Q1: How Capacitors Save Money
- A: Capacitors lower electrical costs two ways: In many areas, the electrical rate includes a penalty charge for low power factor. Installation of power capacitors on the electrical distribution system within a facility makes it unnecessary for the utility to supply the reactive power required by inductive electrical equipment. The savings the utility realizes in reduced generation, transmission, and distribution costs are passed on to the customer in the form of lower electrical bills. The second source of savings derived through the use of power factor correction capacitors is in the form of increased KVA capacity in the electrical distribution system. Installation of capacitors to furnish the non-productive current requirements of the facility makes it possible to increase the connected load by as much as 20 percent without a corresponding increase in the size of the transformers, conductors, and protective devices making up the distribution system which services the load.
Q1: Power Factor - What does it mean?
- A: Where open electricity markets have been introduced, the supply of electrical energy becomes competitive between the supply utilities. Although private distribution companies are obligated to run a profitable and successful business, they are also committed to maintain the quality of supply at a high level. Competition in an open electricity market creates new opportunities for even better quality of supply of electricity. One very important aspect of improving quality of supply is the control of power factor. Low power factor means poor electrical efficiency. The lower the power factor, the higher the apparent power drawn from the distribution network. This means that the supply company must install larger generation capacity, larger size transmission lines and cables, transformers and other distribution system devices, which otherwise would not be necessary. This results in a much higher capital expenditures and operating costs for the Electricity Supply Company, which in many cases is passed on to the consumer in the form of higher tariff rates. This is the main reason behind why the Electricity Supply Companies in modern economies demand reduction of the reactive load in their networks via improvement of the power factor. In most cases, special reactive current tariffs penalize consumers for poor power factors.
Q1: Individual compensation(Reactive compensation systems)
- A: This type of compensation is applied to motors, transformers, and in general to loads with a high time of operation. Capacitors are directly connected in parallel to the terminals of the loads. This system minimizes the reactive current circulating through the installation, enabling the use of smaller switchgear and power lines or cables, which means a lower capital expenditure for new installations. In the case of existing installations, utilising capacitors for power factor correction will increase the maximum apparent power that can be supplied to the installation. However great care must be taken in selecting the size of capacitor because of the risk of self excitation of the electric motor.
Q1: Group compensation(Reactive compensation systems)
- A: Several inductive loads can be grouped together and equipped with a common capacitor bank. This system usually applies for users that have their own installations with distribution transformers and high voltage power lines/cables. The reactive power that is consumed by the transformers is compensated by the permanently connected capacitors to the secondary side of the transformers.
Q1: Centralised compensation(Reactive compensation systems)
- A: Centralised compensation by means of an automatic capacitor bank with automatic regulation offers the most simple and economical solution. The reactive power is subdivided in a number of capacitor steps that can be connected independently. A reactive power controller continuously measures the needs of the installation and connects or disconnects the capacitors until the target power factor is achieved. The advantage of this system is that the total capacitor power is smaller than the sum needed for individual compensation. Therefore this system is a good economical solution.
Q1: Where should the power factor correction equipment be installed
- A: After determining the required size capacitor in kVAr, the next step is to decide on the location for installation of the capacitor bank. It is difficult to set definite guidelines for location of capacitor installation. However, the following general rule should be kept in mind: As close as possible to the load to be compensated.
Q1: Power factor correction control relay
- A: When selecting a power factor correction relay the following main functions should be considered: 1.Measurement of the required reactive power and control the capacitor switching according to the power factor desired or pre-set value. 2.Indication of power factor, preset parameters and specified installation data. 3.Disconnect the capacitors when a system voltage drop occurs, this will prevent significant overvoltages in the installation and the subsequent damage to switchgear insulation. 4.Allow manual control. 5.Provision for a visual display of signal lamps for monitoring the number of capacitors steps switched into the system. 6.Possible implementation into a building management system
Q1: Why to improve the power Factor?
- A: A good power factor makes it possible to optimize on electrical installation and provide the following advantages • No billing for reactive energy. • Decrease in the subscribed power in kVA • Limitation of active energy losses in cables given the decrease in the current conveyed in the installation • Improvement in the voltage level at the end of the line • Additional power available at the power transformers if the compensation is performed in the secondary winding
Q1: Non-characteristic harmonics
- A: Those harmonics that are produced as a result of imbalance in the AC power system or asymmetrical delay of the firing angle of the converter. They are also produced by other non-linear, time-varying devices, for example frequency converters, fluorescent lamps, arc furnaces, electric welding machines, etc. (IEC 61642)
Q1: Reactive power compensation
- A: Most of the apparatus and loads connected to the electrical power system consume both active and reactive (inductive) power. Some examples of such components are transformers, transmission and distribution lines,induction motors, rectifiers, induction furnaces, etc.The most economical method of reducing reactive power consumption in electrical power systems is by installing capacitor banks. This method is called reactive power compensation.
Q1: Harmonic filtering
- A: In a perfect world, the voltage and current in an electrical AC power system have a sinusoidal waveform, with specific amplitude, frequency and phase angle. In the real world however, this is seldom the case. If the voltage is measured with an oscilloscope, the sinusoidal curve is always more or less distorted by sinusoidal waves different from the fundamental frequency. These disturbances called harmonics are generated by nonlinear loads in the system. The degree of distortion is dependent on the magnitude of the individual harmonics and can be expressed as Total Harmonic Distortion, THD. Active Harmonic Filter and Passive harmonic filter are the solutions of harmonics mitigation.
Q1: Apparent power (S)
- A: Apparent power or total power is a combination of active power and reactive power. Apparent power is measured in VA, kVA, MVA.
