DG Syncronisation

http://en.wikipedia.org/wiki/Synchronization_(alternating_current)

Reasons for Operating Generators in Parallel:

When a constant load is to be supplied with electrical power, a single generating unit may be installed to provide the energy, its capacity being just large enough to take care of the load, since it operates at highest efficiency fully loaded. On the other hand, when the load varies greatly from one part of the day to another, it would be uneconomical to supply power from a single unit because it would be operating considerably below full load, and therefore at a low efficiency, for much of the time. Under such circumstances it is usual to provide two or more units of such capacities as will allow of their operation at as nearly full-load conditions as possible at all times. When two or more generators are furnishing power to a common load, they are said to be operating in parallel.

The two generators can be synchronized when the following conditions are set:

1. The phase rotation of both generator systems must be the same. Check this with a phase rotation meter to determine ABC or ACB rotation.

2. The AC voltages of both generators should be equal. In practice the voltage of the generator required to be parallel is usually have 1-2 volts higher than that of the operating generator.

3. The frequencies of the both generators must be equal. In practice the frequency of the generator required to be parallel is usually have 1-2 Hzs higher than that of the operating generator.This can be observed by using a synchroscope. By adjusting the RPM of the generator, frequency can be adjusted.

The speed (frequency) and output voltage of the incoming generator is kept slightly higher to prevent it from becoming a load to the system when it is connected.

A synchroscope is a device that indicates the degree to which two generators are synchronized with each other. If the generator is turning at a lower frequency than the grid, the synchroscope needle rotates continually in the direction (usually counterclockwise) marked "slow" or "lag" on the dial to indicate that the generator is running slower than, or lagging behind, the grid. If the generator is running faster than the grid, the needle rotates continually in the opposite direction, marked "fast" or "lead". As the frequency of the generator nears that of the grid, the synchroscope needle slows down and when the frequencies match, the needle stops rotating.

Is this a homework question like your last one?

Vinu has as usual given information overload without referring to your question on interlocking.

Synchroscopes and voltage relays can provide automated interlocking for synronisation of generators.

it is not that easy

he needs much more that synchronoscope and voltage relay

he needs, AVR with ability to remotely adjust the voltage

Electronic speed governor to adjust RPM/frequency/Phase, as monitored by the synchronoscope

he needs a switchgear device, motorised CB or contactor

he needs a power share module and or a droop kit module

he needs a reverse power protection relay

he needs a loss of excitation, reverse KVAR module

or an automated multifunction module including all above as WOODWARD easygen3000

DEIF AGC 2, Deepsea 5510

and he needs to know how to install adjust and commission these equipments

if you dont know how to do, dont do

By birth no one becomes scientists or experts.

Every one aquires knowledge by study.

He just asked a help to study and work out his project.

this was an innocent advice,

if you do not know how to do, don't do, learn first.

This is not a kind of project where we can be involved without knowledge, even with all the good wills of the posters trying to help.

I can figure that a DG is the prime source of power for this hospital. any false step will be disastrous on the equipments and the working personal, and the hospital will be devoid of its vital source of energy for a long time compromising many human lives .