Meter Verificatioin Issue

[Arsyad_Azhari]

Dear All,

i Have this issue

i have experience on Power Meter Commissioning (using PM5000 series, ie pm5300 and 5500) like this :

- i had install metering normally (input voltage RSTN is correct and input CT RST and +- is correct), but the meter read leading power factor, and when i see the phase angle degree it says  V1-A1= 306 degree, V2-A2= 30 degree, and V3-A3=306 degree which means it may be the Phase sequence must be rotated and CT must be inverted (if we see from phasor diagram based on angle degree that we have)

- when i do wiring correction (Phase Shifting and CT inverting) the meter read is ok (sistem is lagging), but it is not correct if we see by the wiring (i mean, now after correction input voltage R meets CT input phase S, input voltage S meet CT phase T, and input voltage T meet CT phase R), however the reading is good/ok

how about that ?

can anyone explain it ?

[greg_expoenergy]

Meter commissioning can be quite challenging if one assumes that CT's are correctly internally wired?



My experience is that often CT's in a batch from any supplier will have their internal wiring with incorrect polarity.



Typically CT's are labeled P1 ---> P2 for primary and S1 ---> S2 and some use K as the symbol



The first step is to ensure that the meter voltage and current connections are in the same phases (A, Ia    B, Ib.   C, Ic )



Once the meter is up and running note the following



Ptotal = Pa + Pb + Pc



If the individual powers are all positive then they should be additive. Let us assume that each phase is 20 kW then the total power should be 60kW.



If the active powers are correct then the reactive power and power factors will follow suit.



Now short the B&C CT's either at the CT or at the meter terminals.



The meter should read 20 kW.  If it is -20 kW then the CT polarity is incorrect so change it so it reads 20 kW



Now remove the short on CT B and the power reading should be 40 kW. If so then polarity is correct and if 0 kW then change the polarity of CT B.



Now remove the short on CT B and repeat.



What I have suggested does not require one to read the individual powers and one may use the total power only.



This problem may be compounded if one uses a POTENTIAL TRANSFORMER in an open delta connection and not a direct connect