POWER QUALITY

The mains frequency indicates the speed at which the alternating voltage oscillates. In Europe, the nominal frequency is 50 Hz. Deviations indicate an imbalance between generation and consumption.

Limit values:

1. 50 Hz +- 1% during 99.5% of the year -> 49.5 Hz … 50.5 Hz
2. +4% / -6% for 100% of the time -> 47 Hz … 52 Hz

The voltage level describes how much the effective mains voltage deviates from the nominal value. Permanent deviations can damage devices or cause malfunctions.

Limit values (10 min. average values):

1. +- 10% of the nominal value for 95% of all measured values in a week
2. +10% / -15% for 100% of the time 

Flicker describes rapid voltage fluctuations that cause visible flickering of lamps. This is often caused by heavily fluctuating loads (e.g., welding equipment).

Limit values:

1. Plt <= 1.0 for 95% of all measurements taken in a week

Short-term drop in voltage, usually caused by short circuits or the switching on of large loads. They can interfere with controls or sensitive electronics.

Definition:

1. Voltage: 10% to 90% of the nominal voltage
2. Duration: 10 ms to 1 minute

Complete failure of the supply voltage. They are classified according to duration.

Limit Values:

1. Voltage: <1% of the nominal voltage on all phases
2. Duration: >= 10 ms 
    

Classification:

1. Short: ≤ 3 minutes
2. Long: > 3 minutes

➡ The number and duration are not limited by standards, but are documented.

Short-term voltage increases above the permissible range, e.g., due to switching operations or ground faults.

Definition:

1. Voltage > 110% of the nominal voltage
2. Duration: 10 ms to 1 minute

Uneven distribution of voltage in three-phase systems. Leads to additional heating of motors and transformers.

Limit value (95% of 10-minute average values):

1. ≤ 2% imbalance (ratio of negative sequence voltage to positive sequence voltage)

Harmonics are voltage components with integer multiples of the fundamental frequency (50 Hz). They are caused by non-linear consumers such as converters or switching power supplies.

Limit values:

1. Total harmonic distortion THD ≤ 8% (low voltage)
2. Individual harmonics (selection):
3. 5th harmonic: ≤ 6%
4. 7th harmonic: ≤ 5%
5. 11th harmonic: ≤ 3.5%

Interharmonics lie between the integer multiples of the fundamental frequency. They can cause flicker and acoustic disturbances.

Limit values:

1. No uniform percentage value
2. Evaluation is based on flicker limit values and spectral assessment

Superimposed signals for grid control (e.g., tariff switching, load control).

Limit values:

1. Signal voltage typically ≤ 9% of nominal voltage.
2. No impairment of the supply permitted.