LEAs vs. PTs

[jfpe]

I'm reviewing the preliminary drawing package for a small (5MW) solar farm. The design engineer has specified low energy analogue (LEA) voltage sensors instead of PTs for the customer owned recloser.

Does anyone have concerns or reservations about LEAs? Is the accuracy comparable to PTs?

Thanks,
-JFPE

 

[DTR2011]

LEAs may present a challenge for the relay techs for connections and accuracy / range of test equipment.

 

[scottf]

Voltage sensor designs vary widely.

Some designs, normally internal to the recloser, are simple capacitive dividers normally with ratio accuracy in the range of 2-3% and the phase angle error is normally not very good.

External voltage sensors are normally resistive dividers or RC dividers. Ratio error is typically in the range of 1-2% and phase angle error can vary widely with design.

PTs will typically have better accuracy ratings, but the question is what is really needed for a protection application. It is quite common in the US voltage sensors to be used for recloser applications.

 

[thermionic1]

I placed in service last week a 34.5kV Recloser with regular PT's on the source side and LEA's om the load side. There are Ratio correction factor calibrations supplied with the unit for the LEA's. After the RCF was applied, the primary voltage was within 200V at the final load check (L-N). The phase angle, was about 13 degrees difference between each phase on the source vs load side.