UPS and its effects on certain studies

In Load Flow, the UPS component in PTW has three Operating Modes, here is how PTW handles it in each case:

1. For the Normal Operating Mode, "UPS Rating" represents the maximum load of the UPS. We use this as the Power Base to calculate the SC contribution and LF losses. The actual loading condition is defined by the user when he connects loads and motors to the secondary and/or the down below system. The Load Flow solves two separate networks (one with the equivalent load and UPS losses connected to the primary, another from the secondary down) and the solutions from the two networks need to be iterated until the mismatch is within the limit.

2. For the Recharging Operating Mode, same as 1), but the Battery Charging (% on UPS Rating) is added to the line side of the UPS to represent the DC battery recharging condition.
3. For the Emergency Operating Mode, the UPS is a source. The per unit Voltage and Angle from the Initial Operating Conditions group is used to represent a Swing Bus.

The power factor is typically variable based on the UPS load (can actually be leading power factor under light load condition), this is not modeled yet.

In Short Circuit, When the Bypass mode is checked, the UPS model is now replaced by an equivalent lossless transformer. The UPS contribution entered under page 2 subview is used to calculate the impedance, but this impedance is only used when the Bypass mode is unchecked. This is not necessarily the transformer impedance, but is something like the utility internal impedance. If the transformer's impedance in user's UPS is very big, we suggest using a equivalent transformer plus the UPS to model your UPS. If Bypass is unchecked, the 3-Phase and SLG SC contribution are included like a source to the primary. Change of "Operating Mode" does not affect SC results.

In TMS/I*SIM, the UPS is model in the same way as Load Flow.

In HI_WAVE, the UPS is just modeled the same was as Short Circuit.

In Equipment Evaluation, UPS is not evaluated yet.

In Reliability, UPS does not have a Reliability subview in V6.0. But V6.5 will include UPS in Reliability.

The user can associate harmonics source from the library with loads/motors on the secondary of the UPS for HI_WAVE in V6.0. In V6.5, the user can assign a harmonics source for the UPS, it will be a constant harmonic current source in the primary. The impedances for the UPS branch for harmonics orders are infinite.