In
this theory, formula for capacitance of three core to core cable and core to
sheath is given.

# Capacitance of Three Core Belted Cable

- Let us consider the three-core belted cable.
- As there is potential difference exists between core to core of cable and core to sheath of cable, electrostatic field set up between them.
- There is
core to core capacitance C
_{c}and core to sheath capacitance C_{e}exists in the three-core cable. - The core-to-core capacitance is delta connected whereas core to sheath capacitance is star connected.

Core to core capacitance = C_{c }and Core to sheath capacitance = C_{e}

- The three cores to core delta connected capacitance is converted into equivalent star connection.

_{eq}= 3C

_{c}

- Where C
_{eq}= Equivalent star connection of delta connected core to core capacitance - Therefore, the total capacitance is equal to parallel combination of core to sheath capacitance and equivalent star connection of core-to-core capacitance of cable. The capacitance between core to neutral
- C
_{N}= C_{e}+ C_{eq}= C_{e}+ 3C_{c}

_{Measurement of capacitance of cable Three Cores Bunched Together The three cores of cable are bunched together and capacitance is measured between cores and sheath of cable. As the three cores are bunched together, there is no capacitance between cores. There exists capacitance between core and sheath Ce which are in parallel. Let us consider that this capacitor is C1 therefore C1 = 3Ce Ce = C1 / 3…….. ( 1 )}

### Capacitance Between Two Cores Is Measured with Third Core Connected to The Sheath

- The capacitance between two cores is measured with the third core connected to the sheath.
- This eliminated one core
to sheath capacitance. Let us consider that this capacitance is C
_{2}.

C_{2} = C_{c} + C_{c}
/ 2 + C_{s} / 2

= ( C_{c} + C_{c}
/ 2 ) + C_{s} / 2

= ( 3C_{c} / 2 ) + C_{s} / 2

= ½ ( 3C_{c} + C_{s} )

= ½ C_{N}

### Capacitance Between Two Cores Shorted with The Sheath and Third Core

Let us consider that this capacitor
is equal to C_{3}.

C_{3 }= 2C_{c} + C_{s}

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