ELECTRIC POWER SYSTEM GROUNDING - Exacterinc
ELECTRIC POWER SYSTEM GROUNDINGBySteve Blumeswblume@gmail.com(760) 612-8488GND1
Electric Power System GroundingPresentation Outline3-Phase Power SystemsReasons for Grounding and BondingSubstation, Transmission, and Distribution GroundingPower Faults and Lightning StrikesFault current distributionGround Potential Rise (GPR)Touch and Step PotentialsSafetyCopyright Protected – Blume Consulting 2
3-Phase Power SystemsSingle Phase GenerationCopyright Protected – Blume ConsultingFaraday’s Law:Voltage is produced on any conductor ina changing magnetic field! VoltsN- VoltsS3
3-Phase Power SystemsThree Phase GenerationNCopyright Protected – Blume Consulting Volts- VoltsS4
3-Phase Generator3-Phase AC GeneratorControlsAC Voltage OutCopyright Protected – Blume ConsultingExciterField/RotorNSStatorSlip Rings5
3-Phase Power SystemsCopyright Protected – Blume ConsultingSymmetrical ConnectionsWinding 1Winding 3Winding 1Winding 2ToLoadWinding 2NeutralToLoadWinding 3DeltaWYE6
3-Phase Power SystemsNeutral vs. Ground vs. BondLWinding1 Winding 2LWinding 3NeutralTo the loadNBondGroundL Grounding: the neutral is connected to earth viaground rods, grids, or conductors. Unbalancedneutral currents flow through the earth connection. Bonding: electrical connectionsbetween equipment andgrounded conductors to provideequipotential during faults.7Copyright Protected – Blume ConsultingWYENeutral
3-Phase Power SystemsReasons for Grounding and BondingControl power fault and Lightning strike currentsProtect equipment and trip energizing equipmentEquipotential GroundingEffects of Ground Potential RiseTouch and Step PotentialsDetect and minimize unbalanced currentsCopyright Protected – Blume Consulting 8
3-Phase Power SystemsCopyright Protected – Blume ConsultingSystem Grounding9
3-Phase Power SystemsSubstation GroundingCopyright Protected – Blume ConsultingGround gridsEquipmentStructuresFence10
3-Phase Power SystemsTransmission Line Shielding and GroundingShield Wires andOptical Ground WiresCopyright Protected – Blume ConsultingLightning Protection through Grounding60º60ºRodLine60º shield angle is typical11
3-Phase Power SystemsDistribution Lines: Wye ConfigurationCopyright Protected – Blume ConsultingMulti-grounded Neutral: Atleast four times per mile per theNational Electric Safety CodeMulti-GroundedNeutralCBNANGrounded neutralA12
3-Phase Power SystemsDistribution Lines: Delta ConfigurationCCopyright Protected – Blume ConsultingDelta three-phase distribution lines use three wires, no neutral. Transformertanks and lightning arresters are connected to ground rods at each pole.BBAANo groundedneutral!13
3-Phase Power SystemsBalanced ConditionsBalanced 3-Phase CurrentsGeneratorLoadTransformerCopyright Protected – Blume ConsultingSourceGridGridNO Earth Return Current!14
Power System FaultSubstation FaultLightning RodsCopyright Protected – Blume ConsultingPower Faultor Lightning StrikeGround Grid WiresGround Rods15
Power System FaultGround Potential Rise (GPR) – unbalanced currentPhase CurrentsGPRsXFMRCopyright Protected – Blume ConsultingGGridGridAssumptionsEarth Return Current Homogenous Soil (i.e., round contours) Power Fault at substation transformer bushing16
Power System FaultMultiple Ground Paths and GPR’sUn-Balanced 3-Phase CurrentNeutral CurrentsGGPRsCopyright Protected – Blume ConsultingShield Wire CurrentsXFMRGridGridEarth Return Current17
Power System FaultMetropolitan GridsGCopyright Protected – Blume ConsultingUn-Balanced 3-Phase CurrentXFMRNO Earth Return Currents!!!NO GPR!!!Current flow through grid: YESVoltage drop on grid: YES18
Power System FaultGPR - Zone of InfluenceSubstationGnd GridCopyright Protected – Blume Consultingx300 volt pointGPR“Zone of Influence”Homogeneous Soil19
Electrical Grounding SafetyTouch & Step PotentialsCopyright Protected – Blume ConsultingSubstationsStructuresGround GridTouchStepGround Potential RiseDistance From Fault20
Electrical Grounding SafetyHuman CharacteristicsNOTE: Current path through body is a critical factor!The average 155-lb man takes the following currents:1.2ma to produce a slight tingling feeling, called perception threshold9ma can produce a painful shock, but still below lock-on conditions16ma can cause the loss of muscle control23ma can cause difficulty breathing50ma approximately can cause burning100ma for 3 seconds can cause heart fibrillation1 amp for 30ms can cause heart fibrillationCopyright Protected – Blume Consulting 21
Electrical Grounding Safety2-Ways to be Safe!CONDUCTION – Equipotential GroundingThe use of materials in situations where good conduction (low resistance) will result in small potentialdifferences and high current flow. (Ground Jumpers)Copyright Protected – Blume ConsultingISOLATION – Personal Protective EquipmentThe use of materials in situations where good insulation (high resistance) will result in large voltagedifferences and low current flow. (Rubber Insulation)22
Electrical Grounding SafetyConduction - Ground Source PreferencesCopyright Protected – Blume Consulting1. Substation Ground Grid2. Multi-Grounded Neutral (MGN)3. Steel Tower or Steel Pole4. Driven or Screw-in Ground Rods5. Anchor Rods23
Electrical Grounding SafetyConduction - Jumper Voltage Drop ProtectionYOUCopyright Protected – Blume ConsultingFAULT CURRENTYOURJUMPERSEarth"TRUE" GROUND24
Electrical Grounding SafetyCopyright Protected – Blume ConsultingConduction - Transmission Structure SafetyExample:Single PointGrounding ametal latticetowerSteel TowersExample: Single Point Grounding for one workeron a wooden “H” frame structure with overheadground wiresWood Structures25
Electrical Grounding SafetyConduction - Distribution Structure SafetyCopyright Protected – Blume ConsultingExample: Worker minimizingexposure to touch potential byoperating equipment controlsfrom a conductive matSingle Point GroundingVehicle Arrangement26
Electrical Grounding SafetyCopyright Protected – Blume ConsultingConduction - Underground EquipmentNeutrals and Lightning Arresters are Grounded.27
Electrical Grounding SafetyCopyright Protected – Blume ConsultingIsolation - Personal Protective Equipment (PPE)28
Electric Power System GroundingAny Questions?Thank you!BySteve Blumeswblume@gmail.com(760) 612-8488
Presentation Outline Electric Power System Grounding 3-Phase Power Systems Reasons for Grounding and Bonding Substation, Transmission, and Distribution Grounding Power Faults and Lightning Strikes Fault current distribution Ground Poten
Grounding Study and Analysis: Substation Grounding Practices Grounding Concepts - GPR and Touch Potential AEP Innovative Grounding Study Methods Grounding Installation: Traditional Approach and Challenges Grounding Application and Installation Change Management Testing: Grounding Integrity Testing Conclusion and .
Grounding Electrode System and Grounding Electrode Conductor Part III zNEC 250.50 (Grounding Electrode System) 250.52 Electrodes Water Pipe if 10 ft. or more of metal water pipe is in contact with the earth. Metal Frame of the Building or Structure where the followin
Article 250.1 Scope. Article 250 is organized into 10 different parts that deal with specific requirements with regards to bonding and grounding. The specific parts are as follows: (I) General (II) System Grounding (III) Grounding Electrode System and Grounding electrode Conductor (IV) En
NEC Table 250.122 - Minimum size equipment grounding conductors for grounding raceway and equipment Table 2 – Minimum size equipment grounding conductors for grounding raceway and equipment Aluminum Cable Tray Systems Table 392.60(A) – Metal area requiremen
grounding bar in the service equipment. The grounding electrode conductor shall extend to a grounding electrode (a ground rod or other effective electrode). 6.2.3 An equipment grounding conductor shall originate at this service equipment and shall be installed with the circuit conductors to the waterer. 6.2.4 The equipment grounding conductor .
buried depth of the grounding grid, the resistance reducing effect is not obvious, in particular to areas with high soil resistivity. Therefore, in general, this method is not adopted in the engineering. The buried depth of the substation grounding grid is about 0.8 m generally. Long vertical grounding electrodes, blasting grounding and deep well
the point of grounding for the time necessary to clear the line. NOTE: Refer to ASTM F-855-04 [B24] for specifications for protective grounding equipment. 2. Initial connections Before grounding any previously energized part, the employee shall first securely connect one end of the grounding device to an effective ground.
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