The basic concept of the safe operation of the generator to ensure the normal operation of power systems and power quality plays a decisive role, while the generator itself is a very expensive electrical components, therefore, should be a whole variety of different faults and abnormal operating state improve the performance of protection devices installed. Fault type and not a normal operating condition. Fault types include stator winding phase short circuit between one phase of the stator winding shorted gate, single-phase stator windings, rotor windings or two little ground to ground, the rotor excitation current excitation circuit disappear 2. Not normal operating conditions are: Since the stator windings external short circuit overcurrent; due to the three-phase exceed the rated capacity of the generator and other symmetrical load caused by overload; due to external asymmetry caused by a short circuit or an asymmetric load generator negative sequence Over-current and over-load; stators caused due to sudden load rejection winding over-voltage; rotor due to the strong excitation excitation circuit failure or prolonged overload caused by winding; turbine generator reverse power, etc. Due to the sudden closure of the main valve caused. Type of protection: 1. The longitudinal differential protection Generator protection is the main generator of internal phase short circuit protection, depending on the starting current, there are two principles selected, its corresponding wiring, there are some differences. Because the various failures within the scope of protection of the protection can be removed without delay, but do not overload and response system generator oscillations, and the sensitivity coefficient is generally higher, so, without exception, used longitudinal differential protection capacity 1MW or more main protection of the generator. a. Under normal operating conditions, the current transformer secondary circuit protection should not malfunction when disconnected. To prevent malfunction differential protection, protection should start tuning current is greater than the rated current of the generator. Introducing a reliable factor Kk, the starting current protection devices, and relays were Idz = Kk * Ie.f Idz.j = Kk * Ie.f / nl as external short circuit after the break occurred, the relay circuit to flow Over the short-circuit current, malfunction protection still so broken differential protection monitoring device installed in general, making the longitudinal differential protection in this case can promptly quit working. b. starting current protection device according to the maximum external fault current imbalance dodge tuning, this time, the starting current of the relay should be Idz.j = KkIbp.max According 4-5 type of unbalanced current analysis into the type, then: Idz.j = 0.1KkKfzqKlxId.max/nl when using saturated core with speed differential relay, Kfzq = 1; When the current transformer model with the same Ktx = 0.5; reliability coefficient is generally taken as Kk = 1.3. For turbo-generator, three-phase short circuit occurs at the exit of its maximum short circuit current is approximately Id.max = 8Ie.f, into the above equation, the starting current differential relay for: IDZ.J = (0.5-0.6) Ie .f / nl for hydro, because reactance Xd "values ??greater than turbo-generator, which occurred at the exit of the maximum three-phase short circuit current is approximately Id.max = 5Ie.f, the differential relay start current: Idz.j = upper (0.3-0.4) Ie.f / nl Fully visible, press escape unbalanced current conditions tuning differential protection, the starting values ??are much higher than the current transformer secondary circuit according to escape off Conditions lines is small, and therefore, to protect the sensitivity is high, but after such a setting, the occurrence of the current transformer secondary circuit break under normal operating conditions, the role of the load current, differential protection may malfunction , on this point of view its reliability is poor and therefore need to consider whether the break in is still controversial. 2. transverse differential protection principle difference between the two branches using reactive currents, and realize the power stator winding inter-turn short circuit protection is that it has two transverse differential protection wiring:.. a per-phase installation of two current transformers and relays made a separate three-phase protection so that a total of six mutual inductance. and three relays. Due to the complexity of wiring to protect the current imbalance is large, so in fact been rarely used. b. currently widely used wiring is essentially half of the three-phase windings and go with another half-phase winding currents and compares the various inter-turn when a short circuit occurs when the foregoing, this neutral line still associated with Loop through, so you can relay 3 action, due to the use of only one transformer, it Because there is no unbalance current transformer errors generated, therefore, the starting current is small, the sensitivity is higher. Moreover, this wiring is also simpler than the first wiring. operating experience shows that when the excitation circuit occurs permanent The two ground, because the generator excitation magnetic potential distortions caused by the occurrence of a large air gap flux distortion generator will produce abnormal vibration, then two excitation circuit protection should be action on the ground to trip in this case, although the transverse differential protection according to the principle of action should not view it, but the need for removal of the generator has therefore transverse differential protection tripping operation is permissible based on the above consideration, the field has not used Ground loop protection action when two transverse differential lockout protection measures in order to prevent accidental malfunction moment two ground loop occurs when the excitation caused, therefore, when a little ground after excitation circuit occurs, grounding protection put into two while the differential protection should also be switched to cross 0.5-1s delay action on the trip three single-phase ground to protect a generator stator winding single-phase ground features: Neutral point of modern generators are ungrounded or Petersen coil grounded, so that when the internal single-phase generator, the current flowing through the ground where the generator voltage network remains capacitance to ground currents, and the difference lies in the point of failure The zero-sequence voltage generator internal position will take place with the different changes. b. use stator ground protection c zero sequence current composition. use stator ground zero sequence voltage protection d constitutes Use 100KW power constituted the third harmonic voltage machine 100KW generator http://www.shtgfdj.com/power/100kw.html