4 minutes tan delta (TD) where it comes from?

Electrical Testing Talk Apparatus Testing
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Hi everyone,

I’ve noticed that we consistently apply 4 minutes for the tan delta (TD) test at each voltage step. I was wondering if anyone knows where this 4-minute duration comes from, or if there is a standard, calculation, or reference table that defines it.

It seems to be common practice (and I use it as well), but I’d like to understand the technical or standard-based justification behind it.

Thanks in advance.

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It usually depends on the test set your running but you need enough time is the test to collect data points. I believe ieee specifically calls for 7 points. Hv diagnostics reccomends 3 minutes with an external td unit.

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As mentioned previously IEEE recommends collecting 6-7 Data points at minimum. When I worked at HV Diagnostics we collected 12 data points (2 Minutes) of Data. It would take about 60 seconds for the older external TD units to start outputting data. So if you wanted to collect 2 minutes of data you would need to set the timer for 3 minutes to account for the ramp up time. I have a feeling someone has taken that 3 minutes as collected data time and said to add and extra minute resulting in 4 minutes. I was an instructor at HVD for about 5.5 years so I feel that is what happened because I have never heard of 4 minute tests.

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Per IEEE 400.2 5.4.2 Method: “Each step should include at least six single TD measurements at intervals of 10s between each measurement at 0.1Hz. The intervals will be correspondingly longer at lower frequencies.”
This is where you set your step times, typically between 2 and 4 minutes to ensure the test set actually captures the minimum of 6 TD measurements.

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