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Power Quality

The Power Quality screen provides analysis of the electrical supply quality. Access it from the Status tab by selecting the Power Quality sub-tab.

[Screenshot: Power Quality screen]

Harmonic Distortion

Total Harmonic Distortion (THD)

THD measures how much the voltage or current waveform deviates from a pure sine wave. ESP-GUARDX displays:

  • Voltage THD (%) -- Per-phase and average
  • Current THD (%) -- Per-phase and average
  • Current TDD (%) -- Total Demand Distortion, referenced to full-load current

High THD values indicate the presence of harmonic-producing loads (such as VFDs) and can cause:

  • Increased motor heating
  • Reduced motor efficiency
  • Interference with protection relays
  • Increased cable losses

Harmonic Spectrum

The detailed harmonic analysis is available on the dedicated Harmonics screen (see Harmonics Analysis).

Phase Unbalance

Phase unbalance occurs when the three-phase voltages or currents are not equal in magnitude or are not 120 degrees apart. The Power Quality screen displays:

  • Voltage Unbalance (%) -- Indicates supply-side issues
  • Current Unbalance (%) -- Can indicate motor winding problems

Unbalance Limits

Condition Typical Limit
Normal < 1% voltage unbalance
Warning 2--3% voltage unbalance
Critical > 5% voltage unbalance

Important: Even a 3.5% voltage unbalance can cause a 25% increase in motor temperature rise, significantly reducing motor life.

Power Quality Events

The Power Quality screen tracks and counts the following event types:

Event Type Description
Voltage Dips Brief reductions in voltage below normal
Voltage Swells Brief increases in voltage above normal
Interruptions Complete loss of voltage
RVC (Rapid Voltage Changes) Sudden voltage transitions
Transients Very fast voltage spikes (lightning, switching)

Each event type shows a running count and can trigger automatic event recording when thresholds are exceeded.

IEC 61000-4-30 Compliance

ESP-GUARDX harmonic measurements follow the IEC 61000-4-30 standard:

  • Gapless window analysis
  • 5th harmonic RMS buffering
  • Equation 2 calculations for harmonic assessment
  • Pass/fail harmonic testing against standard limits