The phase reversal function is intended to protect machines in pumped storage power stations that are operated either as motors or as generators, depending on the demand. In such applications it is common practice to swap two phases in order to facilitate the pumping operation. Because of this, the P632 phase reversal function can maintain correct operation of all protection functions even if phase reversal is carried out within the protected zone.

The processing is done right after A/D conversion, such that the link between physical transformer input and internal numerical signal will be swapped, depending on the setting. (The measured values stored in the respective measured value memories are swapped.) Thus all further processing of measured values and protection functions remains unchanged.

Phase reversal can be set independently for each transformer end and in each parameter subset. The parameters are included in function group MAIN because phase reversal affects not only the differential protection function (DIFF), but also the negative sequence elements of Inverse and Definite Time Overcurrent protection functions (IDMTx, DTOCx) as well as Current Transformer Supervision (CTS) and Measuring- Circuit Monitoring (MCM_x) functions.

Using parameter subsets readily allows phase reversal to be activated via any control interface (LOC, PC, COMMx) or via appropriately configured binary signal inputs.

Since the currently active parameter subset is shown on the LC-display and may be recalled from the recordings, phase reversal information is accessible. There are however applications where an additional display of a phase reversal may be useful. Such would be the case when recordings by a P632 are to be compared with those by other devices not featuring phase reversal (e.g. Backup overcurrent-time protection device) and without knowledge of the P632 setting file. For this the following display is used:

Phase reversal is active (Yes) when at least one of the setting parameters in the active parameter subset has a value other than No swap.

The setting file must be viewed to determine which phases are swapped.