Power System Protection - Science topic

Indeed, transient simulation using tools like EMTP or PSCAD can be useful in field testing power system protection schemes, especially for complex networks for which traditional short-circuit simulations may provide misleading results. While short-circuit testing is appropriate for steady-state fault conditions, it has a tendency to overlook transient phenomena such as CT saturation, DC offset decay, or evolving faults that influence relay performance. Open-loop transient simulations may be employed to test relay performance under real-life conditions, particularly for distance protection, line differential relays, and protection schemes which are affected by switching transients. They are not very useful in the field test, though, because of the lack of real-time interaction and the need for special test equipment. A more realistic alternative for transient-based relay testing in the field is Hardware-in-the-Loop (HIL) testing with Real-Time Digital Simulators (RTDS), which allows dynamic testing under simulated transient events for more accurate and reliable protection scheme verification.

Taking ground as reference for 220 AC and Negative for DC supply via Peak detector ….

I can suggest you this journal

Dear Ravi,

Number 20 is good enough to accommodate most of the fault levels that are beyond load current (5P20). This is the reason, CTs can offer the correct replica of fault current in linear region (without saturation) even if the fault current is up to 20 times the rating of CT without saturation. Certainly, there are also some CTs that can offer a correct replica of fault towards its secondary side up to 10 times only (5P10). Such CTs are used in the system where fault currents are not going to be very high (beyond 10 times its rating). There are some other protection class CTs as well such as 5P30, but such CTs are not often needed. Mostly, 5P20 type CTs (protection class CTs) are used as in offer accuracy level of within 5% deviation, and cannot saturate even if the fault is up to 20 times its rated primary current. Short circuit studies is a planning problem and we are required to do it for protection planning such as selection circuit breakers, CTs and calculating relay settings.

Hoe that you go the point.

Hi

I hope you are okay,

I am looking for a Ph.D. opportunity in power systems.

If you or anyone find a team I would be very appreciated if you could provide recommendations or guidance.

Best regards,

EVs charge their batteries from the power grid and may cause severe effects if not managed properly. On the other hand, they can provide many benefits to the power grid and get revenues for EV owners if managed properly. A good overview of potential negative impacts of EVs charging on electric power systems mainly due to uncontrolled charging and how through controlled charging and discharging those impacts can be reduced and become even positive impacts is provided in the following paper.

Nour, M.; Chaves-Ávila, J.P.; Magdy, G.; Sánchez-Miralles, Á. Review of Positive and Negative Impacts of Electric Vehicles Charging on Electric Power Systems. Energies 2020, 13, 4675. https://doi.org/10.3390/en13184675

The negative- and zero-sequence networks are passive, no "source" behind the relay. The fault (unbalance, in general) acts as a source that excites the V2 and I2 quantities at the relay location. So for a forward fault (the Thevenin source in front of the relay), V2 = -I2*Z2SYS_LOC, and for a reverse fault (the Thevenin source behind the relay) V2 = +I2*(Z2LINE+Z2SYS_REM). Similarly for the zero-sequence and incremental-quantity directional elements. More details in this primer (paper and presentation): Sequence Component Applications in Protective Relays - Advantages, Limitations, and Solutions

The following article may be helpful.

It may be by suitably extrapolating from exact neighboring element data (bus or line depending upon the system) at that very point of time. It is some sort of estimation to be applied.

you can find in this web site the different Postdoctoral offers

Kind regards

The selection of an appropriate modeling details is based on the target. If you would like to capture more details electromechanical/electromagnatic dynamics, then more details are preferable. It is a matter of compromise between simplicity and accuracy. In many transient stability studies, only the 2nd order dynamic model of the machine is used for simulating the electromechanical dynamics. If the field circuit dynamics are of interest, then the 3rd order dynamics is used.

Dear syed taha Ahmed

you can see the attach file for more details

Obviously for the same amount of power if voltage is half, current would be double. But think of low voltage system, insulation depending on voltage would be less. However metallic conductor carrying current would be costly. For developing countries like India question of affordability would come with low voltage operation with more amount of costly conductor material. Voltage level of 110 is not so fatal as 220 volts. Thus the former is rather safe, but a costly matter for the wire to be used for the same amount of power to be handled.

Etap is a powerful software which is designed to perform simulations, analysis and design of Power systems

I agree with Mr Zia Hameed

As Mohamed EL-Shimy mentioned, please cite the paper.

In general, the Z matrix in power systems analysis stands for the Z bus matrix. there are 2 ways to produce this matrix:

1) For small systems, build the Y_bus matrix and take its inverse. note that the system must have at least one line connected to the ground with a shunt admittance. otherwise the matrix is invertible/singular

2) For large systems, finding the inverse of Y_bus becomes computationally intensive. if you need to repeat this over and over, then it slows down your code. there is a method to build the Z_bus matrix directly (without inverting the Y_bus matrix). it is explained in Hani Saadat's book. it is very important to keep in mind that the Z_bus matrix is NOT built simply by adding impedances.

Please take a look at these attachments links

https://duepublico2.uni-due.de/servlets/MCRFileNodeServlet/duepublico_derivate_00033640/Masterthesis_Wildenhues_Uni_Duisburg_Essen_Germany.pdf

https://fr.mathworks.com/matlabcentral/fileexchange/57985-four-area-performance-of-distance-relays-on-transmission-lines-with-upfc-and-statcom

https://fr.mathworks.com/help/physmod/sps/examples/statcom-phasor-model.html

https://fr.mathworks.com/help/physmod/sps/examples/statcom-detailed-model.html

http://eu-sysflex.com/wp-content/uploads/2018/12/D2.3_Models_for_Simulating_Technical_Scarcities_v1.pdf

Please take a look at these sites

http://www.ea-energianalyse.dk/reports/1236/ready_congestion_in_distribution_grids.pdf

Because that all the electrical lines including power transmission lines have distributed parameters - resistance, inductance, capacitance, conductivity and impedance. Just their wave impedance does not depend on length.

Problem faced by the integration of renewable energy is a new research field now a days.

Please see these researches in the attachments

symmetrical faults are most severe faults that may occur in Power systems. same stands true for generators

Dear Muhammad

Please see the attachements subjects

Best regards

* Effect of distributed generation on protective device coordination in distribution system

* Reviewing the impacts of distributed generation on distribution system protection

* A novel neural network and backtracking based protection coordination scheme for distribution system with distributed generation

Thank you both for your answers.

CERTS Microgrid Concept seems to be widely used.

@Alberto Numerous challenges and requirements are exactly what makes microgrids so interesting for research.

Do you know where can I find the CERTS Microgrid Concept system parameters, or maybe already developed model?

Recently I came accross this reference:

S. Hanninen, Single phase earth faults in high impedance grounded networks, Espoo: Technical Research Centre of Finland, VTT Publications , 2001

It reports on measurement data collected during the two years period. Hope this helps...

Theoretically the tarnsmissibilty will decrease while the ratio r is increasing and the limit of transmissibility is 0 when r goes to infinity, there for the isolation officiency will be 100%, but this depends on the damping of the spring more the damping is high less the isolation is good (after resonance)

see image below 

Lower power factor will draw more current. Optimization of efficiency point is determined by best power factor. Standards are same for energy efficiency market.

As you mentioned you have done phasor estimation of voltage and current. I hope next step should be of finding impedance measured by relay by using phase and ground distance elements. If the measured impedance (R and X cordinates on impedance plane) lies inside your quadrilateral zone, then develop a logic that it should generate 1 or 0 as output (as per required to open breaker).

During normal operating condition it acts like a invisible impedance however offers a significant amount of resistance in the fault path resulting a reduced current.  For more detail refer the following attached files

can you specify what your model is?

ANNs are universal approximators, so with the right network, yes, you can model your problem.

In our experience, we use differential relay for bus bar protection. So the relay will work very fast. We have used this term in some factories.

Hi Srete,

I would request a clarification, please.

By ideal power balance, I presume you imply that the islanded network is capable of handling its own load when isolated ? (Or have I got it wrong ?)

If my interpretation is correct, then further, is the subsystem to be islanded assumed to exchange zero power from the remaining network prior to islanding ??

Please do correct me in case I have missed something.

With best wishes.

-Sanjay

maybe i can help you but need more explanation what you want exactly!

 It will definitely cause loss of dependability or securityof the directional relay! However, not in every situation or every operating conditions. Thus, the task is to find out those conditions where the directional relay will see a forward fault as reverse or vice versa!! There are enough literature's available related to  this issue. 

Generally, the maximum power transfer through a transmission line can be increased by reducing the line reactance. To achieve this goal, series compensation of the line (by putting series capacitors) has been practiced for long. Interestingly, once the series capacitance is put in the line and varied, resonance phenomenon is observed which is created between the electrical network and the mechanical components of the whole power system. The resonance creates low frequency oscillations (lower than the power freq.) whose magnitude grows with time and ultimately damages the shafts.

For further detail and modeling you can go through the following books:

1. Anderson, P. M., Subsynchronous resonance in power systems, New York, IEEE

Press, 1990.

2. Yu, Y., Electric power system dynamics, New York, Academic Press, 1983

100\5 could be used as CT would not be saturated with raised 10 amp on 100 amp range......

Hello dear friend,

Your question might not have a clear answer, but I guess reading the following pdf may help you to get your answer.

Your question is quite odd. Only one bus serves as the reference (swing) bus. Period. The thing is, you probably have more than one generator connected to the swing bus. After the PF converges, the program calculates P, Q in the swing bus, and shares them among all the generators in the swing bus. Try to increase the P and Q limits of the generators in the swing bus and see what happens.

 Thanks.

Josef,

Thank you for the pertinent tutorials. 

While I am away for the weekend, 

I will read through both.  

They look like well prepared tutorials.

   

Already, I see the Weinbridge Osc with the light bulb , 

which I recall using, far back.  These will be good to read again.

Now, looking around my lab shelves, 

I find a single 6x6 perf-board with several oscillators 

which I used years back.  Also,. my old digital Hex-Decoder-Readout, 

and a multiplexer which I designed to display eight channels of digital onto a single channel Oscope.  

I kept all these circuit things, along with 10 Proto-Boards and four power supplies in a Suit-Case, along with my NLS-Mini-Oscope for school labs.   I did school work at home, went to the college lab and just opened the suit-case and demonstrated my working circuits "Pronto!".  PIctures of these things are on my website.  Now-a-days, I use this set-up most every day.  It is very convenient to just close the lid and protect all the wiring.  From that I transfer modules to the soldered-up Perf-Boards with bus-pad-per-hole patterns.   Has been very convenient way to keep my work "straight and true" during construction.     

Now, I find  my old  Weinbridge Osc section,  with Germanium diodes,

and the much more used cousin ,

which produced Square-Waves and Triangles,   

Now-a-days, I pull Radio Signals from the Ham Bands to test filters. 

Thanks again, Josef,

very appropriate texts to review for this week-end. 

Good things to read

as I think about anayzing the Varient OPA Diode Limiter. 

the apprentice, Glen

Fusing in the photovoltaic array system is well introduced in the attached document presented in the link: http://www1.cooperbussmann.com/pdf/1b416a65-f5ac-4730-ab77-9e2faa147945.pdf.

It is the parallel combination of he modules which dictates the use of fuses for each string to protect the other strings from possible short in one module of the bundle. String fusing is required only if three or more than three strings are connected in parallel as given in such document. The protection is inside the array itself because of parallel combining. I thin the document is very useful and answers many raised question in the discussion.

The use of the dc fuses at the input of subinverters is to prevent the short circuit in one inverter to interrupt the operation of the other inverters for long time in case the shortcircuit resides for longtime, Its function is to interrupt the energy flow path in the shortcircuited branch. That is isolating the shotcircuit fault from the other branches. So, this fuse must get blown after a specified time when the highest shortcircuit current of the array passes in it. This would be its maximum I^2t rating and so could be sized.

The placement of the AC fuses as in the picture of Aalok may be better than placing them after the filter. In this configuration as it is assumed that the short may occur inside the inverter , the presence of the filter in the path of the current  will impede the current flow from the mains and therefore limit the short circuit current. It is so that the grid connected iverters are controlled to to limit their current injected to the grid. So, there output current is known. How much is the  maximum current capability of wiring and of elements is the mater of system design. And so the fuse current must be lower than this maximum current capability.

thank you

Rajeev,

Are you talking of small distribution cable routes, or EHV stuff like underwater tie lines etc ?

-Sanjay

Strong cyber security is the main drawback to smart grids technologies. However, such security can be provides but need continuous monitoring. 

In my opinion some suggestable topics are

1) Mal-operation of 3rd Zone of relay during critical conditions(e.g- load encroachment and  power swings etc.)

2) Different kinds of  fault location algorithms

3) PMU performance during Transient conditions ( including special cases . e.g- communication link failures )

4) Power Quality issues

I wish to know the phase difference of fundamental superimposed components at relay bus. Travelling wave is a function of one-dimension space, moving with a constant speed.

Be careful if you want to use the classic Ziegler Nichols tuning rules. The use a global gain and then some integrating time constant for gain "1" but they omitted a clear transfer function. Matlab uses a different transfer function definition which results in different values. If the measurement gain changes in Matlab all terms have to be adapted. Why not simply use Nyquist with at least 40° phase margin often gives satisfactory results, Pay attention to model the time delay between measurement and control also as a phase margin. Other methods use Z-transform, but also the (parasitic) time between measurement and action is important.

Bikash, I think that the previous responses answer your question accurately.  We refer to numerous studies in the literature in my most recent paper.  Our measurements in a real world setting show that EE did actually reduce energy use.  Energy use has also declined across the UK since around 2005.  Energy prices fluctuate wildly and I think that rather than focus on monetary savings due to EE it is better to focus on the overall carbon impacts of differing lifestyles - for eample the amount of air travel or high mileage car use.  These are much more significant than relatively minor changes to domestic EE.  Focus on EE and "rebound" or "backfire" is in my view not particularly helpful.  In my view the key issue is the degree that our energy related technologies overall become less carbon intensive within a similar apparent consumption envelope.  And I agree that GDP itself is a deeply flawed measure.

Lload shedding is one of the main approach adopted to avoid overloading of transformaers.   It is posible to control the loading pattern educating your valuable consumers to flatten the load curve.   Incentives may be offered to shift the use of power at off pak periods.   Power supply can be regulated to agricultural conumers.

On the ground on that big land mass to be considered as zero point and all parts of the ground connected to the ground potential or the potential to be ground zero.

Grounding is done for two reasons, one is the correct behavior of electrical systems, in other words the protection of electrical appliances (electric field) and the protection of people who are connected in some way with electric devices (protective earth).

Maybe you get some Informations from this Cigre-publication, maybe some contact Points to get more Information/data

I think CYME DIST can be useful..

Without much analysis, it may behave lake an open conductor, because there is no return, so the voltage in that phase may jump to almost twice nominal.  If it is intermittent, then the phenomena would repeat itself, and a voltage escalation may result.  An EMTP model of the situation will show the details.

Flow of electrons(current) are from higher potential to lower potential, hence during negative half cycle flow of electrons would be from neutral to phase via load.

Hi Mr. Akbar

i have request like another! can u tell me how was your solved? i need simulation a standard 39 bus IEEE .

thanks

Dear Nithin,

Not any one particular class will be used.

For Example,

Wire enamels are used as inter-turn insulation, I mean the insulation varnish on the winding conductor which falls under Class E. In some cases the impregnated paper is used for the winding which falls under class A.

Glass fibre, mica or porcelain strips/ plates are used for insulation between different layers of windings. The windings will be in different layers for different reasons.

For insulation between the core/windings and the tank, usually the transformer oil will be used which also helps in heat dissipation. 

Porcelain bushings are used for insulation between the terminals and the tank.

Yousef

I have compiled a 100 page + document adressing the following topics. It is currently in a review stage. I will share it with you in February 2015.

Ø  Can the impedance function in transformer IEDs be set to reach through transformers? ( two winding and 3-winding, auto transformers)

Ø  Will the relay correctly measure the distance to fault through a transformer?

Ø  How will the vector group of a transformer affect distance measurement for various fault types?

Ø  What percentage error will the tap-changer introduce?

Ø  Is vector group compensation required for instrument transformers when used for transformer distance protection?

Ø  How to prevent the impedance function in the relay from operating during transformer inrush conditions.

Settings etc.

Document consists of literature review of current practices.

Please see Prof Eric Laithwaite's   work . Here is a nice website showing an actual demo

by Prof Laithwaite himself !

Cheers

For residential load, no need to have insulator string, as the voltage is low(230/110V), simple bobbin type single, porcelline insulator will work even for bare wire.

Usually the values of  R,L,C  and tan delta are the parameters to measure the effect of any insulator on Power System Protection.

May be the temperature,humidity,density etc which  directly or indirectly affects the tan delta value of insulators  are the additional measurements to evaluate its effect.

Dear Hossein, 

You may take a look at the following report for a comprehenssive information regarding the communication in power system protection.

Bests,

Amin

The LEM is suitable but it is expensive .You can use china brand  ,

@Ahmed.From my experience in Distance protection settings, there are various numerical methods to compute the Resistive and reactive Zone reach for Series Compensated lines. As a thumb rule, Zseen =Zactual + ZComp + Rf . Therefore, if you know the impedance of the compensator (Give due regards to MOV's if any) and the fault resistance,You can compute the relay setting.

Also Various Relay manufacturers provide product specific guidelines and factors to avoid Under/Over reach of the protection. Some of the Relays which offer the Protection for Series Compensated lines are RED670, 7SD522 etc. Also GE and SEL also offer relays for the purpose.

As per my beliefs, the relay setting (practically)shall done using deterministic numerical methods and not using probabilistic optimization methods. Therefore, I suggest you to go through the manuals provided by major Relay manufacturers like ABB, GE, Siemens etc.. to get a better clarity on the approach.

Regards

Sujith

Dear Rasbnidu,

Nuclear power creates radioactive waste which are harmful to living organisms (can cause cancer, genetic mutation),  also require substantial amount of cooling water.  Solar and wind energy may be good in the subcontinent and can create local jobs  and supply of local electricity 

Most modern microprocessor relays have a fault location function that use an algorithm to determine the location of a fault based on the fault current and the line impedances entered in the relay settings.

Send link

i will try to Download ..

i think, some problem is in relay coil,

On 8A your relay coil produces that much sufficient attractive force so that, relay produces trip signal..

My suggestion is remove relay from circuit, and check separately that " your relay is producing trip signal at what amount of current" ..

Friend, you are most probably trying to find a single shot meta-heuristic population based search algorithm (simply an evolutionary or a swarm intelligence algorithm), that will result in the best outcome for your problem. But, In this field no algorithm can perform the best in all kind of problems (Cost Function).

Some of the issues (which make these algorithms so problem dependent) which determine the entire search process are:

1. The representation of individual (each solution string, equivalent to chromosome in GA),

2. Internal parameter setting (being a numerical algorithm, these dependence in non-negligible),

3. Neighborhood strategy (how is each solution get influenced by the others in the same population (like velocity update equation in PSO), or others (DEGL, JADE, ALCPSO, FFA etc.),

4. How each tool (Parallelism: like Niche based approach; Tools of PSO like velocity and position update equation; Selection, Crossover, Mutation in EAs) is modeled.

5. Population Size (Diversity and Computational pressure)

and many more.

What you can do, is first model your Fitness function. Study recent algorithms and its overviews, if your function matches exactly with any standard cost functions (refer CEC), you can use the algorithm which has performed best in that cost function. Generally it is a trial and error procedure, and nobody can firmly claim to the best (Refer to NO FREE LAUNCH THEOREM).

This is quiet embarrassing, yet, a hope is some algorithms and strategies are there which can give very good and acceptable results. Good luck.

Try lookin at the book Voltage Sourced Converters in Power Systems by Reza Iravani....It gives some good background theory and example applications on the STATCOMs, Hope that helps

Optimized Design of Transformer by Genetic Algorithm

For this you have to generate fault signal by simulating the considered system on any dynamic simulation platform. For this purpose I generally use PSCAD. Once signal for different fault conditions are available you can test relaying algorithm implemented on MatLab.

Hi David.

Firstly, no mention was made of de-rating any conductors.

Secondly I am referring above to the rating of the AT itself and not any conductors.

This is a simple, cost effective and practical way to reduce the effects of copper theft as mentioned by Tallal.

Well, that is a question asked by many. The answer depends on the type of material of the cable (oil paper or for instance XLPE) and the voltage type applied on it (AC or DC or another frequency). What I have seen in the laboratory regarding AC XLPE cables is that the apparent charge can be low to suddenly increase and one minute later lead to a breakdown. I have also seen cases, there the level increased, to suddenly be almost zero and then fast increase to a breakdown. There are many varations and that is why it is so difficult to predict a breakdown with help of partial discharge measurements in good time. BUT, partial discharge measurement can be a good tool to get an indication about possible failure areas.