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IntroductionThe protection of generators is very much complexdue to the following reasons:

The generators are very large machines producing

very high voltages and are connected to busbars.Various other equipments such as prime movers,

excitation systems, voltage regulators, coolingsystems etc. are always associated with thegenerators. Thus protection of generators mustconsider the presence of these other equipmentsalso.

The protection scheme must be such that it shouldnot shut o the generators as far as possible. The

shut o generators result in a power shortage.

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Generator FaultsStator faults

otor faults

!bnormal running conditions

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Stator faultsThe main types of stator faults are:

"hase to earth faults

"hase to phase faults#nter$turn faults involving turns of same phase

winding

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otor %aultsThe conductor to earth faults and short circuitbetween the turns of the &eld winding, are the

commonly occurring faults with respect to arotor.

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!bnormal unning

'onditionsThe abnormal conditions include:

(ver$loading

(ver$speeding)nbalanced loading

(ver$voltage

%ailure of prime mover*oss of excitation +%ield failure

'ooling system failure

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Basic DiferentialProtection Scheme ForGenerators

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Basic PercentageDiferential ProtectionScheme For Generators

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Merz-Price Protection OAlternator Stator

Windings

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IntroductionThe transformers are static devices withouthaving any rotating part and are totally

enclosed. -ence the chances of faults occurringon transformers are much rare as compared tothe faults occurring on generators.

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ransormer FaultsThe various possible transformer faults are:

(verheating

inding faults

(pen circuits

Through faults

(ver /uxing#ncipient i.e. slow developing faults

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!arious Schemes Forransormer Protection

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Percentage DiferentialProtection For

ransormers

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Buchholz "ela#

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