Load Impact calculations

Load Impact identifies changes in the steady state electrical loads of a power system triggered by a voltage disturbance, such as a voltage sag or interruption. To assess the impact of a disturbance on the load, the software compares the real power (kW) measurements of the monitored circuit before and after the event.

Load Impact is calculated as:

Load Impact (%) = ((Ppost-event - Ppre-event) / Ppre-event) ×100

• A negative Load Impact value between -100% < X < 0% means a load loss. The real power (kW) of the monitored circuit has been reduced by X%.

  NOTE: Load loss is the most common load impact caused by voltage disturbances.

• A positive Load Impact value, X > 0%, means a load gain. The real power (kW) of the monitored circuit has increased by X%.
• A negative Load Impact value, X < -100%, means a potential load reversal. The energy flow in the monitored circuit might have been reversed. The percent value less than -100% is the portion of pre-event real power (kW) flowing in the opposite direction. For example, a Load Impact value of -125% means that the power flow has been reversed and 25% of the pre-event real power are now flowing in the opposite direction.

A voltage disturbance event can result in any or all of the above load changes. For example, starting a large load, such as a motor, can produce a voltage sag that causes another load to disconnect. In this case, the motor load circuit would show a load gain and the other circuit a load loss.