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
Year: 2015
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
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
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.
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
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
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
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
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
Having decided the voltage that are required to be created at any substation it is necessary to establish a common insulation level for all items of equipment of each system voltage. It is to be ensured that the breakdown or flashover strength of all insulation (particular voltage) in the station
