c-5 insulation resistance calculations

8/9/2019 C-5 Insulation Resistance Calculations

1/43

Insulation ResistanceCalculations of Aireld Lighting

Circuits

35TH

ANNUAL HERSHEY CN!ERENCE

"ose#h $igilante% &E


2/43

&resentation '(ecti)e

To develop a formula to calculate insulation resistance

for an airfield lighting circuit and provide theoretical

and real-life examples.


3/43

&resentation Agenda

Cable insulation resistance (IR) background

!! IR guideline recommendations

ormula development

!irfield lighting circuit calculations "ummar#

$pen %&!


4/43

Anato*+ of insulation current ,o-

Capacitance charging currents' C

!bsorption current' RA

Conduction current' RL

Circuit model

C $*T!+,"$RC,

R!

C

R*

"


5/43


CURREN

T -

MIC

ROA

MPE

RES

10

0

90

80

70

60

50

40

30

25

20

15

10

9

8

7

6

5

4

3

2.5

2

1.5

1

0.1 0 .15 0 .2 0.2

5

0.3 0.4 0.

5

0.

6

0.

7

0.

8

0.

9

1.

0

1.5 2 2.5 3 4 5 6 7 8 9 10

SECONDS

CAPACITANCE CHARGING CURRENT


6/43


CURREN

T -

MIC

ROA

MPE

RES

10

0

90

80

70

60

50

40

30

25

20

15

10

9

8

7

6

5

4

3

2.5

2

1.5

1

0.1 0 .15 0 .2 0.2

5

0.3 0.4 0.

5

0.

6

0.

7

0.

8

0.

9

1.

0

1.5 2 2.5 3 4 5 6 7 8 9 10

SECONDS

C!!CIT!/C, C0!R+I/+ CRR,/T

ABSORPTION

CURRENT


7/43


CURREN

T -

MIC

ROA

MPE

RES

10

0

90

80

70

60

50

40

30

25

20

15

10

9

8

7

6

5

4

3

2.5

2

1.5

1

0.1 0 .15 0 .2 0.2

5

0.3 0.4 0.

5

0.

6

0.

7

0.

8

0.

9

1.

0

1.5 2 2.5 3 4 5 6 7 8 9 10

SECONDS


!1"$RTI$/

CRR,/T

CONDUCTION

CURRENT


8/43


CURREN

T -

MIC

ROA

MPE

RES

10

0

90

80

70

60

50

40

30

25

20

15

10

9

8

7

6

5

4

3

2.5

2

1.5

1

0.1 0 .15 0 .2 0.2

5

0.3 0.4 0.

5

0.

6

0.

7

0.

8

0.

9

1.

0

1.5 2 2.5 3 4 5 6 7 8 9 10

SECONDS


TOTAL

CURRENT

!1"$RTI$/

CRR,/T

C$/CTI$/

CRR,/T


9/43

T+#es of insulation resistance testing

"hort-time2spot reading

3 TI4, 53 sec

4,+$04

"

!*, R,! !/

R,C$R,

TI4, (4$/T0")

4,+$04"

!*," C0!RT,


10/43

T+#es of insulation resistance testing

Time-resistance method

3 TI4, 63 4in

4,+$04

"

I/"*!TI$/

"",CT

I/"*!TI$/R$1!1*7 $8


11/43

Testing aireld lighting circuits

!C 69329:;3-:3' Design & Installation Details for

Airport Visual Aids - Chapter 66' Installation & Splicing of Underground

a!le


12/43

Resistance )alues for *aintenance

!C 69329:;3-


13/43

!AA.C./30/ Installation 1 S#licing ofUnderground Ca'les

"pot Test= Take readings no less than 6 minute after readings

stabili?ed

Cable IR values @ 934A' ;34A & :34A

*oop IR reduced due to parallel summation

Cable IR never less than above values


14/43

Insulation resistance for*ula

Constant current series lighting circuit= rovides for parallel summation of circuit components

: components= *-B


15/43

!AA *ini*u* IR )alues

*-B


16/43


*-B


17/43


*-B:3 isolation transformers= !C 69329:;9-;C' Specification for

Series to Series Isolation Transformers

for Airport )igting S0stems

= Table : Insulation Resistance '933 4A


18/43

2ase for*ula

#1I/ 2 #1/ ( #1/3 ( #1/T

RT RN RC

I

VIR


19/43

Ca'le euation

The insulation resistance of cable for a certain length canbe calculated b# the folloGing formulaH

4ere5 RC @ Insulation resistance in 4egohms of cable

8 @ "pecific IR in 4egohms - k ft at 53 of insulation

@ $uter diameter of insulation

d @ $uter diameter of bare copper Gire

* @ *ength of airfield cable in feet

alue of 8 for ,R insulation @ 93'333 4egohms


20/43

Ca'le euation

JACKET

INSULATION

CONDUCTOR

OD

D d

@ >.6B mm

d@ ;.9B mm


21/43

Ca'le euation

RC @ 93'333 4A-k ft J *og ( >.6B2;.9B) J (6'3332*)

RC @ 69'3>B'B53 4A 2 *


22/43

Connector euation

The insulation resistance of *-B


23/43

Isolation transfor*er euation

The insulation resistance of *-B:3 isolationtransformers can be calculated b# the folloGing

formulaH

/T 2 /t13t4ere5

RT @ Insulation resistance in 4egohms of all transformers

Rt @ Insulation resistance of *-B:3 isolation transformers

/t @ %uantit# of *-B:3 isolation transformers

/T 2 6,7$$M13t


24/43

2ase for*ula

RT RN RC

I

V

M

I/

#1I/ 2 #1/ ( #1/3 ( #1/T


25/43

4e)elo#ing IR calculation for*ula

*-B


26/43

"ection 6 "ection

c-5 insulation resistance calculations

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