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Gaeilgenah Éireann
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Tips
When two transformers are in parallel operation, there are steps for pre-operation inspection;
After comparing the test reports, the electrical parameters are the same;
Check the production requirements, and the same current is required for multiple places;
The same voltage is a good outlet, and the digital accuracy of the meter is high;
The phase sequence of the high and low sides is the same, and the mother coupling determines the neutral plan;
Protection is based on parallel intention, some are withdrawn and some are switched on;
After parallel switching, check the current, and switch on the capacitor if the current is the same;
Capacitor oscillation cuts off the harmonic source, and capacitor balance is a good sign.
(1) Check the test reports of the two transformers. The electrical parameters of the same content are not much different. Whether the two transformers have been overhauled, the test reports after overhaul must also meet the relevant parameter requirements and be compared. (2) Check the certificates of conformity of the two transformers. The relevant requirements during production should be the same or consistent, that is, the voltage transformation ratio is the same, the connection group is the same, the absorption ratio is the same, the high and low voltage side voltages are the same, the winding material is the same, and the cooling method is the same. It is best to be the same batch of products from the same manufacturer. (3) Check the input and output voltages of the two transformers in operation, and use a multimeter to measure whether the actual output voltages are the same or the error is small. A digital multimeter is required, which has relatively high accuracy, so that the display is accurate. (4) Whether the transformation ratio of the zero-sequence current transformer at the neutral point of the transformer needs to be replaced. (5) Use a phase sequence meter to measure whether the phase sequence of the high-voltage side and the low-voltage side of the two transformers is the same; whether the high-voltage power sources of the two transformers are the same; if they are connected in parallel, whether the neutral line needs to be changed in position. (6) Check whether the busbar circuit breaker used for parallel operation is three-pole or four-pole. If it is a three-pole circuit breaker, the two sections of the neutral line need to be connected. (7) Check the high-voltage protection of the part that needs to be withdrawn for parallel operation, and withdraw them to avoid the action of the small current grounding line selection device; at the same time, check the high-voltage protection of the part that needs to be put into operation for parallel operation, and put them into operation. (8) After the two transformers are put into operation in parallel, closely observe the electrical parameters of the two transformers and any abnormal loads on the two transformers, such as reverse rotation of the motor; and whether there are any major changes in the original capacitance compensation paths of the two sections of the line, to prevent the reactive output voltage from being unbalanced due to the different capacitor capacities in the capacitor groups carried by the two sections of the busbar, causing harmonic oscillation of the line and damage to the transformer.
