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How many pilot wires used in translay relay scheme?
2
3
4
5
2
The Translay relay scheme, commonly used for the protection of feeders and short transmission lines, utilizes two pilot wires to provide a balanced circulating current protection system. This scheme is a form of unit protection that compares the currents at the two ends of the protected zone.
The Translay relay scheme, commonly used for the protection of feeders and short transmission lines, utilizes two pilot wires to provide a balanced circulating current protection system. This scheme is a form of unit protection that compares the currents at the two ends of the protected zone.
IRтАЛ=I1тАЛтИТI2тАЛ тАФ Net relay operating current in the pilot circuit
VpтАЛ=IsтАЛ├ЧZpilotтАЛ тАФ Voltage drop across pilot wire impedance
The relay works on the principle of current balance. Under normal conditions or external faults, the secondary currents produced by the current transformers (CTs) at both ends circulate through the pilot wires such that no current flows through the relay coils. During an internal fault, the balance is disturbed, causing current to flow through the relay coils, which then trips the circuit breaker.
Translay system is a differential protection scheme.
It is highly sensitive to internal faults.
The pilot wires carry circulating currents proportional to the line currents.
The scheme is generally limited to short distances due to pilot wire resistance and capacitance.
Simple construction and installation.
High sensitivity for internal faults.
Does not require a pilot wire monitoring system for all applications.
Distance limitation due to pilot wire length.
Susceptible to induced voltages if pilot wires are not shielded correctly.
Protection of distribution feeders.
Short transmission lines in urban areas.
The use of two pilot wires is sufficient because the relay operates on the difference between the rectified or phase-shifted currents derived from the primary line currents.
Option B, C, and D are incorrect as the standard Translay configuration specifically requires only two conductors for the pilot circuit.
A is correct тАФ The Translay relay scheme requires only 2 pilot wires to establish the differential protection circuit.
Always remember that in unit protection schemes like Translay or Biased Differential, the number of pilot wires is minimized to reduce installation costs and complexity.