# Questions tagged [power-engineering]

Power electrical engineering. Includes industrial electrical engineering (i.e. motors, switchboards), transmission and distribution (poles, wires, transformers, grids) and generation.

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### What causes power losses in transmission lines?

From my understanding there are two causes for power losses in transmission lines: Losses due to resistance: $R = \frac{\rho l}{A}$, where $\rho$ is the resistivity, $A=\pi r^2$ and $l$ ...
97 views

### What will be Resistance for maximum Power transfer from network A to network B?

simulate this circuit – Schematic created using CircuitLab Can we apply Maximum Power transfer theorem if we are given two networks both with voltage sources. In solution it was said that for ...
94 views

### Does using HVDC for distance transmission make theft of electricity easier to detect?

In particular, if you were going to try to steal power from HDVC transmission lines you'd need one cable attached to current going in 1 direction and the other attached to current flowing in the ...
117 views

### can someone help with this question with capacitors

Please I need help solving this one, the book is Thomas Floyd 3rd edition Electric circuit fundamentals. The final answer is supposed to be $\text{0.0052 } \mu F$ The ac source frequency \\$f=...
132 views

### Harmonics in power system [closed]

I have seen in some text books that power converters produce harmonics in power systems. How do power converters inject harmonics in a power system?
454 views

### Instantaneous power

A sinusoidal voltage source v =10V sin(ωt) is connected across a 1k resistor. Make a sketch of p(t), the instantaneous power supplied by the source. Determine the average power supplied by the ...
136 views

### How to have Wye-connected Potential Transformers(PTs) and Neutral Ground Resistor short circuit detection at my ground fault protection relay?

Detecting if the Neutral Ground Resistor (NGR) is shorted is something that must be checked at the Ground Fault Protecting Relay. The typical way to do this is to inject a DC component and to measure ...
1k views

### What is the direction of negative reactive power

In a R+1/(jwC) load (AC)voltage lags current with θ degrees. Reactive power Q is negative because sin(θ) is negative. My question is how can a capacitive load deliver power to the source wich is ...
217 views

### Off grid LED solar lighting without batteries

I have 2 COB LEDs (12-14V DC, 50W, I think with 3,75 A in data sheet). I need to run them with a solar panel, it should only run when there is sunlight no batteries needed. Using a 270W panel (open ...
4k views

### When a wind turbine does not produce enough electricity how does the power company compensate for the loss?

I heard once that when a wind turbine power plant doesn't produce enough electricity the power companies are sometimes forced to turn on a couple of jet engines in order to compensate for the loss, is ...
2k views

### How is Line and Phase Voltage the same for a Delta connected system?

I am having a little bit of confusion for some reason understanding how the phase and line voltage can be the same for a delta connected system, i understand why the current is different for the phase ...
3k views

### Why is parking not allowed under some overhead power lines? [closed]

At work, among others, we have overhead power lines for the main grid connection (400 kV, about 1600 MW). The power lines cross a parking lot, and the positions directly under the power lines are ...
2k views

### Convert kW generated per minute to kWh

I have the data of power generated by a solar panel per minute in kW. I need to calculate the total number of kWh generated per day. How do I do this? So far, I divided each value of kW by 60 and ...
185 views

### Frequency of AC for electronic devices

I was wondering why using different AC frequency makes some devises not working. I found that I do not need to adjust frequency for using electric heat or electromagnetic wave such as ・rice cooker ・...
56 views

### How much power can transit through a power line linking generation and load?

First things first I am not an electrical engineer at all so please bear that in mind when you reply/comment. I am looking at the following problem, I have a power line which connects a windfarm to a ...
121 views

### What determines the phase difference between two voltages at an AC bus?

At an AC bus, the power flow is given by the following equation : In normal operation, the voltages (V1, V2), as well as the inductive resistance (x), are constants. So the parameter δ defines the ...
102 views

### Assemble Peltier Cooler to Li-poly Rc Battery

I have procured a thermoelectric cooler (TEC, this one) and my purpose of the TEC is to produce current for the Li-poly RC battery to increase its battery life. The Li-poly RC battery has 7.4V stated ...
95 views

### Startup and auxiliary/station transformer power parallel to bus

This question is in regard to switchyard/electrical distribution operations in a utility power plant. During a startup, the electric distribution system is lined up so that the startup transformers ...
106 views

### What are the practical differences between AC and DC transmission?

I have a long (2m) but thick wire between transformer-based power supply and low frequency power amplifier. Know your best advice ahead, but no, I cant get rid of it. I can put it in two ...
38 views

### What is the effect of very small AC frequency deviations from the grid on invertors and transformers for normal comsumer objects?

What additional wear or inefficiencies are there from inverting a AC signal to DC from say, 59.99 hertz instead of 60.00 hertz? And is there additional wear on transformers? How do small deviations ...
137 views

### Capacitance of short length transmission lines

I would like to simulate a short length transmission line in MATLAB/Simulink. In the library, there is a block that simulates a transmission line. The parameters that are required are the resistance R,...
88 views

### How do you close a switch on a high-voltage network?

This is something I've been curious about for a long time. Let's say you're a utility trying to connect two segments of a distribution grid. Both segments will have about the same frequency, because ...
1k views

### Why maximum power transfer condition is suitable for communication system but not for transmission of electricity?

A fundamental concept that i have learned from basic electrical circuit study is to receive maximum power by a load of resistance RL from a source the necessary ...
323 views

### DC-DC step down 12V to 5V source versus straight 5V source

Here is the scenario: I have a project needing 3 supply powers: 3.3V to run the microcontroller (max 100mA) 5V to run a bunch of adressable LEDs (max 8A, the most current intensive) 12V to supply op ...
378 views

### How fast do power plants need to respond to demand?

I've heard the layman's description of electrical grid response time before - it usually contains the word "instant" or "real-time". But I'm interested in the actual response times of the various ...
105 views

### Chimp climbing wires not electrocuted? [closed]

Reference video: https://www.youtube.com/watch?v=U5-Fy4ULdPg The chimp is climbing both wires out of phase (i would have to assume, it is in Japan), do the power lines have to be closed for the chimp ...
2k views

### How many horsepower does an alternator take from an engine at different speeds? [closed]

I want to know how much horsepower the engine deliver to the alternator at idle rpm,normal rpm and maximum rpm
191 views

### How much power do power stations in parallel supply?

In modern power systems, the power is supplied by effectively connecting multiple generators in parallel. However, not all these generators are equal, some stations supply more power than others (I ...
488 views

### How to plot input reflection coefficient in dB scale using Matlab

So I have a problem that asks to plot the input reflection coefficient of a transformer in dB scale between 0.5 GHz and 4 GHz using Matlab. Here is the code I have thus far, it is plotting in ...
153 views

### What is the typical voltage of power distribution in rural North America?

I mean the electrical utility power that connects to the transformer outside of the home or other buildings. i.e. what is the primary winding voltage of the transformer having 220 VAC center-tap ...
166 views

### How is power out one side of 220 only - Problem is with incoming 3-phase. But how?

[EDIT] Can someone who understands what I wrote explain this? [EDIT 2] Sorry I didn't say I'm in the USA, the power is 110/220vac 60Hz. The input to the main power transformer is 3-phase, underground,...
234 views

### Use of 3 phase transformers which are ∆-Y connected and Y-∆ connected

Different literatures say different things regarding ∆-Y and Y-∆ 3 phase transformer connection... Some say that ∆-Y is used for step down and Y-∆ is used for step up while others say just the ...
1k views

### Why is a short circuit in the secondary winding of a transformer reflected on the primary side?

I was reading this answer and I would like to understand why if the secondary is short circuited the primary winding will also reflect the short circuit despite the fact that they are isolated. Would ...
166 views

### Why does a End-Of-Line Voltage Drop Calc yield a different result than a Point-To-Point Calculation?

I can't grasp the concept on why these two different voltage drop calculations yield different results. They should both arrive at the same answer. In our intro EE classes when we were doing any ...
58 views

### Does a supergrid approach confront with distributed generation?

I have heard many times about supergrids and distributed generations (small scales generation connected close to the loads). In a supergrid scenario, a efficient and clean production of electricity (...
1k views

### Connecting a 48 V battery to a grid tie inverter

I am working on a grid tied wind system project. I am planning to use a battery in the system which will be the source to the grid-tie inverter. Also the battery will be used only as a source to the ...
6k views

### Why does power dip during a lightning storm?

If lightning were to strike power lines, wouldn't you expect it to increase the power, and hence your room lights get brighter? Why do they go dim for 1 second at a time?
74 views

### Regarding Power Market demand and supply

As I have read, that power supply should be equal to demand. As it can't be stored .So basically this means power is generated in real time. Consider an area where power comes from a Substation A, ...
2k views

### Process for Making a Flyback Transformer

I am looking to make my own flyback transformer that can put out a DC voltage from 0 to -40 kV DC and a power of 400 watts, as most commercial flybacks do not go up to the specified power and ...
85 views

### Engineering approach to choosing a motor, voltage and gears

I am working on a project to automate the opening and closing of my venetian blinds at home, by attaching a motor with an H-bridge to them. I started with a practical trial and error approach to it. ...
782 views

### Capacitor and inductor working principle

I want to know that there is opposition mechanism of current in inductor say back emf than what is opposition mechanism of voltage in capacitor ??? And also want to know that when inductor suddenly ...
75 views

### Controlling electrical flow from generator

I'm working with a factory which has a backup generator which is used during grid instabilities or whenever the factory must disconnect from the grid for maintenance. In these cases, the generator is ...
2k views

### Why am I getting shocked from “hot” line and touching “ground” (Earth)

So I live in an EU country and don't have Earth grounding for my house. Still I am getting shocked when touching "hot" line (220VAC) and standing on "ground" (Earth). How is this possible? From my ...
592 views

### How is the amount of outgoing power controlled in a grid tie inverter?

I'm trying to figure out how grid tie inverters work on a basic level. From what I understand, the inverter would have to monitor the grid wave create its own wave exactly like the grid make it a ...
635 views

### Why does a fault lead to increased reactive power demand?

When we have a fault, say on one line out of three, the reactive power demands increase, which leads to voltage instability if the source can't provide it. My question is, what causes reactive power ...
1k views

### How is it possible to use a phase as a return path?

On the 3 phase system, it is possible to supply a 380V load using 2 phases, say L1 and L2. I understand that the phases alternate and that one phase acts as a return path for another, but this doesn't ...
392 views

### What could be the transmission loss per metre of using DC current for a low voltage solar system?

I think that it shouldn't be much but I wanted to get a ballpark numerical figure. We've installed a 2kW solar power unit at our home, which is installed on our rooftop. To convert the DC current ...
57 views

### State estimation in power system [closed]

Regarding state estimation in electrical power grid, does the voltage phasor magnitude at each bus(P-Q bus and P-V bus) considered as a static state variable or a dynamic state? I am a little bit ...
115 views

### Understanding power system lines and their capacity

First of all, I am no engineer so forgive me if I confuse concepts (or show lack thereof). When constructing the power grid, I was wondering about the following: Do engineers use 'standard lines' (...
83 views

### How do I keep DC voltage high in a building grid?

I'm trying to create an off-grid installation. I have 200W PV panels, 20A charge regulator and two 150Ah, 12V batteries in parallel. How can I keep the voltage constant through all the grid in the ...