The International Electrical Testing Association (NETA) publishes a “Frequency of Maintenance Tests” Appendix as part the ANSI/NETA-MTS Specification. This specification is updated every four years.

A review of this appendix first requires that we have a bit of information before we can determine the “Frequency”. We first need to know what the equipment reliability requirement is. Is this VCB a main breaker, critical to the operation of a Data Center? In this example we would likely make the case that this is a “high” requirement. The second piece of information we must have is “Equipment Condition”. This is somewhat of a qualitative measurement unless maintenance is already being performed on a regular basis and we have the data to prove what the condition is. For the sake of this example we will give this an “average” condition. Utilizing these two pieces of information and applying it to the provided matrix in Appendix B, we have a .5 factor. We can now review the Frequency table and look at 7.6.3 Vacuum, Medium Voltage. There are 3 columns, Visual, Visual & Mechanical, and Visual, Mechanical, & Electrical. The frequency in months is 1, 12, & 24 respectively. If we apply the .5 factor from above we would have the following:

  • Visual – twice monthly
  • Visual & Mechanical – every 6 months
  • Visual, Mechanical & Electrical – once every year

As you can see this is a great tool when you are in need of a standard maintenance program. This will provide the consistency you need to ensure your equipment is maintained properly. Once you get started you can always reassess your equipment Reliability and condition to adjust your Frequency, as needed.