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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Volume risk in an electricity market

I have been reading lately about electricity markets and I have stumbled upon the term "volume risk". Volume risk is often used to denote the phenomenon whereby electricity market participants ...
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0answers
21 views

How to model P, V variations in PV buses in a load flow problem?

I'm trying to use the DC power flow results as a base, and modify it to approximate AC power flow results more accurately. So far, I have been able to do that in a few simple test cases from Matpower, ...
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1answer
56 views

signal propagates in bending transmission line (unequal length between signal path and return path)

Suppose I have a square wave signal generated from a signal generator and its outputs are connected to the two terminals of a paired PCB traces (left side of the picture below). The other end of the ...
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2answers
89 views

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 \$ ...
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1answer
73 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 ...
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1answer
72 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 ...
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1answer
114 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=...
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2answers
67 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?
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1answer
94 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 ...
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0answers
23 views

What does 'Rectifier Loading Effect and Loading Factor' mean

I came across the terms 'Rectifier Loading Effect' and 'Rectifier Loading Factor' when reading IEEE Std 421.5-2005 Recommended Model for Power Stability Studies, mentioned in those ACxA models. What ...
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0answers
29 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 ...
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2answers
84 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 ...
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3answers
131 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 ...
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2answers
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 company's are sometimes forced to turn on a couple of jet engines in order to compensate for the loss, is ...
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2answers
315 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 ...
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0answers
103 views

Trapezoidal Rule of Complex RLC Circuit using MATLAB

I am having difficulty trying to figure out how to solve this circuit using the trapezoidal rule. I know how to do so in a first and second order RLC circuit however this particular circuit is giving ...
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1answer
292 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 ...
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3answers
92 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 ...
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2answers
49 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 ・...
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1answer
45 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 ...
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1answer
56 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 ...
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1answer
64 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 ...
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0answers
29 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 ...
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2answers
90 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 ...
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1answer
36 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 ...
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1answer
48 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,...
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1answer
72 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 ...
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2answers
305 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 ...
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1answer
208 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 ...
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1answer
115 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 ...
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3answers
98 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 ...
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1answer
328 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
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1answer
76 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 ...
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1answer
124 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 ...
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1answer
96 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 ...
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1answer
103 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,...
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0answers
109 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 ...
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1answer
541 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 ...
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2answers
60 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 ...
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1answer
43 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 (...
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1answer
353 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 ...
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3answers
5k 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?
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2answers
62 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, ...
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3answers
820 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 ...
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2answers
69 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. ...
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2answers
564 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 ...
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2answers
63 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 ...
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6answers
812 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 ...
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2answers
148 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 ...
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1answer
248 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 ...