Parallel Operation of Transformers

                           
                                                   The transformer is said to be in parallel operation when their primary

windings are connected to a common voltage supply and the secondary windings are connected to a

common load.

Advantages of Parallel Operation
  
  • It increases the reliability of supply system.
  •  The size of transformer increases with the increase of its rating,its transportation and instalation is difficult.On the other hand transportation and instalation of small size transformers are easy.
  • One ore more transformers may be taken under maintenance and the remaining will supply the load.
 Disadvantages of Parallel Operation 

  • Increasing short circuit current that increase breaker capacity.
  • Bus rating could be high.
  • Parallel operation reduces the transformer impedence which creates the high short circuit current.
  • The control and protection is complex. 

Conditions of Parallel Operation 

  • The line voltage ratio of two transformers must be equal.
  • The per unit impedence of each transformer should be equal and the ratio of equivalent leakage reaactance to the equal resistance X/R .
  • The transformers should have same secondary winding polarity.
  • The transformers have same phase sequence.
  • The transformerss have the zero relative phase replacement between the secondary line voltages

Comments

Post a Comment

Popular posts from this blog

What are delta connections,current voltage anf power in delta connections,summery of delta connection,uses/advantages of delta connection

Image
Delta Connection            A delta connection is a connection used in a three phase electrical system in which three elements in series form a triangle ,the supply being input and output at the three junctions.            It is also known as 3 phase 3 wire system.It is preferably used in AC transmission.It is denoted by  Δ . The other name of delta connection is Mesh connection .               In case of Delta connection all the three coils are connected in series to form a close circuit.From each junction we take out one wire and out-going current from each junction assumed to be positive.In case of delta connection it look like a short circuit but in case of balance load the sum of all voltage should be zero.              In the following fig. all values Current,Voltages and power for 3 phase delta connection can be shown. fig ...
Read more

What is a full wave Rectifier? Comparison of HW-rectifiers and FW-rectifiers,Simple FW-rectifier with center-tapped transformer its working,Efficiency of FW-rectifier

Image
Full-Wave Rectifiers                There are two types of full-wave rectifier circuits.one is uses two diodes with a center tapped transformer and the transformer have equal turns Ns1 and Ns2 of the secondary windings which is shown in the fig. below The second type of FW-rectifier is having bridge-rectifier circuit and uses four diodes and it does not require a center-tapped transformer it only have simple transformer. fig. Comparison of HW Rectifiers and FW  Rectifiers                  The FW-rectifier circuits are better if we compare with HW rectifier circuits in all most all respects.FW-rectifiers have double the value of dc voltage delivered to load their efficiency is also double and their ripple factor is low.Due to these reasons FW-rectifiers are preferred over HW-rectifiers. Simple FW-Rectifier with Center-Tapped Transformer fig        ...
Read more

What is Current Transformer(CT)? ,Function Of CT,Construction of CT,Ratio of CT,Working Principle of CT,Uses /Advantages and Disadvantages of CT

Introduction                A Current Transformer(CT) is a type of transformer that is used to reduce or multiply an alternating current (AC) (used along with measuring or protective device).It produces a current in its secondary which is proportional to the current in its primary. Function of Current Transformer                The current transformers are basically a step up transformers.In case of high magnitude supplies we can not connected the measuring devices directly.we used current transformer to the supply of those devices with currents of magnitude proportional to these of power.Current transformer also isolates the measuring instruments from the high voltage circuits.current transformers supply the protective relays with current of magnitude proportional to those of power circuit but sufficiently reduce in magnitude. Construction of Current Transformer          ...
Read more