Which of the following is not installed in substation

Question

Examoogle · Accepted Answer

excitors

Explanation: Excitors are essential components of synchronous machines used to supply direct current to the field windings, and therefore, they are installed within the power plant at the generator site, not in the substation.

Working Principle: The excitor (typically a DC generator or an AC alternator with a rectifier) provides the necessary excitation current for the field winding of a synchronous generator to establish the air-gap magnetic flux. Because the excitor needs to be mechanically or electrically coupled directly to the generator's rotor or control system, it is an integral part of the generating station equipment rather than the transmission or distribution substation infrastructure.

Key Formulas: $V_{f} = I_{f} 	imes R_{f}$ — Voltage required for excitation as a product of field current and field resistance

Key Points: Substations primarily handle voltage transformation, switching, and reactive power compensation.; Excitors are auxiliary equipment specifically for synchronous generator operation.; Series capacitors are used in transmission lines to compensate for line reactance.; Shunt reactors are used to compensate for the Ferranti effect in light-load conditions.

Advantages: Excitors allow for reactive power control of the generator.; Proper excitation ensures stable operation of the synchronous machine.

Disadvantages: Excitation systems add complexity to the generator maintenance schedule.; Potential for thermal stress in field windings if excitation is not monitored.

Applications: Used in hydroelectric and thermal power stations for generator field excitation.; Critical for maintaining the stability of the grid under varying load conditions.

Additional Info: Series capacitors: Installed in series with transmission lines to neutralize inductive reactance ($X_{L}$).. Voltage Transformers (PTs): Used for metering and protective relaying purposes in substations.. Shunt Reactors: Connected in shunt (parallel) to absorb excess reactive power, preventing overvoltage due to the Ferranti effect.

Answer: C is correct — Excitors are integral components of generating stations, specifically for synchronous machines, and are not installed in electrical substations.

Exam Tip: Remember that components involved in the generation of electricity, such as exciters or governors, are found in the generating plant, while components involved in power flow management, like transformers and shunt/series elements, are found in the substation.

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