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Power systems neutral grounding and the elimination of ferroresonance


Second side of the fuse overheating. Ferromagnetic resonance over-voltage power grid phenomenon more obvious signal for the system ground, voltage meter pointer kept swinging, electrical equipment than the sound of a strong corona. Measures to eliminate resonance. The idea is to eliminate resonance: imposed by the zero-sequence network to suppress or eliminate vibration damping, or by improving the pressure was 100 * Guangxi Normal University (Natural Science) Volume 24 HV winding of the zero sequence impedance to destroy resonance generated conditions. Damping applied to the zero-sequence network there are two specific ways: one is the low resistance of the variable damping resistor connected in open delta voltage winding circuit, the transformer winding voltage reflected to the high side, applied to the system zero-sequence network; Another change in the pressure of high-voltage winding neutral point directly between the string and the earth people and other high-value resistors or inductors. Power system in our country some of the more commonly used influential ELIMINATION (devices) are: (1) the imposition of linear resistive damping harmonic elimination method; (2) the imposition of nonlinear harmonic elimination method of damping resistance; (3) high-pressure side of the neutral cascade RXQ Harmonic elimination; (4) adding a zero sequence voltage change harmonic elimination thyristor device components; (7) Intelligent harmonic elimination devices; ( Other ELIMINATION. One method (1), (2) present in the medium voltage power grid has been basically eliminated, no longer used. After five Harmonic Elimination Method in the grid is applied more widely. Here we focus on the Four pressure change Wiring Method harmonic elimination method. 10kV voltage transformer in the original high-pressure side of the neutral point and to a zero sequence voltage between the change in series to form a group of four pressure change the connection mode, as shown in Figure l. . ,-,/-,/-,/-,. · YH mouth / a -,/-,。 / - / -,. *. ---- GHb, -, ,/-,. ,/-,/-,[link widoczny dla zalogowanych],· YHC ,,_,/-,. ,, A -,/-,,· x11 Figure 1 Four pressure transformer zero-sequence connection mode change access pressure, significantly improved the primary loop pressure transformer zero sequence impedance characteristic is to appear in a single grid phase ground fault of no saturation occurred and, therefore, virtually eliminating the resonant production conditions. Supply voltage during normal operation in the symmetric case the same model as the pressure of selection changes, the main pressure change of a coil voltages are the respective phase voltage, the voltage of the pressure change on the phase difference of 120. , Zero-sequence voltage changes the voltage on a winding is zero, the secondary winding is also no voltage. If the power voltage imbalance or three main pressure changes the impedance of the asymmetric, variable zero sequence voltage imbalance is only a small voltage, the voltage leak detection relay is also very small. A phase to ground, such as A phase to ground, A relatively voltage is zero, non-fault phase voltage to line voltage. At this point the main pressure change the voltage on a coil of the original phase voltage remains unchanged, but pressure changes on the zero sequence voltage from zero up to phase voltage, the voltage on the leak detection relays rose from zero and close to 60V start, the sensitivity is very high. The pressure did not change the phenomenon of over-voltage transformer, it will not appear over the rise of core due to voltage excitation, the system pressure change ground running time constraints, can be a long ground run. In the Neutral Ground zero sequence voltage change, the equivalent inductive reactance of the neutral point grounding large enough to compensate for any length of line to ground capacitance, which also includes the transformer coil-to-ground capacitance, but also to undermine the fundamental harmonic resonance condition. To increase reliability, the three main pressure change in the secondary auxiliary coil connected into a closed triangle. Ping County Power Company ll0kV 10kV substation bus voltage transformer bridge years ago, on several occasions since 1999 to produce single-phase ferromagnetic resonance, the burning of high insurance and voltage transformers, after transformation as above, run the place has no similar accident. With the development of electronic technology, Harmonic Cancellation by the analog devices have begun to digital, smart development. Harmonic elimination device features smart strong anti-interference performance, and can store a certain historical information, the new generation of harmonic elimination device has a certain representation, has been widely used, and increasingly replacing analog devices trend harmonic elimination .