What maintenance should the generator be equipped with? What are their functions?
Generator maintenance is somewhat different from other complete load maintenance. Because the excitation current and voltage of the generator are quite different from the current and voltage of the general switchgear, there is also a big gap in the maintenance and installation. In order to ensure the safe and reliable operation of the whole generator set and even the whole power plant, we will discuss in detail about the generator can be generated. The following maintenance shall be installed selectively according to the capacity of the generator for faults and abnormal task patterns.
1. Longitudinal Differential Maintenance: Maintenance of short circuit between stator windings and their lead-out wires.
2. Transverse differential maintenance: maintenance for one-phase inter-turn short circuit of stator winding. This kind of maintenance is installed only when one phase stator winding has two or more parallel branches and constitutes two or three neutral point lead-out terminals.
3. Single-phase grounding maintenance: single-phase grounding maintenance for generator stator windings.
4. Grounding maintenance of excitation circuit: Maintenance for grounding fault of excitation circuit.
5. Low excitation. Loss of excitation maintenance: In order to avoid large generators with low excitation (excitation current is lower than the static stability limit corresponding to the excitation current) or get excitation (excitation current is zero), a small amount of reactive power is absorbed from the fragments, which adversely affects the fragmentation. Generators with 100 MW or more capacity are equipped with this maintenance.
6. Overload Maintenance: Maintenance of the signal when the generator works long hours beyond the extra load. Small and medium-sized generators are only equipped with setter overload maintenance; large generators should distinguish between setter overload maintenance and excitation winding overload maintenance.
7. Stator winding over-current maintenance: When short-circuit occurs outside the maintenance range of generator longitudinal difference, and the maintenance of short-circuit components or circuit breaker rejection measures, this maintenance is used as backup of internal short-circuit, but also as backup maintenance of longitudinal difference maintenance.
8. Stator winding overvoltage maintenance: To avoid stator winding overvoltage caused by sudden drop of all loads. Hydro-generators and large turbo-generators are equipped with overvoltage maintenance. Small and medium-sized turbo-generators are usually not equipped with overvoltage maintenance.
9. Negative Sequence Current Maintenance: When the power is fragmented and asymmetrical short circuit or three-phase load is asymmetrical (such as electric locomotive and electric arc furnace, the proportion of single-phase load is too large), it will overheat the parts with high current density, such as the inner and outer surface of the retaining ring, and form partial burns of the rotor, so negative sequence current maintenance should be installed.
10. Out-of-step maintenance: Out-of-step maintenance that responds to large generators and piecemeal oscillation processes.
11. Reverse power maintenance: When the main valve of a steam turbine is wrongly closed or the main valve of a steam turbine is closed by furnace maintenance measures and the generator outlet circuit breaker is not tripped, the active power is absorbed from the power piecemeal to form a steam turbine accident. Therefore, large units should install reverse power maintenance consisting of reverse power relays to maintain the steam turbine.
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