Zs Readings from a 20KVA UPS system

[Guest 004]

Hi peeps

I have been asked to test a 'continuous' 20KVA UPS system. Which means the supply goes through the UPS first, and in effect with loss of power you will have changeover instantly.

The consultant has suggested to just get the dead readings, and calculate. Whilst I am happy doing this, I wonder what his reasons are?

Will the UPS throw the live readings out?

Would there be 'sensitive' fuses inside the UPS kit that might blow?

 

[cossie400]

We never take zs readings downstream of a UPS as they have high earth leakage and will give you false readings.

If possible, and the system has an external maintenance bypass switch, try and arrange a time this can be operated as it will bypass the UPS without loss of power to the load and then you can take your zs readings.

 

[Guest 004]

Thanks cossie

 

[Farmelectrics]

Yes agree with above you get false readings with ups involved found out the hard way few years back couldn't work it out till some old maintenance spark explained to me