Microbuzzer.com · Posted on 29-12-2008 by microbuzzer

In order to facilitate the production of the electrical appliances industry standardization and seriation, the state provides for standard voltage range. In the design, we should choose the most suitable level of rated voltage. The so-called rated voltage, that is a by electrical appliances (electric motors, lights, etc.), generators and transformers in the normal run-time with the greatest economic benefit when the voltage.

China’s power equipment provides a unified standard voltage. Power grid points in the voltage is different.
Based electricity to the power grid voltage generator S is running under U1, as the line voltage in the landing, for direct distribution by the generator part of terminal voltage U1 line before the end of voltage greater than U2. In order to facilitate the discussion, set up a straight line U1U2 (the actual line should be) on behalf of voltage changes in the law, by the electrical l ~ 4 will be a different voltage. By electrical appliances is based on the standardization of production, it is not possible in accordance with the icon points to create different voltage electrical appliances, and power grid points in the voltage is not constant. In order to make all the practical side of electrical voltage and its rated voltage difference between the smallest, obviously should be taken to an intermediate value that what is taken Ue = (U1 + U2) / 2 years as a rated voltage electrical appliances. The voltage power network will be provided for the rated voltage.

If that generally allow voltage electrical equipment offset ± 5%, while the voltage drop along the normally l0%, which requires only terminal voltage lines for the 105 percent rating in order to end voltage rating not less than 95% . Generators on line before then end, therefore, generators
Rated voltage of the electricity grid access for 105% of rated voltage.

Receiving the power grid before the end of that generator busbar voltage transformer (such as T1), as a result of generator voltage power grid in general than the high-five percent rated voltage, and generator to the transformer connection between the smaller drop, in order to enable a winding voltage transformer with generators rated voltage of it, can be higher than rated voltage electricity grid 5 percent voltage transformer as the first winding rated voltage.

Received by the electric power grid side of the transformer (such as T2), the first by the electrical windings can be viewed as a result of its rated voltage check with the rated voltage electrical power grid that is equal to rated voltage.

Since the transformer secondary winding rated voltage refers to the case of transformer no-load rated voltage. When the transformer with the load run-time, first, the secondary windings are voltage drop, the second winding terminal voltage will be lower than its rated voltage, such as fully loaded, according to the transformer secondary winding voltage drop of 5% to consider, in order to enable fully loaded, the secondary winding terminal voltage power grid is still higher than 5% rated voltage, you must choose the transformer secondary windings (such as T1, T2) of the rated voltage than the rated voltage power grid by 10%.
When the power grid by the end of the transformer power supply lines are short-term, such as irrigation and drainage stations dedicated transformer, the line pressure drop is very small, may also have recourse to higher rated voltage power grid to add 5% (such as: 3.15,6.3,10.5 kV), as The transformer secondary winding rated voltage.

Due to the electricity grid points in voltage is different, but also load and run with the changes in the way, the electricity grid points to changes in voltage, in order to ensure the points grid voltage in a variety of circumstances to meet the requirements, transformers are used to change transformer tap than the number of windings (usually high, medium voltage windings). Choose the right transformer tap, adjustable voltage transformer exports, the use of electrical equipment Department to close its voltage rating. No high-voltage regulating transformers excitation (or pressure) winding tap for Ue ± 5% or Ue ± 2 * 2.5%. OLTC transformer HV winding tap for the Ue ± 3 * 2.5% or Ue ± 4 * 2%.

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