The following describes the internal limits of the on-load tap changer in the autotransformer components.
On-Load Tap Changer Internal Limits
The tap value is limited internally so that the (HV-LV) and LV voltage ratios never exceed 50. This translates to tap position limits that maintain the LV-side voltage between:
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For example, the tap limits for a 115 [kV] : 230 [kV] autotransformer would be:
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This translates to tap input signal limits of:
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NOTE: It is important to remember that the tap limits for the autotransformer are not fixed, but dependent on the values of HV and LV. Also, when a change in tap position is mandated, it is not changed until the next winding current zero-crossing.
