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FAQs: Automatic LTC Tap Setting Datablock attribute
If PTW has run a load-flow study that includes modelling automatic LTCs (Load Tap Changers), the load-flow results are shown as they would be with the transformers at their ideal taps. The ideal tap can be displayed using the "ubLF_LTC Pri Tap", "ubLF_LTC Sec Tap", "LF_LTC Pri Tap", "LF_LTC Sec Tap" datablock attributes. 
If the LTC Transformer option is "greyed-out" in the load-flow set-up, this is probably because it is not available with the "current injection" calculation method.
Changing to the Newton-Raphson calculation method will make the LTC Transformer option available. (See the two screenshots on the left).

This does not apply to PTW versions V7.0 and later; these versions do not allow the "current injection" calculation method. If you are using V7.0 or later and you still have trouble with the LTC Transformer option, please contact us. 

(Right): Screenshot of the Load Flow Study options dialogue box for PTW versions V7.0 and later. Note how the "current injection" calculation method is no longer a selectable option; only the Newton-Raphson method (designated "Newton Method") is used. 
Note: The "LF_LTC Pri Tap" and "LF_LTC Sec Tap" datablock attributes are not available in V6.0 and earlier, so the ubLF ones need to be used instead.