Power Quality Analysis for Electricity Utilities

Power Quality Analysis for Electricity Utilities - blog post image

Power Quality Analysis for Electricity Utilities

The needs of Australian & New Zealand power utilities differ significantly from those overseas where most analysers are designed.

Our distribution network is predominantly overhead through extremes of environments requiring the analysers and accessories to be lightweight, fully weather and dustproof and easily attachable to poles. For monitoring underground networks and customer premises, the analyser has to be sufficiently compact to fit inside service pillars and switchboards.

More Demanding Requirements

Now with demands for compliance with standards such as AS/NZS 61000, the desire for remote communication, the need to record transients and in some cases ripple control signals, higher specification power quality analysers are required.

There are many Power Quality Analysers produced internationally which come close to the above requirements, but most lack the first requirement for Australia and New Zealand of being weather proof and easily pole mounted.

Easy to Connect

Most, if not all, overseas products are supplied with leads coloured to the phase identification of the country of origin. These can be any combination of colours including green or black as phase colours! Expecting these to be correctly connected when we are schooled that green or green/yellow is ALWAYS earth and black is ALWAYS neutral is a guaranteed recipe for mistakes!

A third problem is lead length. Unlike Europe, where most products originate, Australian overhead conductors are uninsulated, meaning the separation is much greater to prevent wires from touching in winds. The leads must have sufficient length to span the extremities of cross-arms which can exceed 2m.

Sonel Power Quality Analysers

Sonel’s PQM-702/3 are weatherproof to IP65, only requiring modification with 3m Australian & New Zealand phase coloured leads and adaptable connections suitable for bare overhead, aerial bundled overhead, pad-mount and service pillars.

The result is that the Sonels have become the preferred power quality analysers for many power utilities.

Two Models to Cover All Requirements

Sonel identified that some customers only require basic analysis while others require more capabilities and offer two models.

The PQM-702 offers complete power analysis comprising voltage, current, power, power factor, sags & surges, harmonics, flicker etc while the PQM-703 adds transient and ripple control analysis.

Both models supplied by Pacific Test Equipment to Australian and New Zealand come standard with correctly colour coded voltage leads and current probes

Compliance with Local & International Standards

Sonel Analysis software which powers the PQM-702/703 was upgraded to include assessment to AS/NZS standards for low and medium voltages in addition to the customary European EN50160. If the pre-programmed standards are not applicable, the user can reprogram all limits and save the program as a template for future use.

Other software enhancements for Australia & New Zealand included quick graphical summary and daily max/min tables.

Sonel PQM’s can be maintained with the latest software and firmware which users can download at any time for no cost.

Rogowski Coils

The major benefits of Rogowski coils are not always understood. Apart from the obvious inherent weather protection, ease of connection, light weight, and almost unlimited current range, there is a misconception that because they are typically rated to 3,000 Amps, conventional iron-cored current transformers are still necessary for accurate measurements of 100 Amps and below. This misunderstanding is because the accuracy statement for iron-core probes is % of range whereas the accuracy of Rogowski coils is % of measured value.

For example a 3,000A 1% iron-core probe has an error of 30A which applies across its full measurement range. While insignificant at 3000A, 30A error at 100A is unacceptable. A similar specification Rogowski coil has an error of 1A at 100A.

Choice of Three Coil Sizes

The PQM-702/703 is supplied standard with 120mm diameter Rogowski coils with larger 235 and 360mm diameter coils optional. All will measure from 1 to 3,000 Amps with an accuracy of 1% of measured value.

Class A Power Measurement

It is now almost universally mandatory that power analysers are compliant to Class A to IEC 61000-4-30. This is to ensure that measurements made by different instruments can be compared. Non-compliant instruments can derive measurements differently preventing comparative analysis.

Suitable for all Systems

The PQM can be used on all types of power systems comprising single, 3-phase 3 and 4-wire and DC. The PQM power supply is rated from 90 to 760V AC or 127-760V DC allowing it to be self-powered on all systems, such as 415V 3-phase, 3-wire.

Up to four test configurations can be programmed into each PQM and the applicable test plan selected on site. This eliminates the need for analysers to be constantly reprogrammed for the next job. Once the recording is downloaded and cleared, the analyser can be connected at the next location, a test plan selected and recording commenced.

Theft Protection

A unique feature of the PQM is the built-in GPS and GSM modem. If the analyser is programmed with a mobile phone number it will send an SMS every time the analyser configuration or location is changed. Even if switched off and stolen the analyser will automatically notify its new location the moment it is switched on.

Summary

The Sonel PQM’s offers the following advanced features:

  • Compact design – will fit inside most service pillars
  • Weatherproof to IP65
  • Supplied with 2m pole straps and DIN rail mount
  • Current measurement with 4 x flexible Rogowski coils
  • Optional 10 Amp current probes for CT secondary applications
  • Voltage leads in AS/NZ colours with interchangeable large insulated clips for overhead and small clips for switchboard/service pillar installations
  • Measures & records:
  • oVoltage, current & unbalance
  • oActive, apparent & reactive power
  • oPower factor
  • oActive, apparent and reactive energy
  • oTHD, voltage & current harmonics
  • oShort term & long term flicker
  • oTransient & ripple control analysis (PQM-703 only)
  • On-screen display of real time measurements.
  • Inbuilt GSM modem for remote communications
  • Wireless & USB PC communication
  • GPS for clock synchronisation and location
  • Anti-theft protection with SMS notification of tamper or position change
  • Internal 8 GB memory
  • Class A measurement to IEC 61000-4-30
  • Pre programmable with up to 4 individual test plans
  • Included Sonel Analysis software with no license fees
  • Fully calibrated, supported and serviced in Australia by factory trained technicians
  • Priced less than old generation analysers!

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