1. Stray & Fault Current Interference Leading Gas Leak and Fire PSC 2018 09th March 2018BY
Presenter Name: G.V,Reddy
DESIGNATION: Sr. General Manager
ORGANIZATION: reliance
LOCATION: hyderabad

2. Contents Incident Description Contributing Factors
Analysis of the Incident
Mitigation Measures
Conclusion

3. Incident Description
In One of our Installation Gas released through the pin hole on impulse tubing of actuator . Which cached-up the fire .
The pin hole on SS impulse tube was caused by partial melting due to arcing across the gap between SS tube and aluminum clamp under the influence of stray and fault electric current.
The source of ignition is suspected either the arc or the discharge of static electricity built-up by the release of natural gas through pinhole leak with high velocity.
The incident did not cause any personal injury or damage to public and property.

4. Pin hole Power gas Tubing
Incident Description
Pin hole Power gas Tubing

5. Close-up view at the damaged Tubing

6. Main Line Valve Station P & ID

7. Stray and Fault currents
Stray current is an uncontrolled electrical current which is flowing through equipment due to electrical supply system imbalances etc.
An electrical fault is a breakdown in insulation that sends current in an unwanted direction. A fault condition occurs when one or more electrical conductors contact ground and/or each other.
L-G Fault
LL-G Fault
3ɸ -G Fault

8. Contributing Factors Stray current Electro Magnetic Interference (EMI)
Imbalances in load distribution
Insulation failures
Improper earthing of electrical equipment’s
Fault current
Equipment failure
Lightning strikes
Falling of trees or branches on the transmission lines
Switching surges
Insulation failures and other electrical or mechanical causes.

9. Contributing Factors Improper earthing of Foreign Electrical Equipment
Lightning strikes on Power Lines

10. 3 phase 4 wire Transformers located in nearest farmhouse
Contributing Factors
3 phase 4 wire Transformers located in nearest farmhouse
Agriculture transformer 3 phase 4 wire with improper earthing system.
Farmer utilized ground as a neutral conductor for lighting purpose.

11. Contributing Factors
High Tension Transmission and Distribution lines Crossing over Pipeline

12. Analysis of the incident- Steady State
33/11KV ELECTRICAL S/s
(TSSPDCL)
EHV line
Gas Pipeline
11/0.433KV ELECTRICAL S/s
(RGTIL)
25KVA 3-ø Tr.
15KVA 1-ø Tr.

13. Analysis of the incident- Steady State
33/11KV ELECTRICAL S/s
(TSSPDCL)
Continuous stray currents
Gas pipe line
11/0.433KV ELECTRICAL S/s
(RGTIL)
25KVA 3-ø Tr.
11KV Feeder
15KVA 1-ø Tr.

14. Analysis of the incident- Fault Current
15KVA 1-ø Tr.
11/0.433KV ELECTRICAL S/s
(RGTIL)
25KVA 3-ø Tr.
11kv feeder from SEB S/s
33/11KV ELECTRICAL S/s
(TSSPDCL)
Gas Pipeline
Fault

15. Mitigation Measures SWER transformer shifted away from pipe line.
3 phase 4 wire agriculture transformers earthing system rectified and neutral conductor provided.
Installation of Insulation Flange (IF) Gaskets for 4 inch above ground piping at all MLV’s with surge diverters across the flange.
Exciting di-electric isolators reviewed in instrument tubing and Potential Equalization Clamps (PEC) installed.
Installation of polarization cells at MLVs
Additional zinc ribbon anodes at all identified HT line crossings and high earth resistance locations.
Excess flow valve installation at MLV’s.

16. 1) Single Phase Earth return transformer shifted
Mitigation Measures
1) Single Phase Earth return transformer shifted
2) 3 Phase 4 Wire agriculture distribution Transformer provided the neutral conductor

17. 3) Installation of Insulation Flange (IF) Gaskets
Mitigation Measures
3) Installation of Insulation Flange (IF) Gaskets
4) Installation of Potential Equalization Clamps (PEC) & Di-electric Isolators
Insulation Flanges
Equipotential Clamp

18. Mitigation Measures 5) Installation of polarization Cell at MLVs
6) Installation of Additional Zinc Ribbon Anodes until R Anode < 5Ω

19. 7) Installation of Excess Flow Valve
Mitigation Measures
7) Installation of Excess Flow Valve
Excess Flow Valve

20. Mitigation Measures Pipeline protected
Zinc Ribbon anodes installation at HT crossings
IF gaskets
PEC
Pipeline protected
Gas Pipeline
Anode
Polarization cell
EHV line
Excess Flow Valve

21. Conclusion
The lightning discharge and AC surge, stray currents are continuous challenges for Pipe line .
The failure of SS impulse tube is caused by partial melting due to gap between SS tube and aluminum clamp, due to arcing under the influence of electric current.
Mitigation are implemented and minimized the risk to significant level.