ELECTRICAL REACTOR  

What are electrical reactors?

 

•  A reactor is a coil which has a large number of turns and whose ohmic resistance value is much greater. Reactors are used to limit the short circuit currents which can cause damage to the equipment of the power system. The additional reactance added in series with the system for protection are called reactors.
• In an electric power transmission grid system, switchyard reactors are installed at substations to help stabilize the power system

• A line reactor (also referred to as an electrical reactor or a choke) is a variable frequency drive (VFD) accessory that consists of a coil of wire that forms a magnetic field as current flows through it. This magnetic field limits the rate of rising of the current, thus reducing harmonics and protecting the drive from power system surges and transients.

• The reactor is essentially an inductor. Physically, it is a wire coil that allows the magnetic field to form around the coil when the current flows through it. Once energized, it is an electromagnet with a field power that is equal to the amperage flow and the number of turns. The simple wire loop is the inductor of the air core.

 

 

Uses of Reactors

• They are used to limit the short circuit currents according to the capacity of circuit breakers.
• Therefore while doing changes in the system, we don’t have to replace the circuit breakers, instead we can add reactors and utilize the same circuit breaker due to which time and money both can be saved.

• Reactor is also used to filter out harmonics present in DC power. The reactor used in the DC power network for this purpose is called a smoothing reactor.

• Reactors are also used to protect the circuit breakers of different ratings.

 

Current Limiting Reactor

 

• A current limiting reactor is a type of reactor which limits the heavy flow of current through other sections of the system. 
• In this way, we don’t have to shut down the whole system, we can just isolate the faulty section.

Working of Reactors  

• Reactor is a coil which has high inductive reactance as compared to its resistance and is used to limit the short circuit current during fault conditions.
•  To perform this function it is essential that magnetic saturation at high current does not reduce the coil reactance. 
• If an iron cored inductor is expected to maintain constant reactance for currents two to three times its normal value it will turn out to be very costly and heavy. 
• Therefore air-cored coils having constant inductance are generally used for current limiting reactors.

 

Types of Reactors

Reactors have many roles to play in the electrical power system. The reactors are normally classified according to their modes of applications. Such as, 1.Shunt Reactor 2.Current Limiting and Neutral Earthing Reactor 3. Damping Reactor 4. Tuning Reactor 5. Earthing Transformer 6. Arc Suppression Reactor 7. Smoothing Reactor                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 Shunt Reactor  

• Connected in parallel in the system.
• Normal purpose of a shunt reactor is to compensate the capacitive component of current in the system.
• This reactor is mainly used for absorbing VAR (Reactive Power) generated due to the capacitive effect of the system.
• Shunt reactors are connected normally between line and ground.
• Shunt reactor can be either air cored or gapped iron cored depending upon its design feature.
• This can also be magnetically shield or without magnetic shield.
• The shunt reactors can also be designed with additional loading winding for supplying auxiliary power to the system.

                                                                                                                                                                                                                                                                                                                                                    Series Reactor                                  

• Current limiting reactor is a kind of series reactor. 
• Series reactors are connected in the system in series. 
• They are normally used to limit the fault current in the system or to facilitate proper load sharing in a parallel power network.

 

Neutral Earthing Reactor                                                                                                                                                                                                                                

When a reactor of suitable rating is connected between neutral and earth connection of a system to limit the line to earth current during earth fault in the system, it is called a neutral earthing reactor. 

   Bus Bar Reactor                                                                                                                                                                                                             

• These reactors are connected with bus bars. Busbar reactors divide the bus bar in smaller sections. If the voltage level is the same, no current passes through these reactors and every section acts as an independent bus bar. If a fault occurs on a section of a bus bar, the reactor prevents the fault from reaching other sections and only the fault section is affected. 
• Hence a bus bar should be large enough to protect the system but it should not disturb the synchronism of the system. 
• A reactor which drops the voltage about 30 to 50% at full current is suitable. 
• However, the reactance of a single busbar reactor should be about 0.3 to 0.5 pu.

  Neutral Reactors            

• These reactors are used to earth the neutral terminal of a system. 
• They provide a passage for the current in case of a single-phase to ground fault.
• Peterson coil is also a neutral reactor. 
• In normal conditions, no current passes through this reactor. 
• These reactors are used below 70kV