What are the Functions of Substation Equipment?

Functions of Substation Equipments: Sl. No. Equipment Function   Bus-Bar Incoming & outgoing circuits Connected to bus-bar   Circuit Breaker Automatic switching during normal or abnormal conditions   Isolators Disconnection under no-load condition for safety, isolation and maintenance.   Earthing switch To discharge the voltage on deadlines to earth   Current Transformer To step-down...

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What is REF relay?

It is restricted earth fault relay. When the fault occurs very near to the neutral point of the transformer, the voltage available to drive the earth circuit is very small, which may not be sufficient to activate the relay, unless the relay is set for a very low current. Hence the zone of protection in the winding of the transformer is restricted to cover only around 85%. Hence the relay is called REF relay...

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What are the errors in Current Transformer?

(a) Ratio error Percentage ratio error = [(Nominal ratio – Actual ratio)/Actual ratio] x 100 The value of transformation ratio is not equal to the turns ratio.(b) Phase angle error: Phase angle =180/π[(ImCos δ-I1Sin δ)/nI...

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What is an arc? Give the two methods of arc interruption?

Arc is a phenomenon occurring when the two contacts of a circuit breaker separate under heavy load or fault or short circuit condition. Methods of arc interruption:  High resistance interruption:-the arc resistance is increased by elongating, and splitting the arc so that the arc is fully extinguished  Current zero method:-The arc is interrupted at current zero position that occurs 100 times a second in case of 50Hz power system frequency in ac. ...

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What do you mean by current chopping?

When interrupting low inductive currents such as magnetizing currents of transformer, shunt reactor, the rapid deionization of the contact space and blast effect may cause the current to be interrupted before the natural current zero. This phenomenon of interruption of the current before its natural zero is called current chopping...

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How to calculate voltage drop?

How to calculate voltage drop: In situations where the circuit conductors span large distances, the voltage drop is calculated. If the voltage drop is too great, the circuit conductor must be increased to maintain the current between the points. The calculations for a single-phase circuit and a three-phase circuit differ slightly. Single-phase voltage drop calculation: Three-phase voltage drop calculation: OR 3øVD = (SQRT(3)*L*R*I)/1000 VD...

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How much voltage drop is Acceptable?

The national Electrical Code (NEC) recommends that the combined voltage drop of the electrical system (brunch circuit and feeders) not exceed 5% for optimum efficiency. This recommendation not only can improve safety but can ensure proper equipment operation and power efficiency. Foe Example, In a 220 volt 5 ampere circuit, this means that there should be no more than a 11 V drop (109 volts) at the furthest outlet when the circuit is fully loaded. Related Link: How to calculate voltage dro...

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What are the Components of the power system?

The various components of power system are: Generator (alternator),  Transformer,  Transmission line,  Induction motor, Synchronous motor, Resistive and  Reactive loads. ...

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