# 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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92 views

### The materials used in an electrical grid going from power station to house [closed]

In getting an overview about how Electrical Grids work, I was hoping to connect the dots from voltage up to the materials (used in modern electrical grids). I am wondering if one could outline ...
79 views

### What are the methods to measure distribution transformer vibration in 0.5g range?

It may seem obvious to use widely available analog devices MEME accelerometer for measurement in range of 0.5g. I did thorough study on this and found out that MEMS sensors either doesn't work or ...
242 views

### Not understanding why in overcurrent protection only a certain section will isolate (why not the whole system)

I'm having an issue understanding a simple concept for faults. I understand the principles of how the relays cause the circuit breaker to open etc when a larger current goes through them to provide ...
3k views

### Factors that limit maximum power transfer through transmission lines?

I have read that the maximum power transfer is limited by (1) Thermal Limit, (2) Voltage Regulation and (3) Transmission angle (Stability). Thermal limit is self-explanatory. Is voltage regulation ...
47 views

### From how wide a range of angles can a grid of dipole antennas efficiently receive a power beam?

This paper on solar power satellite concepts makes brief reference to the ground receiver receiving an elliptical beam due to the angle it is at to the transmitter (2nd paragraph). The angle isn't ...
326 views

### Identification of a part on a power line's lightning arrester

I recently spotted an arrangement of wires on a lightning arrester on top of a power line. The power line is IIRC a 110 kV, 16.7 Hz, two phase line for railway systems. The lightning arrester is of ...
872 views

### BOOST CONVERTER Simulation Problems in Multisim

I am trying to simulate a boost converter to step up the voltage to 70V from a 40V source on the Load resistor. Based on the formula: Vout =Vs(1/1-D), i calculated the duty cycle to be 42.85% however ...
44 views

### How to decide where to place devices for power quality handeling [closed]

In a facility that experienced voltage sags where 175 KVA of the load is sensitive, and we are asked to implement MG set or flywheels to handle the power quality issues. where should the MG set/ ...
715 views

### How to choose the receiving end voltage for a transmission line using a short line approximation

I am confused as to how to choose the receiving end voltage for a short line approximation For example if i have a 220kV transmission line at 50Hz at 60Km. At the end of teh line theirs a load of ...
68 views

### Transmission Line Voltage Terminology Confusion (Very Basic)

I have a issue interpreting what transmission line voltage actually means (I have tried researching but nothing clearly explains in detail, just says its a 110kV line etc).For example if i have a ...
584 views

### Is the Nyquist plot useful in actual electrical engineering?

I am currently doing a course on linear control theory, and we are covering Nyquist Plot to study phase and gain margin. I find myself unable to appreciate this concept. One, the proof of the Nyquist ...
2k views

### Do electricity meters contain inverters?

In Germany the low-voltage grid is 0.4kV whereas the plugs in flats have 230V. Who is responsible for this conversion? Smart meter?
1k views

### what is the temperature equilibrium for a copper conductor conducting 4000 Amps

I have a copper conductor with a total resistance of 1 miliohm and a passing current of 4000 Amps. I want to know what the temperature equilibrium is for a conductor in the electrical grid (conductor ...
3k views

### Why do generators have to rotate at a slower frequency if demand outpaces the supply?

EU residents might have noticed that some of the clocks in their house have been running out of sync with other clocks. Apparently, the cause for this is that power suppliers had to reduce the ...
86 views

### How is the inverter connected to the grid?

I just finished circuit designing of an inverter which converts 440V DC to 230V AC. Now my manager asked me what kind of connectivity does it has. I answered him: "The current connectivity is AC as ...
41 views

### Low voltage grid frequency with renewable feed-in

If a low voltage grid's consumption equals to that grids renewable energy production, does it mean the transformator basically does nothing, like an open circuit? Are grid-tied inverters (smart) ...
956 views

### Reactive power overcompensation causing voltage increase at generator buses?

Consider the following system below, nine buses, 3 loads and 3 generators. From my understanding of reactive power, lagging power factors (per unit voltage less than 1) causes the reactive power to ...
47 views

### PV energy feed-in to the grid

I'm reading about integrating PV into legacy grids, and I saw the following scheme: Left side is middle voltage grid, and right side is low voltage grid (400V AC). It is talking about communication ...
101 views

### Coordinated relay tripping for Protection in Modern Power System

I have been working on Etap Software to understand the basic protection scheme using Current Transformer, circuit breaker and Relays. But i am having trouble in the coordination of the tripping in the ...
4k views

### Synchronising Power & Synchronising Coefficient

I am really confused with the concept of synchronising power and synchronising coefficient. I was taught 2 simple formulae in class. P = 3VEsin(del)/X Sp = dP/d(del) = 3VEcos(del)/X Now, I am ...
104 views

### What are important metrics of high voltage power lines? [closed]

Upfront: I am not an electrical engineer and therefore apologize upfront if I am asking a stupid question. TLDR; What are important / relevant metrics of high voltage power lines that can be ...
86 views

### Why did the Tesla battery in Queensland respond to grid frequency? Why isn't this stable? [duplicate]

The RenewEconomy article Tesla big battery outsmarts lumbering coal units after Loy Yang trips details the recently installed Tesla battery in Queensland Australia's response to a sudden change in ...
708 views

### Negative Wires for Parallel LED Strips

I'm working on a large scale LED project and I have a power supply question. I am using multiple power supply units and I'd like to wire a large amount of strips in parallel and control them with a ...
3k views

### Designing a BLDC generator

I am trying to design a brushless DC generator system for portable use of charging batteries and if suitable possible hybrid power system of an aircraft. The "BLDC" motor/generator will be connected ...
50 views

### Mixer Audio output xlr small contact with pin power suply of guitar pedals , possible damages?

Last night after a gig my audio Mixer output cables has had a small contact with the pin of the power supply of my guitar pedals that was on electricity. The mixer was not on electricity but the VU ...
5k views

### What is the purpose of the cylindrical layered conical discs in power stations? [duplicate]

You can see them everywhere. On towers of overhead lines, in power stations, converter stations, transformer stations, etc... Sometimes they are rubber, sometimes metallic, sometimes glass, sometimes ...
506 views

### Do fiber optics make any noise/sound that can be heard by the human ear?

In regards to, "...the noise sources in a fiber optic link include noise from the RF amplifiers in the transmitter, the laser diode, the photodiode and RF amplifiers in the receiver. Of which laser ...
147 views

### Electrical Engineering - Transformer

A transformer of primary voltage 220 V and turns ratio of 11:1. The secondary of the transformer is connected to a 30 Ω inductive reluctance in series with a load resistance (R). If the current ...
164 views

### Pass power to components on a high speed spinning motor

I have a small Emax RS2205 2600kv 16v DC Motor that is turning a PCB with IC chips that needs to be powered. I want to send 2 power cable (VCC and GND) from to stationary battery to the rotating PCB. ...
92 views

### What research has been done on Smart Grid software agents that both cooperate and compete? [closed]

Background For my master's thesis in Applied Mathematics, I am looking for ways to apply game theory to problems related to the so-called "Smart Grid". I have found many papers in which all involved ...
88 views

### What is the range of a direction protection relay?

I am modeling a hypothetical backup protection system for a power transmission grid and need to know if a directional relay can detect a fault if there are multiple lines and buses between the relay ...
673 views

### Why measure potential with a three winding transformer?

I have a single line diagram where it's shown that the voltage is measured with a three-winding transformer on the busbar (22kV), and two-winding transformers on the feeders. I've seen this on many ...
3k views

### Can we use 125VAC 20A switch in place of 12VDC 20A switch?

Can we use 125VAC 20A switch in place of 12VDC 20A switch? I have searched my local market and found 125VAC 20A switch. Can i use this AC switch in place of 12V 20A switch as it is not available in ...
429 views

### How can an insertion loss provide gain

I've been reading J.White's High Frequency Techniques, and in one passage is says: If the two port is a passive network, one might expect that the insertion loss could range from 0 dB (no loss) ...
225 views

### 3 phase ac vs single phase [closed]

A single phase supply requires 2 wire one for forward and next for returning path. However a 3 phase supply only requires 3 wire why? How does the circuit complete with 3 phase supply?
3k views

### What is this device attached to a high-voltage power line?

I noticed this white, cylindrical device on a power pole near Seattle that facilitates a 90-degree turn of the transmission line. It looks like the lightning conductor comes down the pole into a sort ...
597 views

### Postmortem: on a PDU with low Power Factor, why did all of our servers reboot?

I am a Unix SysAdmin with a crude understanding of electricity. We had this scenario: 4 dual-PSU servers were plugged into a ServerTech Sentry Switched PDU with PIPS with Y cords. The circuit is 208V/...
151 views

### Back-EMF related question

If a circular dipolar magnet is set to roll down an incline through an array of coils set out as found in a bicycle dynamo – one above and one below per set, but linearly along the incline. Arranged ...
405 views

### How do power grids keep AC frequency synchronised across long distances with multiple generators? [duplicate]

Let's consider a simplified electricity grid - say there are two power plants (A and B) 1000km apart. There's a town (L1) half way between them, and another town (L2) some distance downstream from B. ...
223 views

### How can a drone take down a high-tension power line? [closed]

This news article -- in which a drone reportedly took down the power grid in Mountain View CA -- caught my eye: Thursday night power outage the result of a drone crash Despite the compelling photo ...
3k views

### In the USA, the grid transmits power at/around 60Hz. How big of a frequency deviation can the grid handle before relays trip and cause a blackout?

I understand that small frequency deviations will result in automatic load shedding or other control actions to restore system frequency, but when does a blackout occur? When the deviation exceeds + ...
681 views

### Electrical System Harmonics

I'm a mechanical engineer so I don't know much about electric circuits and power generation to begin with. Can somebody explain what a harmonic is in the power grid and what is the reason why it is ...
113 views

### Alternator Synchronization in Smart Grid

Recently I was studying on the web that in the smart grid we need to synchronise the alternators. My beginner question is: Why do we need to synchronise alternators in a power system grid?
77 views

### Smart grid communications

For my final project, I am looking about smart grid. What I want to know is that what kind of communication is done in smart grid and the appliances, protocols used etc. Can I extract a data whether ...
7k views

### How does the speed of a synchronous generator changes with load?

When the generator is rotating at rated speed and let us say that the load decreases then the mechanical torque will be more than​ the electrical torque which will lead to increase in the speed of ...
536 views

### Can I use offline UPS for a PC? Will the delay affect my PC if it is running when the power goes out? [closed]

Can I use offline UPS for a PC? Will the delay affect my PC if it is running when the power goes out? im planning to set up an offline UPS at my home i need my PC running without any disruption but i ...
265 views

### How practical would it be to field rewind a large power transformer that's suffered damage from a geomagnetic storm?

It is commonly accepted in power distribution circles that large (large substation-sized or larger -- smaller substation-class transformers are much more readily replaceable) distribution transformers ...
861 views

### Can TRIACs work on 1MHz sine wave?

This is a short circuit and overload protector for 220V 50hz. Does TRIAC also work on 1MHz sine wave?