# NCEES Voltage Drop Question ### Help Support Professional Engineer & PE Exam Forum: #### wfg42438

##### Active member
In the question below we are asked to find the voltage at panel A due to a voltage drop across the conductor  Based on Table 9 I did the following:
Zeff_ohms= (0.029 *PF + 0.048*sin(Arccos(PF)) ) * 250/1000 = 0.013 ohms

So then i simply said VpanelA_LN= VLN_mainPAnel- Vdrop_Cable_LN= (480/root(3)) - (0.013)*(400<-arccos(0.8))= 273 Volts

So VPanelA_LL=Vdrop_LN*root(3)=473 Volts

however if instead i do the following then i get the solutions answer:
So then i simply said VpanelA_LN= VLN_mainPAnel- Vdrop_Cable_LN= (480/root(3)) - (0.013)*(400)= 271.9 Volts
So VPanelA_LL=Vdrop_LN*root(3)=471 Volts

When we adjust the value of Zeffective of the cable did we already account for the PF which is why we use the load current without its angle?

Also in the solution i know they don't use Zeff they use the complex representation. However table 9 of NEC gives values for a PF=0.85 wouldn't the R and X need to be adjusted prior to using the values?

#### mikeengineer1

##### New member
In the question below we are asked to find the voltage at panel A due to a voltage drop across the conductor

View attachment 27278
View attachment 27279

Based on Table 9 I did the following:
Zeff_ohms= (0.029 *PF + 0.048*sin(Arccos(PF)) ) * 250/1000 = 0.013 ohms

So then i simply said VpanelA_LN= VLN_mainPAnel- Vdrop_Cable_LN= (480/root(3)) - (0.013)*(400<-arccos(0.8))= 273 Volts

So VPanelA_LL=Vdrop_LN*root(3)=473 Volts

however if instead i do the following then i get the solutions answer:
So then i simply said VpanelA_LN= VLN_mainPAnel- Vdrop_Cable_LN= (480/root(3)) - (0.013)*(400)= 271.9 Volts
So VPanelA_LL=Vdrop_LN*root(3)=471 Volts

When we adjust the value of Zeffective of the cable did we already account for the PF which is why we use the load current without its angle?

Also in the solution i know they don't use Zeff they use the complex representation. However table 9 of NEC gives values for a PF=0.85 wouldn't the R and X need to be adjusted prior to using the values?
The 500mcm wire is only good for 380amps

#### wfg42438

##### Active member
The 500mcm wire is only good for 380amps
Sorry not following how this pertains to the question at hand

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