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

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Modelling grounding reactor as transformer

First: This is not a question about electronics, it's about large (three-phase) power systems where the components have ratings in kV and MVA. I'm mainly interested in symmetrical components, and how ...
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0answers
78 views

Physical Sensation When Driving by Electric Utility Fault/Arc?

While driving home from work this afternoon during somewhat-cloudy daylight, I suddenly noticed a bright bluish glow on nearby objects, heard a loud hum that sounded like it had 60/120ish Hz ...
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10answers
7k views

Why three-phase power? Why not a higher number of phases?

Is there a reason, beyond historical reasons, that three phases has become the dominant number of phases? I am aware of the advantages against one phase and two phase, namely the reduced amount of ...
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0answers
13 views

Circuit Breaker Upgrade Complications [migrated]

I'm currently renting a unit in a commercial warehouse complex. Each unit has individual MLO panels inside the unit, and then a large split meter base with individual breakers for each unit in a ...
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1answer
73 views

Voltage drop-out after lightning strike

A powerful thunderstorm rolled through my area yesterday and something happened that I had never noticed before. Many times before when powerful thunderstorms with lightning rolled through, the AC ...
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0answers
48 views

Does the direction of power distribution blocks matter?

I've seen several instances of people using power distribution blocks e.g. like this one http://www.grainger.com/product/BUSSMANN-Distribution-Block-5A671 - in reverse of how they are specified e.g. ...
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1answer
97 views

range of transmission line?

I am not electrical engineer by profession. So, accept my apology if my question sounds stupid. I am simulating a situation on computer where electric power is being send from one point to another ...
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1answer
167 views

Low voltage power lines - formula for spacing between poles?

What is the distance or separation between pole-pole in a 230 VAC distribution line? Is there any formula for this, or we can take any distance?
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1answer
44 views

Connecting shielding for high and low voltages

I have design a power distribution PCB with high AC(230V) and low DC(<10V) voltage power rails. Both are going to be connected to my board by separate cables. Each of those cables have shielding ...
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1answer
74 views

What's the thick wide aluminum tape used for in last mile grid transformers?

This YT video (scrolled to 0:45) shows the process of fabricating a pole mount transformer. At 0:45 the following is shown: there's a wooden brick used to hold everything together, it's covered in ...
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1answer
92 views

What does “mod 2” mean in these multi-level inverter switching equations?

I am working through a paper that discusses the design of a multi-level inverter to connect photovoltaic arrays to the grid. It uses 4 PV modules (only two are shown in the design image below, but it ...
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1answer
3k views

What is this object found on transmission lines?

What are the components, circled in red in the figure, on this transmission line ?
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96 views

PCB Power grid trace

I am currently working on my PCB layout and having trouble laying the power traces. I am trying to avoid running any tracks under signal traces and keeping power somewhat separate. I tried doing ...
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4answers
3k views

Why are consumers located near high-voltage lines typically not connected to those lines but instead are connected through a lower high-voltage line?

A typical grid uses 110..500 kilovolts lines to deliver electricity to substations which lower that to 6..20 kilovolts and then lines with that lower voltage get to consumers where yet other ...
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2answers
158 views

How much ground current vs. neutral wire current?

This is a follow-on question to an earlier question of mine; I think it deserves its own question, though. I am trying to learn as much as I can about how current in a power grid (transmission and ...
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2answers
106 views

Understanding ground current

I am trying to understand ground current in a power distribution system. The basics, of course, are simple: in the power grid, the "hot" wires carry high voltage, while the return path (the neutral ...
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2answers
226 views

Can we short the neutral to earth (ground) at entry point of our home electrical supply?

Normally in our 230V power outlet, the voltages are as given below. Neutral to Earth - Less than 2V Neutral to Phase - 200V to 230V Earth to Phase - 200V to 230V But nowadays, after around 10 am, ...
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3answers
321 views

Short circuit protection of cable

I know cables are protected from short-circuit by using fuses / circuit breakers. Cables have I²t curves, which should be checked with fuses or cb's I²t curves in time / current chart. Here I have ...
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2answers
402 views

How do I, as a consumer, gain or lose when the utility company line voltage varies from rated value?

A little background; the line voltage supplied here in my part of India varies as a function of the load. At dusk, the measured value is as high as 248V. Household appliances are rated at either 220V, ...
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2answers
62 views

How exactly does the grid handle small deviations in power consumption?

I've heard many times that the grid electricity production and consumption must be balanced and imbalances lead to overvoltage or undervoltage. I've never seen an explanation of that phenomena from ...
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5answers
351 views

Which is harder on the power grid: a winter cold spell, or summer heat wave?

Just a wonder of mine, as I sit here listening to my heat pump struggle to maintain. For the Q, assume the North East USA. I think Summer heat waves are more difficult for the grid due to A/C load ...
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0answers
33 views

What's the typical harmonic distortion on the secondary side of a distribution substation?

What's the typical harmonic distortion and waveform found at the low-voltage side of an urban substation (I.e: the aggregate of appliances and secondary distribution system impedance)?. If you can ...
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1answer
164 views

Is it a problem in a single-phase system, if a generator shares neutral with the grid?

I'm planning to use a generator to bridge longer power outages. Both the house and the generator are single-phase. If the main breaker is off, it will only disconnect the phase, the neutral will still ...
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1answer
45 views

Fault on a tri-phasic circuit

I work on a industry as an intern and I'm having a trouble. Clearly there's a fault on the net, but I can't figure out which type it is since I'm having strange readings from a basic multimeter. I'm ...
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0answers
25 views

How can I enter per-unit values on ATPDraw software?

I'm studying the AOV (Area of Vulnerability) of certain distribution system with distributed generation and I'm using ATPDraw software. As the real system is so big and its data is given in p.u. ...
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1answer
138 views

How are power flows between multiple power systems (tie-line flows) determined?

In Europe, for example, there are multiple transmission system operators (TSOs), which are responsible for their own region of the grid. These TSOs must exchange power to ensure reliable operation of ...
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0answers
308 views

What is a Thyristor Switched Series Capacitor (TSSC)?

I'm struggling to understand the physical difference between the Thyristor Switched Series Capacitor (TSSC) and the Thyristor Controlled Series Capacitor (TCSC). From this book, I understand that a ...
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2answers
297 views

Why is it desirable to inject reactive power into a transmission system?

This website explains the basics of FACTS technologies and how they can be used to exchange active and reactive power with the transmission system, namely: SSSCs - can exchange active and reactive ...
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1answer
232 views

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 = ...
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2answers
255 views

Zero resistance transmission lines?

I am using the IEEE 14 bus test system for a simulation and was wondering why some of the resistances of lines are set to zero, e.g. see lines (4,7), (4,9), (5,6) below (only part of the full data is ...
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1answer
297 views

Convert transformer resistance data from Watts to Ohm

Short version: How can I convert transformer resistance values from Watts to Ohms? Long version: In PSS/E, transformer resistance can be entered as either per unit values (system base or transformer ...
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2answers
256 views

What do the terms “cuts” and “jumpers” mean?

specifically, with respect to the electrical grid. Here's an excerpt from something that I'm reading that I don't understand: Switching operations, including applying cuts and jumpers, can be ...
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4answers
205 views

How to step-down voltage without a transformer?

Say I am running a line from a transformer to a distribution panel that doesn't quite need 240V but less. How do you go about creating the required voltage drop? I was asked this in a interview for ...
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2answers
87 views

Electrical measurements of Chicago substation from where can I get it? [closed]

I am doing a project on electrical load prediction using machine learning. Machine learning involves creating models based on past data. For creating these models where can I get data regarding ...
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2answers
118 views

Power Conducting Stepper Motor?

I have a question that I'm not really sure how to ask, so here goes: So I know there's such a thing as a power conducting slip ring motor, which I assume allows the passthrough of power through the ...
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1answer
85 views

Prevent EPROM powering from IO pin

I consider using a cheap Microchip 3-pin EPROM with single bidirectional data line as ID storage on various daughter boards. Since I don't want to waste daughter board connector pins on a device ...
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3answers
487 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
427 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
822 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
291 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
271 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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2answers
6k 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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7answers
7k 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
469 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
154 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
1k 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
1k 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 ...
2
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3answers
2k 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
105 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 ...
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1answer
1k 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 ...