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GIC Calculations Using PSS®E

Live Demonstration February 16, 2017

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Unrestricted © Siemens Industry, Inc. 2017


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NERC TPL-007-1 GMD Vulnerability Assessment Process

Source: NERC GMD Task Force Documents


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How to run GIC analysis in PSS®E?


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PSS®E GIC analysis GUI


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Development of DC system model

Power flow network data reduced to just resistance network with these modifications: • Transmission lines modeled as resistor in series with induced voltage • Line reactors / charging ignored • Grounded two- and three-winding transformers modeled with their winding

resistance to ground • Grounded auto-transformers are modeled with their common and series

winding resistance • Grounded Bus shunts are modeled • Equivalent station grounding

resistance is modeled • Transformer GIC blocking devices

are modeled


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GIC flow in various transformer configurations

The effective GIC (Ieff) flow in a transformer due to GICs flowing in one or more of its winding is dependent upon transformer type.

Refer PSS®E Program Application Guide, Volume 1


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Effective GIC Two-winding transformer


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Effective GIC Two-winding auto transformer


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Mvar/Ampere Scaling Factor (Kfactor)

• One of the effects of the GICs flowing in transformer windings is that the transformer is subjected to half-cycle saturation resulting in increased reactive power (Mvar) losses in these equipment.

• Using GIC to Mvar scaling factors transformer reactive power losses are calculated.

• When a specific Kfactor value is provided for a transformer:

• Using generic scaling factor value based on the transformer type: where VH is Transformer Windings highest voltage in kV.

factoreff KIQ ×=

500H

factoreffVKIQ ××=


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Generic Scaling Factors

(a) Kfactor determined based on transformer cores

Core Design Cores Kfactor

Three-phase, shell form -1 0.33 Single-phase (three separate cores) 1 1.18 Three-phase, 3-legged, core form 3 0.29 Three-phase, 5-legged, core form 5 0.66 Three-phase, 7-legged, core form 7 0.66 (b) Kfactor determined based on base kV of transformer windings

Windings Highest Voltage Kfactor Unknown core, <= 200 kV 0.6 Unknown core, > 200 kV and <= 400 kV 0.6 Unknown core, > 400 kV 1.1

Source: X. Dong, Y. Liu, J. G. Kappenman, “Comparative Analysis of Exciting Current Harmonics and Reactive Power Consumption from GIC Saturated Transformers”, Proceedings IEEE, 2001, pages 318-322


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GMD events modeled in PSS®E

Uniform Geoelectric Field E(t) • Ignores effects of local earth conductivity and local geomagnetic latitude

Benchmark GMD Event E(t)

• E = 8 V/km • Considers α, the scaling factor to account for local geomagnetic latitude, and

β, the scaling factor to account for the local earth conductivity structure Non-uniform Geoelectric Field E(t)

• Considers 1-D local earth conductivity models • Calculates E(t) using Complex Image Method

GIC Data File usa.siemens.com/digitalgrid



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GIC Data File

• The data required to run GIC analysis which does not exist in PSS®E power flow case is provided using this file.

• The accuracy of GIC calculations will depend on the data provided in this file.

• GIC data file • Text file • Default extension: .gic


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GIC Data File Identification and substation data


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GIC Data File Transformer data


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GIC Data File Fixed shunt and branch data


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GIC Data File User Earth model data


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GIC Data File – Branch Data Notes

• GMD induced electric field can be specified in branch data record in terms of INDVP and INDVQ.

• PSS®E determines branch GMD induced efield as below. 1. When INDVP and INDVQ are specified in GIC data file, the total branch GMD

induced electric field is then determined as:

Induced Efield = INDVP + j INDVQ volts 2. When INDVP and INDVQ are not specified (blank) in GIC data file, branch induced

efields are calculated as per selected GMD event and branch geographical location.

3. When INDVP=0 and INDVQ=0 are specified in GIC data file, the branch is treated as underground cable. It is part of dc network, GICs can flow in this branch, but does not have induced efields.

For uniform and benchmark GMD events, Induced efield is real value, but for non-uniform field modeling this will be complex value.

Induced electric field will have positive polarity at branch “To Bus” (J bus).


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GIC Data File User Earth model notes

• TPL-007-1 defined Earth Conductivity Models for US and Canada are modeled as standard earth models (just use its name in GIC data file).

• If any other Earth Model is required, use this data record to define such an earth model.

• A total of up to 50 user earth models are allowed. • Each earth model may have up to 25 layers. • Use as many records needed to specify the data. • The thickness of the last layer is infinity.

• This is specified as any value less than 0.0 (= -999.0 for example). • The thickness value less than 0.0 is also used as end of earth model data.


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GIC Data File Example Create from Python™ Script

(A) Generate GIC data Microsoft® Excel template import psse34 import psspy, gicdata psspy.psseinit() savfile="nerc_gic_app_guide_exam_v33.sav" excelfile="template_2.xlsx" excelfile=gicdata.template_excel(savfile,excelfile, showexcel=True)

(B) Edit template as required (C) Create GIC data file from template import psse34 import gicdata excelfile="template_2.xlsx" gicfile="template_2.gic" gicdata.excel2gicfile(excelfile, gicfile)

GIC Analysis usa.siemens.com/digitalgrid



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PSS®E GIC Calculations

PSS®E GIC Module

GICs,

Transformer Q Losses

PSS®E Power Flow Network

PSS®E GIC Data

PSS®E Power Flow Network with GIC

Losses

GMD Storm Scenario

AC Power flow studies Contingency analysis PV/QV analysis Dynamic analysis


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Run GIC Analysis from PSS®E GUI


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Run GIC Analysis from Python™ Script

(A) Run GIC activity (gic_3) using psspy module This runs GIC activity and produces GIC analysis results in PSS®E Text

reports.

(B) Run GIC analysis and retrieve results in Python™ objects using arrbox.gic OR pssarrays modules This runs GIC activity and returns GIC analysis results in Python™ objects.


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arrbox.gic.GIC OR pssarrays.GIC objects

This provides pythonic interface to GIC activity and also retrieves results into Python™ objects. import arrbox.gic gicobj = arrbox.gic.GIC(savfile, gicfile, efield_mag, efield_deg, tielevels=0, study_year=0, thermal_ana_optn=0, substation_r=0.1, branch_xbyr=30.0, transformer_xbyr=30.0, efield_mag_local=0.0, efield_deg_local=0.0, efield_type='uniform', efield_unit='v/km', addfile_optn='rdch', gic2mvar_optn='kfactors', earth_model_name='', scan_storm_event='', power_flow_optn='', ejet_million_amps=0.0, ejet_halfwidth_km=0.0, ejet_period_min=0.0, ejet_height_km=0.0, ejet_center_deg=0.0, addfile='', purgfile='', rnwkfile='', pygicfile='nooutput', basekv=[], areas=[], buses=[], owners=[], zones=[], basekv_local=[], areas_local=[], buses_local=[], owners_local=[], zones_local=[], pf_itmxn=_i, pf_toln=_f, pf_tap=_i, pf_area=_i, pf_phshft=_i, pf_dctap=_i, pf_swsh=_i, pf_flat=_i, pf_varlmt=_i, pf_nondiv=_i) OR import pssarrays gicobj = pssarrays.GIC(savfile, ...)


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Example IEEE GIC Test Case Network

R. Horton, et.al., “A Test Case for the Calculation of Geomagnetically Induced Currents”, IEEE Transactions on Power Delivery, Vol. 27, No. 4, October 2012, pages 2368-2373


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IEEE GIC Test Case Calculations with Activity GIC

Refer files in folder ..\PTI\PSSExx\EXAMPLE ieee_gic_test_case.sav ieee_gic_test_case.gic ieee_gic_test_case.sld


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GIC Calculations Report


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GIC Calculations Report (continued)


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GIC Results on Network Maps

• Python Module arrbox.gicmaps.GICMAPS OR pssarrays.GICMAPS

• Use “arrbox.gicmaps” python module to display GIC calculation results on

network map.

• ‘pygicfile’ file produced by activity GIC or arrbox.gic.GIC used as input to ‘GICMAPS’.

• Need open source python modules: numpy, matplotlib, basemap

• Get details as >>> import arrbox.gicmaps >>> help(arrbox.gicmaps)


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GIC Results on Network Maps (continued)


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GIC Results on Slider Diagrams

• Open sample.sav and sample.sld files in PSSExx. • Run GIC analysis using: • sample.gic • GMD event as: Benchmark, ‘scan degrees’

• Show GIC results on slider diagram:

• Select slider tab • Menu Diagram >Results to show >GIC results • Press “Title” Tool Button to show title on slider diagram


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GIC Results on Slider Diagrams (continued)


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scan_d_m option scan results

Conclusion usa.siemens.com/digitalgrid



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TPL-007-1 Requirements and PSS®E Conclusion

TPL-007-1 Requirements How to meet?

R1 Identify individual or entity Company policy

R2 Maintain System models and GIC System (DC) models

PSS®E Case and GIC data files

R3 Have acceptable voltage criteria during the benchmark GMD event

Company policy

R4 GMD Vulnerability Assessment studies PSS®E GIC Module and other PSS®E activities

R5 1) Provide GIC flow information for worst case geoelectric field orientation

2) Effective GIC time series, GIC(t)

1) PSS®E GIC module output 2) Implemented, will be available

in next PSS®E release R6 Conduct a thermal impact assessment with

Ieff/phase > 75 Amps Need transformer thermal response capability data

R7 Develop corrective action plan a) company policy: based on grid knowledge develop this

b) implement in PSS®E Case and GIC data files


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PSS®E GIC Module Conclusion

• Fully integrated in PSS®E • Uses standard PSS®E networks (.sav or .raw files) • No Sequence data required • Additional data required for GIC calculations supplied through external GIC

data file • GIC data files can be prepared using interactive tools, GIC Python™ module

and Microsoft® Excel or a text editor • Activity GIC creates comprehensive and customizable text report • Python™ scripts can be used to run GIC calculations, create custom reports

and show GIC results on Network maps • GIC calculations automatically run orientation scans to find worst orientation

and magnitude scans to find maximum possible storm strength that system can withstand


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Contact

Krishnat Patil Senior Staff Software Engineer Siemens PTI

Phone: +1 518 395 5081

E-mail: [email protected]

Jyothirmai Chittyreddy Staff Consultant Siemens PTI

Phone: +1 972 621 5699

E-mail: [email protected]

usa.siemens.com/digitalgrid

mailto:[email protected]

mailto:[email protected]