Date: 02/06/2024
Time: 11:00:45
Ref.No.
Revision 0
CT & PT SIZING CALCULATION
Date 01.02.24
Client
Consultant Senthur Power Services PVT LTD
Project 10 MW POWER PLANT.
SYSTEM DETAILS
Generator Rating 10.5 MW Generator PF 0.8
Generator Voltage : 11 KV Generator FLC : KW 10500 = 10500 688.90405206802
Ö3VCosF (1.732*11*0.8) 15.2416
Generator FLC 688.904052068 Amps
After 25% of Over ucrrent 861.130065085 Amps
Hence the Selected CT ratio will be 1000/1-1 Amps.
References :
1. Secquer Meter Catalogue
2. MICOM Relay manual
1. TIE CB -1 TG Bulding Metering
Sl. Description PT Circuit (PT1: Core-1) Metering core
No. Burden in VA Qty Total Burden in VA
1 Ammeter - - -
2 Voltmeter 1.5 1 1.5
3 Digital Frequency Meter 1 1 1
4 Digital TVM Meter 2 1 2
5
6
7
8 Double Voltmeter 2 1 2
9 Double Frequency Meter 2 1 2
10 0
14 0
15 Synchroscope 3 1 3
16 Autosynchroniser 0.2 1 0.2
17 Check Synchronising Relay 2.5 1 2.5
18 No Volt Relays 3 2 6
19 PT Fuse failure 11 1 11
20 PQM Meter 2 1 2
Total Burden 33.2
2. AVR Panel
Sl. Description CT Circuit (CT 6.1-6.3) Metering Core PT Circuit (PT2: Core-1)
No. Burden in VA Qty Total Burden in VA Burden in VA Qty Total Burden in VA
1 Voltmeter - - - 2 1 2
2 PF Meter 1 1 1 1 1 1
3 AVR Droop Ckt. 5 2 10 - - -
4 AVR Cards - - - 10 2 20
Total Burden 11 23
3. Generator Relay Panel (GRP)
3.1 Generator Protection Relay(GPR-1 & GPR-2)
Sl. Description CT Circuit (CT 7.1-.3) Protection core
No. Burden in VA Qty Total Burden in VA
1 Multifunction relay(G60-1) 0.2 1 0.2
Total Burden 0.2
Sl. Description CT Circuit (CT 8.1-3 ) Protection core
No. Burden in VA Qty Total Burden in VA
Prepared by Approved by.
Page 1 of 4
VINAY MOHAN PATHI
Date: 02/06/2024
Time: 11:00:45
Ref.No.
Revision 0
CT & PT SIZING CALCULATION
Date 01.02.24
Client
Consultant Senthur Power Services PVT LTD
1 Multifunction relay(G60-2) 0.2 1 0.2
Total Burden 0.2
Sl. Description CT Circuit (CT 4.1-3) Protection core
No. Burden in VA Qty Total Burden in VA
1 Multifunction relay(G60-2) 0.2 1 0.2
Total Burden 0.2
Sl. Description CT Circuit (CT 5.1-3 ) Protection core
No. Burden in VA Qty Total Burden in VA
1 Multifunction relay(G60-1) 0.2 1 0.2
Total Burden 0.2
Sl. Description CT Circuit (CT 2) Protection core
No. Burden in VA Qty Total Burden in VA
1 Multifunction relay(G60-2) 0.2 1 0.2
Total Burden 0.2
Sl. Description CT Circuit (CT 3 ) Protection core
No. Burden in VA Qty Total Burden in VA
1 Multifunction relay(G60-1) 0.2 1 0.2
Total Burden 0.2
Sl. Description PT Circuit (PT1 : Core-2) Protection Core
No. Burden in VA Qty Total Burden in VA
1 Multifunctional Relay (G60-1) 0.25 1 0.25
Total Burden 0.25
Sl. Description PT Circuit (PT2 : Core-2) Protection Core
No. Burden in VA Qty Total Burden in VA
1 Multifunctional Relay(G60-2) 0.25 1 0.25
2 Directional Earthfault Relay(67N) 2 1 2
Total Burden 2.25
3.2. Directional Earth fault Relay(67N)
Sl. Description CT Circuit (CBCT-1) Protection core
No. Burden in VA Qty Total Burden in VA
1 Directional Earthfault Relay(67N) 2 1 2
Total Burden 2
3.3.Restricted Earth Fault (64R)
Sl. Description CT Circuit (CBCT-2) Protection core
No. Burden in VA Qty Total Burden in VA
1 Restricted Earth fault Relay(64R) 3 1 3
Total Burden 3
Sl. Description CT Circuit (CT 1) Protection core
No. Burden in VA Qty Total Burden in VA
1 Restricted Earth fault Relay(64R) 3 1 3
Total Burden 3
4. Tri Vector meter (TVM)
Sl. Description CT Circuit (CT 9.1-3 ) metering core PT circuit (PT3:core-1 )metering core
No. Burden in VA Qty Total Burden in VA Burden in VA Qty Total Burden in VA
1 Tri Vector Meter 1 1 1 1.5 1 1.5
Total Burden 1 1.5
Prepared by Approved by.
Page 2 of 4
VINAY MOHAN PATHI
Date: 02/06/2024
Time: 11:00:45
Ref.No.
Revision 0
CT & PT SIZING CALCULATION
Date 01.02.24
Client
Consultant Senthur Power Services PVT LTD
5. Tri Vector meter (TVM) - 3.3kV SWITCHBOARD
Sl. Description CT-2,3,4&5 metering core PT circuit (BPT:core-1 )metering core
No. Burden in VA Qty Total Burden in VA Burden in VA Qty Total Burden in VA
1 Tri Vector Meter 1 1 1 1.5 5 7.5
Total Burden 1 7.5
CT BURDEN CAL. BURDEN SELECTED BURDEN
Total Burden on Phase side CT-1 ((64R) 3VA 20VA,CL: 5P20
Total Burden on CT 2 (MICOM P343-2) :0.2 VA 20VA,CL: 5P20
Total Burden on CT 3 (MICOM P343-1) :0.2 VA 20VA,CL: 5P20
Total Burden on Phase side CT 6.1-6.3(AVR) :11 VA 20VA,CL: 0.2
Total Burden on Phase side CT 7.1-3 (G60-2) :0.2 VA PS CLASS
Total Burden on Phase side CT 8.1-3 (G60-1) :0.2 VA PS CLASS
Total Burden on Phase side CT 9.1-3 (TVM) :1VA 10VA CL: 0.2
Total Burden on Phase side CBCT-1(67N) :2 VA 20VA CL: 5P20
Total Burden on Phase side CBCT-2 (64R) :3VA 20VA CL: 5P20
PT BURDEN CAL. BURDEN SELECTED BURDEN
Total Burden on PT1: Core-1 ( Metering Core) :48.2VA 50VA, CL. 0.2
Total Burden on PT1: Core-2 ( Protection core-G60-1) :0.25VA 50VA, CL. 3P
Total Burden on PT2: Core-1 (AVR)( Metering Core) :23VA 50VA, CL. 0.2
Total Burden on PT2: Core-2 ( Protection-G60-2) :2.25VA 50VA, CL. 3P
Total Burden on PT3: Core-1 (TVM)(Metering Core) :1.5VA 50VA, CL. 0.2
Total Burden on PT3: Core-2 Spare - 50VA, CL. 0.2
Prepared by Approved by.
Page 3 of 4
VINAY MOHAN PATHI
Ref.No.
KNEE POINT VOLTAGE CALCULATION Revision 0
Date 09.02.22
User M/s.
Consultant M/s. Senthue Power Services PVT LTD
Project 1X10.5 MW POWER PLANT.
SYSTEM DETAILS
Generator Rating : 10.5 MW
Generator Voltage : 11 KV
Generator PF : 0.8
Generator FLC : 688.90 Amps
Sub transient reactance Xd" : 19.1 % 0.191 p.u. (Assumed)
CT winding resistance Rct : 4 Ohms
Primary CT current : 1000 Amps
Secondary CT current : 1 Amps
or Cable consider
resistance RL : 0.87 ohms ed 100M 8.7 Ohms/KM
Internal resistance of Relay Rp : 0.2 ohms
CT Knee point voltage primary side Vkp = 2*If*.(Rct+RL+Rp)
If = 40000 A
= 40.000 kA (System fault level)
If(sec) = If(pri)/CT ratio
= 40.000 Amps
CT Knee point voltage Vkp = 2*If*.(Rct+RL+Rp)
= 405.6 Volts
Selected Vkp = 250V. Hence safe.
