ISOLATORS

-


What do we do if a circuit breaker or any other power flow controlling device gets faulty and we want to gain control over a device(say a bus or line or transformer,etc) ,Yes there have to be some sort of back up for it ,a master manual switch, which could be used for isolation of one network part from another, called Isolator. It enhances the safety of the maintaining part in the power system by complete de-energizing it. Well ,lets lean on it.



The mechanical power switching device used in the field of high level power handling



Just visualize a switch having capability of circuit disruption, handling of load current, mechanical properties needed for its operation and more importantly as we are dealing with high voltage there has to be a provision for its separation from metal parts in which it is fixed about, for this usually the solution is solid porcelain core type insulators,having high mechanical strength and dielectric strength.


Operation
             
               The main Isolator and earth switches shall be individual pole electrically ganged motor operated for 400 kV and mechanically gang operated in case of 220/132/33 kV. The operating mechanism of the three poles shall be well synchronized and interlocked.

                 The Isolator blades shall be in positive continuous control throughout the entire cycles of operation. The operating rods and pipes shall be rigid enough to maintain positive control under most adverse conditions and to withstand all torsional and bending stresses arising from operation. Operation of the switches at any speed should not result in improper functioning, in displacement of parts / machines after final adjustment has been made. All holes in cranks, linkages etc. having moving pins shall be drilled and fitted accurately so as to prevent slackness and lost motion

              Another feature is the dead center mechanism to prevent the accidental closing/opening by vibration,wind and other factors.


Based on the cicuit disruption there are mostly two types of isolators which are,
  1. Single Break Isolators ; used for the applications up to 11 kV. By single break the operation does not allow much spark up to 11 kV applications 
  2. Double Break Isolators ; used for the high voltage levels (usually greater than 11 kV )
  3. Pantograph type Isolators ; used for the high voltage levels (usually greater than 123 kV ) 


Here the voltage across isolator terminals splits into two to reduce the amount of discharge during operation



Single Break Isolator






Double Break Isolator




Pantograph type Isolators


                         Let me remind you something that an isolator switch is usually not intended for normal control of the circuit, but only for safety isolation and can be operated either manually or automatically, and by for assuring safety it preferably operated by manual mode.

Comments

Post a Comment

Popular posts from this blog

Electrical Substations

-
Image
     Electrical Substations An electrical substation forms an integral part of the power system. It is placed at the both ends of the long distant transmission line... but why??!! Of-course to transform voltage!  A substation at the beginning End or say generation side normally used to boost up the voltage to higher magnitude suitable for transmitting the generated power to long distant load with minimum losses.( Uses a step up transformer )!! Yes the other type is at the other end of the long distant transmission line nearer to load centre... here the high voltage is stepped down to a relevant magnitude which may be used for distribution purpose or another voltage level transmission for near by substations.                    The heart of a substation is nothing but our transformer, depending upon the purpose transformer can be step up or step down!! Now we are considering a load end substation as an example. Here our hero is step down transformer 😎!! A substation h
Read more

Differential Protection Scheme (Transformer)

-
Image
Hey friends! you are familiar with the power system equipment which we discussed earlier.! Now it's time to protect it to total safety. As soldiers protect our country from enemies likewise our system should be protected from fault. The line of control is decided by fixing the current transformers on the right place. So our boundaries is decided by their location. Here in a substation, we have many equipments such as transmission lines, bus-bar, transformers, etc in the system which need atmost care. Starting from the bulkiest, transformers are having different level of protections such as phase to phase and phase to ground. In other words differential protection and earth-fault protection. Over-current protection is also implemented in it. Let's talk about the differential type of protection for transformers. It's quite simple to explain the theory but some complicated while coming into the calculation. The term itself gives a brief idea about the
Read more

Capacitor banks and reactors

-
Image
Capacitor banks and Reactors We have already discussed the significance of reactive power in a power system, As we know the availability of reactive power depends on the excitation of the alternators.This reactive power can be provided by the generators themselves, through the adjustment of generator excitation, but it is often cheaper to provide it through capacitors, hence capacitors are often placed near inductive loads to inject reactive power.the so called capacitors are mainly of two, static condensers and synchronous condensers. The synchronous condensers have a variable value of VAR which can be varied by the excitation of the synchronous motor and the static capacitors have a fixed value of VAR.                                       The capacitor bank simply means that a group of  individual capacitors connected in  parallel and series accordingly to the design of the capacitor bank and together have a value in KVAR or MVAR. Capacitor Connection  A reactor is connected i
Read more