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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smart grids systems for undergraduate final year engineering project [closed]
I am an Electrical and Electronics Engineering student. I have been interested in smart grids designs and i would like to present it as my final year engineering project in my under graduate sturdies. ...
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3
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Photovoltaic generated power: Why is my PV system selling back to the grid while at the same time it is consuming energy from the grid? [closed]
I've noticed on my power bill that there are times during the day when my PV system is selling power back to the grid, while at the same time, I am consuming from the grid (see screenshot below).
That ...
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Busbar short circuit rating vs. cubicle rating
First: This question is about medium and high voltage switchgear, not electronics.
A 7,2 kV switchgear has a short circuit current rating of Ik = 40kA/3 s. The ...
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Simple way to achieve constant output current from a boost converter for battery charging in an EV penetration simulation study using EMTP simulation
I am simulating Level 1 and Level 2 EV chargers to test the impact of such chargers on a grid in a developing country. I am simulating in EMTP-RV (software for simulation and analysis of power systems)...
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What are the highest permissible current harmonics input to the grid?
I'm in the process of completing my Master Thesis and I need to model the current harmonics input of large-scale PV plant into the grid. We're talking about 100MW connected to the 110kV line, using ...
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Solving an AC Circuit Inverter Estimate
This is an electric power engineering question not electronic so this circuit doesn't actually solve. I added it for illustration purposes. Srate = Sout.
I'm trying to solve this below circuit for Vg ...
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Does a control panel that will start/stop two pumps require its own circuit protection?
Does a control panel used to start/stop two pumps require circuit protection for the main 208V feeder lines if those lines are already protected at the main panel in a separate room?
The main panel ...
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What is Vac(peak) in this question?
Bit confused at what Vm/Vac(peak) is. Either 230V or 325V. rest seems simple
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Transmission Line Powering Load
Consider a long transmission line (4 km). Its a single conductor line with the inner conductor insulated. The outer shell is steel ground.
Consider two scenarios.
Scenario A: 120 V DC power supply, ...
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EV charger power distribution in an apartment complex
I am on the executive committee for an apartment complex. We have had a number of requests from residents to add EV chargers to the basement carpark. It's obvious that the number of these requests ...
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Disappearing voltage [closed]
I'm an 30 yr electrician. I have a problem neither I nor my co workers have ever seen nor can we find an answer to. Here's the situation.
In a particular 60' length of EMT, (metallic conduit), we had ...
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Power and energy of pumped hydro versus grid scale batteries
A company is proposing a pumped hydro system where they state on their website as “capable of producing up to 335 MW of electricity with around 8 hours storage”.
The same company is proposing a ...
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What are these jumpers between phases and earth in a residential distribution grid?
In my city, in quite a few locations there appear to be wire jumpers from each phase to the earth(?) wire. They appear to have ceramic insulators, so I suspect they aren't just directly connecting ...
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Resistor That is neither Series or Parallel
My textbook says that the 5Ω and 2Ω resistor are neither in series or parallel. My understanding of the reasoning is that the current from the 5Ω resistor has two pathways it can travel - either to ...
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Decoupling tri-state power
There is a power supply BAT1 that provides +5 V power (the schematic shows 9 V, but it's providing 5 V):
After a certain period of time it shuts down, leaving its output in a strange tri-state (or ...
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For Delta-Wye transformers, with neither side grounded, can one get electrocuted by standing on earth and touching one of the Delta side wires?
It seems to me that there is no path to ground in this case. So, the voltage on the Delta-side of the transformer cannot drive a current through the ground (ie, through the one touching the wire), ...
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How to replace potentiometer with MCP4725 with separate 5v lines
I'm not an electrical engineer, so maybe my concerns are not valid here:
I want to replace a physical potentiometer on a high voltage power supply, which takes 0-5v as the potentiometer input. I have ...
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How do grid tie inverters sense the mains phase and quality and at the same time feed current into it?
Grid-tie inverters synchronize the phase and also check the quality (frequency, magnitude) and shutdown in case of errors to prevent what's called islanding, i.e. to prevent feeding current to network ...
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How does a solar / PV inverter get preference over grid source for the house load?
I've got a solar PV inverter and grid feed supplying the house. They are both connected (via their respective circuit breakers) before the switchboard, so from the junction to the house switchboard it'...
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Digital control root locus verification
I am stuck answering coursework questions with the following Z-transform open loop transfer function
(𝑧) = (0.04𝑧(𝑧 + 0.675)/(𝑧 − 1)(𝑧 − 0.584)(𝑧 − 0.563))
I need to design a digital lead ...
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Correct use of circuit breaker before/after 220-24 converters in distribution board
Say I have a distribution board where 220VAC comes in and goes into a 220VAC-24DC converter. 24V DC is subsequently fed into a KNX-driven RGBW dimmer which powers a LED strip directly along a 5x1.5 ...
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Wind turbine power characteristic
The following graph was obtained using the MATLAB Doubly-Fed Induction Generator (DFIG) wind turbine model.
I'm confused about why spikes occur at the points A to B and C to D.
If you have any ...
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How do power grid operators regulate the power flowing through their networks?
My question:
How do grid and transmission line operators regulate the amount of power flowing in their networks, both to utilize the network optimally and to enact delivery policies like those in the ...
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4
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The voltage created in the transformer
The voltage generated in the transformer must be due to the change in the flux in the coils, but if the voltage is DC, why is no voltage induced?
Of course, we know that voltage is created by the ...
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Cost of pin insulators
H. Cotton's Transmission and Distribution of Electrical Energy states that the cost of pin insulators increases exponentially with voltage. Why is this, and why isn't it linear?
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How many winding turns in a HV power transformer?
I'm creating a simplified 2D model of 3 three-winding 132/22 kV, 40 MVA transformers that I'll use to calculate the magnetic field surrounding them.
Now, the turn ratio is of course 132/22, but is ...
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Cutting a 1500 W heating coil into two halves and using one half for a project
I have a heating coil (Nichrome coil) of 1500 W working at 230 V. I need to cut it into two halves and use one half for my requirement at 230 V without burning my coil.
I know that if I use half the ...
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2
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Inverse temporal power-law increase of DC voltage under the application of constant DC current
Is there any material in which the DC voltage follows an inverse temporal power-law increase, under the action of a constant DC current? This implies a situation in which a constant current, I, is the ...
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Why aren't stranded wires used more widely if conductivity is improved and price is reduced?
Why aren't stranded copper coated aluminum cables (CCA) widely used outside a small niche of speaker wires or 12 VDC applications?
According to this post the issue is with the insulation jacket which ...
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Matching generation and consumption in renewables
To balance power generation and consumption, traditional power plants such as thermal and hydro have governors that regulate the steam/water that flows into the turbine.
The energy that renewables ...
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Grid Voltage Ride Through using PSSE
I am trying to simulate a low voltage ride through (LVRT) lagging case (Qgenerator = max). The inverter seems to be going to momentary cessation, and although the output power at the inverter ...
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2
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137
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Transmission Line model [closed]
Can some one explain me why exactly classical circuit theory fails to account for the wave nature of EM fields and how the transmission line model accounts for it better
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RMS voltage between two arbitrarily phased AC lines
As part of a thought experiment to determine the barriers to electrification of a street running railway using 25kVAC single phase overhead line, I found myself consulting the clearance rules in the ...
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Increasing Power Line Voltage to Reduce Current?
I need to deliver 5V, 1A (5W) of power to a load that's 5+ meters away from the power source, however I'm keen to use small-ish wires and connectors, which I know will result in volt drops through the ...
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What is the reason for these utility poles with a 6-sided hole in the middle for conductors
What would be the technical (Electrical, structural, safety) reasons for a utility pole like those shown below? This picture was taken in Arkansas and is what I assume to be 3-phase power. Note how in ...
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What happens on a DC-DC grid connection after a perturbation in the synchronous grid?
Consider the Continental Europe synchronous grid. This power system has some DC-DC connections with other countries (for example one with Great-Britain). Suppose now there is a sudden big outage ...
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A question regarding reactive power
Why does the production of reactive power not require extra fuel unlike active/real power?
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What does "CON LAY" mean when it comes to conductor stranding?
I am reading the book "Distribution System Modelling" by Kersting, and in the Appendix there is a Conductor data. Under stranding it says CON LAY for some conductors (like 250,000 AA). What ...
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Is there anything to limit LED output dimming 50% while the wall dimmer controls 50% to 0%?
We got a project for a client but our lights are too bright for the space, we still want to sell the the lights because we have extra inventory and need a way to dim the LED output to 25W instead of ...
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Feasibility of 30MW DC transmission over 400m?
We have an electric motor final load of 10-30MW, in an isolated industrial location.
The power source could be (Li-ion) battery packs, where each pack outputs 1500VDC, ~500A. Having 10-30 of these ...
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Sorting very different voltages and use them to charge batteries
I'm working on a project to produce electricity from a source that can produce sometimes negative, sometimes positive voltages, ranging from mV to kV depending on the situation, with very little ...
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why does voltage drop across a resistor
I have seen the explanations about the energy lost in from of heat, but that energy comes from the net reduction of kinetic energy of the electrons (reduction of current). More over voltage is a ...
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How is frequency measured in a power grid?
I know that voltage and current are measured with voltmeter and ammeter, but how is the frequenc measured in power grid applications? I know that a phase locked loop (PLL) can be used, but is this ...
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Duty cycle in flyback transformers
I have a small doubt. If the flyback transformer is designed to vary duty cycle from 5-50% and obtains an output voltage of 5 to 100 V. Here, can we increase the duty cycle beyond 50% (70-80%) as to ...
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How do I connect a three phase transformer with three center taps?
I have a three phase step down transformer with three center taps like shown below:
How can I connect it to get the 90 V three phase lines or the 45 V three phase lines at a time for circuits that ...
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How to (theoretically) capture 59 megajoules of power in 5 seconds to store like a battery for a month? [closed]
On Dec 21, 2021 EUROfusion Scientists in Culham, UK produced 59 megajoules in 5 sustained seconds from their nuclear fusion experiment.
What theoretically would be required to capture that energy and ...
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Deriving power formulas for transmission lines
I'm trying to derive formulas for active power (\$P_s\$) and reactive power (\$Q_s\$) at the sending end of a transmission line shown below:
Where:
\$E_s\$ and \$E_r\$ are voltage magnitudes
\$X\$ is ...
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1
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Semiconductor chip shortage [closed]
Does anyone have an answer why do chip distributors have almost virtually zero stocks? Is there a shortage?
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Pilot light, logic and Opto issues
First time poster, long time lurker.
I’m an electrician to start with, so excuse my lack off EE expertise. Trained in the elevator industry but now float around a few industries.
I’m putting together ...
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1
answer
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Calculating the new per unit impedance of a transmission line
The per unit impedance of 98 km of 412 kV transmission line is (0.768 + 4.823i) x 10^-3 to bases of rated voltage and 115 MVA. Calculate the magnitude of the per unit impedance when the apparent power ...
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