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

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

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.

Pin hole Power gas Tubing Incident Description Pin hole Power gas Tubing

Close-up view at the damaged Tubing

Main Line Valve Station P & ID

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

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.

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

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.

Contributing Factors High Tension Transmission and Distribution lines Crossing over Pipeline

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.

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.

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

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.

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

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

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

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

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

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.