In high voltage circuits, special installations are often used, which are called power capacitors. They can be used to stabilize the flow of electricity in the network, to increase the power of the installation, a special design allows you to gain a large capacity. Also used for reactive power compensation.
Power capacitors
Devices used in power electrical networks with high or low voltage, as well as in installations with increased frequency. Power capacitors can be used both independently and assembled into batteries. Unlike capacitors used in radio electronics, power ones have significant weight and dimensions, as well as a large capacitance and reactive power. Exceptions are devices used for control electronics in power networks, the so-called capacitors for power electronics.
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Depending on the application, power capacitors are divided into the following main types:
- Instruments for electrical installations with variablecurrent frequency widely used in industry.
- Power capacitors in high-frequency electrical networks.
- Communication, power take-off and voltage measurement devices.
- Filter.
- Pulse.
Power frequency capacitors
This type includes devices for increasing the power factor in AC installations with a certain, constant frequency of 50 Hz. Such devices are made for both indoor and outdoor use at a temperature not exceeding 50 °C. They are available in both single-phase and three-phase versions. With a three-phase design, the power cosine capacitor is connected in the form of a triangle. Sometimes a fuse is used to protect against breakdown.
Automatic interruption of the power supply of capacitors in case of current overload of the power network due to increased voltage is provided by a special electric current relay. Protection against short circuit currents is achieved by installing fuses. In the control circuits, large magnetic starters are used to turn on and off, the units are equipped with the ability to adjust and indicators of the operating status.
Capacitors for high frequency installations
This type includes power electrical capacitors to increase the consumption of useful power in electrical installations with a frequency of 0.5 to 10 kHz with a specialcooling. A package of devices is assembled from separate independent sections connected to each other in parallel, or, if necessary, in series, on the one hand, a special cooling coil is soldered to the plates, which is a curved copper tube through which coolant is supplied during operation of the device. The cooling coil is used as a current lead, the other section plates on the opposite side of the capacitor pack are isolated from the housing and connected to the current leads. Sections connected in parallel form steps with independent leads through porcelain insulators to the housing cover.
Coupling, power take-off and voltage sensing capacitors
To ensure a stable capacitive component of communication over power lines, for telemechanization and protection in a wide frequency range from 36 to 750 kHz, devices in insulated porcelain cases with an insulated dielectric made of mineral oil impregnated capacitor paper, voltage class 36 to 500 kV are used. Power capacitors with a voltage of 500 kV are also used to measure voltage on power lines and take power to provide electricity to switching and control points, which are specially located along high voltage power lines.
The design features of this type are a porcelain tire, covers that are terminals, seals that ensure the tightness of the capacitor, as well as oil expanders.
Filter and impulsecapacitors
Filter devices are designed to operate in the high-frequency filter circuits of specialized traction substations both indoors and outdoors. They operate with simultaneous application of DC and AC voltages with a frequency of 100 to 1600 Hz, while the value of the AC voltage should not exceed 1 kV, respectively. This type is also used for operation in DC converters containing pulsed thyristors.
Filter capacitors are used to smooth out surges of the variable component in high-voltage rectification devices in the network, as well as in double-voltage circuits in the environment of dielectric transformer oil and in high-frequency filter circuits of traction substations.
In electrical installations used for high-voltage impulse substations, as well as installations used for magnetic stamping, seismic exploration and rock crushing, impulse power capacitors are used. They are used in electrophysical installations for the creation and study of high-temperature plasma, as well as for superstrong pulsed currents. To create powerful light sources of a pulsed nature, as well as for research using laser systems, it is precisely pulsed power capacitors that are used.
The peculiarity of the operation of these devices is a slow current charging moment, and, conversely, the discharge occurs quickly, impulsively. In addition to these capacitors,more surge voltage generators.
The network impulse voltage generator is mainly used for electro-hydraulic installations using electric discharge for technological purposes, due to special production or process conditions. Such generators are designed for mains voltage 380, 400, 415, 440 V. Rated output voltage is 50 kV, total output power is 18 kW, reactive power factor is 0.73.
Pulse voltage generators are made of two blocks of the charging and high-voltage compartments. The charging unit includes a step-down transformer and a cabinet with a converter containing a capacitive-inductive component. The high-voltage compartment is represented by a cabinet with power capacitors, a protective device and a surge arrester, as well as a separating ground.
