Author name: Engr. Aneel Kumar

One type of overvoltage in a generator is that due to transient surges caused by lightning or switching surges. These transients are protected by surge protective devices that are designed for this purpose. Power frequency over-voltages are possible if the generator controls are defective or have inadequate transient response. A defective voltage regulator, for example, […]

There are two types of backup protection that might be applied to a generator: backup of relays protecting the generator protection zone and backup of relays protecting external zones. Some types of backup protection may be graded to coordinate with both internal and external protective devices. The negative-sequence relay might be considered a form of

There are several different types of rotor protection, each type guarding the rotor from a particular type of fault. From this viewpoint, the protection against unbalanced loading, using negative sequence relays, can be considered a type of rotor protection since the effect of negative sequence currents is likely to result in rotor damage. 1) SHORTED

Under normal operation of a synchronous generator, the field created by the rotor windings locks in with revolving mmf of the stator windings and the rotor moves at synchronous speed, at least in the steady state. When excitation is lost, the rotor field suddenly loses its mmf and the rotor begins to move away from

Some of the larger generators have stator windings that are cooled by water circulating through the windings. If the flow of cooling water is impeded or stopped for some reason, the winding will quickly overheat. The cooling water is circulated by water pumps, which are backed up by standby pumps. Flow detectors placed in the

Special fire protection equipment is sometimes used to quickly extinguish fires within the generator housing. One method that has been used releases water into the generator enclosure on detection of a fire. A better system injects carbon dioxide into the generator rather than water. This is safer and does not add to the damage caused

Vibration protection is also a part of the turbine protection system and is not normally supplied or specified by the electrical protection engineer. Still, as noted above, vibration detection is the backup for faults that cause unbalanced rotor heating due to rotor faults or negative-sequence rotor heating. It is important that there be coordination between

Motoring protection is provided for the steam or hydraulic turbine, or for the power system, and not for the generator. Motoring is not harmful to the generator in any way. The protection is usually considered as part of the generator protective system since it uses electrical quantities, usually in the form of sensitive power relays.

It has been noted above that over-speed causes overvoltage, which may be protected against using overvoltage relays. Basically, however, over-speed control is part of the turbine control system. Most large steam turbine controls have two or three separate speed control units, with one of these being strictly a mechanical centrifugal device that will close the

It is astonishing to realize that there is hardly a home, office block, factory, car, sports hall, hospital or theatre without an application, and sometimes many applications, of power electronic equipment. Some typical applications are given below: Industrial processes in the chemical, paper and steel industries; Domestic and theatre lighting; Motor drives from food mixers and