What is the Advantage and Disadvantage of Capacitor Bank Supplier

The active power which is generated from the power plant can be expressed in MW (Mega Watts) otherwise kW (KiloWatts). Even though the reactive power within alternating power system can be expressed in Mega VAR or Kilo VAR. The reactive power demand is mainly created from the inductive load which is connected to the electric system. So, these loads are usually electromagnetic circuits of transformers, motors, fluorescent lights, distribution networks, etc.

For more information, please visit our website.

This reactive power must be compensated properly otherwise, the ratio of actual power utilized through the load, to the whole power of the electric system will become very less. Here whole power is the sum of reactive power & active power. This ratio is called the electrical pf (power factor). If the pf of an electric system is low then a load of ampere for the transmission, alternators, transformers which are connected to the system will become high for necessary active power. Thus the compensation of reactive power will become so essential. So this is usually done through a capacitor bank.

What is a Capacitor Bank?

Capacitor bank definition is when a combination of several capacitors are connected in series or parallel connection with the same rating then it is called a capacitor bank. Generally, an individual capacitor is used to store electrical energy. So once capacitors are increased within a bank then it will increase the energy capacity that is stored within a single device. The basic capacitor bank symbol or diagram is shown below.

In a substation, it is used to enhance the power factor & reactive power compensation. While installing a capacitor bank in a substation, some specifications need to consider. So capacitor bank specifications are voltage rating, temperature rating, KVAR rating, and basic instruction range.

Capacitor Bank Types

Generally, the unit of a capacitor bank is known as a capacitor unit. The manufacturing of these units can be done similarly to 1- phase unit. These units are mainly connected in the form of a star/delta connection to make a whole three-phase capacitor bank. At present most frequently available capacitor units are 1-phase type whereas 3-phase capacitor units are rarely manufactured. There are three types of capacitor banks which are discussed below.

• Internally Fused
• Externally Fused
• Fuse Less

Internally Fused

The designing of an internally fused can be done within a particular arrangement. According to its rating, various elements are allied in series and parallel. The protection of each capacitor element can be done separately through a fuse unit. As the name suggests, the capacitor elements, as well as fuse units, are arranged within the same casing. In this type of bank, the size of every capacitor element is extremely small within ratings.

So if any of the capacitor elements are broken down, then there will be no effect within the act of the bank. This kind of capacitor bank can run suitably even one or above capacitor elements are broken.

The main advantages of an internally fused type are, it is very simple to install as well as maintenance is simple. The disadvantage of an internally fused is, once several capacitor elements are failed, then the whole bank needs to be changed. So there is no possibility for the replacement of a single unit.

Externally Fused

In an externally fused type, the fuse unit for every capacitor unit is given externally. If any fault occurs in any capacitor unit then the fuse unit will be damaged. When the fuse unit detaches the defective capacitor unit, then this bank will maintain its service without any break.

In this type, the connection of capacitor units can be done in parallel for each phase of the bank. Once one unit fails, then there will be not a lot of effect on the whole bank's performance. Whenever one capacitor unit is not there within a single phase, then the capacitance of that single phase will be less as compared to the other two phases.

This will affect high voltage in the remaining two phases of the bank. In this type, the identification of a faulty unit can be done through visual inspection once the fuse unit blows. The capacitor unit rating typically ranges from 50 KVAR ' 40 KVAR. This is one of the main specifications.

The main disadvantage of this bank is, once any fuse unit fails, then an unbalance can be detected even all the units within the bank are well.

Fuse Less

In a useless type, the connection of several fuse units can be done in series to make a capacitor string. These strings are connected in parallel to make a capacitor bank for each phase. After that, three similar phase banks are connected in the connection of star/delta to make a whole three-phase bank.

Through an arrangement of fusing in internal or external, the capacitor strings are not protected. So in this type of system, if any one of the string units fails because of the short circuit or fault, then there is no change within the flow of current throughout this string because there are several other capacitors allied in series connection through this path.

When the short circuit effect within the string unit is small, then the capacitor bank can be accumulated to extend the time before faulty unit replacement. So this is the main reason, why the fuse unit is not necessary to change the faulty unit from the system within the bank instantly once the unit turns defective.

Capacitor Bank Connections

The capacitor bank is connected in two ways like star and delta but most of the time, delta is used. So there is a bit of confusion about which connection is better for a bank. So here we are going to discuss these two connections along with benefits and drawbacks. The main application is power factor correction because, in a 3-phase system, a 3-phase capacitor bank is used for the power factor correction which may be connected in star or delta.

Capacitor Bank in Delta Connection

When these banks are used in delta connection then it is utilized for less to average voltage. The capacitor bank in delta connection can be utilized for high voltage however it is not achievable sometimes as in delta connection; the complete phase voltage is given across every capacitor while in star type connection, it is lesser as compared to applied phase voltage across the capacitor. So, 3 phase capacitor bank wiring diagram using two connections is discussed below.

So if we employ a delta connection at high voltage, then the capacitor's voltage rating must be high. Consequently, manufacturing of high voltage capacitors is expensive & it is impossible sometimes.

Advantages

The advantages of a capacitor bank in delta connection include the following.

When the capacitor generates Kilovolt-Ampere Reactive (KVAR) then that is proportional to the square of the voltage applied. So, if the voltage is higher, the KVAR is also more. So the capacitor in this connection will provide high KVAR compared to the bank connected in star connection because, in star type connection, the applied voltage is low compared to delta connection.

The capacitor bank in this connection can flow the harmonic current, thus it can decrease the effect of harmonic within an electrical system. When the bank is connected in delta connection, then it gives a balanced capacitance to every stage of the electrical system & keeps a balanced voltage.
If a capacitor cell within a single phase is not succeeding in the bank, then voltage beyond every phase remains the same, simply KVAR falls.

Disadvantages

The disadvantages of a capacitor bank in delta connection include the following.

The main drawback of the capacitor bank in delta connection is, the pressure of voltage across every capacitor is maximum which decreases the capacitor's life & it may not be utilized in the applications of high voltage.

Capacitor Bank in Star Connection

The star connection-based type is mainly used in the applications of medium to high voltage. In this type of connection, the voltage beyond every capacitor is smaller as compared to the voltage of the phase, so the pressure of voltage beyond the capacitors is less even in the applications of the maximum voltage. In the capacitor bank, there are 2 types of connections used like the following.

• Grounded Star Connection
• Ungrounded star Connection

Grounded Star Connection

In this type of connection, the unbiased point of the bank is stably earthed, which means the neutral should not be insulated toward the BIL level of the complete system. Thus, some price reductions can be realized with this connection. In addition, TRV (transient recovery voltage) may be less harsh within this connection. An error on the 1-phase of the bank will not affect the rise of voltage within the remaining legs of the bank. So a fault on one phase of the capacitor will not affect other phases.

Ungrounded Star Connection

In this kind of connection, the capacitor bank's neutral point is not connected toward earthing. So this type of connection does not allow the supply of GND currents & zero series harmonic currents.

Advantages

The advantages of capacitor bank in star connection include the following.

• It is a simple connection
• The voltage pressure across every capacitor is low, thus the capacitor's life span is high.

Disadvantages

The disadvantages of capacitor bank in star connection include the following.

• Star-connected type provides less KVAR than delta-connected type because the voltage across the capacitor is less.
• A star-connected type cannot circulate the harmonic current in an electrical system.
• The ungrounded star-connected type cannot maintain the balance voltage and cannot provide the balance capacitance.
• If a capacitor cell in one phase is failed, the unbalanced voltage occurs in the electrical system.

From the above two connections, the delta connection provides more benefits as compared to the star connection. For a capacitor bank, this connection is suitable so, most of the banks are connected in a delta connection.

Capacitor Bank Calculation

The main purpose of the capacitor bank calculator is to get the necessary kVAR for enhancing power factor (pf) from low range to high. For that, the required values are; current power factor, real power & the value of power factor to be enhanced over the system. So that we can calculate to get the value in kVAR.

If we want to measure the value in VAR or MVAR then the real power in MW/ W is necessary. For instance, if the value is used in kW then you can get the value in kVAR simply. Similarly, it works for MW & W. The required reactive power like Q(kVR) is equivalent to the real power like P(kW). The formula for the capacitor bank calculator is shown below.

• Required Reactive Power (kVAR) = P(kW) * tan (cos-1(PF1) ' cos-1(PF2))
• Required Reactive Power (VAR) = P(W) * tan (cos-1(PF1) ' cos-1(PF2))
• Required Reactive Power (MVAR) = P(MW) * tan (cos-1(PF1) ' cos-1(PF2))

Why Capacitor Bank Testing is Important?

Capacitors banks within the power system provide accurate power factor (pf) correction. So pf correction unit includes different functioning settings based on the installation position. The different factors like time, moisture, change in temperature & harmonics will change the correction of power factor for capacitor banks.

If already connected capacitor banks are not tested properly in a specific time then they will turn incapable to utilize. The capacitor's operation can weaken; reducing the power factor (pf) of your power system can cause power factor loss. During the testing, ANSI/ IEEE or standard is employed. There are three types of tests done like type tests/design tests, routine/production tests & pre-commissioning & field Tests.

Applications

The applications of capacitor banks include the following.

• Capacitor banks are mainly used to enhance the electrical supply quality & also to enhance the power systems efficiency.
• This is most frequently used for the correction of AC power supply in industries where electric motors and transformers are used.
• As this bank uses an inductive load, then they are vulnerable to power factor lags & phase shifts within the power supply, so it results in a system efficiency loss.
• When these are used in the system then the power lag can be solved at less cost for the organization by making some changes in the power grid
• These are used in radars, pulsed lasers, Marx generators, detonators, coilguns, fusion research, nuclear weapons, electromagnetic railguns, etc.
• Generally, capacitor banks decrease the phase difference among the current & voltage.
• The power factor (pf) can be maintained close to unity.

In the early days of electricity, capacitor banks were essential only for public powerhouses with low-level technology in an isolated setting.

But nowadays, capacitors have all kinds of technological applications, ranging from small-sized MEMS devices to large-scale wind farms.

No matter where you use capacitor banks, it has a simple application: storing electrical energy and regulating the flow of energy.

This post makes you aware of capacitor banks, their types, testing, applications, and reasons for capacitor bank failure.

What is a Capacitor Bank?

By definition, a capacitor bank is a device where several capacitors of the same capacitance are joined together. These capacitors can be connected in a series connection or a parallel connection. 

SINAVA supply professional and honest service.

The role of a single capacitor is to store electrical energy, and the capacitor bank's purpose is to store electrical energy in a greater volume.

By increasing the number of capacitors in a capacitor bank, you can increase the capacity of a capacitor bank to store electrical energy. 

A capacitor bank can be used both for AC power supply and DC power supply. With AC power Applications, capacitor banks are used to correct the power lag factor or to counter the phase shift. On the other hand, with DC power applications, capacitor banks are used to increase the total amount of stored energy or uplift the ripple current capacity.

Capacitor Bank Diagram

Capacitor Bank: Theoretical Knowledge

To understand the importance of capacitor banks, you must be aware of electrical power systems. Here is a brief overview.

Types of loads in electrical power distribution systems

Power loads can be categorized into three types in all electrical energy distribution systems.

• Resistive load
• Inductive load
• Capacitive load

Incandescent bulbs and heaters use resistive loads.

Motors, refrigerators, and air conditioners use inductive load.

Capacitors use capacitive load.

There are three types of power in electrical power distribution systems.

• Active power
• Reactive power
• Apparent power

Active power does the work and is calculated in watts.

Reactive power creates the magnetic field that is required by the types of equipment to function properly. It is calculated in VAR.

The apparent power is created by the combination of active power and reactive power addition. It is calculated in Volt Amperes.

You get the power factor by dividing actual power by apparent power.

A lot of equipment requires consistent reactive power to function properly. And a capacitor bank provides consistent reactive power when it is installed in parallel to the load.

Also, a capacitor bank helps to correct the power factor by reducing the phase difference between current and voltage.

In short, a capacitor bank acts as an instrument in all electrical substations to correct the power factor and compensate for reactive power.

How to Calculate Capacitance?

Capacitor manufacturers give every capacitor a rating, which is its capacity to store electrical energy and ability to correct power faults. It is measured in Farad.

The capacitance of a capacitor bank is measured by adding the rating of all capacitors present in the capacitor bank.

Capacitor Bank Connections

There are two ways to connect a capacitor bank in an electrical distribution system: star connection and delta connection. The purpose of these connections is to correct the power factor in a 3-phase electrical system. Both connection types have their benefits and drawbacks.

Capacitor Bank in Delta Connection

The delta-connected capacitor bank is best for low to medium-voltage applications. It uses the full phase of voltage. That's why the delta connection is not feasible for high-voltage applications.

Delta-connected capacitor bank circulates the harmonic current and reduces the harmonic effect in an electrical system. Also, it delivers a balanced voltage and capacitance.

There is only one drawback of delta-connected capacitor banks. Its life is too short. That's why you have to replace them often.

Capacitor Bank in Star Connection

Star-connected capacitor banks are best for medium to high-voltage applications. The voltage is rooted three times lesser than the phase voltage across each capacitor in a star-connected capacitor bank.

There are two types of star connections

• Grounded star connection 
• Ungrounded star connection

Grounded star connection uses a neutral point that is connected to the earth. On the other hand, an ungrounded star connection uses a neutral point that is not a connection to the earth.

Star-connected capacitor bank has a simple working, and its life is long.

However, star-connected capacitor bank has disadvantages.

It provides less voltage than a delta-connected capacitor bank and does not provide harmonic current. Moreover, it does not supply a balanced voltage and capacitance.

Capacitor Bank Applications

Electrical appliances and equipment need a lot of electrical energy to operate productively. Also, the flow of energy needs to be smooth. For that, capacitor banks are ideal instruments because they are made to store electrical energy charges and streamline the flow of electrical energy.

Typically, capacitor banks are used for the following purposes.

1. Capacitor banks are used for shunting in electrical systems. Shunting is when the electrical current is passed through the least resistance path to save the electrical system. In other words, shunt capacitor banks improve the efficiency of electrical distribution systems.
2. Capacitor banks are used for power-factor correction. Such an application is very useful for motors, transformers, and large electrical machines.
3. Capacitor banks are used to store energy. Such an application is very useful for equipment that requires reactive power on demand to maintain the operations of the machine.
4. Capacitor banks are also used in large-scale electrical energy equipment, such as wind farms.
5. Capacitor banks are widely used in manufacturing, where machines require balanced voltage and current.
6. Capacitor banks are also used in micro-electro-mechanical systems (MEMS)  that use radio frequency and wireless space for the convenience of mankind. Smartphones are the best examples of it.
7. Capacitor banks are also used in weapons, such as laser guns.
8. Capacitor banks are also used to create high-intensity electromagnetic fields required for scientific research.
9. Scientists are working on using capacitor banks to create electromagnetic armour and weapons. Initial research has created rail guns and coil guns.

Advantages and Disadvantages of a Capacitor Bank

Advantages

1. You can store energy quickly for the latter and immediate usage.
2. Capacitor banks supply energy quickly without any delay.
3. Capacitor banks have low losses of electrical energy.
4. You can enjoy the service of a capacitor bank for a long time.
5. Capacitor banks are simple to operate and install.
6. You can use capacitor banks with both AC and DC power supplies.
7. Capacitor banks are inexpensive devices. If they malfunction, you can replace them cheaply.
8. Capacitor banks can be used all over the industrial, residential, and commercial electrical distribution systems.

Disadvantages

1. Capacitor banks cannot compete with batteries.
2. You can store a limited amount of electrical energy.
3. If you leave the capacitor bank, its energy will deplete with time.
4. Capacitor banks provide variable levels of voltage.

How Can a Capacitor Bank Fail?

Nowadays, capacitor manufacturers use self-healing technology in capacitors. In case of any dielectric fault, the capacitor heals itself by emitting gases. Yet, a capacitor bank can fail due to many reasons. Here are two frequent ones.

Harmonics and Detuned Capacitors 

A capacitor bank can fail due to overloading, which can be caused by harmonics. You can understand harmonics as a current or voltage with a too-large frequency. When a capacitor bank is exposed to harmonics, its elements get fused. As a result, the capacitor bank malfunctions or fails to perform.

Resonance

Resonance happens when the most dominant frequency enters the electrical system and the capacitor bank, along with the transformer, provides the low-impedance path. As a result, the capacitor bank malfunctions or fails to perform.

What is Capacitor Bank Testing, and Why is It done?

The most common role of a capacitor bank is to correct the power factor in an electrical distribution system. But several factors lower the ability of the capacitor bank to correct the power, such as temperature, moisture, harmonics, and time.

Capacitor bank testing is necessary before installing it because it ensures the proper functioning of an electrical distribution system.

Types of Capacitor Bank Tests

Capacitor bank testing falls into three types of different tests.

1. Design Tests or Type Tests
2. Production Test or Routine Tests
3. Field Tests or Pre-commissioning Tests

Conclusion

A capacitor bank helps to maintain the quality of operations of any electrical distribution system. Also, they are the best instruments to store electrical energy for frequent usage. Moreover, capacitor banks are inexpensive devices that provide splendid value with their long life and usability.

Without capacitor banks, the world we are living in is not possible.

However, before installing a capacitor bank, it should be tested. So, there can never be a performance issue in the electrical distribution system.

For more Capacitor Bank Supplierinformation, please contact us. We will provide professional answers.