[NTYNUT (OP)]

hello
How capacitor bank are used in substation why they are installed there
i have seen polarize AC capacitor but unfamiliar with these in substation

[Bored chemist]

They are probably for power factor correction; this may help.
http://www.eaton.com/ecm/groups/public/%40pub/%40electrical/documents/content/sa02607001e.pdf

[evan_au]

Yes, almost certainly power factor correction.
- The efficiency of an AC network is maximised if the current is in-phase with the voltage.
- This reduces resistive losses in the network, and maximises chargeable electricity generation
- If the load in an area is very inductive, the electricity supplier can save money if they correct the phase (or power factor) by installing capacitors across the power lines
- Old-fashioned fluorescent lights had an internal inductor to limit current, and a capacitor to correct the power factor of the inductor.
See: https://en.wikipedia.org/wiki/Power_factor#Power_factor_correction_of_linear_loads

Interestingly, you can create a large and variable "virtual" capacitor with a synchronous condenser, which is actually a rotating electric motor, and looks nothing like a capacitor, physically or electrically.
https://en.wikipedia.org/wiki/Synchronous_condenser

Electricity suppliers have often seen domestic solar panel installations as a nuisance that complicates their life, and have demanded that solar panels turn themselves off if the power supply voltage gets too high (which typically happens on sunny days).
- However, more recent models of solar cell inverters have functions like power factor correction and network voltage regulation which actually help the local electricity supplier.
- Whether the electricity suppliers will embrace this assistance or see it as a further threat is another question...

[NTYNUT (OP)]

hello
here is image of it
how to install what is inside it

[evan_au]

The term "coupling capacitor" suggests that it is for coupling a signal voltage into the high-voltage network.
- This is used in some countries to remotely control loads such as slab heaters or storage water heaters
- These can operate at frequencies of a few hundred Hertz, or in the kiloHertz region
- These are not intended to carry mains voltage (50Hz or 60Hz) or power supply currents, but only higher frequencies at low currents
- It needs to be used with a generator system at the central transformer, and slave devices at every controlled load.
- You must not use a frequency used by any nearby area, or you could be switching off the wrong devices
https://en.wikipedia.org/wiki/Load_management#Ripple_control

Follow the advice in this thread, and get professional help.

..and if it were power factor correction capacitors, you do not know if they are needed in your area, with your loads.

Capacitors store charge even after the power is disconnected, and I don't want to kill you - or any innocent bystanders.

[NTYNUT (OP)]

what is inside this capacitor

[evan_au]

Search for "ripple control coupling capacitor" (and specify the manufacturer's name, if you have it)...
A typical data sheet is here: https://www.zez-silko.com/en/products/ripple-control-coupling-capacitors

[NTYNUT (OP)]

Hello
How this Ct work
what is inside theory

[NTYNUT (OP)]

Regulator calculates the basic harmonic factor of the active and reactive currents using the FFT algorithm.

i get this please explain how FFT algorithm work with it

[evan_au]

How this Ct work

A current Transformer (CT)  measures the current flowing through a high-voltage busbar, while keeping the measurement instruments electrically isolated from the high voltage. They are used for monitoring MVA and MVAR in substations, detecting faults, and tripping circuit breakers.
See: https://en.wikipedia.org/wiki/Current_transformer

please explain how FFT algorithm work with it

The supply voltage is usually quite close to a sine wave (eg 50Hz).

But electronic controls used in lift motors and factories can draw currents that are multiples of 50Hz, eg 150Hz, 350Hz, etc. This current causes load on the substation, but delivers no useful power. It can sometimes set up resonances in transformers and power-factor correction components.

So power companies put limits on the amount of harmonics that industrial equipment can inject into the main supply - and charges users penalty rates if the harmonic content is too high.

The current waveform would be measured via a Current Transformer.

See: https://en.wikipedia.org/wiki/Fast_Fourier_transform

[NTYNUT (OP)]

The supply voltage is usually quite close to a sine wave (eg 50Hz).

Does the supply from power station is not Sine waves at 50Hz can you show the images how it look

[evan_au]

not Sine waves at 50Hz can you show the images how it look

The graph in the link below shows the effect of a solid-state light dimmer; the blue curve is the sine wave voltage from the power station.
-The red curve is the voltage delivered to the load (which is not a sine wave, and has lots of harmonics).
- The current drawn by the load will not be a sine wave either, but the exact current waveform will depend on whether the load is resistive, inductive or capacitive. 
https://en.wikipedia.org/wiki/Dimmer#Solid-state_dimmer

[NTYNUT (OP)]

; the blue curve is the sine wave voltage from the power station.

Hello
Synchronous generator can't build sine wave is that true

[evan_au]

Synchronous generator can't build sine wave is that true

Synchronous generators are designed to produce a 3-phase sine wave voltage, where the voltage in each wire has a 120° phase compared to the other wires.
- Grid-scale synchronous generators are usually quite efficient at doing this.
- Some very cheap inverters used on solar cells turned the DC from the solar cells into a square wave, with lots of harmonics. However, electricity suppliers don't approve of this.
- Modern inverters produce something very close to a sine wave voltage.

However, a lot of modern loads draw current which is not a sine wave, and this causes the network to lose efficiency.
Electricity supply authorities penalise industrial users who have loads don't produce sine wave currents (ie the have a lot of harmonics), or which produce currents that are out of phase with the voltage.

[NTYNUT (OP)]

Synchronous generators are designed to produce a 3-phase sine wave voltage, where the voltage in each wire has a 120° phase compared to the other wires. Synchronous generators are usually quite efficient at doing this.

However, a lot of modern loads draw current which is not a sine wave, and this causes the network to lose efficiency.
Electricity supply authorities penalise industrial users who have loads don't produce sine wave currents (ie the have a lot of harmonics), or which produce currents that are out of phase with the voltage.

Hello,
what is material of wire used in it ?

[evan_au]

what is material of wire used in (a synchronous generator) ?

Copper wire is almost always used in electrical generators and motors, as it is a good electrical conductor, and fairly cheap.
- Silver is a slightly better conductor, and corrosion-resistant, but it is far more expensive
- Aluminium is cheaper than copper, and a good conductor, but it is chemically very reactive, and quickly forms an insulating oxide layer on contact with air. This makes it very difficult to form good electrical joints.
- If you can afford the cost of cryogenic refrigeration, high-temperature superconductors can be used to build electrical generators and motors. These have the advantage that they have almost no resistive losses in the windings.
See: https://en.wikipedia.org/wiki/Electrical_conductor#Conductor_materials

This tutorial has 2 examples of a generator:
- A 6MW generator that operates at 35kV and 171A. This is is similar to the current that a car starter motor draws for a few seconds at a time - but this generator must carry this current continually, 24 hours per day. So the wire inside the generator will be much thicker than the wire to your starter motor.
- A 100MW generator also operating at 35kV delivers 3000 Amps (across 3 phases). This calls for a seriously thick copper bar. In practice, an economical design wastes about 1.4MW in resistive losses, which requires a lot of cooling.

[evan_au]

Synchronous generator

Older generators were electromechanical, and had to rotate at exactly the right speed to generate 50Hz, locked to the electrical grid.
Today, power electronics has dropped in price significantly, so that the speed of the generator does not need to be tied to the grid frequency.
See: https://en.wikipedia.org/wiki/AC-to-AC_converter

high-temperature superconductors

Superconductor generators are being considered for wind turbines, to scale up to 20MW power levels.
For a technical and economic comparison, see:
https://spectrum.ieee.org/green-tech/wind/the-troubled-quest-for-the-superconducting-wind-turbine

[Angeou]

The capacitor bank is a working group composed of a plurality of capacitors, and has two forms of series and parallel. In the case of series connection, the withstand voltage is the sum of the two, and the capacity is the reciprocal and the fraction of the two; in the case of parallel, the withstand voltage is the one with the lowest withstand voltage, and the capacity is the sum of the two. Simply put, the series withstand voltage rises and the capacity decreases. The parallel withstand voltage is constant and the capacity is increased.

The capacitor bank has the characteristics of large capacity, large number of cells, and high voltage level. The shunt reactor group can be used to perform reactive power compensation of the line, and the series capacitor compensation technology is one of the effective means to improve the stability limit and economy of the transmission and transformation network.

[guest49538]

Maybe this link can help to understand the topic. I can't post entire links yet (I'm new), but I'll give the hint to reach the website:

Improving power factor to reduce energy demand charges, increase capacity
From: Plant Engineering
URL: plantengineering.c*m/articles/improving-power-factor-to-reduce-energy-demand-charges-increase-capacity/

(add h***s and w3, and replace * with "o").

The formulae for power in main distribution centers are usually written as:

                                 P_P = I.V.cosΦ   and
                                 P_Q = I.V.senΦ
while
                                 P_TOT = I.V (this is what you are paying for, even when you use only P_P.

where Φ is the angle between the real and the reactive (imaginary) power.

If you get  Φ = 0 by using capacitors to compensate inductive charges, then you get that P_TOT = P_P, which saves you a lot of money and spare power for other users, as P_Q circulates into your network (a factory or a home) without even being used. That Φ≠0 artificially increases the power that you seems to consume, but you don't (paying a lot more money if you have an industrial installations).

High or low voltage capacitors (depend where they are used) are put in parallel to the power line to "tune it", compensating the inductance that appears as a load in serie with main.

If you have a two channel's oscilloscope plus a current to voltage converter, you can observe Φ on the screen as the difference between voltage and current entries. They should be "in phase", which means Φ=0. If they are not, you are wasting power and money.

Hope this can help you.

[paul cotter]

This is an old thread but I want to add to what evan au said about mechanical generators. There are two basic types of ac mechanical generators, namely synchronous and asynchronous types. In a synchronous machine the rotor consists of a series of electromagnets in a 2, 4, 6 or more( dependent on rotational speed ) pole arrangement together with a three phase stator. When connecting a synchronous machine to the grid great care must be exercised to ensure the voltage, frequency and phase must match that of the grid: if not, a crash sync operation will occur which can cause mechanical or electrical damage or both. An asynchronous machine is simply a squirrel cage induction motor which has a passive rotor in contrast to the electromagnets in a synchronous machine. An induction motor runs at a speed below that of the grid when on load and above when a net torque is supplied externally. Asynchronous machines are commonly used in wind generators. The reason is that a sudden gust of wind would cause great stress in a synchronous machine as it's speed is locked to the grid and cannot change whereas an asynchronous machine can change speed while still supplying at the grid frequency.