Short Notes: Underground Cables | Short Notes for Electrical Engineering - Electrical Engineering (EE) PDF Download

Download, print and study this document offline
Please wait while the PDF view is loading
 Page 2


 
 
 
 
 
Power Factor Correction 
Usually, to improve the supply side power factor we connect a capacitor device like capacitor 
bank or synchronous condenser (synchronous motor under over excited condition). 
Suppose, initially a load of real power 
1
P & lagging pf 
1
cos ? is connected & we want to 
improve pf to 
2
cos ? lagging ? ?
21
? ? ? & we connect a capacitive device which consumes real 
power ? ?
C
P & thus net real power after connection. 
2 1 C
P P P ?? 
2 2 2 1 1 1
Q P tan ; Q P tan ? ? ? ? 
C 1 1 2 2
Q P tan P tan ? ? ? ? 
In case of capacitor bank, 
C
P0 ? 
12
PP ??  
If we wish to calculate capacitance per phase  
(in both voltage control & pf correction ) 
2
C ph
Q 3 CV    ? ? ?   
C
2
ph
Q
C
3V
?
?
 
 
Insulation resistance 
           
R
R ln
2 l r
?? ?
??
??
?
??
 
           L = length of cable 
           R = Outer radius (sheath radius) 
           R = conductor radius  
 
Capacitance Model 
          
C
C : Core capacitance 
          
S
C : Core to sheath capacitance 
 
 
 
 
 
Page 3


 
 
 
 
 
Power Factor Correction 
Usually, to improve the supply side power factor we connect a capacitor device like capacitor 
bank or synchronous condenser (synchronous motor under over excited condition). 
Suppose, initially a load of real power 
1
P & lagging pf 
1
cos ? is connected & we want to 
improve pf to 
2
cos ? lagging ? ?
21
? ? ? & we connect a capacitive device which consumes real 
power ? ?
C
P & thus net real power after connection. 
2 1 C
P P P ?? 
2 2 2 1 1 1
Q P tan ; Q P tan ? ? ? ? 
C 1 1 2 2
Q P tan P tan ? ? ? ? 
In case of capacitor bank, 
C
P0 ? 
12
PP ??  
If we wish to calculate capacitance per phase  
(in both voltage control & pf correction ) 
2
C ph
Q 3 CV    ? ? ?   
C
2
ph
Q
C
3V
?
?
 
 
Insulation resistance 
           
R
R ln
2 l r
?? ?
??
??
?
??
 
           L = length of cable 
           R = Outer radius (sheath radius) 
           R = conductor radius  
 
Capacitance Model 
          
C
C : Core capacitance 
          
S
C : Core to sheath capacitance 
 
 
 
 
 
 
 
 
 
 
Capacitance per phase 
ph S C
C C 3C ?? 
Calculating 
S
C & 
C
C 
1)  Any of two cores or conductors are connected to  
       sheath & capacitance is measured between remaining  
       core & sheath. 
 
 
1 S C
C C 2C ?? 
 
 
2) All three cores are connected together & capacitance is  
measured between any core & sheath. 
2S
C 3C ? 
2
S
C
C
3
? 
2
C1
C
2C C
3
?? 
12
C
CC
C
26
??
??
??
??
 
               
12
ph S C
3C C
C C 3C
26
? ? ? ? 
3) Any one of core is connected to sheath & capacitance is 
 measured between remaining 2 cores. 
               
CS
3
3C C
C
22
??
 
               
ph 3
C 2C ?
 
 
 
 
 
 
Page 4


 
 
 
 
 
Power Factor Correction 
Usually, to improve the supply side power factor we connect a capacitor device like capacitor 
bank or synchronous condenser (synchronous motor under over excited condition). 
Suppose, initially a load of real power 
1
P & lagging pf 
1
cos ? is connected & we want to 
improve pf to 
2
cos ? lagging ? ?
21
? ? ? & we connect a capacitive device which consumes real 
power ? ?
C
P & thus net real power after connection. 
2 1 C
P P P ?? 
2 2 2 1 1 1
Q P tan ; Q P tan ? ? ? ? 
C 1 1 2 2
Q P tan P tan ? ? ? ? 
In case of capacitor bank, 
C
P0 ? 
12
PP ??  
If we wish to calculate capacitance per phase  
(in both voltage control & pf correction ) 
2
C ph
Q 3 CV    ? ? ?   
C
2
ph
Q
C
3V
?
?
 
 
Insulation resistance 
           
R
R ln
2 l r
?? ?
??
??
?
??
 
           L = length of cable 
           R = Outer radius (sheath radius) 
           R = conductor radius  
 
Capacitance Model 
          
C
C : Core capacitance 
          
S
C : Core to sheath capacitance 
 
 
 
 
 
 
 
 
 
 
Capacitance per phase 
ph S C
C C 3C ?? 
Calculating 
S
C & 
C
C 
1)  Any of two cores or conductors are connected to  
       sheath & capacitance is measured between remaining  
       core & sheath. 
 
 
1 S C
C C 2C ?? 
 
 
2) All three cores are connected together & capacitance is  
measured between any core & sheath. 
2S
C 3C ? 
2
S
C
C
3
? 
2
C1
C
2C C
3
?? 
12
C
CC
C
26
??
??
??
??
 
               
12
ph S C
3C C
C C 3C
26
? ? ? ? 
3) Any one of core is connected to sheath & capacitance is 
 measured between remaining 2 cores. 
               
CS
3
3C C
C
22
??
 
               
ph 3
C 2C ?
 
 
 
 
 
 
 
 
 
 
 
Dielectric loss in a UG cable 
                
2
ph ph
P 3 C V tan ? ? ?            
   where tan loss tangent ?? 
                
ph
1
tan
cR
??
?
 
                 R = Insulation resistance 
            
              
             
              
             
            
                                              
 
  
  
 
 
 
 
 
 
 
 
Read More
69 docs

Top Courses for Electrical Engineering (EE)

69 docs
Download as PDF
Explore Courses for Electrical Engineering (EE) exam

Top Courses for Electrical Engineering (EE)

Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Related Searches

Exam

,

Sample Paper

,

Short Notes: Underground Cables | Short Notes for Electrical Engineering - Electrical Engineering (EE)

,

Important questions

,

video lectures

,

Summary

,

Extra Questions

,

past year papers

,

mock tests for examination

,

Free

,

study material

,

Short Notes: Underground Cables | Short Notes for Electrical Engineering - Electrical Engineering (EE)

,

Previous Year Questions with Solutions

,

Viva Questions

,

pdf

,

Objective type Questions

,

MCQs

,

ppt

,

Short Notes: Underground Cables | Short Notes for Electrical Engineering - Electrical Engineering (EE)

,

Semester Notes

,

shortcuts and tricks

,

practice quizzes

;