ELECTRO MECHANICAL Co. LLC.

ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

PROTECTION RELAY SETTING STUDY FOR NEW 11KV SWITCHGEAR

BUILDING AT MUSSAFAH SUBSTATION

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

1. INDEX

1. INDEX..................................................................................................................................... 2

2. INTRODUCTION.................................................................................................................... 3

3. REFERENCE DOCUMENTS..................................................................................................4

4. DATA...................................................................................................................................... 5
4.1 Network Data.................................................................................................................... 5

5. Setting calculation STUDY...................................................................................................7

5.1 11kV CABLE FEEDER.....................................................................................................7
5.1.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)................7
5.2 11/0.433kV TRANSFORMER FEEDER.........................................................................10
5.2.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)..............10
5.3 11kV CAPACITOR BANK FEEDER...............................................................................13
5.3.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)..............13
5.4 11kV BUS SECTION......................................................................................................16
5.4.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)..............16
5.5 11kV BUS INTERCONNECTOR....................................................................................17
5.5.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)..............17
5.6 11kV INCOMING TRANSFORMER FEEDER................................................................19
5.6.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)..............19

6. Final Relay Setting Table :....................................................................................................21

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

2. INTRODUCTION

 The Scope of this document is to provide a guide for Protection relay

setting.

 O/C and E/F relay setting is calculated considering that only one
transformer is feeding the fault current for outgoing cable feeders,
capacitor feeders and station transformer feeders in case -1.

 Based on above time multiplier setting operating time of the O/C & E/F
relay is calculated when two transformer in parallel in case-2.

 O/C & E/F relay operating time for all cable feeders and capacitor
bank feeders shall be kept at 0.5 Sec.

 O/C & E/F relay operating time for station Transformer shall be kept at
0.2 Sec.

 O/C relay operating time for bus-section shall be kept at 0.8 Sec (Time
grading of 0.3 Sec with outgoing feeders). E/F relay shall be kept OFF.

 O/C & E/F relay operating time for bus Inter-connector shall be kept at
0.8 Sec and 0.6 Sec

 O/C relay operating time for Incomers shall be kept at 1.1 Sec. (Time
grading of 0.3 Sec with bus-section and bus Inter-connector)

 E/F relay operating time for Incomers shall be kept at 0.8 Sec.

 Normal Inverse characteristics curve shall be selected for O/C & E/F
protection.

 High set for O/C and E/F protection for bus-section, bus Inter-
connector and Incomers shall be kept OFF.

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

3. REFERENCE DOCUMENTS

-11kV Single Line Diagram

-11kV Substation Layout

-Siemens Publication : Protection and Substation Control Systems and

Individual Protection relay manuals
-VATECH Publication : Argus1 – DCD125A Restricted E/F Protection relay

DAD-N Busbar Protection relay

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
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RELAY SETTING STUDY

4. DATA

The values below were used for calculation purposes:

4.1 NETWORK DATA

Sr. No. Description Remark

1 Transformer MVA Rating 40 MVA
2 Transformer Voltage Ratio 132/11KV
3 Transformer Percentage Impedance 17.5 %
4 Earthing Reactor Percentage Impedance 0.25 
5 Maximum Three Phase 11kV Busbar Fault Current 31.5KA
6 Full Load 11kV current of 132/11kV Transformer 2100A
Maximum Three phase fault current for one
7 12KA
transformer
8 Maximum single phase-earth fault current 6.925KA
Maximum single phase-earth fault current with earthing
9 6.848KA
reactor connected
Maximum Three phase fault current when two
9 24KA
transformer in parallel
Maximum single phase-earth fault current when two
10 13.852KA
transformer in parallel
Maximum single phase-earth fault current when two
11 13.696KA
transformer in parallel with earthing reactor connected.

FAULT CURRENT WITH ONE 40MVA TRANSFORMER

Maximum three phase 11kV through fault current for one Transformer:

If = 40MVA /1.732*11KV*0.175 If = 12KA

Maximum single phase-earth through fault current for one Transformer:

Ief = 40MVA /3*11KV*0.175 Ief = 6.926KA

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
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RELAY SETTING STUDY

Maximum single phase-earth through fault current with earthing

reactor :

Ief = 40MVA /3*11KV*0.177 Ief = 6.848KA

FAULT CURRENT WITH TWO 40MVA TRANSFORMER IN PARALLEL :

Maximum three phase 11kV through fault current when two 40 MVA
132/11KV transformer in parallel.

If = 24KA

Maximum single phase-earth through fault current when two 40 MVA

132/11KV transformer in parallel.

Ief = 13.852KA

Maximum single phase-earth through t fault current when two 40 MVA

132/11KV transformer in parallel with earthing reactor connected.

Ief = 13.696KA

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

5. SETTING CALCULATION STUDY

5.1 11KV CABLE FEEDER

5.1.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)

The relay type 7SJ612 is intended to be used for three phase over current and
earth protection.

Relay operating time will be kept at 0.5 Sec at maximum fault current considering
that only one transformer is feeding the fault.

Relay operating time when two transformer in parallel is calculated at selected time
multiplier setting with one transformer feeding the fault current.

Technical data:
Available CT Ratio : 600-400/1
Selected CT Ratio : 400/1
Bay nominal current Ipr = 400A

Case-1 :
Time Multiplier Setting Calculation considering one transformer is feeding the
fault current :

Overcurrent Setting:

Bay Nominal Current Ipr = 400A

Plug Setting Ip= 1.0A

Characteristic: Standard Inverse

Operating Time t = 0.5 Sec

Fault Current If =12000A

0.5 = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
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RELAY SETTING STUDY

0.5 = 0.14*Tp/((12000/400*1)0.02 –1)

Tp = 0.251

Set Tp (at 12kA) = 0.25

Earth Fault Setting:

Plug Setting Iep = 0.2 A

Fault Current Ief = 6848 A

Characteristics : Standard Inverse

Operating Time t = 0.5 Sec

Characteristic: Standard Inverse

0.5 = 0.14*Tep/((Ief/Ipr*Iep)0.02 –1 )

0.5 = 0.14*Tep/((6848/400*0.2)0.02 –1

Tep = 0.332 sec

Set Tep (at Ief = 6.848kA) = 0.33

Case-2 :
Operating time calculation of over current and earth fault relay at above
selected time multiplier setting (Tp and Tep) when two 40MVA transformer in
parallel.

Over Current Protection :

Bay Nominal Current Ipr = 400A

Plug Setting = 1.0A

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RELAY SETTING STUDY

Time Multiplier Setting Tp = 0.25

Fault Current If = 24KA

Characteristics : Standard Inverse

Relay operating Time t = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

Relay operating Time t = 0.14*0.25/((24000/400*1)0.02 –1)

Relay operating Time t = 0.41 Sec

Earth Fault Protection :

Bay Nominal current = 400A

Plug setting = 0.2A

Time Multiplier setting = 0.33

Fault Current = 13.696KA

Characteristics : Standard Inverse

Relay operating Time t = 0.14*Tep/((Ief/Ipr*Iep)0.02 –1 )

Relay operating Time t = 0.14*0.33/((13696/400*0.2)0.02 –1

Relay operating Time t = 0.426 Sec

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
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RELAY SETTING STUDY

5.2 11/0.415KV TRANSFORMER FEEDER

5.2.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)

The relay type 7SJ612 is intended to be used for three phase over current and
earth protection.

Relay operating time will be kept at 0.2 Sec at maximum fault current considering
that only one transformer is feeding the fault.

Relay operating time when two transformer in parallel is calculated at selected time
multiplier setting with one transformer feeding the fault current.

Technical data:

Available CT Ratio : 150-50/1

Selected CT Ratio : 50/1
Station Transformer Full Load Current = 33 A
Bay nominal current Ipr = 1.2 * 33 =39.6A

Case-1 :
Time Multiplier Setting Calculation considering one transformer is feeding the
fault current :

Overcurrent Setting:

Bay Nominal Current Ipr = 39.6A

Plug Setting Ip=0.80 A

Characteristic: Standard Inverse

Operating Time t = 0.2 Sec

Fault Current If =12000A

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RELAY SETTING STUDY

0.2 = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

0.2 = 0.14*Tp/((12000/50*.8)0.02 –1)

Tp = 0.172

Set Tp (at 12kA) = 0.17

Earth Fault Setting:

Plug Setting Iep = 0.2 A

Fault Current Ief = 6848 A

Characteristics : Standard Inverse

Operating Time t = 0.2 Sec

Characteristic: Standard Inverse

0.2 = 0.14*Tep/((Ief/Ipr*Iep)0.02 –1 )

0.2 = 0.14*Tep/((6848/50*0.2)0.02 –1

Tep = 0.199 sec

Set Tep (at Ief = 6.848kA) = 0.20

Case-2 :
Operating time calculation of over current and earth fault relay at above
selected time multiplier setting (Tp and Tep) when two 40MVA transformer in
parallel.

Over Current Protection :

Bay Nominal Current Ipr = 39.6A

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
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RELAY SETTING STUDY

Plug Setting = .80 A

Time Multiplier Setting Tp = 0.17

Fault Current If = 24KA

Characteristics : Standard Inverse

Relay operating Time t = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

Relay operating Time t = 0.14*0.17/((24000/50*.8)0.02 –1)

Relay operating Time t = 0.174 Sec

Earth Fault Protection :

Bay Nominal current = 39.6A

Plug setting = 0.2A

Time Multiplier setting = 0.20

Fault Current = 13.696KA

Characteristics : Standard Inverse

Relay operating Time t = 0.14*Tep/((Ief/Ipr*Iep)0.02 –1 )

Relay operating Time t = 0.14*0.20/((13696/50*0.2)0.02 –1

Relay operating Time t = 0.180 Sec

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

5.3 11KV CAPACITOR BANK FEEDER

5.3.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)

The relay type 7SJ612 is intended to be used for three phase over current and
earth protection.

Relay operating time will be kept at 0.5 Sec at maximum fault current considering
that only one transformer is feeding the fault.

Relay operating time when two transformer in parallel is calculated at selected time
multiplier setting with one transformer feeding the fault current.

Technical data:
Available CT Ratio : 1200-800/1
Selected CT Ratio : 800/1
Bay nominal current Ipr = 800A

Case-1 :
Time Multiplier Setting Calculation considering one transformer is feeding the
fault current :

Overcurrent Setting:

Bay Nominal Current Ipr = 800A

Plug Setting Ip= 1.0A

Characteristic: Standard Inverse

Operating Time t = 0.5 Sec

Fault Current If =12000A

0.5 = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
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RELAY SETTING STUDY

0.5 = 0.14*Tp/((12000/800*1)0.02 –1)

Tp = 0.198

Set Tp (at 12kA) = 0.19

Earth Fault Setting:

Plug Setting Iep = 0.2 A

Fault Current Ief = 6848 A

Characteristics : Standard Inverse

Operating Time t = 0.5 Sec

Characteristic: Standard Inverse

0.5 = 0.14*Tep/((Ief/Ipr*Iep)0.02 –1 )

0.5 = 0.14*Tep/((6848/800*0.2)0.02 –1

Tep = 0.278 sec

Set Tep (at Ief = 6.848kA) = 0.28

Case-2 :
Operating time calculation of over current and earth fault relay at above
selected time multiplier setting (Tp and Tep) when two 40MVA transformer in
parallel.

Over Current Protection :

Bay Nominal Current Ipr = 800A

Plug Setting = 1.0A

Time Multiplier Setting Tp = 0.19

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RELAY SETTING STUDY

Fault Current If = 24KA

Characteristics : Standard Inverse

Relay operating Time t = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

Relay operating Time t = 0.14*0.19/((24000/800*1)0.02 –1)

Relay operating Time t = 0.377 Sec

Earth Fault Protection :

Bay Nominal current = 800A

Plug setting = 0.2A

Time Multiplier setting = 0.28

Fault Current = 13.696KA

Characteristics : Standard Inverse

Relay operating Time t = 0.14*Tep/((Ief/Ipr*Iep)0.02 –1 )

Relay operating Time t = 0.14*0.28/((13696/800*0.2)0.02 –1

Relay operating Time t = 0.421 Sec

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

5.4 11KV BUS SECTION

5.4.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)

The relay type 7SJ612 is intended to be used for three phase over current and
earth protection.

Relay operating time will be kept at 0.8 Sec at maximum fault current considering
time grading of 0.3 Sec with outgoing feeders.

Technical data:
Available CT Ratio : 2500/1
Selected CT Ratio : 2500/1
Bay nominal current Ipr = 2500A

Overcurrent Setting:

Bay Nominal Current Ipr = 2500A

Plug Setting Ip= 1.0A

Characteristic: Standard Inverse

Operating Time t = 0.8 Sec

Fault Current If =12000A

0.8 = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

0.8 = 0.14*Tp/((12000/2500*1)0.02 –1)

Tp = 0.182

Set Tp (at 12kA) = 0.18

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

5.5 11KV BUS INTERCONNECTOR

5.5.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)

The relay type 7SJ612 is intended to be used for three phase over current and
earth protection.

Relay operating time will be kept at 0.8 Sec at maximum fault current considering
time grading of 0.3 Sec with outgoing feeders.

Technical data:
Available CT Ratio : 2500/1
Selected CT Ratio : 2500/1
Bay nominal current Ipr = 2500A

Overcurrent Setting:

Bay Nominal Current Ipr = 2500A

Plug Setting Ip= 1.0A

Characteristic: Standard Inverse

Operating Time t = 0.8 Sec

Fault Current If =12000A

0.8 = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

0.8 = 0.14*Tp/((12000/2500*1)0.02 –1)

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

Tp = 0.182

Set Tp (at 12kA) = 0.18

Earth Fault Setting:

Plug Setting Iep = 0.2 A

Fault Current Ief = 6848 A

Characteristics : Standard Inverse

Operating Time t = 0.6 Sec

Characteristic: Standard Inverse

0.6= 0.14*Tep/((Ief/Ipr*Iep)0.02 –1 )

0.6 = 0.14*Tep/((6848/2500*0.2)0.02 –1

Tep = 0.230 sec

Set Tep (at Ief = 6.848kA) = 0.23

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

5.6 11KV INCOMING TRANSFORMER FEEDER

5.6.1 OVERCURRENT & EARTH FAULT PROTECTION 7SJ612 (SIEMENS)

The relay type 7SJ612 is intended to be used for three phase over current and
earth protection.

Relay operating time will be kept at 1.1 Sec for over current protection and 0.8 Sec
earth fault protection at maximum fault current considering time grading of 0.3 Sec
with bus section.

Technical data:
Available CT Ratio : 2500-2000/1
Selected CT Ratio : 2500/1
Bay nominal current Ipr = 2500A

Overcurrent Setting:

Bay Nominal Current Ipr = 2500A

Plug Setting Ip= 1.0A

Characteristic: Standard Inverse

Operating Time t = 1.1 Sec

Fault Current If =12000A

1.1 = 0.14*Tp/((If/Ipr*Ip)0.2 -1)

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
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RELAY SETTING STUDY

1.1 = 0.14*Tp/((12000/2500*1)0.02 –1)

Tp = 0.250

Set Tp (at 12kA) = 0.25

Earth Fault Setting:

Plug Setting Iep = 0.2 A

Fault Current Ief = 6848 A

Characteristics : Standard Inverse

Operating Time t = 0.8 Sec

Characteristic: Standard Inverse

0.8= 0.14*Tep/((Ief/Ipr*Iep)0.02 –1 )

0.8 = 0.14*Tep/((6848/2500*0.2)0.02 –1

Tep = 0.307 sec

Set Tep (at Ief = 6.848kA) = 0.31

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
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RELAY SETTING STUDY

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022
ELECTRO MECHANICAL Co. LLC. ADWEA
Agent for SIEMENS AG G-1456

RELAY SETTING STUDY

6. FINAL RELAY SETTING TABLE :

O/C and E/F Relay in 11KV Switchgear :

Time
Plug High Set Time Setting
Sr. No. Feeder Type CT Ratio Multiplier
Setting Setting for High Set
Setting
P/F : 1.00 P/F : 0.25 P/F : 8A P/F : 0 Sec
1 Cable Feeder 600-400/1
E/F : 0.20 E/F : 0.33 E/F : 6A E/F : 0 Sec
P/F : 1.00 P/F : 0.19 P/F : 8A P/F : 0 Sec
2 Capacitor Feeder 1200-800/1
E/F : 0.20 E/F : 0.28 E/F : 6A E/F : 0 Sec
P/F : 0.80 P/F : 0.17 P/F : 8A P/F : 0 Sec
3 Station Tr. Feeder 150-50/1
E/F : 0.20 E/F : 0.20 E/F : 6A E/F : 0 Sec
P/F : 1.00 P/F : 0.18 P/F : OFF P/F : OFF
4 Bus-Section 2500/1
E/F : OFF E/F : OFF E/F : OFF E/F : OFF
P/F : 1.00 P/F : 0.18 P/F : OFF P/F : OFF
5 Bus Inter-connector 2500/1
E/F : 0.20 E/F : 0.23 E/F : OFF E/F : OFF
P/F : 1.00 P/F : 0.25 P/F : OFF P/F : OFF
6 Incomer 2500-2000/1
E/F : 0.20 E/F : 0.31 E/F : OFF E/F : OFF

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CSD NO 1456 EA 7500 Z 101 A 9/3/2022