Grounding Of Electrical Systems NEW CODE: Grounding
Grounding of ElectricalSystemsNEW CODE: Grounding andBondingPresented ByScott Peele PE
Grounding of ElectricalSystems OutlinezzzzzzzzzDefining the TermsWhy should I Ground?Types of Grounding SystemsSeparately Derive SystemGrounding ElectrodeBondingGround Fault ProtectionGround Reference or Signal ReferenceGrounding for Lightning Protection
DefinitionszzzzzzReview definition as we encounter them.Grounded vs GroundingIsolated GroundFloating GroundGround LoopNet Current
Why am I grounding or Not?zzzzzzSafetyGrounding for Fault Current PathsGrounding for Touch Potential (static)Grounding for Lightning Protection SurgeArresters, TVSS (SPD)Grounding for Signal Reference (RF, Data,static ,etc.)Not Grounding Continuous operation
Three reasons for eference
Grounded vs GroundingzzGrounded vs. grounding in an electricalsystem. Grounded system refers to asystem where a conductor is groundedand is intended to or may carry current inthe normal operation. The neutral on awye system is a prime example of agrounded conductor.The grounding conductor system is notintended to carry operational current in itsdesign. This path is intended to carryunwanted and fault currents for protection.
Types of AC Grounded SystemszzzzzUngrounded systemSolidly Grounded SystemResistance GroundedReactance GroundedGround Fault Neutralizer
Which System to Use?zzzzzzzSafety - Who is Operating the SystemGround Fault DetectionSignal ReferenceTouch Potential (also static)Available Fault Currents?Operation StabilitySystem Response
Ungrounded SystemzzzType of system typically used on is aDelta service.Some time used on a floating WyeDetection System in Place Ground Detection by LightingZigzag Grounding TransformerGround RelayGround Fault ?
Detection Devices
Solidly Grounded SystemzzzzzUsually use in Wye systemsReturn Fault current to trip overcurrentprotection device quicklyUsually better reference and safer systemMuch better for lightning protectionCan be used in Corner Grounded Delta Problems with phase grounded re-groundedNot good on lightning protection equipment
Resistive groundedzLow Resistance zLimit Fault CurrentMinimizes the damage at the faultUsed usually with multiple sources i.e.transformers, and or generatorsHigh Resistance Enables system operation with one phasegroundedEnables current to flow for detection networksCurrent is low enough so that no damage occurs
Reactance GroundingzReactor connected between systemneutral and ground Reduces the ground fault current betweenphase and groundUsually higher fault current than lowresistance groundingBetter coordination with fault currents onmulti-grounded system. Mostly used onsystem above 5kV.
Ground-Fault NeutalizerzzzReactor with relatively high value ofreactance.Usually on system above 15kV phase toground air exposed. (overheadTransmission and Distribution)May provide insulator flashover with selfextinguishing characteristics.
Separately Derived SystemzzzThe system grounding conductor for aseparately derived system shall begrounded at only one point.Main system Disconnecting means for amain utility feed, or a step down or step uptransformer, or a generator could all beseparately derived systems.When grounded it will be grounded at thenearest grounding electrode.
Grounding Electrode System andGrounding Electrode Conductor Part IIIzNEC 250.50 (Grounding Electrode System) 250.52 Electrodes Water Pipe if 10 ft. or more of metal water pipe is in contactwith the earth. Metal Frame of the Building or Structure where the followingmethods are used to make an earth connection: (1,2,3,4) Concrete-Encased Electrode in at least 2” of concretelocated within and near the bottom of a concrete foundationor footing that is in indirect contact with the earth. Ground Ring encircling the building or structure in directcontact with the earth Rod or Pipe electrode not less than 8 ft in length Plate Electrode not less than 2 square ft. Other Local underground systems such as piping,underground tanks and underground metal well casing NOT PermittedMetal underground gas piping Aluminum electrode
Grounding Electrode SystemzInstallation NEC 250.53 zThis requirement clarifies that thesupplemental electrode system must beinstalled as if it were the sole groundingelectrodeBonding NEC 250.53 C This requirement is for bonding ofmultiple electrodes.
BondingzBonding for Main Bonding JumperSystem Bonding JumperElectrode BondingPart V Bonding Wherenecessary to ensure electrical continuityand the capacity to conduct safely and faultcurrent likely imposed.
Ground ?HotNeutralGround
Review Ohms LawVoltage Current X evelop VOLTAGEDevelop VOLTAGECurrent Source LightningAverage current 30,000 ampsGroundRod
Grounding and BondingVoltage DifferenceTransient voltages andcurrents at data port orcable connections
Isolated GroundzzzzNEC 250.146 (D) Isolated groundreceptacle (orange triangle) NEC 406.2(D)NEC 250.96 (B) Isolated GroundingCircuitsNEC 647 Section Sensitive ElectronicEquipment.NEC 647.6 Grounding. “Technical Equipment Ground”
Isolated GroundIsolated grounded receptacle has an isolated terminal from the yoke to the groundLug. These receptacle are usually marked with an orange triangle or all orange.Sub PanelNeutral BusGround Bus
Floating GroundzzzzThe neutral on a wye system is notintentionally groundedSignal conductor shielding is notintentionally groundedProblem is high transient voltage orovervoltages may exist causing damage.Not a good way for lightning protection
Ground LoopzzzzGrounds from two different derived systemare connectedOpen ground loops. Grounds are notbonded properly and cause damage.Ground loops cause circulating currentbetween systems and cause transformercoupling (CT’s)Signal reference can be compromisedcausing data errors.
Grounding for Signal ReferencezzzzzzDon’t Burst the Bubble.Ground on one endGround on both endsGround on neither endFiber Optic Best AnswerOptical Coupler
Don’t Burst the Bubble
Ground Fault Interrupter Function
Net CurrentzCurrents that are not apart of the normaloperation of a derive electrical system. All positive, negative, and zero sequencecurrents added and the resultant currentare net currents.
Books On GroundingzNECzIEEE zGreen Book 142-1991“Recommended Practice forGrounding of Industrial and Commercial PowerSystems”Emerald Book 1100-1999 “RecommendedPractice for Powering and Grounding SensitiveElectronic Equipment”Industrial and Commercial Power systemHandbook
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
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 .
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
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
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.
System grounding has been used since electrical power systems began. However, many companies and industrial plants have used system grounding methods differently. The problem of whether a system neutral should be grounded, and how it should be grounded, has many times been misunderstood completely. Therefore, grounding of many systems has
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