How to calculate the size of Diesel Generator for my office ?

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In most of the interviews for an electrical engineer, one question is regularly put in and most of us are like “ok it is pretty easy but I don’t know how to start the calculations”.  I faced the question a couple of times and my answer would be followed in these steps   First of all these are the requirements which we need to know before we start the calculations Starting kVA and starting current Running kVA and running current Load in kW, P.F., type of load, diversity factor Future expansion   For eg:–   If we have following loads […]

Single line diagrams of 220kv-66kv-11kv transmission-DG 0131 and 0131A

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Click to download PDF  —> sld_substation Above PDF contains two SLDs of substations (220kV into 400V). Below are screen shots.   In the right corner of the image, we can see a SLD of 11kv to 400 v step down. This is frequently asked in interviews. In India generating voltage is 11 kV mostly, but 6.6 kV or 33 kV generation also likely possible.     Single line diagram 0131A In dg 0131A, we used (i) Bus Bar – 220 kV double bus bar, 66 kV double bus bar, 11 kv Bus, (ii) Incoming – 2 X incoming 220 kV, 5 […]

Notes on electrical switchgear Part -II

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Bus Bar size depends upon these factors Bus bar current – (Rated Voltage, maximum current rating of the bus bar, Fault current in kA and duration of fault) Temperature – Operating temp, max. temp during the fault, temp rise due to fault, ambient temp and max. allowable temp rise. Enclosure Detail – Installation area (indoor/ outdoor, natural ventilation), Panel size, Panel plinth level. Bus bar – Material of bus bar, arrangement (vertical or horizontal) Current density of bus bar material Material constant (K) Material strength (kg/cm2) Bus bar Support Insulator Details – Distance between insulators on Same Phase(l), Insulator Height […]

Notes on electrical switchgear

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Components of switchgear assembly Low Voltage switchgear components MCCB – Moulded case circuit breaker with or without over current protection Interlocking Provision Switchgear Cradle PT and control PT CT Control switches Indicator lights Main bus bars, Run backs Bus risers and cable lugs Fused interrupter switches Relays – Protective and monitoring auxiliary relays Protective fuses for breaker control Measuring meters   Medium Voltage switchgear Circuit Breakers (oil, air, SF6, vacuum) Switching device Instrument transformers Capacitor tripping device Relays Meters & instruments Main bus Control & indicating devices, jumpers, cable lugs, cable supports and potheads Barriers and shutters Instrument compartments Test switches […]

How to calculate size of a cable for 11kV or 33kV line

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There are three factors affecting the size of a cable Load Length & Voltage drop Short Circuit Current of the system Now, we can consider these four points one by one and choose a cable which complies all these requirements. Load – The load of circuit is available in kW or watts. For example if you are calculating the size of cable for a 1 kW single phase pump. Load on the circuit is 1 kW. Now, calculate the current that will be running in the circuit due to 1 kW load of the pump. P=Volt X Current X Cos […]

1 kW solar power bill of material

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1 kW solar roof top plant is now affordable at as low as INR 95000 in Delhi (*after subsidies by Govt.). You can save upto INR 8500 per year for 1 kW PV power plant. The estimated life of one PV module is 20 yrs and with increase in electricity tariffs every year, the maintenance cost of the PV plant will be economical. Here is a list of materials you would require to install a roof top PV plant, solar BOM If you are willing to install and find yourself a newbie, ask for our help. It is free :). Let’s […]