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  • i am a aungkyawthu from myanmar ,i have got graduate in 2007.My graduate is BSc Industrial chemistry.however i intrest in electrical engineering work,i had a diploma in electrical installation (city and guilds of London institute). now i works in electrical field,so i must need electrical knowledge more,can u send me electrical design and drawing to my email.
    thank a lost if u will help me

  • Current flow in the electrical circuit is analogous to the water flow in the closed pipe system. Different electrical parameters are also similar to the different equipments of water system. the new learners of electrical engineering can easily understand the current flow in the circuit by comparing with the water sysem.

    • Wel said Mr Ziauddin,but why r you just comparing electrcal circuits to hydal systems .rn’t they even analogous to mechanical systems.lke resistance in an electrical circuit is similar to damper in a mechanical system.

  • Thanks for your great blog! I find it very useful. I hope to see more and more topics in your blog.

    I have a proposal to discuss in this blog.

    Uninterruptable power supply is essential nowadays in both commercial and industrial buildings. However, short circuit protection is not that simple matter, at least I think, when using UPS.

    Normally, when network is available, UPS goes to bypass mode during short circuit. When network is unavailable, UPS has to draw the current to supply short circuit from its battery. Typical short circuit feeding capability seems to be around 1,5…3 times nominal current. Usually UPS can feed short circuit about 0,1…0,3 seconds.

    A larger UPS network has its own main switchboard, feeders and switchboard for final circuits. I would like to know how you take into account these limitations in design. What size of MCBs are you using in UPS switchboards? How about selectivity between breaker in final switchboard and main switchboard? Do you find current selectivity be enough? If you take into consideration selectivity (energy) and short circuit during the battery operation it results in surprisingly low current level MCBs, usually B6 or B10 in socket outlet circuits. Or do you reckon short circuit to happen during battery operation such a rare occasion that it is ignored?

    Do you have some rule of thumb to design UPS network?

  • I performed my final year project on wireless power transmission for home appliances,unfortunately it worked for very small distance ,though more then induction,Can u guys help me some problems that i faced throughout this project or wireless power transmission is not economical?

    • Wireless power transmission has its own limits because of power consumption of devices. However, there are some applications using wireless power for mobile phone and laptop computer battery charge. Check a Finnish company’s site Perhaps they have some technology in the field of your interest.

  • Hello, I’d like to see the topic of arc flash and more specifically new technologies addressing this subject in electrical engineering. I’d like to send to you materials for your review on this topic. Thoughts?

    • Hello Angela,
      It’s OK, you can send me your proposal:
      – 250 to 500 words max
      – with pictures and links to technical websites & sources
      – please no promotion of offers
      – if possible give me your major keywords
      before publishing i will ask for your validation
      François (

  • To understand the electrical circuit physically the circuit can be thought as a closed water system. It is just for the novice learners so that they can understand the electrical network physically without complex imagination. It is not like that electrical system is not analogous to other mechanical system. But for the learners who are first learning this they may find it difficult to compare it with mechanical system. Besides this a water system is easy to understand physically. If a student wants to think further about the electrical characteristics he can easily do it.

    Now what is this comparison? Let the water connection of your washroom. Here the water initially stored in the overhead tank. Then through the pipe connection it reaches to the every taps in the washroom. When the taps are not opened still they contain the water inside the pipe. And they are ready to flow the water when the tap will open.

    water connection 1

    Further we consider the connection of the pipe can be made in two systems.

    In the first system small pipes are connected with one big pipe and this big one is directly connected to the overhead tank.

    In the second way consider all the pipes are directly connected to the tank.

    Now you wish to go to the washroom and open a tap then the water from the tap will fall down. This water will reach to the drain.

    If you open all the taps of the second system then there will be no disturbance in water flow in different taps. All they will give the water with full volume.

    If you open one pipe in the first system then you will get the water in full volume. But when you will open all the taps simultaneously then you will not get the water from the tap with full volume. The nearest tap will give the more water than the far one.

    water connection 2

    Again consider in the second case one pipe has been broken down. Water from that pipe will fall down. But the others pipe are ok and there will no disturbance in their water flow.

    On the other hand if one pipe breakdown in the first system it will disturb the other. And most of the case no water will flow in the other taps.

    Now we consider a dc circuit. Here we have a dc source, which have a positive terminal and a negative terminal. This positive terminal is analogous to the overhead tank and the negative terminal is similar to the drain. The pipes here can be compared with the conducting path. In the case of a parallel circuit if one branch does not conduct it will not disturb the other branches. The second washroom is analogous to this parallel circuit.

    In the first case the physical system represents the series circuit. Here if water flow in the main pipe is blocked then water flow in the others will off.

    The overhead tank and the drain play the role of potential source. As the water goes down to the drain, the potential decreases.

    Here the short circuit phenomena and the open circuit phenomena can also be explain. The level of overhead tank and the drain will be same if excessive flow (infinitive) in a branch makes the two levels equal. Then there will no flow in the other pipes because two levels are equal. And the open circuit phenomenon is simply the blockage of water in a pipe.

    water connection 3

    • We are going to publish your article properly from the Blog Home page then we will cancel this a comment.
      François, moderator

  • I have a query on earthing system design. One designer has submitted me an earthing plan which interconnects the earth electrodes meant for equipment earthing and those for lightning protection purposes. By combining the earth electrodes he achieves overall earth resistance below one ohm required by IS 3043. But my question is whether this is an acceptable practice followed by industry or the earth electrodes of the two systems (protective earthing and lightning protection) can not be combined this way?
    Would appreciate feedback. thanks in advance.

  • So we can request to write about anything related to electricity/electrical engineering? Is there a certain length the article needs to be or a set of guidelines?

  • Hello Jitendra,

    “reponse” of human body to electric schock has been described by International Electrotechnical Committee in its report 60479.
    Chapter 3 reports effects of AC while chapter 4 describes effects of direct current.
    To summarize these two chapters, the risk of injury appears :
    – if alternating current exceeds 35 to 40 mA (which explains the 30 mA tripping threshold standardised for protection against direct contact by means of RCD)
    – if direct current exceed 150 mA.
    Both these values under assumption the situation lasts more than one second.
    In addition that same report mentions (§ 2.5.3) that impedance of the human body is higher to DC voltage than to AC voltage.

  • I need to hire the services of an Electrical Installation Inspector who can study the Installation of Electric System and tell us whether it is satisfactory or not. We have had cased of equipments getting burnt out during normal operation and hence we need to inspect the same.


  • I want to work on the energy harvesting from lightning. Is is actually possible or not?
    I choose this subject from my own interest. Can you suggest me further on this subject?

    Basic Requirement of any Electrical Utility(SEC) company is:
    Energy Generated = Energy sold (Billed) + Energy Losses (Should be
    Energy sold is assessed/ calculated by Energy Meters. Conventional Energy meter (KWHR) measures Voltage, current and phase angle (Power factor correction).
    Energy meter also consume some power (wasted). In pressure coil (voltage coil),
    Power is wasted in the form of heat. Except measuring power, the energy meter has no purpose besides it consumes power; periodically meter reading should be taken in the consumer premises and also not error free.
    CONCEPT and Merits of AH Meters
    • The concept is, the consumer draws (uses) only current to operate his equipments (Lighting fans, A/C, Fridge etc.). He should be charged only for the current, he uses. When he does not use electricity, no current is flowing even though voltage is available at his premises. The Energy meter also does not record any consumption (as there is no current flow), even though voltage is available to energy meter. The moment, the consumer draws current, the energy meter not only calculate current but also the voltage for which the consumer pays (the supplier also do not get any benefit). Also the energy meters consume some power.
    • The maintenance of rated Voltage (supply) is the responsibility of the supplier. The consumers draw current from the system supply and hence the consumer should be charged only for the current and also he may be levied, if required P.F. is not maintained.
    • One Unit = 1 KWHR = {v*Cos(phi)}*AHR

    AHM – Amp Hour Meter
    IG – Current @ PP Generation.
    I 380 KV Current @ 380KV GIS.
    I132KV – Current @ 132KV GIS
    I13.8KV – Current @ 13.8 KV SWGR
    ITRF – Current Distribution TRF
    I 220V – Current @ 220V distribution Board
    IC – Current @ Consumer end

    IG = I 380 KV = I132KV = I13.8KV = I 220V = IC

    1. The Ampere Hour Meter requires only current coil (CT). No Pressure coil is required. Wastage of power is eliminated.
    2. Size is compact and very less than Energy meter.
    3. Wiring and fixing of AH meter require less space. It can be fixed at any point.
    4. It is feasible, by fixing the AH meter in the distribution box or at supply point, where the cable origins- instead of termination point (consumer premises). Just like telephone billing, the current billing also can be done. Consumer privacy is safe guarded.
    5. Losses can be accurately assessed instantly by installing AH meter at Power Plant, sub stations,13.8 KV feeders, Distribution Transformers and Distribution boxes as per Kirchhoff’s Law (Current entering a node= Current leaving the node).This is not possible in the case of Energy meters.
    6. Perfect, accurate and Effective Load shedding (Voluntary) where exactly required can be implemented as required by DSM.
    7. For the Distribution Engineer, he can instantly see the Load of the Transformer in each phase there by the load balancing can be done in all phases. The Unbalance load is the major cause for Transformer failure. Further he can assess what is the current (zero sequence current) flowing in the neutral (unbalance current). The unbalance current is the measure of loss of energy. This is also the case for Power Transformer in Substations.
    The AH meter provides accurate data of energy generation, the energy sold and the loss of energy.
    It is cheap, economic, technically feasible and a perfect solution for DSM, Energy losses and improvement in system stability etc.
    I have done a project on the above subject for my Post Graduate in Energy Management and Energy Audit (Annamalai University)-2005.
    Also Received innovation award from L-RAMP (American Establishment) at Indian Institute of Technology/ Chennai for my thesis in the year 2006.


    • Power factor is dependent only on Load (R/Z).

      also power factor can be extracted from current wave.

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