Thermal Overload Protection Of Generator

Figure 2 protection schematic for generators over 5 mva.

Thermal overload protection of generator.

For understanding motor thermal overload protection in induction motor we can discuss the operating principle of three phase induction motor. Suitable over voltage relays preferably with volt cycle characteristics shall be provided. Schematic diagram of a basic motor control scheme. Protection against overload using thermal relays.

The heat produced by the overload current is utilized to trip the motor circuit. Set overload protection function so that it falls to the left of the generator thermal withstand curve. Generator protection should take into account the importance of the generator and its technical characteristics such as power voltage and earthing arrangement. The most basic safety scheme of the motor is thermal with load protection which mainly covers the protection of all the above conditions.

Refer to figure 1 for graphical representation. A thermal overload relay works on the heat produced by the excessive overload current. 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. Due to such symmetrical distribution when three phase power supply.

Generator over voltage protection 59g. There is one cylindrical stator and a three phase winding is symmetrically distributed in the inner periphery of the stator. No one would do that of course because you d sacrifice much of the full generator capacity. To understand the basic principle of thermal overload protection let s examine the schematic diagram of a basic motor control scheme.

These are mostly used for protection of low voltage squirrel cage induction motors or dc motors of lower output rating. 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. The relay shall have high reset ratio and adequate continuous thermal rating.