What is rotor earth fault relay?
Rotor earth fault relay 64R which is used to protect the generator or alternator rotor against earth fault (the short circuit between rotor’s winding to ground). It senses the alternator’s rotor earth leakage current. The ANSI code for rotor earth fault relay is 64R.
What are various faults that occur in the rotor of an alternator and how the rotor is to be protected from these faults?
The rotor of an alternator is wound by field winding. Any single earth fault occurring on the field winding or in the exciter circuit is not a big problem for the machine. But if more than one earth fault occur, there may be a chance of short circuiting between the faulty points on the winding.
What causes earth fault relay?
Any leakage to the earth causes an imbalance between the phase and neutral currents. Earth fault relay senses this current and trips the circuit breaker.
What happens when earth fault occurs?
When fault occurs, short circuit current flows through the equipment and into the grounding electrode. The resistance of the Earth is non-zero, so current injected into the earth at the grounding electrode produces a potential rise with respect to a distant reference point.
What is rotor protection?
The Rotor Protection relay is used in synchronous motors and generators to identify the presence of an earth fault in the rotor winding. While the winding in the rotor is insulated from the ground during normal operation, the Rotor is subjected to stresses due to vibration, heat, etc.
Which relay is used in alternator?
Under frequency relay: Under frequency relay is used to protect the alternator when the frequency drops below the operating frequency.
What is balanced earth fault protection?
This scheme provides protection against earth-faults only (in small-size alternators where Differential protection is not possible to apply). It provides no protection against phase-to-phase faults, unless and until they develop into earth-faults.
How can we stop earth faults?
A ground fault is an unwanted electrical connection between a line and the ground. It can be caused by insulation breakdown, bad weather, or physical stress. You can protect against faults using protective devices, including CTs, PTs, relays, circuit breakers, and fuses.
What is a 59 relay?
59 Overvoltage relay A relay that operates when its input voltage is more than a predetermined value. 60 Voltage or current balance relay A relay that operates on a given difference in voltage, or current input or output, of two circuits.
What is Burden relay?
Burden in current transformer terminology is the load connected to the secondary terminals and is expressed either as VA (volt-ampere) and power factor at a specified value of current, or as total ohms impedance with the effective resistance and reactive components.
Which earth fault is used in alternator?
This is to be noted that, the star point or neutral point of stator winding of an alternator is grounded through an impedance to limit the ground fault current. Reduced ground fault current causes less damage to the stator core and winding during ground or earth fault.
What is the use of ref relay?
Restricted earth fault (REF) protection is a sensitive way to protect a zone between two measuring points against earth faults.
What is earth fault protection in rotors?
That means simple potentiometer methods of rotor earth fault protection, is blind to the faults at the center of the field winding. This difficulty can be minimized by using another tap on the resistor somewhere else from the center of the resistor via a push button.
What is a rotor protection relay?
The Rotor Protection relay is used in synchronous motors and generators to identify the presence of an earth fault in the rotor winding. While the winding in the rotor is insulated from the ground during normal operation, the Rotor is subjected to stresses due to vibration, heat, etc.
How to detect rotor earth fault of alternator?
There are various methods available for detecting rotor earth fault of alternator or generator. But basic principle of all the methods is same and that is closing a relay circuit through the earth fault path. There are mainly three types of rotor earth fault protection scheme used for this purpose.
What happens when an earth fault occurs in a relay circuit?
Here, if any earth fault occurs in the field winding or in the exciter circuit, the relay circuit gets closed via earthed path and hence secondary voltage of the auxiliary transformer will appear across the voltage sensitive relay and the relay will be operated.