Multi-loop analysis method for internal combustion sensitivity calculation of the generator. The classification of the two is from the Foreword Three Gorges Power Station is divided into the left bank power station right bank power station and the right bank underground power station independent power station, the left bank power station installed 14 units, the right bank power station installed 12 units, the right bank underground Power station installed platform.
The rated capacity of the single-machine generator of the Three Gorges Left Bank Power Station is water cooling, the stator is a branch structure, the number of stator slots is slot, and each branch slot adopts self-excitation excitation mode.
The rated parameters of the generator are recognized by the two-component two-speed transformer and the equivalent reactance of the system (converted to the generator voltage level. Because the cost of the generator set of the Three Gorges Power Station is expensive, the structure is complicated, and once the fault occurs, not only the maintenance period is long, but also a huge Direct and indirect economic losses, therefore, the refusal or misoperation of the internal fault protection device of the Three Gorges Power Station will have serious consequences, and must not be taken lightly. The selection and optimization of various protection schemes must be based on the internal faults of the generator. Based on the careful analysis of comprehensive calculation and protection sensitivity, the internal fault type of the generator is briefly introduced to the type of internal fault that may occur in the generator of the Three Gorges Power Station. The main discussion is the inter-turn short-circuit and the phase-to-phase short-circuit according to the development of the generator winding of the Three Gorges Power Station. Analysis, if it is assumed that a short circuit occurs between the upper and lower layers of the stator slot, the number of faults in the same slot is kind (equal to the number of stator slots through the analysis of the fault characteristics of the same slot, and it is found that the number of short circuits between the same branches is the same, accounting for the same phase There are several types of short-circuit between different branches, and the number of short-circuits between phases is kind, accounting for the same phase. There are several types of short-circuit turns in the branch, among which the minimum number of short-circuit turns is åŒ, and the turns ratio is. 2 8 is less than the sensitivity of various protection schemes. The high-in-phase different branches have only one type of short-circuit, and the phase-to-phase short-circuit There are a few species.
In recent years, through the statistics and analysis of the internal faults of the stator windings, it is found that the end of the stator winding is a frequent occurrence of accidents, and there are many factors causing accidents. The main types of foreign materials are the following types of foreign body wear and insulation, which leads to poor fixation of metallic short-circuit ends. The natural frequency of the structure is close to or larger than the electromagnetic and mechanical vibrations caused by the insulation wear of the nose, the insulation quality of the nose, or the end bandage is contaminated, causing the water failure of the partial discharge end (infiltration failure caused by water leakage and the like).
Therefore, it is necessary to calculate and analyze the stator winding end faults in the simulation calculation.
According to the analysis of the unfolded diagram of the generator winding, if it is assumed that a short circuit occurs at the intersection of the ends of the stator winding, the number of end faults in the end cross fault is simply 10.
By analyzing the nature of the end faults, it is found that the number of short circuits between the same branches is the species, the number of short circuits between the different branches in the same phase is the species, and the number of short circuits between the phases is the species, and the majority of the end faults are phase-to-phase short circuits.
Although the number of end faults is large, the time taken to calculate an end fault is not long, and it is not difficult to perform end fault calculation in terms of the current computer operation level.
In addition, due to the symmetry of each phase winding, each phase only needs to take one branch for calculation, and the calculation result of any branch of each phase can be derived from the calculation results of the remaining branches of the phase, thereby greatly reducing the calculation amount.
Internal fault calculation of generators This paper uses the multi-loop analysis method to analyze the internal fault calculation and protection sensitivity of the generators of the Three Gorges Power Station in the first phase of the Three Gorges Power Station under the single operation mode of the Three Gorges Power Station generators. The protection scheme of the internal fault of the generator stator indicates that the phase-to-phase short-circuit indicates the same phase, the same branch, the short-circuit between the turns, one card, the same phase, the different branches, the short-circuit, the split-phase, the cross-section protection, the incomplete differential protection, the high-sensitivity unit, the cross-section protection. . The spears are connected to the grid half load and the grid rated load. All possible slots and end cross faults are calculated and analyzed, and each branch under each fault condition is provided with short circuit additional branch current. The size and phase of the steady-state fundamental component), and then based on this, the sensitivity of the various protection schemes is calculated, and the number of possible actions and the number of inoperable actions of the various protection schemes are counted.
Due to the limited space, the following is only for the single-machine no-load and grid-connected rated load operation modes, and several typical examples are selected for analysis.
The branch of the fault phase of the same slot (the short circuit occurs at the opposite end of the phase (the minimum possible short circuit of the neutral point side, the first branch of the phase, the maximum possible short circuit of the end of the circuit, the first branch of the phase) At the branch where the inter-turn short-circuit phase occurs, the phase-to-phase short-circuit occurs at the first branch of the phase. 2 2 The end of the fault phase at the end of the fault occurs at the opposite end of the neutral point. The smallest possible short-circuit at the neutral point is at the first branch. The first branch of the phase (the maximum possible number of short-circuit turns on the machine side) occurs, and the first branch of the phase (the maximum possible number of short-circuits on the end of the inter-turn short-circuit at the opposite end of the phase) Neutral point side small number of interphase short-circuit welding faults Single-machine no-load and grid-connected rated load type operation mode, the phase is separated a) the branching current fault (when the short-circuit additional branch) steady-state fundamental current The effective value and phase angle are listed in the table. The correct calculation of the stator branch current and other fault electrical quantities is the basis for determining the internal fault protection scheme of the generator. The multi-loop analysis method has been applied in China. The generator set of a large hydropower station has been simulated by internal faults. The accuracy of the calculation results has been fully verified. The sensitivity of the main protection scheme of the internal fault of the small generator is calculated. The multi-loop analysis method is used to accurately obtain the fault electric quantity of the internal short circuit of the generator. On the basis of the calculation, the sensitivity of the common internal protection scheme of the internal fault of the generator and the sensitivity of the new protection scheme of the internal fault of the new generator are calculated.
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