Utility-scale power distribution, i.e. electricity grids, substations, overhead lines.

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106 views

Why is the earth a viable return path for power distribution?

I'm having trouble understanding why the earth is a viable fault path for electricity brought into my home. Isn't there really high resistance? I mean, it's dirt? Also, let's say I connect the hot ...
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1answer
116 views

Why are the ground and neutral bonded in my panel?

I took a look inside my panel today and saw a big green wire connected to the neutral bus bar. Why are these two bonded together? Why not just send the neutral back where it came from? Where does the ...
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3answers
110 views

With a transformer center tap, why are the two resulting circuits out of phase by 180*?

I'm trying to understand how the power in my home works, and the part I'm having trouble with specifically is why in the step-down service transformer, the resulting out-of-phase 120V "hot" lines are ...
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1answer
85 views

Why / how does reactive power help improve voltage quality?

This question is related to my previous question that Olin provided a great answer to. Note that this question is about transmission and distribution systems, not electronics. I believe the claims ...
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1answer
61 views

Bus bar calculation

I am trying to learn bus bar calculations steps . can someone help me how to get started for DC/AC bus bar calculation. how to get started?? what are the parameter need to be considered. 3.when skin ...
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0answers
53 views

Calculating Voltages in phases when a neutral fails

In the above star-connected three phase circuit the neutral is floating. I need to find the voltage across each load and which voltages are higher than 240 (Assuming the Line-to-line voltages are ...
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2answers
310 views

Why does reactive power affect voltage?

Why does reactive power influence the voltage? Suppose you have a (weak) power system with a large reactive load. If you suddenly disconnect the load, you would experience a peak in the voltage. Is ...
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6answers
2k views

What happens to excess energy fed into the power grid?

The closest question to this is Linear useage of excess power generation. I'm no engineer so I may not be able to phrase this correctly and would appreciate an answer which assumes minimal ...
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3answers
110 views

Ensuring that the a circuit breaker in a secondary elec. distribution board will go off before a circuit breaker in the main board

I want to create a small portable single-phase secondary electrical distribution board to safely power up some lights in my back yard. The board will be powered from a wall socket, and will contain ...
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3answers
100 views

3-phase electricity availability in USA [closed]

I want to ask about availability of 3-phase electricity in USA. I live in Europe, in small town (population: 3000). We have 3-phase electricity available everywhere, even in small villages near my ...
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2answers
169 views

Why are twisted pair cables used in electric power distribution systems?

I'm an Electrical Engineer, and understand how twisted pair wires can reduce noise susceptibility in the presence of magnetic fields. I recently noticed the power company replacing a long stretch ...
2
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2answers
268 views

Short circuit current through multi-winding transformer

I have a (radial) system with several multi-winding transformers, for instance one 24 MVA 7-winding transformer from 11 kV to 1.92 kV. I want to calculate what the short circuit current will be on ...
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2answers
250 views

Switchgear vs. power distribution center (PDC) vs. motor control center (MCC) - what's the difference?

Here's what I've observed so far: All three contain circuit breakers. All three supply power to motors, although switchgear and PDC-fed motors are obviously higher-voltage, larger motors. ...
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1answer
66 views

Photo-voltaic power source connecting to a grid: can I feed the greed? [closed]

Let's say I have a PV power source generating 50/60 Hz 230VAC power. I could connect this power directly to the grid assuming that I will consume all generated power for my own needs or, if the power ...
2
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1answer
300 views

What happens to a transformer if the supply side is shorted?

Suppose I have an industrial plant, where a switchboard is fed through a transformer. The switchboard have only "passive" loads, i.e. they don't contribute with short circuit currents. If there is a ...
2
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1answer
113 views

Disconnectors Symbol in Single Line Diagrams (SLD)

where should the moving part of a disconnector be located when breaking gets applied, on the energized side or on the disconnected side? Is there any standard?? Suppose a non ring, simple grid and ...
1
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2answers
103 views

Why does power go both to and from a power station?

It is common practice that wires in power lines send power both to and from a power station. Suppose that, instead of forming a closed circuit between a substation and a consumer, both the substation ...
2
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1answer
142 views

Modelling of dynamic behavior of a weak power grid?

I'm modelling the dynamic behavior of a weak power grid. I know the voltage level and short circuit capacity, and that's about it. Short circuit max = 400A, 3-P Voltage level = 66000 V My problem ...
3
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1answer
318 views

What is the percent impedance of a typical residential power line transformer?

Power transformers are rated by percent impedance. A 5% transformer, when loaded to full spec secondary current, will show a ~5% deviation from nominal output voltage. What is the percent impedance ...
2
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1answer
90 views

Parallel Transmission Lines

I am studying the RTS 96 test system for a power system simulation in Matlab. I have noticed that under the Branch Data file, there are some buses which have two lines connecting them. For example ...
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1answer
111 views

What is a SRF? (This is used in AC power distribution system with isolation transformer)

Following image shows a block diagram of a AC power system. What is that SRF equipment comes with the isolation transformer? What SRF means and what it does?
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1answer
65 views

How power supply companies can measure the time of blackout in households? [closed]

Literally the event when the household does not get and electricity in case of cable snap or some accident on local station. Imagine coming home, turning the switch on, but getting no light in the ...
4
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3answers
1k views

How is transition from three-phase distribution without neutral to three-phase consumption with neutral achieved?

A typical distribution grid supplies 6 or 10 kilovolts AC to a substation near the consumers. This is typically done with a three-phase line without neutral - just three wires going in parallel. Then ...
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1answer
182 views

Effect of corona on overhead transmission line [closed]

In text book, it has been said that corona reduces the effects of transients produced by surges. But, how does corona reduce the transient effect?
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3answers
528 views

How are multiple power sources synchronized in a grid that uses a distribution ring?

A large distribution grid can work like this. There're several power station each outputting 50 Hz AC. Each power station feeds energy into a substation next to it which raises the voltage and then ...
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3answers
794 views

How big current I can commutate using D-sub connectors?

The question Did someone knows what are the current capabilities of the standard D-sub (aka Cannon) connector. I want to use it for power source connection together with the signal. I need pretty ...
2
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1answer
92 views

A confusion about radial schemes in power distribution

My lecture notes about distribution systems/radial schemes say the following: •In this scheme, feeders radiate from a substation in all directions and feed distributors at one end only. • SA is the ...
5
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2answers
158 views

mains frequency accuracy worldwide

I like to build a device that needs long term time stability. In germany, one of the best simple clocks use the mains power frequency to obtain a time measure. While the frequency is allowed to change ...
22
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4answers
2k views

How do transposition towers in transmission lines work?

There're such things as transposition towers in power distribution powerlines. The idea is that for example you have three conductors running in parallel at the same height and the leftmost of them is ...
0
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2answers
91 views

Barrier strip for power distribution

I'm working on a project where I need to supply power to multiple strings of LEDs, operating at 12VDC, with a max current draw of 20mA per string. What I'm looking for a quick and easy way to connect ...
3
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2answers
406 views

Can power theft on a large scale be stopped

Reading this article, I started wondering if there is any way to stop people stealing electricity from a power grid. Let me clarify, the only techniques I have seen (and can think of) is either to ...
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2answers
2k views

Guessing power line voltage from the number of disc insulator

Is there a good way to guess the power line voltage based on the number of insulator discs that attach the line to the transmission tower? Wikipedia seems to suggest that there is a "Typical number ...
28
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2answers
756 views

If we could start our electrical grid from scratch with today's technology, which would be the most efficient choice? AC or DC?

Lately, I’ve been reading about the many advantages of HVDC transmission systems for long distance transmission, undersea links, and others. The historical reason of why AC was picked over DC was ...
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1answer
1k views

3-phase power calculation when phase to phase voltages are different

I have a 3-phase power supply rated at 230VAC per phase. However, the phase to phase voltages are not equal. Suppose \$V_{RY}\$, \$V_{YB}\$ and \$V_{BR}\$ be the three phase-to-phase voltages between ...
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3answers
1k views

Why are the power transmission/distribution systems AC and not DC?

Is there a good reason why we are not in the process of completely converting our electrical transmission system to DC? The main reason for using AC on the grid (no offense Tesla, I love you man) was ...
4
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4answers
275 views

Is it practically possible to transfer electrical power around the World by wires?

Assume that we installed plenty of solar cells in all continents; mainly in Asia, Africa and America. Can we transfer the electrical power harvested from them around the World through wires? So that ...
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1answer
225 views

Draw busbars in qelectrotech

In qelectrotech how can I draw a busbar?
2
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2answers
209 views

Can current be drawn from ground in a SWER transmission setup?

I am almost certain that this is a ridiculous question, but cannot figure out why this scenario would not work. From what I understand, current from the electrical station is distributed to houses ...
5
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2answers
301 views

Why the delay between transformer failure and power outage?

A friend witnessed the explosion of the 14th street substation. I believe these transformers, about 1 city block in extent, delivered power to most of lower Manhattan. I am guessing the flood water ...
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1answer
49 views

Routing Current to Many Individual Channels [duplicate]

Possible Duplicate: How to implement an isolated connection matrix I need to put current on up to 30 lines; one at a time. What kind of electronics solutions are there to this kind of ...
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2answers
121 views

What is the name of a device that would send input current out to my home and maybe upstream from a power device?

Please edit this since I'm too ignorant of electronics and electrical equipment to explain this well. I'm looking for a device that I can create that would take AC or DC current from a power source ...
3
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2answers
273 views

Connections in load flow analysis

I have a very theoretical doubt. I'm trying to fully understand the load flow analysis and its application. So I have a network with about 300 nodes (AC transmission network). Inside every node I have ...
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1answer
160 views

Power Grid in depth explanation [closed]

I am looking for links, books, papers, documents or any other reference type that allows me to get a very in depth overview of the power transmission and distribution network (preferably of the UK). ...
5
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3answers
2k views

How does DC transmission require several times less wire than AC?

In this YouTube video (scrolled to 5:55) there's a claim that replacing an AC high voltage transmission line with a high voltage DC transmission line allows for having seven times fewer powerlines ...
2
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1answer
145 views

Transients and shielding in power transmission/distribution lines?

I've been lurking for some time on the board here - but hadn't had occasion to ask a question until now: Does anyone have experience with power distribution networks and their impacts on sensitive ...
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8answers
4k views

Why do utility companies supply at a frequency of either 50/60 Hz?

It just struck me that Utility Companies world-wide supply domestic users at either 50/60Hz. It could have been selected to be 10 Hz, or 100 Hz ... whatever Was 50/60 chosen at random? Is there some ...
1
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1answer
423 views

IEC 60320 power cord rating

I am trying to determine what power cords I need to get to connect computer servers to 208v PDUs. I know the PDU has C13 receptacles I need a C14 to C13 power cord. However, I noticed there are ...
4
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2answers
226 views

What causes sub-second mains voltage outages?

Many times I observed a following electrical event: mains voltage will suddenly drop and then immediately restore. This causes lights to blink and computers to restart. I can't imaging what could ...
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2answers
4k views

What causes unequal phase-to-neutral voltages in three-phase distribution systems?

A four-wires cable runs into an apartment building to supply it with three-phase 380/220V alternating current. Each apartment is connected to one phase, different apartments are connected to different ...
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4answers
1k views

Why does electric arc in a switch prefer a curved path over a straight path?

Recently I found this video of a 500 kilovolts line being opened under load. When the switch contacts are pulled apart an electric arc predictably starts. While the contacts are close to each other ...