Synchronizing or Paralleling of Generators

March 26th, 2019 | Posted in Electrical distribution
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Synchronous Generator or Alternators is one of those inventions which had changed the face of the world. It has allowed us to make use of mechanical energy into electrical energy making life simpler.

Furthermore this electrical power is used for various conveniences in Industries, Educational Institutes, Transportation, Shopping Malls etc. Let’s read what Engineer B.B has to say about Paralleling of Generators and Synchronization.

 

Paralleling of Generators

Synchronous Generator Introduction

A single alternator supplying the load independently is a very rare sight for today’s observer. Regardless of its purpose-based application in case of emergency, we find it more useful to connect multiple generators to a single distribution box or common bus bar on large scale of production.

Many power Grid is connected with hundreds of Generators acting in parallel to share the load of whole system. This technique is used in all sorts of utilities. There are several advantages for the necessary operation of Generators in parallel.

Advantages of Paralleling of Generators

If we use a single Genset and it becomes faulty at any particular time than such system would be questions for its reliability.

A parallel system of multiple Genset would allow us to sustain the system’s reliability with zero down time and maximum efficiency of the system. This would further ensure no power loss for the building as well and this becomes a necessary for buildings like Hospitals and Pharmaceutical Labs. This would also increase the cost but convenience of multiple Generators is preferable over the cost.

Similarly, when multiple Generators are operated in parallel it gives us a time window for its maintenance and shutting down for inspection as well. This mode of operation also increase efficiency of the system in term of fuel consumption as multiple generators will supply fraction of load each instead of single Generator working nearly on full load.

 

Steps to Follow for Paralleling of Generators

However, synchronization of Generators is not a cakewalk when it comes to practical applications.

In Alternating Current (A.C) system voltage, phase and frequency of two or more set of Genset should be synchronized before each of Genset Circuit Breaker is connected to a common bus bar or distribution panel. Now this is one complete exercise to execute when it comes to practical implication.

We cannot connect an alternator to live busbar directly as it will induce Electro Motive Force EMF is zero which may lead to the flow of infinite current causing short circuiting. To get paralleling done with proper standards following conditions should be met and practiced:

 

Paralleling of Generators

 

Connect onrushing Genset G1 with the current system but make sure the switch is open. Parameters for G1 will be decided by the current system as well. We need to adjust all the requirements for the synchronization before connecting G1.

First, we need to ensure that field current of the onrushing generator must be adjusted in such a way that its operating voltage is equal to line voltage of the current system.

Second, by using “three light bulb method” we can ensure that both Generators have same phase sequence as it is also the requirement for paralleling the Generators.

Third, Frequency of oncoming Generator is set higher than the running system Generators. This task is achieved by Frequency Meter on the display of synchronization panel. We can change the frequency of the onrushing Genset by changing the speed of the motor or prime mover, as we can recall the relation for slip with frequency of the Genset. Frequency is set at higher ratio to ensure that it will come on the line supplying power as a generator rather than being a load/motor in the system.

Once we are done with frequency, voltages of the system will start changing their respective phase with respect to each other. When two set of Genset are in phase with similar voltages than they are said to be synchronized to one same bus bar.

 

Paralleling of Generators switch

 

Close the switch when phases are equal with each other by looking at the Phase Sequence Indicator.

Paralleling of Generators Remarks

Paralleling the Generators provide us an overview of the system. It provides us statistical report of Generator, oil pressure report. It has also increased the efficiency and life of Power systems to great extent.

However, when a distributed network is established where source of electricity and consumption of load is at some great distance than an independent Genset providing the need of energy is preferred. Paralleling Generators give us a management tool for Power Systems at small scale level.

 

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