Iacdrive|Automation Solution

India renewable energy

Refer to the REI seminar, wherein Government of India representative stated that the VGF payment is spread over 5 year period.

1) Any profit Making Company, must have had the benefits from the Government (subsidies etc) / Eco system.

The profit must be taxed for the improvement of the Economy of the Country.

2) Present renewable energy policy is allowing these profit making companies to avoid paying taxes, and own the assets due to such FREE EQUITY, which belongs to the Government, thus Accelerated Depreciation (AD) is a killer of Economy.

Thus, we are unable to develop the NICHE technology as unrelated industries are owning the project due to avoidance of paying taxes and just to own the assets due to such loop hole in the policy, later making an early exit to make quick money without serving the Nation.

AD promotion is not a level playing field apart from Tax loss to the Government.

3) The Tax thus saved, is again allowed to earn 19 to 24% Return On Equity (ROE), which is very unfair (actually this should have been disallowed to have rs.3/kwh less tariff), due to a fact that, this is public money, hence, should not be allowed to have such wind fall gains.

4) By loading ROE, showing high CAPEX and taking back more than 30% project equity, getting EXIM Bank or such low cost funding to reduce the interest burden, but, Tariff claimed of rs.18 or 15 or 10/kwh is once again a kind of Tariff subsidy, thus, a common man is paying more money for RE power tariff, which is a great killer of economy and making people poor.

5) Viability Gap funding in addition to AD will be an Economic suicide as a project promoter will be allowed to take back 60 to 70% of project cost without paying tax on profit earned !!

This is likely encourage poor equipment buying / its maintenance due to such immediate undue / windfall gains.

6) Despite taking such huge wind fall gains, again these project promoters will be allowed to sell the project to others, to make further wind fall gain to make few existing companies to get undue benefits due to such wrong policy guidelines, despite many representations made to the Government, which states that they have go clearance from Finance Ministry to further ruin the Economy !!

What is SynRM motor?

Many others thirty years ago, synchronous reluctance motors (SynRM) have finally replacing the traditional AC induction motors in the industry. ABB has claimed achieving IE4 efficiency with SynRM, a great improvement from IE2 efficiency with the traditional induction motors, for the same motor envelope size and input power.

A SynRM is a true AC machine with or without permanent magnets on the rotor. It is totally different from the closed-loop controlled, permanent magnet brushless DC machines (BLDC) in that one would never be able to get rid of torque ripples as that have been achieved in commonly used BLDC machines.

The difference is on the rotor: copper or aluminum bars for inductance motor (squirrel cage after joining end disks) vs. flux barriers (air pockets) in SynRM. The SynRM rotor can be further enhanced by inserting permanent magnets in the air pockets for a machines called PM assisted SynRM. High efficiency is achieved for two reasons: 1) no copper loss due to the lack of rotor bars and end disks; and 2) high inductance difference between d- and q-axes (Ld-Lq) because of flux barriers and motor torque linearly proportional to (Ld-Lq).

In comparison with the traditional AC induction motor, a SynRM motor needs a frequency inverter and when permanent magnets are present in the rotor, a rotor position feedback sensor. The drawbacks of SynRM are the motor torque ripples due to switching operation, inherited small air gap, etc.

Special Protection System Advantages and Disadvantages

Quite a few yrs. ago around 1988, I was a Protection and Control Engineer at a large utility in the SE. We were doing our planning to bring the final unit of a large 4 unit plant on line, when it was discovered that we could encounter some unusual instability scenarios. The funny thing was that with all units on-line and above a certain MW output, all that would need to occur would be opening of a remote 500kV breaker on one of the particular lines and the event could trigger, eventually bringing ALL 4 units at the plant out-of-step and tripping off all of the generation in just a few minutes (3600 MW).

The studies were performed numerous times by internal and external experts but the results were always the same. The key problem seemed to be the existing network configuration of 4 units and only 3 transmission lines. Adding a 4th 500kV line from the plant seemed to cure the problem under all conditions, including close in 3 phase faults with breaker failure. Unfortunately, the cost and timeline to build a new t-line was a real challenge!

In order to proceed with commissioning the 4th unit and remediating any scenarios for tripping all generation, a Special Protection System (SPS) was developed. A transfer trip channel was installed at the remote substation, keying on the breaker contact opening. At the plant, a Unit Trip scheme was installed that had a MW meter supervising tripping of any one unit selected by the plant operator (U1-U2-U3-U4). If all units were on line and generation was above 2500 MW (margin of safety added), then a receipt of remote breaker opening would trip the selected unit to avoid having all units cascade into out-of-step condition.

Advantages: Clearly, this Special Protection System saved the day, and bought time until an additional line was added 4 years later.

Disadvantages: The downside was the challenge of installing and testing such a complicated scheme with the potential for mis-operation. I don’t recall any mis-operations occurring, but it was still a bit “dicey”. I have been at that same plant during a full load unit trip (Generator differential) and it was an “exciting” experience to say the least! While I did recommend that we conduct a “live test” to see what would really happen and perhaps test our system BLACK START procedures, this suggestion was not well received by management (LOL).

This was my only encounter with such a special protection system scheme in my 35 years of utility work, but it was very interesting to be involved with this project.

TIA portal, a nightmare!

I have been using TIA since it was launched and it has come on leaps and bounds since it was first launched. Its a great tool and as already mentioned it has its bad aspects but it also has its good aspects. The biggest improvement (in my opinion) is the drag and drop functionality in the WinCC part and the code editor. Just need a field PG to be launched with screens to fold out so you can have multiple screen!!

They are moving in the right direction and it was always going to be resource hungry WinCC was bad enough for that in previous versions.

New improvements make a long list but one of the most recent is being able to switch a DB to and from optimised. How many times in previous versions did I forget to check the box then have to delete the DB and create it again. PID loop tuning function within TIA is useful and if you look on the Siemens Automation website (UK/Europe) the example files are growing all the time and they have some great examples that can be integrated easily in to application, I have used the ASi maintenance and monitoring example which was very well put together along with a few others. Even if you don’t use them but need some pointers on which way to go they are a good starting point.

I could list the gripes I have, but all in all its coming together nicely, just need a decent well priced Field PG to run it on £5K is a bit steep for an M4 which maybe no great improvement on the M3 which, in my opinion, wasn’t very good.

Few months ago I had a project with TIA Portal v11. Hardware targets: Simatic S7-300 and Simatic Comfort Panels.
Compared to RSLogix 5000 / FactoryTalk View for example, TIA Portal is a nightmare, especially on commissioning and start-up, when the pressure is huge and you have to work FAST.

The main problems:
1. Very slow on every operation (compiling, downloading, on-line editing, project printing/documenting).
2. Requires a very high resolution display (it is almost unusable on a 1366×768 laptop)

3. Weird behavior (HMI display alterations, crashes).

Synchronous generator operating frequency

When synchronous generators (alternators) are connected in parallel with each other on an AC grid, they are all operating at a speed that is directly proportional to the frequency of the AC grid. No generator can go faster or slower than the speed which is proportional to the frequency.

That is, when a synchronous generator and its prime mover is operated in parallel with other synchronous generators and their prime movers, the speed of all of the generator rotors (and hence their prime movers if directly coupled to the generator rotors) is fixed by the frequency of the grid. If the grid frequency goes up, the speed of all the generator rotors goes up at the same time. Conversely, if the grid frequency goes down, the speed of all the generator rotors goes down at the same time. It is the job of the grid/system operators to control the amount of generation so that it exactly matches the load on the system so that the frequency remains relatively constant.

Isolated or is landed generators that are not in parallel with other generators have an added limitation in that keeping exactly 50Hz is somewhat difficult, or puts too much demand on controlling/governing systems. In such environments it is normal to accept some small deviation from the nominal frequency.

The vast majority of power for industry is supplied by large rotating AC generators turning in synch with the frequency of the grid. The frequency of all these generators will be identical and is tied directly to the RPM of the generators themselves. If there is sufficient power in the generators then the frequency can be maintained at the desired rate (i.e. 50Hz or 60Hz depending on the locale).

An increase in the power load is accompanied by a concurrent increase in the power supplied to the generators, generally by the governors automatically opening a steam or gas inlet valve to supply more power to the turbine. However, if there is not sufficient power, even for a brief period of time, then generator RPM and the frequency drops.

By operating transformers at higher frequencies, they can be physically more compact because a given core is able to transfer more power without reaching saturation and fewer turns are needed to achieve the same impedance. However, properties such as core loss and conductor skin effect also increase with frequency. Aircraft and military equipment employ 400 Hz power supplies which reduce core and winding weight. Operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetizing current. At a lower frequency, the magnetizing current will increase. Operation of a transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. For example, transformers may need to be equipped with ‘volts per hertz’ over-excitation relays to protect the transformer from overvoltage at higher than rated frequency.

Stiff voltage sources

Stiff voltage sources are not problematic as long as they don’t get in the way of the solver’s attempts to linearize the behavior of the circuit matrix via step size reduction. It is the highly nonlinear stiff sources that are heavily fed back into the rest of the circuitry that can cause the solver to hang. Linear sources that are ground referenced or nonlinear ones that don’t feed back anywhere are not likely to cause problems.

In the initial versions of SPICE there were a few elements that could not be simulated directly with nodal analysis in the circuit’s admittance matrix, ideal inductors and voltage sources being the most common among them. However, starting with some version of SPICE 2 this deficiency was removed when modified nodal analysis (MNA) was added to the simulation engine (requiring an additional computational enhancement sometimes called the auxiliary matrix, I believe).

Modified nodal analysis is an extension of nodal analysis which not only determines the circuit’s node voltages (as in classical nodal analysis), but also some branch currents. This permits the simulation engine to crunch ideal inductors and voltages sources (true Thevenin circuit elements) but at a cost of incrementally increasing the matrix size and difficultly about twice as much as for when “easy” Norton type elements (e.g., resistors, capacitors and current sources) are added.

In other words, adding one ideal inductor slows down the simulation about as much as adding two ideal capacitors. However, there is a small additional silver lining to this, as it also comes with the possible advantage of “free” (whether you use it or not) automatic sensing of instantaneous inductor current.

LTspice (my simulator of choice) treats inductors in a special way in that they are normally given a default series resistance of 1 m-ohm unless a value of zero is explicitly entered for that parameter. Having a non-zero series resistance allows LTspice to “Nortonize” the inductor such that it can be processed as a normal branch within the circuit matrix, thereby allowing the simulation to run marginally faster. This also makes the inductor “look” like any other of the “easy” elements so that it is not a numerical problem to parallel it with a stiff voltage source. If a series resistance parameter is entered for a voltage source, it also becomes Nortonized by LTspice.

Nortonizing an inductor or voltage source comes at the cost of giving up free sensing of the instantaneous branch current, which is not a cost at all if this current is not being used elsewhere. However, as soon as you call out the inductor current in *any way* in any b-source behavioral expression, LTspice changes the default series resistance for that inductor back to zero ohms and reverts back to the standard MNA way of processing it within the circuit matrix so that it can get access to the inductor’s instantaneous current.

Only true Thevenin type elements have the possibility of being used as the instantaneous current sense for a current controlled switch (or other similar current controlled devices). The SPICE standard is to only allow voltage sources for this purpose, but apparently LTspice accepts zero ohm inductors as well.

One last note, LTspice is indeed able to measure the current in any element, including Norton type devices, but for these devices the current measured will necessarily be a time delayed version that may not be suitable for tight feedback loops (there is a warning about this in the LTspice Help file section on b-sources).

Variable Frequency Drive Basics (Working Principle)

Variable Frequency Drive (VFD) Basic Configuration
The basic configuration of a variable frequency drive is as follows.
VFD Basic Configuration
Fig. 1 Basic configuration of variable frequency drive

Each part of a variable frequency drive has the following function.

Converter: Circuit to change the commercial AC power supply to the DC
Smoothing circuit: Circuit to smooth the pulsation included in the DC
Inverter: Circuit to change the DC to the AC with variable frequency
Control circuit: Circuit to mainly control the inverter part

Principle of Converter Operation
The converter part consists of the following parts as following figure shows:

Converter
Inrush current control circuit
Smoothing circuit

Fig. 2 Converter part

Method to create DC from AC (commercial) power supply
A converter is a device to create the DC from the AC power supply. See the basic principle with the single-phase AC as the simplest example. Fig. 3 shows the example of the method to convert the AC to the DC by utilizing a resistor for the load in place of a smoothing capacitor.

Fig. 3 Rectifying circuit

Diodes are used for the elements. These diodes let the current flow or not flow depending on the direction to which the voltage is applied as Fig. 4 shows.
Diode
Fig. 4 Diode

This diode nature allows the following: When the AC voltage is applied between A and B of the circuit shown in Fig. 3, the voltage is always applied to the load in the same direction shown in Table 1.

Table 1 Voltage applied to the load

That is to say, the AC is converted to the DC. (To convert the AC to the DC is generally called rectification.)

Fig. 5 (Continuous waveforms of the ones in Table 1)

For the three-phase AC input, combining six diodes to rectify all the waves of the AC power supply allows the output voltage as shown in Fig. 6.

Fig. 6 Converter part waveform

Input current waveform when capacitor is used as load
The principle of rectification is explained with a resistor. However, a smoothing capacity or is actually used for the load. If a smoothing capacitor is used, the input current waveforms become not sine waveforms but distorted waveforms shown in Fig. 7 since the AC voltage flows only when it surpasses the DC voltage.

Fig. 7 Principle of converter

Inrush current control circuit
The basic principle of rectification is explained with a resistor. However, a smoothing capacitor is actually used for the load. A capacitor has a nature to store electricity. At the moment when the voltage is applie

Different brushes at same ring

Recently I had to do a report explain why is impossible join brushes, at same time, from different companies, even with same characteristics.
I used the follow points:
1 – Even with same characteristics the final results is different because tue proportion of material and/or manufacturing process different lead to a different brushes;
2 – Guarantee, because our machine is new, and is a good practice use brushes recommended by Manufacturer;
3 – The film, that is formed on the rings by the brushes could change (but I don’t have any sure if chage for bad);

Unfortunately my report was based on experience for old engineer and recommendation of Manufacturer.

One
of the most important thing about brushes in high current density
environments is uniformity. If there are any variations in material
composition, manufacturing methods, dimensions, porosity, density,
surface hardness, friction coefficient, pig-tail attaching means, size
of pig-tail conductor, etc., there will be a variation in the current
division and/or wear.

Ultimately some brushes will carry more current than others and the increased current density in those brushes will lead to overheating, pitting, scoring, and ultimately costly repairs to the commutator/slip-rings. You might also accidentally mix brush grades when dealing with multiple vendors.

Although manufacturers publish data for brush materials which may prove to be very close to one another, mixing them on a collector surface is not a good practice. Any signs of undesirable performance would be difficult to identify the root cause for and small differences in electrical resistance can produce staggeringly varied performance from each brush.

While the materials used have good material data supplied with them, the manufacturing of the cable connection does not which can account for many times the resistivity differences of the material. Brush manufacturers do use a variety of materials here also and so some brushes, even of the same grade and from the same supplier but with different connection material, cannot be used together.

Mixing of grades is an uncontrolled practice which leads to variable surface conditions especially where the numbers of each grade used is not controlled.

Lower resistance brushes will “grab” the current possibly over filming the collector surface leaving the higher resistance brushes to run at lower than prescribed minimum current densities which results in higher coefficients of friction at the brush/collector interface. You would never know when your film is stable which endangers machine life.

Most machine manufacturers select a grade of carbon to use which is useful at the machines fully rated capacity. However, manufacturing tolerances, specifications etc can produce a machine vastly over rated for your application. Running the manufacturers supplied brushes at reduced load can be very damaging. Most Manufacturers will accept that you need another brush grade for your specific use and will maintain warranty provided they have been consulted regarding any changes.

Many overlook that by moving a machine from one position in their plant to another, that they well need to consider the brush grade at that time also. Sometimes a simple and cost effective reduction of brushes (of the same grade) within the machine can increase plant reliability and longevity dramatically. Other times a consultation with a brush expert can lead to an alternative grade to produce better performance.

The cause of harmonics in variable frequency drive

Before you attempt to dissipate causative factors of harmonics verbally, you take a look at several studies done by NEMA regarding such, and look into variable frequency drive (VFD) a bit better. You can view articles and studies by subscribing to the NEMA newsletter, and find other sources quite readily through NEMA. It’s an easily accessible place for many current dissertations on this and other electrical topics, with excellent subject matter.

Categorizing all VFDs into the same bucket doesn’t get it. You can also look at EPRI reports done better than 15 years ago on this and other VFD oriented subjects. Of course, all VFDs use Pulse Width Modulation to create the AC type wave form output (AKA ‘Sinusoidal Flows) and of course all have rectifiers at the top end, as do all computers, PLCs, and many solid state control components. The differences of transient creation on the outputs of variable frequency drives depend upon the quality of the wave form output. The more transients or ‘spikes’ in the wave form, the more disruption potential. The quality of outputs of variable frequency drives can clearly be seen in testing with oscilloscopes. Several VFDs on the market significantly reduce this effect with chokes up front, and on the output. It really is a garbage in/garbage out situation that lesser drives don’t bother to address.

Anytime AC is rectified to DC a field is created, and this is at best an elementary statement. The solution is good grounding to bleed it off. It isn’t a problem to do so as long as the grounding pathway is adequate, a simple and proven fix. All drives employ capacitors. Motor field generation, field collapse of any wound coil has the potential of creating conductive/inductive reactance, and capacitors create capacitive reactance. To claim otherwise flies in the face of electrical fact. Phase balancing capacitor banks serve to bring about the same effect. As far as ‘putting drives on a pedestal’, you seem far more inclined to pursue a defensive posture than to take a better look at the correlation between capacitive and inductive/conductive reactance. Again, when these two factors meet the same frequency is when the distortion issue is brought to a peak, with these harmonics becoming the face of disruption.

I successfully remedied these situations by working with engineers in DOD and DOE facilities, as well as with a host of different independent companies, Iacdrive, General Electric, Shaw Nuclear, being a few among them.

Renewable Energy in India

Holistic and Combined i.e Hybrid Renewable Energy Generation per Taluka / District of Each state with Energy Potential study with Investment seeking proposal with land (barren) identified with Revenue department clearances and also with a clear MAP of Evacuation with existing Transmission lines and future lines to planned, which shall be appended to RfP and not ask each developer to identify the location and struggle with Government Administration (which will increase time and Costs (read wrong costs)) complying to Land Acquisition bill and also eliminate the real estate babus to relinquish 5000 acres of land per state, which is BENAMI now…..I do not know how this excess land in BENAMI exist when we have Land ceiling Act!!

In order to do an extensive and credible study to explore renewable energy potential in each Taluka, State and Central Government Can hire international Consultancies with Video Documentation with GPRS MAPS to know the real truth and there shall not be much difference between reports and the ground reality, otherwise, hold these agencies responsible with necessary punitive clauses.

These costs can be recovered in the form of Bid document charges, which any serious developer will pay. However, the Equity selling proxy promoters, who have access to the power corridor and bid with Net worth Financial capacity, but, not worthy of any Renewable energy promotion as we saw in JNNSM wherein a large corporate bought equity from the other bidders and later an investigation took place…..

Following is the excerpts of the Mail written to MNRE and KREDL, in Jan 2012 (now we see their web site showing Biomass study is under progress):

For Power evacuation, we need to know the following (as we can’t use the existing data):

a). Distance from the Power generation site, which normally comes under KREDL (single window agency) i.e where one can put up the plant by undergoing NA or KREDL has identified land bank in Yadgir, but, how many km is the Substation from these sites, which we verified, was difficult to ascertain due to patch lands and the distance was over 10 km in certain cases.

b). Whether these substations can accept 20 MW or 10 MW or 5 MW of intermittent Solar PV load (non firm power which at times may create grid related disturbances etc). Biomass power is firm power as long as Firm biomass feed stock is available.

Therefore, we have been writing to many agencies involved to come out with a common approach, wherein the bidding documents identify clearly the SLDCs where the Project Developer can upload (evacuate) the energy generated with an in principle approval (with location MAP with transmission distances etc) from SLDC and ESCOM to accept such Renewable energy as the States are bound to buy the RE under RPO.

If the investor or RE Generator has to run around to know the fundamentals, then, please try to imagine how many man hours will be wasted and how much money gets drained from many participants for the same location? Instead, these data is available with KPTCL / KREDL / KERC / ESCOMs or such multiple organisation, but, Single window agency KREDL does not produce such VITAL information in their bid documents, hence, we as entrepreneurs are trying to tie the loose ends and make things happen for the good of our state.

I hope you understand our concern and append the finer details of evacuation, project site, land bank, the maximum capacity of MWh the substation can take or any upgrade is needed etc be appended in the bidding documents or even in your web sites also.

Further, any new substations are under development, the same with a clearly identified MAP with distances will help the people to understand the grid network to ensure the grid sustainability, reduction in transmission lines and hence the losses can be planned while making the bids, which otherwise will be a