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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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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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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Quantify Grid Stiffness
Being the stiffness of the grid its capability of maintaining the voltage constant despite small variations on load. Whereas, a weak grid would be easily affected by load variation and the voltage ...
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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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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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Why are twisted pair cables used in electric power distribution systems?
I'm an Electrical Engineer, and understand how a twisted pair of wires can be used to reduce noise in the presence of magnetic fields.
However, I recently noticed the power company replacing the ...
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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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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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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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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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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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Why is the supply voltage 400V when the neutral is disabled in a three phase supply?
Why is the supply voltage 400V when the neutral is disabled in a three phase supply?
Phase voltage is 230V. Line Voltage is 400V.
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Arlec grid connect bulb and power points DC convert smart WiFi hack
These devices works off 240V AC.
I was looking to convert them to run off DC and keep the grid connect app function.
https://www.bunnings.com.au/arlec-9w-950lm-4000k-grid-connect-bc-smart-...
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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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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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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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Wireless power transmission calculations
I have been able to calculate and fix components for the transmitter circuit of wireless power transmission system but I am still having some challenges. They are:
1. How can I calculate theoretically ...
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Can a bird, previously at earth potential, get electrocuted by landing on a powerline at high-enough voltage due to the initial "equalization charge"?
At the voltage levels of typical overhead transmission lines in the US, a bird can land on one and be just fine (as long as it doesn't do something like spread its wings and touch a tree or something ...
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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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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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A question regarding reactive power
Why does the production of reactive power not require extra fuel unlike active/real power?
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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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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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Solved - FAULTY BATTERY - Solar power - 6149 Watt-hour battery bank but only 1 hour of inverter time at 300W after dark
Turns out one of the 4 batteries was bad.
Many thanks to @SamGibson for his insight in solving this problem.
The well-deserved Accept is on his answer.
Here is what the charge plot looks like now:...
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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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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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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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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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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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Method for measuring power flow in a distribution network
Considering a mostly meshed distribution network (with some radial spurs) connecting zone substations (loads) to grid exit points (GXPs or sources).
I am attempting to find the proportion of the ...
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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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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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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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Comparison between AC and DC power flow analyses
Consider a power flow problem. Injected real and reactive power at a bus are functions of voltage magnitudes and voltage angles and are given by
\begin{align*}
P_i = \sum_{k=1}^N|V_i||V_k|(G_{ik}\cos(...
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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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