Synchronising: G.k.thayanithy

Synchronising G.K.Thayanithy

Synchronising A simple analogy…… At the instance of opening the valve in hydraulic circuit if the pressure difference across both sides of the valve is ZERO; • Fluid will not flow through it after opening. P At the instance of connecting two different sources, if the potential difference between them is ZERO • Current will not flow in between two sources when they are paralleled.

V GKT/syncronising/2008

Synchronising

Basic Requirements Conditions to be checked on Incomer & Busbar supply: 1

Check equal voltages

V

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2

Check equal frequencies

1 /  freq

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3

Same phase sequence



X G

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G

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4 Sources in synchronism (Check for synchronism) Incomer 300 Ahead

Incomer Busbar GKT/syncronising/2008

Incomer 600 Ahead

Incomer 1800 Ahead

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Synchronising

Incomer 2700 Ahead

Sources in Synchronism

GKT/syncronising/2008

Synchronising

Recommended settings for synchroscope V

•

Difference in Voltage

•

Difference in Phase Angle  

10 deg

•

Time Delay

 t

0.5 sec

GKT/syncronising/2008

5%

Synchronising

Control system requirement 

Compare magnitude & frequency and indicate their relative status  Facilitate adjustment of voltage & frequency  Check for synchronism  Facilitate synchronising breaker closure  Isolate synchronising systems after breaker closure

GKT/syncronising/2008

Synchronising

Operational requirement • •

Maintain speed & voltage higher to prevent reverse power & reverse kVAR trip. Neutral isolator condition to be checked. (For medium or low resistance grounding Neutral of any one machine should be kept closed. This precaution is taken to prevent earth fault relay operation due to circulating currents)

•

It may be necessary to float all DG neutrals during grid parallel operation.

GKT/syncronising/2008

Synchronising

Devices used  

  

Double voltmeter Double frequency meter Synchroscope with check synchronising relay Auto synchroniser Programmable logic controllers

GKT/syncronising/2008

Synchronising Synchronising First Time! Employ ‘Phasing out’ techniques - using following. A. On secondary side of PT  Phase Sequence Indicator • Check phase sequence of existing source on its PT • Switch on incomer breaker on Dead Bus & check phase sequence on the same Bus PT.  Multimeter • Check Voltage across PT reference of two sources while both PT’s have same primary reference. GKT/syncronising/2008

Synchronising 

Lamp method / Analog Multimeter • To be used for checking the wiring between check synch relay & the point where phasesequence & voltage reference have been checked.

B. On HT side 

HT phasing probes



By starting an AC motor whose direction of rotation is already confirmed with an existing source.

GKT/syncronising/2008

Synchronising

Questions ??

GKT/syncronising/2008

Synchronising

THANK YOU

GKT/syncronising/2008

Synchronising

Bus PT

G

Incomer PT

   

V

Breaker close

Auto Synchro-niser

Fuel Increase Decrease Excitation Increase Decrease Breaker close Fuel Increase Decrease

PLC

Excitation Increase Decrease

Breaker close

GKT/syncronising/2008