Relays in generator protection system consists of:
1) Overcurrent Relays
Function detects overcurrent flowing in the generator stator coils. Overcurrent may occur in the generator stator coil or coils in the rotor. Flow over the stator coils can also occur due to excessive load on the generator.
2) Differential Relay
Function detects disturbances in the generator stator coils and should work faster than overcurrent relays. Working principle is to compare the current differential relays are in and out of the generator stator coils. If there is a difference, there is a disturbance in the generator stator coils and the difference will move the current differential relays.
3) Relay circuit fault ground
Ground circuit interruption is the most common disorder. Ground circuit fault currents that occur are not necessarily big enough to be able to move the overcurrent relays, so there must be a relay ground circuit current that can detect ground circuit interruption. The working principle is the ground circuit current relays detect zero sequence currents, because every circuit fault zero sequence current land produces.
Ground-fault relays mounted on the stator through a series of 3 phase transformer. If no ground circuit interruption occurs, the amount of current in the three phase transformer is equal to 0 (zero), but if there is a ground circuit fault number is not equal to 0 (zero) and the relay works. Relay will detect a disturbance in the circuit of the generator stator.
For detection circuit fault occurs on land that used only the generator stator ground relay circuit is limited. Total current of 3 phase currents are summed again detected by the current transformer at the generator neutral point earthing conductor. Limited ground relay circuit is a special differential relays for ground circuit interruption.
4) Relay rotor circuit ground
Ground circuit in the rotor circuit, the short circuit between the conductors of the rotor with the rotor body and can cause vibration (vibration) on the redundant generators. Because the rotor circuit is a direct current circuit, the relay rotor circuit is basically ground overcurrent relays for direct current.
5) Relay strengthening missing
Strengthening the missing can cause overheating of the head of the stator coil and a weak system and strengthening the synchronous generator can be separated from the lead generator synchronous relationships with other generators. In an off sync, generator gains still weak coupling given by the player so that the engine driving the generator is turned into an asynchronous generator.
The result is overheating because the synchronous generator rotor is not planned to operate asynchronous and should be prevented by strengthening relays missing. The working principle of this relay is to measure the impedance of the generator stator coil. In case of missing reinforcement, stator coil impedance will be measured small and relays missing reinforcement will work.
6) overvoltage relay.
Overvoltage can occur if the generator is overloaded then breaking strength (PMTnya) trip due to one or several relays work. Overvoltage can damage the insulation and the generator including the connecting cable insulation. Should be prevented by using more voltage relays. Its working principle is to detect inter-phase voltage through a voltage transformer. If the voltage exceeds a certain level, then the relay will trip download PMT PMT field generator and amplifier (magnet) generator.