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Carelabs

IEEE 1584 · Engineering

Harmonic Study & Analysis - Carelabs South Africa

Get Your Harmonic Study Report Right Away Carelabs measures total harmonic distortion with a harmonics analyser and models system impedance versus frequency to identify resonance risk before it causes equipment failure, nuisance breaker trips, or generator problems. Where levels exceed applicable limits, mitigation options include harmonic filters, relocated power-factor correction capacitance, or higher-pulse-number rectifiers. Every engagement concludes with a SANS 10142-aligned report package.

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Distortion is worse on the generator

A generator is a much weaker source than the utility. The same harmonic current produces considerably more voltage distortion, and sites that run on standby regularly discover this the hard way.

What We Deliver

Distortion measured on both sources

Harmonic voltage distortion is recorded on utility supply and on generator supply separately, because the same load produces a substantially worse waveform behind a higher source impedance.

WHY IT MATTERS

It works on the grid and misbehaves on the set

Equipment that operates normally on utility supply can fault repeatedly during generator running. The load has not changed; the source impedance has, and with it the voltage distortion the plant is exposed to.

  • Measurement taken during genuine generator operation rather than extrapolated from utility conditions, since the two are not comparable.
  • Generator parameters and manufacturer derating requirements obtained, as harmonic loading limits are frequently stated and rarely checked.
  • Capacitor behaviour assessed on generator supply specifically, because the resonant point shifts with source impedance at changeover.
  • AVR response reviewed where voltage instability occurs on the set but not on utility supply.
  • Non-linear load proportion established, since a generator supplying mostly electronic load is in a very different position from one supplying motors.
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DELIVERABLES

What you receive

Issued against SANS 10142 and the applicable distortion limits, with measurements from both supply sources.

  1. 1Measured voltage and current distortion on utility supply and on generator supply
  2. 2Generator derating assessment against manufacturer harmonic limits
  3. 3Resonance assessment for existing power factor correction under both source impedances
  4. 4Findings on voltage regulation behaviour where instability occurs on the set
  5. 5Mitigation options with their effect on both supply conditions stated
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How the study runs

01

Establish the operating pattern

How often and for how long the site runs on generation, and which loads are carried, since that determines what the assessment must cover.

02

Measure on utility supply

Baseline distortion is recorded across a representative period so the generator condition can be compared against something.

03

Measure during generator running

Recording is repeated on generator supply with a comparable load, which is the only way the difference in source impedance is captured.

04

Assess the generator position

Measured distortion is compared against the manufacturer's harmonic limits and any required derating is quantified.

05

Model both sources

A frequency scan is run for each source impedance, identifying resonance that exists on one supply and not the other.

06

Report and options

Mitigation is presented with its effect on both conditions, since a remedy that suits the utility case may not suit the generator case.

Frequently asked questions

Because a generator is a much weaker source than the utility. Voltage distortion is the product of harmonic current and source impedance, and a generator's impedance is considerably higher. The same load therefore produces substantially more voltage distortion, which is why equipment that behaves normally on the grid can fault on the set.
Yes. Harmonic current heats the damper windings and rotor, and manufacturers commonly specify derating where distortion exceeds a stated level. A set sized on kVA alone, supplying substantial electronic load, can be thermally overloaded while appearing to run within its rating.
Resonance depends on source impedance, which changes entirely at changeover. A bank that sits clear of resonance on the utility supply can resonate directly on an order the plant produces once the generator is the source. That is why failures cluster around periods of generator running.
Not reliably. Utility measurements can be modelled forward to predict the generator condition, and that is useful for planning, but the prediction depends on generator parameters that are often approximate. Where the site runs on generation regularly, measuring during genuine operation is worth arranging.

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