitors in each circuit, near Parry Sound.

They work great, when they work; but alas, it is not unknown for their behavior to be somewhere between temperamental and downright twitchy . . . but I digress way off topic.

Has it fallen out of favour to use grossly oversized synchronous motors to drive major plant loads with the balance of the motor's capability being employed in power factor correction? I thought I found mention of that earlier in this thread but cannot at the moment see where.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

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