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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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 ...
21k 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. ...
210 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 ...
7k 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 ...
579 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 ...
3k 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 ...
1k 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 is ...
5k 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 ...
1k 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 (...
3k 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?
4k views

What does this symbol indicate (line with brackets)?

I'm modelling a power system, and encountered a few symbols I have never seen before in a single line diagram. I believe the first one is a switch with three possible position. Closed, open and ...
14k 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 ...
747 views

How to modify a router's antenna? [closed]

I have tried to extend the antenna of my router in order to increase its range. I added a wire few cm long. There was no modification however in the range. The power (-db/m) was the same. Why is that?
9k 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 ...
21k 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 ...
275 views

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 ...
513 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 ...
17k 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 ...
597 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 ...
2k 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 ...
16k views

What is the purpose of the thin wire at the top of power transmission lines?

I know a power transmission line carries usually two sets of 3 phase conductors. But I have noticed a relatively thin wire at the center-top of the power transmission line. What is the purpose of this ...
51k 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 ...
1k 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 ...
10k 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 ...
25k 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 ...
422 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 ...
1k views

Draw busbars in qelectrotech

In qelectrotech how can I draw a busbar?
454 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 it wouldn't work. From what I understand, current from the electrical station is distributed to houses through power ...
1k 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 ...
55 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 problem. ...
167 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 ...
411 views

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 ...
230 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). ...
5k 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 (...
183 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 ...
10k 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 ...
15k 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 ...
3k views

Parallel Operation Problems

How do I set up a Woodward 2301A load sharing device when operating generators in parallel? Currently, when running two generators in parallel, the first generator takes too much load, and the second ...
24k 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 ...
4k 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 ...
2k views

How do utility companies treat voltage deviations in distribution networks?

I live in a region where nominal mains voltage is 220 volts and state standards permit deviations within 5 percent continuously and within 10 percent for short periods. So if I measure the voltage in ...
24k views

What causes overvoltage in power grid?

In the region where I live there's a state standard that says that mains voltage deviation can be within 5 percent continuously and within 10 percent for short periods of time, so if the mains voltage ...
316 views

Localized Star Network From Bulk Cap?

I was reading the Power Integrity article on Altera's website and came across the recommendation for the Bulk Capacitor (47uF to 100uF). I'm supposed to have one 47uF-100uF capacitor for every two ...
439 views

how grid tie invertor works?

I read it somewhere that it should be a current source as grid is low impedance voltage source. ( whatever that means. ) I get the part where voltage is converted from DC to AC via Inverter. But what ...
418 views

Is direct current really better for pumped-storage hydroelectricity facilities?

Currently the article equivalent to War of the Currents in Russian Wikipedia section says that direct current is beneficial to pumped-storage hydroelectricity plants and provides no reference to that ...
247 views

What could be this “transient electric deviation”?

On August 7th, 2011 a lightning hit a transformer powering one of Amazon EC2 facilities in Dublin. The status report said Normally, upon dropping the utility power provided by the transformer, ...
520 views

Why are power distribution systems so prone to massive faults?

Many region-wide blackouts (like this one or this one) are described as follows: some high-voltage equipment (like a generator or a transformer) fails and the grid gets overloaded and then protective ...
13k views

How does earthing work when earth is dry?

Earthing is meant to provide reliable contact of an electric appliance to earth so that if there's an insulation fault current goes into earth instead of through a person's body. This requires ...