PANEL MANUFACTURER: SEP CONTRACTOR:CAPTIAL LIGHTS CO.
CERT'D
AP
APPR'D
KR
CHK'D
MD
13.8KV CT ADEQUACY CALCULATION
Upgrading Protection System in Madinah Network
UPGRADING OVER CURRENT PROTECTION AT MEDSO SUBSTATION
TYPICAL FEEDERS:AH01,AH02,AH03,AH04,AH08,AH09,AH10,AH11,AH12,
AH16,AH17,AH18,AH19,AH20,AH21,AH22,AH23,AH24,AH25,AH26,AH30,AH3
ISSUED FOR BASE DESIGN
1,AH32,AH33,AH34,AH35,AH36,AH37,AH38
DESCRIPTION
CT DATA FOR OUTGOING FEEDER OC&EF
600-300/1A
CLASS:5P20, Rct=2.967Ω, VK=655V, 30VA
SHF
BY
SEPT.2021
DATE
NO.
REVISIONS
DRAWN
BY:- JS
DATE:-
CHECKED
BY:- MD
DATE:-
OPRG. DEPT
BY
DATE:-
ENG'G. DEPT.
BY:-
DATE:-
CERTIFIED.
BY:-
DATE:-
AS BUILT BY DATE
DRAWING TITLE INDEX PLANT DRAWING NO. SHEET NO. REV NO.
THIS DRAWING IS NOT TO BE
USED FOR CONSTRUCTION 13.8KV CT ADEQUACY CALCULATION
OF FOR ORDERING
MATERIALS UNTIL CERTIFIED UPGRADING OVER CURRENT PROTECTION AT MEDSO SUBSTATION X CE-XXXXXX 01 OF 04 A
AND DATED
RIYADH SAUDI ARABIA JOB ORDER NO. DWG. CONT. SHT.
PANEL MANUFACTURER: SEP
CONTRACTOR:CAPTIAL LIGHTS CO.
CERT'D
AP
APPR'D
KR
1 SYSTEM PARAMETERS
CHK'D
MD
Nominal Voltage : 13.8 kV
Max. SC current capacity : 25 kA
System frequency : 60 Hz
System time constant : 80 ms
Resistivity of the Copper
ρ75 = ρ20 [(1 + α (θ - 20)]
ISSUED FOR BASE DESIGN
DESCRIPTION
where:
ρ20 Resistivity of the copper at 20 deg c = 0.01786 Ωmm2/m
α Cofficient of resistance = 0.00393
ρ75 Resistivity of the copper at 75 deg c = 0.021720439 Ωmm2/m
Copper Prperties
Resitivity of Copper at 20oC, ρ 17.2 nΩm
Temperature Coefficient of Copper, α 0.0039
First Temperature 20 o
C
Second Temperature 75 o
C
Change in Temperature, ∆t 55 o
C
SHF
BY
CT Secondary Cct Cable Data For 4mm2
SEPT.2021
Size
DATE
Area of Cross Section, A 4 mm2
Length of the Conductor 1000 mm
Resistance per 1000 mm at 20 oC, R20 = ρ x l / A 0.0043 Ω
NO.
First Teperature, T1 20 OC
REVISIONS Second Teperature, T2 75 OC
DRAWN Difference in Temperaturwe, ∆t = T2 - T1 55 OC
BY:- Resistance at 75oC, R75 = R20 x ( 1 + α x ∆t ) 0.00522235 Ω
DATE:-
CHECKED
BY:- CT Secondary Cct Cable Data For 10mm2 Size
DATE:- Area of Cross Section, A 10 mm2
OPRG. DEPT Length of the Conductor 1000 mm
BY Resistance per 1000 mm at 20 oC, R20 = ρ x l / A 0.00172 Ω
DATE:- First Teperature, T1 20 OC
ENG'G. DEPT. Second Teperature, T2 75 OC
BY:- Difference in Temperaturwe, ∆t = T2 - T1 55 OC
DATE:- Resistance at 75oC, R75 = R20 x ( 1 + α x ∆t ) 0.00208894 Ω
CERTIFIED.
BY:-
DATE:-
AS BUILT BY DATE
DRAWING TITLE INDEX PLANT DRAWING NO. SHEET NO. REV NO.
THIS DRAWING IS NOT TO BE
USED FOR CONSTRUCTION 13.8KV CT ADEQUACY CALCULATION
OF FOR ORDERING
MATERIALS UNTIL CERTIFIED UPGRADING OVER CURRENT PROTECTION AT MEDSO SUBSTATION P 02 OF 04 A
AND DATED
RIYADH SAUDI ARABIA JOB ORDER NO. DWG. CONT. SHT.
PANEL MANUFACTURER: SEP CONTRACTOR:CAPTIAL LIGHTS CO.
CERT'D
AP
APPR'D
KR
1.1 CT Designation : 50/51/50N/51N
CHK'D
MD
Application : O/C & E/F protection
Relays : 7SJ80 SIEMENS
System Data
System Voltage 13.8 Kv
System Frequency 60 Hz
System fault level 25 kA
Time constant 80 ms
ISSUED FOR BASE DESIGN
20
Accuracy limitig factor (ALF)
DESCRIPTION
132kV SWGR CT
CT Ratio 600-300 A
CT used tap 600 A
Class 5P 20
CT resistance (Rct) 2.967 Ω
CT secondary 1 A
CT knee voltage 655 V
CT Burden 30 VA
Rb = CT Burden / Current2 30 Ω
Cable data
Cable Length (L) 7m (Assumed)
SHF
BY
Size 4 mm2
Lead Resistance per meter 0.005310801 Ω / meter
SEPT.2021
Total Lead Resistance, PL 0.037175607 Ω
DATE
Relay data
NO.
Relay Description Relay Type Make Relay Type
O/C & E/F
REVISIONS 7SJ80 SIEMENS 0.05 VA
protection
DRAWN Rp 0.05 Ohms
BY:-
DATE:-
CHECKED
BY:-
DATE:-
OPRG. DEPT
BY
DATE:- Other Burden 0.00 VA
ENG'G. DEPT.
BY:-
DATE:-
CERTIFIED.
BY:-
DATE:-
AS BUILT BY DATE
DRAWING TITLE INDEX PLANT DRAWING NO. SHEET NO. REV NO.
THIS DRAWING IS NOT TO BE
USED FOR CONSTRUCTION 13.8KV CT ADEQUACY CALCULATION
OF FOR ORDERING
MATERIALS UNTIL CERTIFIED UPGRADING OVER CURRENT PROTECTION AT MEDSO SUBSTATION P 03 OF 04 A
AND DATED
RIYADH SAUDI ARABIA JOB ORDER NO. DWG. CONT. SHT.
PANEL MANUFACTURER: SEP CONTRACTOR:CAPTIAL LIGHTS CO.
CERT'D
AP
APPR'D
KR
CT Calculations:
CRITERION FOR OC & EF RELAY (7SJ80) IN GENERAL
CHK'D
MD
a) K'ssc = Kssc . (Rct + Rb) / (Rct + R'b)
Kssc 20
R'b = Connected Burden =Rlead + Rrelay 0.087175607
Ω
K'ssc = Kssc . (Rct + Rb) / (Rct + R'b)
K'ssc = 20 x (2.967 + 30) / (2.967 + 215.88149629931
0.087175607)
b) K'ssc > Ktd . ISCCmax / Ipn
Ktd N/A
ISCCmax / Ipn 25000/600
41.6666666666667
ISSUED FOR BASE DESIGN
Now, based on the results
DESCRIPTION
K'ssc > Ktd . ISCCmax / Ipn
1
215.88>41.66
Above condition is satisfied, So the CT is suitably sized
Kssc = Rated symmetrical short-circuit current factor
(example: CT cl. 5P20 Kssc = 20)
K’ssc = Effective symmetrical short-circuit current factor
Ktd = Transient dimensioning factor
Issc max = Maximum symmetrical short-circuit current
Ipn = CT rated primary current
Isn = CT rated secondary current
Rct = Secondary winding d.c. resistance at 75 °C / 167 °F
(or other specifi ed temperature)
Rb = Rated resistive burden
R’b = Rlead + Rrelay = connected resistive burden
TP = Primary time constant (net time constant)
Uk = Kneepoint voltage (r.m.s.)
Rrelay = Relay burden
SHF
BY
with
l = Single conductor length from CT to relay in m
ρ = Specifi c resistance = 0.0175 Ωmm2 / m (copper wires)
SEPT.2021
at 20 °C / 68 °F (or other specifi ed temperature)
DATE
A = Conductor cross-section in mm2
C) Vk=((Rct+RBN)*Is NOM/1.3)*KALF V-Kn(V)=655.648V
NO.
(from Relay manufacturer manual formula taken) (Received from CT Test Report)
A
Vk-Knee Point Voltage
REVISIONS Rct-Internal Burden Resistance
DRAWN RBN-Nominal Burden Resistance
BY:- ΙsN-Secondary nominal transformer current
DATE:- KALF-Rated accuracy limiting factor
CHECKED Us.t.max-Sec. terminal voltage at 20 ΙpNom
BY:- Ual-Sec. magnetization limit voltage
DATE:- K-Dimensioning factor
OPRG. DEPT KSSC-Factor symmetr. Rated fault current
BY TP-Primary time constant
DATE:- Vk=((Rct+RBN)*Is NOM/1.3)*KALF Vk=((2.967+30)*1/1.3)*20
ENG'G. DEPT. 507.18
BY:- 655.648V>507.18V 2
DATE:- Above condition is satisfied, So the CT is suitably sized(Adequate)
CERTIFIED. The CT satisfy conditions 1,2
BY:- The CT is suffieiently Dimensioned
DATE:-
AS BUILT BY DATE
DRAWING TITLE INDEX PLANT DRAWING NO. SHEET NO. REV NO.
THIS DRAWING IS NOT TO BE
USED FOR CONSTRUCTION 13.8KV CT ADEQUACY CALCULATION
OF FOR ORDERING
MATERIALS UNTIL CERTIFIED UPGRADING OVER CURRENT PROTECTION AT MEDSO SUBSTATION P 04 OF 04 A
AND DATED
RIYADH SAUDI ARABIA JOB ORDER NO. DWG. CONT. SHT.
PANEL MANUFACTURER: SEP CONTRACTOR:CAPTIAL LIGHTS CO.
CERT'D
AP
APPR'D
KR
Accuracy limit factory Fa should be chosen using the formula:
Fa > 20 * Ipickup ∕ I1n
CHK'D
MD
Where,
I pickup : is the primary pickup current setting of the IED. Is normally from ( 1.5 to 2) In. ,
So, we can consider it 2In is a maximum
I pickup = 1200 A
Fa > 20*Ipickup/In
3
0A > 40 A
The CT satisfy conditions 1,2,3
ISSUED FOR BASE DESIGN
The CT is suffieiently Dimensioned
DESCRIPTION
SHF
BY
SEPT.2021
DATE
NO.
REVISIONS
DRAWN
BY:-
DATE:-
CHECKED
BY:-
DATE:-
OPRG. DEPT
BY
DATE:-
ENG'G. DEPT.
BY:-
DATE:-
CERTIFIED.
BY:-
DATE:-
AS BUILT BY DATE
DRAWING TITLE INDEX PLANT DRAWING NO. SHEET NO. REV NO.
THIS DRAWING IS NOT TO BE
USED FOR CONSTRUCTION 13.8KV CT ADEQUACY CALCULATION
OF FOR ORDERING
MATERIALS UNTIL CERTIFIED UPGRADING OVER CURRENT PROTECTION AT MEDSO SUBSTATION P 01 OF A
AND DATED
RIYADH SAUDI ARABIA JOB ORDER NO. DWG. CONT. SHT.
