Thermal Overload Protection Of Generator

Generator protection should take into account the importance of the generator and its technical characteristics such as power voltage and earthing arrangement.

Thermal overload protection of generator.

A thermal overload relay works on the heat produced by the excessive overload current. Set overload protection function so that it falls to the left of the generator thermal withstand curve. In general for a typical non electronic thermal magnetic circuit breaker to provide effective generator overload protection it may need to be sized as low as 50 of the generator fla. Figure 2 protection schematic for generators over 5 mva.

Low vacuum protection this protection usually is in the form of a regulator which compares the vacuum against atmospheric pressure it is normally fitted to the generator set above 30 mw. The heat produced by the overload current is utilized to trip the motor circuit. Suitable over voltage relays preferably with volt cycle characteristics shall be provided. Circuit breaker overload function generator thermal withstand 4.

Generator thermal withstand capability from the generator manufacturer s data. Although over current relays negative phase sequence relays and devises for monitoring constant flow are also used to provide a certain degree of thermal overload protection. These are mostly used for protection of low voltage squirrel cage induction motors or dc motors of lower output rating. Due to such symmetrical distribution when three phase power supply.

Schematic diagram of a basic motor control scheme. Protection against overload using thermal relays. The most basic safety scheme of the motor is thermal with load protection which mainly covers the protection of all the above conditions. For understanding motor thermal overload protection in induction motor we can discuss the operating principle of three phase induction motor.

Generator over voltage protection 59g. One over current relay shall be provided to initiate an overload alarm. Refer to figure 1 for graphical representation. There is one cylindrical stator and a three phase winding is symmetrically distributed in the inner periphery of the stator.