Load management concerns primarily manufacturing enterprises where large loads are switched on and off in random order. In office buildings, power peaks can occur in a break because a majority of the staff uses the coffee machine.

Purely commercial transactions usually have no power peaks as long as no large air conditioning systems are operated. In addition, lighting and air conditioners can cause power peaks.

The electricity bill lists the following information:

• work

• power

• standby power

• rates

• net costs

Here only power and standby power are of interest.

Power costs

Power costs are computed based on quarter-hour measurements. The power drawn is measured every 15 minutes, totaled and recorded. The measured values are compared to the contractually agreed power purchase. If the power drawn is higher than contracted, then an increased power fee is charged for the month.

Improvement measures

Since power liberalization, the costs of current peaks have drastically sunk; thus measures are meaningful only for clear peaks.

Immediate measures

If you suspecting high current peaks, you should consult an experienced advisor or your power supply company for power measurements. The results of measurement are evaluated for peaks. If a peak current monitor is installed, appropriate measures must be set for the reduction of peaks. Unless you take measures, the costs of the peak current monitor are ineffective.

Reactive current

Reactive current is a characteristic of alternating current. Due to a constant change of current between a positive and a negative half wave and the inductive loads (transformers, motors) present on the net, the current lags in relation to the voltage, it comes to the occurrence of lagging reactive current.

The reactive current is measured with a special counter in kVArh. Above a threshold value, the reactive current is billed by the power provider.

Improvement measures

If you are charged for reactive current, consult your provider, an electrician or an advisor. Automatic capacitive compensation is a measure against reactive current. Here the inductive (lagging) reactive current is compensated by capacitive (leading) reactive current.

Future prospects

Power peaks and reactive current will always be issues. On in-house power generation, the limits of the generator and the reactive current must be monitored.

Source: Austrian Chamber of Commerce