Power factor and Harmonic correction

In electrical plants, the loads draw from the network (active power) as a power supply source. For example, in personal computers, printers, diagnostic equipment, etc. It can also convert it into another form of energy (such as electrical lamps or stoves) or into mechanical output (such as electrical motors and fans).

To get to these forms of energy, often the load exchanges with the network (with net null consumption) the reactive energy, mainly of inductive type but in some cases capacitive. This energy, even if not immediately converted into other forms, contributes to increase the total power flowing through in the electrical network, from the generators, all along the conductors, to the users but is not converted into usable energy.

This is a disadvantage to the power provider, lines company and end user. This is especially true as it increases the user’s maximum demand and associated charges, as well as excess kVAR usage charges.To smooth this negative effect, power factor correction of the electrical plants and equipment must be carried out.

Power factor correction obtained by using capacitor banks to generate locally the reactive energy necessary for the transfer of electrical useful power.
Moreover, the present spreading of direct current users, such as electronic circuits and electric drives, involve the generation of current harmonics which are injected into the network. This is with the consequent pollution and distortion of the waveforms on other connected loads. Therefore, the use of harmonic filters (both of passive as well as of active type) contributes to improve the overall powerquality of the network, also carrying out power factor correction at the network frequency, when such filters are properly sized.

There are numerous benefits to power factor correction. These benefits range from reduced demand charges on your power system to increased load carrying capabilities in your existing circuits and overall reduced power system losses. The benefits of power factor correction aren’t just limited to the balance sheet. There are also environmental benefits which means your company is reducing its carbon footprint.

REDUCED REACTIVE POWER CHARGES

Vector and other electric utility companies charge for excess kVAr’s consumed under a power factor of 0.95. For medium-level power consumers, thousands of dollars per month in fees can be created if the site has not installed power factor correction or if the existing power factor correction units are undersized/not functioning. Return on investment periods for installing power factor correction can be as low as a year.

REDUCED MAXIMUM DEMAND CHARGES

Most electric utility companies charge for maximum metered demand based on either the highest registered demand in kilowatts (kW meter), or a percentage of the highest registered demand in kVA (kVA meter), whichever is greater. If the power factor is low, the percentage of the measured kVA will be significantly greater than the kW demand. Improving the power factor through power factor correction will therefore lower the demand charge, helping to reduce your electricity bill.

INCREASED LOAD CARRYING CAPABILITIES IN EXISTING CIRCUITS

Loads drawing reactive power also demand reactive current. Installing power factor correction capacitors at the end of existing circuits near the inductive loads reduces the current carried by each circuit. This may allow the circuit to carry new loads, saving the cost of upgrading the distribution network when extra capacity is required for additional machinery or equipment. This would save your company thousands of dollars in unnecessary upgrade costs in addition to reducing current flow resistive losses in the circuit.

IMPROVED VOLTAGE STABILITY

A lower power factor causes a higher current flow for a given load. As the line current increases, the voltage drop in the conductor increases, which may result in a lower voltage at the equipment. With an improved power factor, the voltage drop in the conductor is reduced, improving the voltage at the equipment.

REDUCED POWER SYSTEM LOSSES

Although the financial return from conductor loss reduction alone is seldom sufficient to justify the installation of capacitors, it is sometimes an attractive additional benefit; especially in older plants with long feeders or in field pumping operations. System conductor losses are proportional to the current squared and, since the current is reduced in direct proportion to the power factor improvement, the losses are inversely proportional to the square of the power factor.