How to measure power supply quality 

By on

Fluke430PA
Fluke 430 Power Analyser
If your are ever called out to troubleshoot something on your electrical system, one of the first things consider is the supply voltage.  You want to ensure you have a good electrical supply before moving on to other possible problem causes. Here are a few things you can quickly measure to get an impression on the quality of supply:

  • Measure the supply voltage, current and frequency - you want to make sure all these are within expected limits.  If any of the readings are more than 10% out of range, this indicates a problem.
  • Check for phase unbalance - for three phase loads (i.e. motors), the system should be balanced; voltage unbalance of greater than 2% or current unbalance of greater than 6% would potentially indicate a problem.  You can expect some unbalance for single phase loads the phase, however if this is excessive it may still indicate problems.
  • Check for transients - these are more difficult to measure and will need some sort of recording instrument.  Look for transients 50 V and more above nominal.  You should measure for the duration in line with the observed symptoms.
  • Check for voltage dip - look for dips 50 V and more below nominal. Again measure for the duration in line with the observed symptoms.
  • Check the harmonics on the system - total harmonic distortion (THD) of greater than 6% could indicate problems.
  • Check the power factor - this should be inline with expectations.

The above should provide a fair indication that everything is ok with the supply.  If the supply looks good, you can then start investigating potential problems with the equipment itself.

In special cases, the power system parameters are more strictly defined (i.e. the CBEMA Information Technology Curve).  Where applicable, you should be looking to ensure the supply parameters are within the specification.

If you have any additional tips or suggestions on how to ensure the power supply is up to scratch, feel free to add them below.



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

myElectrical Engineering

comments powered by Disqus



Equipment Verification (to IEC Standards)

One of the requirements to ensuring that everything works is to have equipment selected, manufactured and verified [tested] to IEC standards. Not all equipment...

Multimeter

Multimeters are undoubtedly the most common item of electrical test equipment in use.  Often it is the first piece of equipment people will turn to when...

Laplace Transform

Laplace transforms and their inverse are a mathematical technique which allows us to solve differential equations, by primarily using algebraic methods...

Motor Insulation

Insulation on a motor prevents interconnection of windings and the winding to earth.  When looking at motors, it is important to understand how the insulation...

Contribute to myElectrcial

Have an opinion or something to say, want to ask or answer questions, share your knowledge then use our site to do it . As a community of people interested...

How a Digital Substation Works

Traditionally substations have used circuit breakers, current transformers (CT), voltage transformers (VT) and protection relays all wired together using...

Voltage Drop in Installations - Concepts

Problems on achieving maximum voltage drop within an installation come up often. Depending where you live, local regulations will have different limits...

Maxwell's Equations - Introduction

Maxwell's Equations are a set of fundamental relationships, which govern how electric and magnetic fields interact. The equations explain how these fields...

Surface Treatment – Ladders, Trays and Baskets

Steel ladders, trays and baskets form the backbone of cable containment systems. Often these items need some form of surface treatment to prevent corrosion...

Harmonised Cable Codes and Colours

Within Europe the European Committee for Electrotechnical Standardization (CENELEC) has standardised the both the designation and colour of cables.   ...

Have some knowledge to share

If you have some expert knowledge or experience, why not consider sharing this with our community.  

By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note