OBJECTIVES TO BE SOLVED BY SCB INSTALLATION:
- Reduction of power losses;
- Voltage level stabilization (voltage loss reduction);
- Improvement of the electrical energy quality;
- Reduction of the reactive energy consumption from powerful networks;
- Increase in the electric network capacity without increasing the power equipment capacity;
- Increase in the power supply system sustainability.
Nowadays, the most demanded SCB type is the open SCB for operation directly on the switchgear without constructing additional facilities. The SCBs fully comply with GOST 15543.1-89 in terms of technical requirements for resistance to climatic factors for areas of УХЛ1.
The batteries are equipped with single-phase cosine capacitors of the КЭПФ type. The capacitor contains the fuses inside installed in series with each capacitive element, providing internal damages localization, and thus preventing the capacitor from failure.
The capacitors are placed in metal frames made of the rolled metal and have a reliable anticorrosive hot-dip galvanized (HDG) weatherproof coating. The internal and external insulation of the capacitors is manufactured taking into account the support frames potential.
The electrical connections of capacitors are made with flexible multicore wires and rigid busbar. The connection of flexible conductors to the capacitor terminals is made with the help of a specially designed parallel groove clamp with special coating to avoid oxidation as a result of creating a galvanic pair with the material of the terminals and conductors. To ensure minimal transient resistance, the contact joints are treated with a special conductive grease.
To detect possible malfunctions, the SCB capacitors are connected with each other according to the “double star” or “H-type” scheme. In case of breakdown of the capacitor section in emergency and pre-emergency modes, the internal fuse of this section burns out, changing the capacity of one of the battery branches. After that in the conductor which connects the neutral points of the stars (for the “double star” scheme) or connects the midpoints of the two parallel branches of each phase, an unbalance current flows controlled by a special unbalance relay separated from the power circuit by the unbalance current transformer. The unbalance relay, for its part, alerts on the occurrence of a non-standard state in the SCB operation or sends a signal to turn off the high-voltage circuit breaker of the supply line.
The lowest value of the natural unbalance current is achieved by forming the layouts of the arrangement and selecting the capacitors individually for each battery.
The “double star” scheme
The “H-type” scheme
The SCB configuration depends on customer’s requirements. The SCB structure includes metal frames to install the hot or cold galvanized capacitors, polymeric or porcelain line and bus insulators, buses for electrical contacts, current measuring transformers, unbalance current protection devices, current-limiting reactors and a set of fasteners.
SCB assembly at the operation site
To limit starting currents at the moment of commutation and disturbances reduction in the supply network, damping reactors are installed in series with the SCB.
|Part type designation||Rated voltage, kV||Maximum voltage, kV||Rated phase capacitance, mkF||Capacitor type|
Principle of the SCB conventional designation:
|БСК (SCB) —||БСК (SCB) —||— static capacitor battery|
|ХХ —||110 —||— rated voltage, kV;|
|ХХ —||52||— rated power, МВАр;|
|Х —||УХЛ||— climatic version according to GOST 15150-69;|
|Х —||1||— placement category according to GOST 15150-69.|
For example: БСК-110-52 УХЛ1 – static capacitor battery, rated voltage 110 kV, rated power – 52 MVAr, climatic version and placement category according to GOST 15150-69 – УХЛ1.
Operating principle. Design features
The main function of the capacitor battery is to improve the electrical network performance, that is, to optimize the operation of the entire power supply system.
From a constructive point of view, the device is a housing which contains two or more separate capacitors with different capacitances and allowed voltage limit. All components of the device are connected in parallel, so that the necessary power value is regulated.
The price of the capacitor batteries will depend on the number of capacitors included into the package, the maximum permissible voltage for each capacitor and other technical parameters.
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