The protection relay has the following power quality monitoring

functions.

• Voltage variation

• Voltage unbalance

• Current harmonics

• Voltage harmonics

The voltage unbalance and voltage variation functions are used

for measuring short-duration voltage variations and monitoring

voltage unbalance conditions in power transmission and

distribution networks.

The voltage and current harmonics functions provide a method

for monitoring the power quality by means of the current

waveform distortion and voltage waveform distortion. The

functions provide selectable short-term 3- or 60- or 300

second sliding average and a long-term demand for total

demand distortion (TDD) and total harmonic distortion (THD).

The phase-specific harmonic content is measured for voltages

and currents, as well as DC component and fundamental

content. The dedicated harmonics measurement page in the

LHMI presents the measurements in a user-friendly manner.