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ElectricalPower System
PrevNext

Which relay is used for feeder?

A

MHO relay

B

Translay relay

C

Merz prize protection relay

D

Buchholz relay

Correct Answer

тЪЩя╕П TE тАв Technical Concept & PrincipleElectricalPower System
Option B

Translay relay

Quick Summary:

The Translay relay is a type of pilot wire differential relay specifically designed for the protection of short feeders and transmission lines. It works on the principle of circulating current or opposed voltage, ensuring fast and selective isolation of faulty sections in a power system.

тЪЩя╕ПTETechnical SolutionConcept & Principle
ЁЯТб Explanation

The Translay relay is a type of pilot wire differential relay specifically designed for the protection of short feeders and transmission lines. It works on the principle of circulating current or opposed voltage, ensuring fast and selective isolation of faulty sections in a power system.

ЁЯФв Key Formulas

Idiff=I1тИТI2I_{diff} = I_1 - I_2IdiffтАЛ=I1тАЛтИТI2тАЛ тАФ Represents the differential current in the protection zone

Vpilot=I├ЧZpilotV_{pilot} = I \times Z_{pilot}VpilotтАЛ=I├ЧZpilotтАЛ тАФ Represents voltage drop across pilot wires

тЪЩя╕П Working Principle

The Translay relay utilizes two identical transformers, one at each end of the feeder, connected by pilot wires. Under normal operating conditions, the secondary currents produced in the two relays are equal and opposed, resulting in zero current flowing through the operating coils. During a fault, this balance is disturbed, causing current to flow through the relay operating coils, which subsequently trips the circuit breaker.

ЁЯУМ Key Points
  • тЦ╕

    Translay relays provide unit protection for feeders.

  • тЦ╕

    They are insensitive to power swings and external faults.

  • тЦ╕

    The protection is based on the comparison of currents at the two ends of the protected line.

  • тЦ╕

    Pilot wire impedance does not significantly affect the relay performance.

тЬЕ Advantages
  • тЦ╕

    High speed of operation

  • тЦ╕

    Excellent discrimination between internal and external faults

  • тЦ╕

    Simple construction

тЭМ Disadvantages / Limitations
  • тЦ╕

    Requires pilot wires between relay locations

  • тЦ╕

    Limited by the maximum length of pilot wires due to charging current effects

ЁЯЫая╕П Applications / Uses
  • тЦ╕

    Protection of short transmission lines

  • тЦ╕

    Feeder protection in industrial power systems

ЁЯУД Additional Information
  • тЦ╕

    MHO relay is a distance relay used for long transmission lines.

  • тЦ╕

    Merz-Price protection is typically used for generator and transformer winding protection.

  • тЦ╕

    Buchholz relay is a gas-actuated relay used for transformer internal fault protection.

ЁЯУК Diagram / Illustration
Translay Protection PrincipleRelay 1Relay 2Pilot Wires
тЬЕ

B is correct тАФ The Translay relay is a specialized pilot wire differential protection scheme widely used for the protection of feeder circuits.

Core Concepts Used
Click any tag to open in AI Tutor
Differential Protection Unit Protection Pilot Wire Relaying
ЁЯТб EXAM TIP

Always remember: Buchholz is for transformers, MHO is for long lines, and Translay is for short feeders.

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