1. Mr. Stephen Ho, MM - PD IMD Oct 2011
MTR Protection System Overview
For DUAT Lines
Mr. Stephen Ho,
MM - PD IMD
Oct 2011
4/19/2017

2. MTR 33kV Power Distribution System
Transformer, cable, switchgear, bus-bar, rectifier all need protection devices. 2 10

3. MTR 1.5kV DC Traction Power Supply
DC Protection need to grade with train service loading 2 10

4. MTR Protection in associate with Switchgear2 10

5. MTR Power System Protection
Objectives :
Discriminate and isolate the
faulty power system apparatus
Minimise damage to equipment
Reduce the extent of personnel injuries
Prevent power supply interruption to
other healthy loads. 2 10

6. Protection Philosophy
Reliability
Selectivity
Speed
Sensitivity
Simplicity 2 10

7. Development of Protection Relay
Electro-mechanical
Static
Digital / Numerical
(Protection/ Control/
Metering) 2 10

8. Key System Parameters For Protection Design
Vector Group of Transformers (e.g. Yyd0, Dyn11)
Earthing (solid earth), Transformer Tap (Max/ Min)
Tx Impedance voltage : 5%, 1.5kVA
Fault Level : 3-phase, 25kA at 33kV
20kA at 11kV
40kA at 415V
143kA peak at 1.5kV DC 2 10

9. Protection elements Current & Voltage transformers
Auxiliary DC Power Supply
Multi-cores and panel wirings
Protection Relay /auxiliary / Trip / Timer Relay
CB Trip Coil
Local Indicators / Remote alarms 2 10

10. Protection Scheme Used at MTR
Unit Protection – Clearly define protected zone
Transformer Differential Prot.
Pilot Wire Prot.
Bus-zone protection
LV Restricted earth fault Prot.
Frame Leakage Protection
Directional OC Prot
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11. Protection Scheme Used at MTR
Non-Unit Protection – Not Clearly define protected zone
Over-current & Earth Fault Prot.
Directional Over-current & earth fault Prot.
High set Over-current Prot.
Standby earth fault Prot.
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12. 33kV Power System Protection
Cable Feeder : Pilot wire protection (Main)
IDMTL OC / Directional OC
(Back-up)
Bus-bar : High Impedance Differential
Protection 2 10

13. Unit Protection (Cable Feeder)
Substation B
Pilot Wire
Substation A
Substation B
Pilot Wire Protection
Substation A
Relay
Pilot Wire
Pilot Wire
Relay CT CT
Substation B
Substation A
Substation A
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14. Unit Protection (Cable Feeder)
33kV Cable Fault
Substation A
Substation B
Clear within 140ms
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15. Principle of Translay “S” Protection Relay (LAR and TKL)
Typical static circulating current feeder unit protection circuit diagram
Use summation transformers with a neutral section that is tapped, to provide alternative earth fault sensitivities.
Phase comparators tuned to the power frequency are used for measurement and a restraint circuit gives a high level of stability for through faults and transient charging currents.
Internal faults give simultaneous tripping of relays at both ends of the line, providing rapid fault clearance irrespective of whether the fault current is fed from both line ends or from only one line end.
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16. Directional Over Current Relay applied at MTR
Transformer side fault
Feeder side fault
Feeder
33/11kV R R R
33kV/
11kV
When there have a fault at either transformer side. Current will flow into the fault side from health side. Directional relay will detect the reverse current to trip the CB to clear the fault at a shorten time.
When there have a fault at the transmission line . Current will flow into the fault side from health bar. Directional relay will detect the reverse current to trip the CB to clear the fault at a shorten time.
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17. Principles of Directional Relay
EHV side
Detect the phase angle between current flow (Ia) and voltage (Vbc) whether it is forward or reverse. If fault falls within the operating zone, trip signal will send out.
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18. Directional relay outlook
Over current relay “MCGG52” +
Directional relay “P127” with OC & EF
Applied in TKL and new extensions
Directional relay with O/C “CDD” (single phase only)
Applied in URL
Directional relay “METI” without over current elements
Applied in LAL METI
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19. Unit Protection (Bus-bar)
Incomers
Feeders
Zone 2
Zone 1
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20. Unit Protection (Bus-bar )
Incomers
Feeders
Zone 2
Zone 1
Fault at Zone-2
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21. 33kV Bus Zone Protection Principle
Circulating current arrangement was applied.
This scheme can protect both phase to phase and phase to earth fault.
Operational principles:
If Ig is equal to -Ih, means that it is a through fault, relay will not operate.
If Ig + Ih = If = non-zero, means that the fault is in between protective zone
(Bus-bar), relay will send out trip signal. Ig Ih
Phase and earth fault circulating current scheme using three-element relay
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22. Relay and Accessories of Bus-zone Protection
Tx LV winding
Metrosil
Connection Diagram
MFAC Relay
Shunt Resistor
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23. 33kV Bus-zone Protection Relay at MTR system
Bus Zone Relay “FAC” used at URL
Bus Zone Relay “MFAC” used at LAR & TKL
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24. 11kV Bus Bar Protection Principle
Frame-Earth Leakage Protection is used in 11kV bus-bar systems in MTR.
Current type relay is used to detect the current flow.
Both of Frame earth path and transformer neutral return path have detected current flow. Then, trip signal will be sent out to all CBs within the zone. Otherwise, no signal given out.
Only protect the phase to earth fault.
Single zone frame earth protection
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25. Relay used at 11kV bus-bar protection systems
URL - CAG Relay
LAR - MCGG22 Relay
LAR - MFAG Relay
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26. Power Transformer Protection (33kV AC)
33/11kV Dist Tx : Bias Differential Prot (Main)
LV Restricted E/F (Main)
Buchholz Surge Prot (Main)
Winding/ Oil Temp High Trip
(Back-up)
HV Over-current Prot (Back-up)
LV Standby EF Prot (Back-up) 2 10

27. Type of Distribution Transformer Protection
Fault Type
Protection Used
Primary winding phase-phase fault
Differential and Over Current
Primary winding phase-earth fault
Secondary winding phase-phase fault
Differential
Secondary winding phase-earth fault
Differential and Restricted Earth Fault
Inter-turn fault
Differential and Buchholz
Over-heating
Winding temperature
Tank fault
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28. Transformer Protection
Substation A
Substation B
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29. Transformer Protection
Substation A
Substation B
RE/F
When the Tx. Star winding has a fault, The R E/F relay will be operated to trip the two breakers.
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30. Theory of Transformer differential Protection
It is a circulating current system, red arrow is indicated the direction of secondary current flow.
Normally, no current will flow into the relay except the fault in between both current transformers.
If there have a fault in between both CT, current will flow into to pick up the relay as figure 2.
In MTRC power systems, only Distribution Transformers is applied.
Fault Point
Figure 1. Normal operation current flow in between both CT
Figure 2. Internal Fault in the transformer
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31. Inrush current when start-up the transformer
Magnetizing inrush current containing a higher harmonic component flows, causing mal-operation of relay.
Restraint second harmonic to avoid mal-operation by inrush current.
Contents and current profile as below of inrush current.
Magnetizing Inrush
Internal Fault current
(Unsaturated CT)
1st Cycle
2nd Cycle
3rd Cycle DC
73.7 58
38.8
80.4
Fundamental
100
2nd Harmonic
14.2
16.4
19.9
5.2
3rd Harmonic
8.5
7.7
13.8
3.5
4th Harmonic
5.6
6.5
3.8
2.7
5th Harmonic
1.3
5.9
2.3
Typical Magnetizing inrush waveform
Relative strength of Harmonics in Typical Magnetizing-Inrush and Internal Fault Currents
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32. Bias Restraint characteristic of Static Relay MBCH
In order to avoid unwanted operation due to spill current and yet maintain high sensitivity for internal faults, when the difference current may be relatively small, the variable percentage bias restraint characteristic as below.
Normally, setting is set at 20% ~40% of rated current depending on max tap and CT mismatch.
Percentage bias characteristics
Actual Bias Characteristics
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33. P631 outline and test plugs
Numerical Differential Relay (P631)
Phase shift compensation, ratio correction and zero sequence filter was applied by software.
Used star-connected line CT’s on all winding of transformers CT winding.
Need no interposing CT. all winding connected directly.
P631 was used at ADM, KBD and PAF.
P631 outline and test plugs
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Connection diagram

34. Transformer LV Restricted Earth Fault
It is a unit protection scheme with circulating current system.
The residual current of three line current transformers is balanced against the output of a current transformer in the neutral conductor.
A large percentage of the winding can be covered when neutral is solidly earthed.
Providing high speed protection against earth fault for the whole transformer with relatively simple equipment.
It is applied at Distribution and Service Transformers in MTR power systems with high impedance type .
Restricted Earth Fault Connection Diagram
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35. Outlook of REF applied in MTR
Starting from LAR, we used the high impedance relay to provide high speed and stabe protection.
In URL, low impedance type relay was used . The three phase current and the neutral current become the bias inputs to a differential element.
Metrosil
CAG relay
Shunt Resistor
FAG relay
High impedance relay and its components
Current type (low impedance) relay
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36. TYPICAL RECTIFIER SUBSTATION CONFIGURATION
AC33kV
33kV / 2 x 586V
RECTIFIER
DC1500V
DOWN TRACK
OVERHEAD LINE
UP TRACK
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37. 33kV Rectifier Transformer Protection
Rectifier Tx : High Set Over-current Prot (Main)
Rectifier Over-current Prot
(Back-up)
IDMT OC/ EF Prot (Back-up) 2 10

38. Purpose of rectifier protection
The Protection of a rectifier differs from that of conventional current maximum application.
A large number of rectifiers can withstand relatively long periods of over-charge without incurring damage, generally 150% for 2 hours and 300% for 1 minute.
Connection Diagram
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39. Rectifier Protection Characteristics
Typical settings for the TMS area:
Light industrial service TMS=0.025
Medium duty service TMS=0.1
Heavy duty traction TMS=0.8
The high set is typically set at 8 times rated current as this ensures HV AC protection will discriminate with fault from HV and LV sides.
Operating Curve for Rectifier Curve
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40. Types of Rectifier Protection Relays
Midos Relay (MCTD)
Micom Relay (P122)
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41. 11 kV Circuit / Transformer Protection
Cable Feeder : IDMT OC/EF Prot (Main)
Bus-bar : Frame Earth Leakage Prot
11kV/415V
Service Tx : IDMT/ Inst OCEF Prot (Main)
LV REF Prot (Main)
Buchholz surge Prot (Main)
Winding/ Oil Temp High Trip
(Back-up) 2 10

42. LV Circuit Protection (415V/ 660V )
Cable Feeder/ Bus-section : IDMT OC/EF (Main)
Bus-bar : LV Standby EF Prot. 2 10

43. Over Current Relay application
Normally, Earth Fault relay applied at chiller system, 3 phase with earth fault used at LV board systems and 2 phase with earth is used at 11kv side with balance load systems (e.g. service transformers).
Earth Fault CT Connection
3 phase with Earth Fault CT Connection
2 phase with Earth Fault CT Connection
Earth Fault Relay (CDG)
3 ph & E/F Relay (Micom 121)
2 Ph & E/F Relay (MCGG52)
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44. Others O/C Relay used in MTR system
Micom Relay (P122 URL new relay alternative)
Midos Relay (MCGG52 LAR used)
Micom relay P127 (Directional relay used at KTT new 33kV board)
Numerical Relay (KCEG used at TKL & DRL)
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45. Discrimination by Time
Breaker nearest to the fault opened first.
Time interval between relay time setting must be long enough to ensure that the upstream relay do not operate before the circuit breaker.
Radial System with time discrimination
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46. Time Grading Principle for IDMT protection
Grading Formula :
Grading Margin –
= 0.1*(T1 + T2) SM (sec)
T1 : Upstream Protection Operation Time
T2 : Downstream Protection Operation Time
SM : safety margin
Apply in Radial- Fed Circuits
Margin : Relay/ CT error + Overshoot time
+ CB Op. Time for Downstream
KCGG 142 got additional 40ms for its pick-up element
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47. Numerical relays (For New Extension)
What is Numerical Relay?
- Microprocessor to replace analog circuit used in static relays to implement relay functions
What is major difference between numerical relay and EM/static relay?
- Numerical Relay operate on digital input, multi-characteristic curve and has memory, which can reproduce fault incidences for post-fault analysis.
How about Data Processing and Trip Decision Making ?
Microprocessor to implement protection algorithm and tripping logic
Minimum Operation Time 20~40ms.
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48. Numerical Relay Architectures
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49. Features of KCGG/ KCEG 142
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50. Characteristic Curves of KCGG/ KCEG
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51. Curves of KCGG/ KCEG 142
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52. AREVA Micom P-series Numerical Relay
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53. Protection feature of Micom P121
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54. Protection feature of Micom P121
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55. Fault Record of Micom Series Relay
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56. Download Setting by use of Micom S1
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57. 1.5kV DC Power System Protection
Cable Feeder : DTL / Instant. OC (Main)
Direct acting OC (Main)
Rate of rise OC (Main)
IDMT OC (Back-up)
Under-volt (Back-up)
Thermal OL (Back-up)
Bus-bar : Frame Earth Leakage Prot 2 10

58. KBD & TWD - DC Switchgear Board
SEPCOS Relay
DC Circuit Breaker
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59. Basic Configuration Of Sepcos Relay
Power supply board
Analog input board
LED indication
A Stat 0v 2 4
d4/dt J1 J2 J3 J4
VPC 196
Output I 1
OK i 3
d3/dt
R H A
Io L m
MELCHER
The Power Partners
output
Fast
VIUC
VMI 12
VMI 12
VMO 12
VMO 12
Slot 10
Slot 11
Slot 12 & 13
Slot 14 & 15
CPU Board
Input board
Output board
(each board occupy two slots
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Slot 12 to 15
Software
Slot 10 and 11
Basic Configuration

60. DC Type Numerical Relay (Protection &Control)
Control : Inter-trip send, CB close/open, auto-reclose, anti-pumping
Protection (feeder)
Ufeeder monitoring (Track Alive) 
DDL (I, T) positive protection 
DDL (I, T) negative protection x
Ufeeder min protection 
Thermal protection x
Imax+ protection 
Imax- protection 
Reverse current protection x
(For incomer CB) 
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61. DC Inter-trip Arrangement
D/A, dI/dt, Imax+, UV, IDMT, Thermal OL (LAR/TKL)
UV (URL)
Inter-trip Signal
1500V OHL
Running Rails
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62. Question & Answer
End of Presentation
Thank You
4/19/2017