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Reply To: پرسش ترانسفورماتور شماره 9 – گروه برداري ترانس


    بطور کلی خیر، البته برخی رواداریها برای انحرافات مختصر در استانداردها پیش بینی شده است که در زیر به برخی از آنها اشاره شده است. The satisfactory parallel operation of transformers is dependent upon five principal characteristics; that is, any two or more transformers which it is desired to operate in parallel should possess: 1. The same inherent phase angle difference between primary and secondary terminals. 2. The same voltage ratio. 3. The same percentage impedance. 4. The same polarity. 5. The same phase sequence. To a much smaller extent parallel operation is affected by the relative outputs of the transformers, but actually this aspect is reflected into the third characteristic since, if the disparity in outputs of any two transformers exceeds three to one it may be difficult to incorporate sufficient impedance in the smaller transformer to produce the correct loading conditions for each unit. Characteristics 1 and 5 only apply to polyphase transformers. A very small degree of latitude may be allowed with regard to the second characteristic mentioned above, while a somewhat greater tolerance may be allowed with the third, but the polarity and phase sequence, where applicable, of all transformers operating in parallel must be the same. Generally three phase transformers are in parallel operation if they are connected in parallel on at least two sides. A distinction is made between busbar interconnection and network interconnection. The following conditions must be satisfied in order to avoid dangerous transient currents: 1. Vector groups should have the same phase angle number; terminals of the same designation must be connected together on the HV and LV sides; Exception: Phase angle numbers 5 and 11 (Table below); 2. The ratios should be as similar as possible, i.e. the same rated voltages on the HV and LV sides; 3. Approximately the same impedance voltages uk maximum permissible discrepancies