Transcription of Substation Grounding Tutorial
1 Substation Grounding TutorialJoe Gravelle, Ramirez-Bettoni, Power Systems ConferenceThursday, Nov. 9, 2017 Joe Gravelle earned BSEEE from NDSU in 1988. After graduation Joe worked in the mining industry in northeastern Minnesota for ten years. Joe is a principal engineer in the Substation Engineering department at Xcel Energy and has held many roles in the department since 1998. In addition to Substation projects, Joe is active in standards work both at Xcel Energy and in IEEE substations Committee. Joe is currently the vice chair of the substations Committee and is active in leadership roles and as an active member in several IEEE working groups.
2 Presenter Joe Gravelle, Grounding TutorialEduardo obtained a BSEE with Power System emphasis from University of Costa Rica in 2002. Eduardo has international experience in Substation construction, O&M, and design in substations up to 500 kV. He has practiced engineering in the , Canada and Costa Rica. Eduardo has a background in protection & control, Substation physical design and power system Grounding . Eduardo works as principal engineer for Xcel Energy in the Transmission & Substation Standards (TSS) department. TSS creates standard documents for design, specification and installation practices for transmission & Substation facilities.
3 Eduardo is an active member in IEEE Substation working Eduardo Ramirez-Bettoni, Grounding TutorialXcel Energy No. 1 utility wind energy provider in the million electric customers 2 million natural gas customers 12,000 Resistivity Testing and Soil & Modelling of Substation Design Variables Soil model variables Seasonal modelling of soil Crushed rock resistivity Fault current design margin Fault clearing time Summary / Combined effectAgendaSubstation Grounding TutorialGrounding BasicsSubstation Grounding Tutorial Definitions per IEEE 80 & 81 GPR, mesh / step / touch Current split Touch potentials: 3 hand-to-foot Step potentials.
4 3 foot-to-foot Safe if Calculated Values < Tolerable Max ValuesGrounding BasicsSubstation Grounding TutorialGrounding BasicsSubstation Grounding TutorialGrounding BasicsSubstation Grounding Tutorial Future fault current: 7000 A Earth current: 4200 A, (split factor Sf= 60%) Grid resistance: GPR nom= x 4200 A = 4500 V Mesh voltage = 210 V Body current IB(500 ms, 50 kg) = ( ) = 164 mAGrounding Basics - ExampleSubstation Grounding TutorialGrounding Basics - ExampleSubstation Grounding TutorialGrounding BasicsSubstation Grounding TutorialSource: IEEE 80-2015 Body current (IB) is based on let-go current per experimentation( % percentile, no ventricular fibrillation) Body resistance (RB) varies based on exposure voltage RB= 500-1000 Future fault current: 7000 A Earth current.
5 4200 A, (split factor Sf= 60%) Grid resistance: GPR nom= x 4200 A = 4500 V Mesh voltage = 210 V Body current IB(500 ms, 50 kg) = / SQRT( ) = 164 mAGrounding Basics - ExampleSubstation Grounding Tutorial Tolerable potential across 50 kg body, body only VB= IBx RB(for TPG calculations)Example - Body VoltageSubstation Grounding TutorialPercentileIB (A)RB ( )VB (V)Body Configuration95% ; Foot-foot95% feet95% hands-both feet95% Tolerable potential across 50 kg body, step voltage, no surface rock Homogeneous soil resistivity: 100 -m Accounts for foot resistance to surface, Vt, 50kg= IBx (RB+ )Example-Touch potential (no rock) Substation Grounding TutorialPercentileIB (A)RB ( )Vtouch (V)Body Configuration95%.
6 Foot-foot95% feet95% hands-both feet95% : IEEE 80-2015 Example-Touch potential (with rock) Substation Grounding TutorialSource: IEEE 80-2015 Tolerable potential across 50 kg body, step voltage, 4 of 2000 -m surface rock; homogeneous soil resistivity: 100 -m Vt,50kg= IBx (RB+ ); (Cs= )Example-Touch potential (with rock) Substation Grounding TutorialPercentileIB (A)RB ( )Vtouch (V)Body Configuration95% feet95% hands-both feet95% BasicsSubstation Grounding TutorialSubstation Grounding TutorialSource: IEEE 80-2015 Grounding BasicsGrounding BasicsSubstation Grounding TutorialSoil AnalysisSubstation Grounding Tutorial Soil BasicsSoil Resistivity ModellingSubstation Grounding TutorialHomogeneousMulti - LayeredActual soil The soil is part of the fault circuit Actual circuitSoil ResistivitySubstation Grounding Tutorial The soil is part of the fault circuit Soil ResistivitySubstation Grounding TutorialSoil Resistivity1000 -m300 -m100 -m400 -m7000 A100 -m300 -m1000 -m400 -m7000 ASubstation Grounding TutorialRock Resistivity100
7 -m1000 -m400 -m7000 A100 -m300 -m1000 -m7000 A300 -m400 -mSubstation Grounding Tutorial Soil boring report Substation location &grading plans Substation size, site area Propose traverses Sources of interference Resistivity test schedule Grading schedule Test form Test equipment check listPreparation Soil Resistivity TestingSubstation Grounding TutorialGeotechnical Exploration &ReviewSubstation Grounding TutorialWater TableWEATHERED SANDSTONE, yellowish Brown, very dense, [Textural Classification: SAND WITH SILT, fine to medium grained, light brown and yellowish brown, moist, very dense (SP-SM)] Sand with Silt, fine grained, yellowish brown, moist medium dense (SP-SM) Wenner SchlumbergerSoil Resistivity TestingSubstation Grounding TutorialSource: IEEE 81-2012 Soil Resistivity Testing - WennerSubstation Grounding Tutorial INSERT FORM!
8 Soil Resistivity Testing - SchlumbergerSubstation Grounding TutorialSoil Resistivity TestingSubstation Grounding TutorialC1P1C2P2C1P1C2P2 Error Range Based on Probe SpacingSubstation Grounding TutorialSoil Resistivity Test LayoutSubstation Grounding TutorialGrounding Design VariablesSubstation Grounding Tutorial How many traverses are required? Are there sources of interference? What is the correct layout of traverses? What pin spacing should we use? What do I do if there is not adequate space?Soil Resistivity Testing SummarySubstation Grounding TutorialSoil Resistivity Testing LayoutSubstation Grounding TutorialSoil Resistivity Testing LayoutSubstation Grounding TutorialSoil Resistivity Testing LayoutSubstation Grounding TutorialPlot of Soil Resistivity ResultsSubstation Grounding TutorialProposed Soil Resistivity Test TraversesSubstation Grounding TutorialWenner Data Comparison Pre-& Post-GradingSubstation Grounding TutorialSubstation Grading Section Drawing Substation Grounding TutorialWenner vs.
9 Schlumberger Soil Models Soil Resistivity TestingWenner vs. Schlumberger Soil Models Substation Grounding Tutorial Test equipment model number Test lead resistance (measured) Ambient Temperature when test was taken Date of test Standard test result form Resistivity & Resistance measurements at various pin spacing NotesSoil Resistivity Test DocumentationSubstation Grounding Tutorial Soil BasicsSoil Resistivity ModellingSubstation Grounding TutorialHomogeneousMulti - LayeredActual soilGround Grid Design & ModelingSubstation Grounding Tutorial Ground grid layout Fault current system analysis &location Split factor modeling Safety analysis Vtouch.
10 Vstep GPR plots Safety & Summary ReportsDesign &Modeling Substation Ground GridSubstation Grounding TutorialGeneral Substation LayoutSubstation Grounding TutorialGeneral Ground Grid LayoutSubstation Grounding area Loop 3 outside fence components adjacent grid grid (s) grading runs - UG all structures & equipmentGeneral Ground Grid LayoutSubstation Grounding TutorialGeneral Ground Grid LayoutSubstation Grounding TutorialGeneral Ground Grid LayoutSubstation Grounding Tutorial UL listed Length, diameter Spacing Perimeter Equipment Open spacesGround Rod Application GuidelineSubstation Grounding TutorialSubstation Grounding TutorialCoffee circuit study , SLG, fault duration, ground connections2.
