Dry shunt reactors are manufactured by KPM, LLC based on the technology that has proven itself in manufacture of current-limiting reactors.
Any power transmission lines have capacitance relative to the ground. This is due to fundamental properties of electrical conductors and insulators. Any two conductors divided by an insulator are a capacitor. Charge capacitance of power transmission lines relative to the ground depends on the line length, its arrangement and may other factors. In general, capacitance of cable power lines is higher than that of overhead lines.
The charge capacitance is stray capacitor. When electric energy is transferred via power transmission lines, part of its power is spent for charging and discharging of this stray capacitor — i. e., this is unproductive. For long power transmission lines such losses are unacceptable.
Connection of the reactor (in a three-phase network — three-phase group of reactors) in parallel to the charge capacitance of the line allows to minimize the transmission losses. The reactor is essentially an electrical inductor. Capacitors and inductors are reactive components. In an AC circuit, these components store and release electric energy back to the circuit in cycles. The cycles of the components are opposite in phase. Thus, when a shunt reactor with reactive impedance equal to the charge capacitance is connected, charging and discharging of the power transmission line stray capacitor relative to the ground will be done by the reactor’s magnetic field energy. Energy of the circuit generators will not be wasted in this case, the system losses will be reduced and transfer capability of the power transmission line will rise.
The traditional solution is to use shunt reactors with oil insulation. Disadvantages of this solution are quite obvious — fire hazard of oil insulation, the necessity in regular oil check, the necessity in mineral oil facilities.
Under current conditions, shunt reactors may be of dry versions.
A three-phase group of dry shunt reactors is represented by three Y-connected reactor coils. The three-phase group may be connected directly to the power transmission line by means of a branch line, or via the special-purpose tertiary winding of the transformer.
If necessary, step-wise adjustment of reactive power may be arranged for by means of several reactors used per phase, with mechanical switching between them. In this case, an individual transformer is used for connection to the network.
Design of shunt reactors is similar to that of current-limiting reactors manufactured by KPM, LLC.
The most important design features of a KPM, LLC reactor are:
- The reactor is a solid construction, its base and main load-bearing element are represented by the reactor winding itself. The winding needs no support framework or other elements to ensure extra strength.
- All metal parts of the reactor are under the same voltage as its winding. Absence of significant potential drops inside the reactor minimizes the probability of its internal damage. E. g., breakdowns between the layers, breakdowns between the cross-piece and winding, etc.
- Secondary elements of the reactor (rods, bindings) are made of fully nonmagnetic materials that have no electrical conductivity. This fully prevents their interaction with the magnetic field of the reactor. Since such elements are secondary, their strength is many times greater than the loads applied to them in the process of operation.
- The reactor windings have absolutely no dismountable mechanical connections (such as screw-and-nut connections, etc.). This ensures highest strength, durability and reliability of the whole structure; prevents the necessity in maintenance of mechanical connections in the process of operations.
- All electrical connections are made by soldering (welding), which prevents their heating, deterioration of contact joints, minimizes the losses.
- The reactor does not contain any liquids and highly flammable materials, it cannot be a source of fire and is explosion-proof. The reactor is designed for long-term maintenance-free service.
- Presence of vertical and horizontal through channels between the windings ensures reliable natural cooling of the reactor.