level 2 certification - sestech level 2... · 3. computer analysis and interpretation of results...

Level 2 Certification Combined AC Interference & Grounding

2

Copyright © 2020 SES ltd. All rights reserved.

Course Schedule

Day 1 8:30 am – 12:00 pm 1:00 pm – 5:30 pm

Introduction of instructors and support personnel

Project description

Overview of training goals

Map data review

Soil resistivity Measurement Interpretation: RESAP

Begin creation of RowCAD model

Entity models for valve and substation in RowCAD, grounding impedance

Circuit definitions in RowCAD

Creation of steady state Right-of-Way model

Day 2

8:30 am – 12:00 pm 1:00 pm – 5:30 pm

Creation of HIFREQ steady state model

o Path coordinates import o Conductor definitions o Transformer definitions o Creation of transmission line

Completion of HIFREQ steady state model

Comparison of steady state results between HIFREQ, Right-of-Way

Day 3

8:30 am – 12:00 pm 1:00 pm – 5:30 pm

Fault Conditions in Right-of-Way

Fault Conditions in HIFREQ

Comparison of fault results between HIFREQ, Right-of-Way

Safety Considerations: pipe, valve, substations, decoupler ratings, etc.

Design criteria

Designing mitigation in Right-of-Way

Day 4

8:30 am – 12:00 pm 1:00 pm – 5:30 pm

Complete fault conditions modeling with mitigation

Confirmation of meeting all design criteria

Advanced Grounding topics and modeling: GIS, transformers; EM Fields, seasonal variations etc.

Day 5

8:30 am – 12:00 pm

Summary AC interference

SESTLC demo

Corrosion (CorrCAD)

Decoupler ratings

Arcing

Auto-Transient

Questions & answers

3


Level 2 Certification: Advanced - Substation Grounding and EMI Specialization Combined

The Level 2 training is designed for Level 1 graduates who wish to learn to perform studies themselves and carry out design work in one of two areas of specialization: substation grounding (including lightning shielding) and power line electromagnetic interference. Level 2 graduates are recognized by SES as having the ability to carry out such studies using the CDEGS software package, without supervision, and evaluate the work of others.

Prerequisites:

Practical Experience: At least two years of work experience in electrical engineering; alternatively, a degree in electrical engineering or physics and one year or more of work experience in electrical engineering.

Level I Certification

Period of Validity:

Six years. After this period, the certified candidate must attend an updated course and pass the associated exam.

Course Description: There are three Advanced Certification (Level 2) specializations:

Grounding Performance of High Voltage Substations. Interference from High Voltage Lines (EMI). Grounding Performance of High Voltage Substations and Interference from High Voltage

Lines (EMI) combined.

Regardless of the specialization chosen for Certification Level 2, the next certification level (i.e., Level 3: Expert) focuses on topics that are not covered in Level 2 specialization chosen by the candidate. The Expert Level certification therefore attests to expertise in both subject areas. Candidates must complete and pass an exam at the training session to verify their mastery of the material taught at the course and submit proof of the required industry experience (this can include attendance at SES Users’ Group Conferences, technical reports, publications, etc.). 1. Upon completion of the Advanced Certification course specializing in Grounding Performance of High Voltage Substations, candidates will be able to:

Specify all field measurements required for the completion of a study, including specification of appropriate equipment and test procedures.

Interpret accurately and refine soil resistivity measurements as well as Fall of Potential, touch and step voltage measurements.

Determine the appropriate soil structure models and their limiting cases due to seasonal and geographical variations.

Construct realistic soil models of complex environments using finite volume models. Build accurate models of electric substations located in rural, semi-urban and urban

areas and carry out the required fault current distribution analysis and complete the design of their grounding systems with all necessary mitigation measures.

Model power cables including pipe-type cables, gas insulated substations (GIS) and gas insulated lines (GIL), as applicable.

4


Include in the computer model various transformers types such as three-phase, three-winding, auto- and HVDC special type transformers, for accurate modeling of circulating currents during fault conditions in a substation or outside the substation.

Evaluate electrical safety concerns and be able to identify unsafe conditions. Carry out comprehensive lightning shielding designs of substations and industrial plants. Apply appropriate insulation coordination that provides overvoltage protection for

communication circuits entering a site. Apply various economical mitigation techniques to insure the safe performance of the

grounding design.

2. Upon completion of the Advanced Certification course specializing in Interference from High Voltage Lines (EMI), candidates will be able to:

Specify all soil resistivity measurements required along a joint-use corridor to be studied for AC interference effects, including specification of appropriate equipment and test procedures.

Interpret accurately and refine soil resistivity measurements. Determine the appropriate soil structure models and their limiting cases due to seasonal

and geographical variations. Build accurate models of transmission and distribution lines entering electric substations

located in rural, semi-urban and urban areas. Select appropriate tower structure configurations and ground impedances along the

lines. Model power cables including pipe-type cables and gas insulated lines (GIL), as

applicable. Select appropriate models of gas and oil pipes, water pipes, railway tracks and

communication lines, as applicable. Understand reasonably well the concerns of gas and oil pipeline companies, railway

companies and communication line companies in order to address all important issues adequately.

Evaluate electrical safety concerns and be able to identify unsafe conditions specific to each utility or industry.

Understand the various mitigation techniques that are applicable to a specific utility and provide economical mitigation techniques to insure the safe performance of the affected utility.

Carry out a comprehensive analysis of the performance of the entire joint-use corridor during steady-state and fault conditions.

1. Resistivity Measurements and Interpretation

Specify all soil resistivity measurements required along a joint-use corridor to be studied for AC interference effects, including specification of appropriate equipment and test procedures.

Interpret accurately and refine soil resistivity measurements.

Determine the appropriate soil structure models and their limiting cases due to seasonal and geographical variations.

5


2. Building Accurate Electric Networks and Exposed Utility Lines

Specify all required information and data that must be collected from all stake holders in order to be able to build realistic and accurate computer models in rural, semi-urban and urban areas.

Build accurate models of transmission and distribution lines entering electric substations located in rural, semi-urban and urban areas.

Select appropriate tower structure configurations and ground impedances along the lines.

Model power cables including pipe-type cables and gas insulated lines (GIL), as applicable.

Select appropriate models of gas and oil pipes, water pipes, railway tracks and communication lines, as applicable.

3. Computer Analysis and Interpretation of Results

Determine the required steady-state and fault scenarios that need to be examined in order to fulfill the requirements of the study.

Carry out detailed computer analysis using the most appropriate software packages, i.e., MultiFields or Right-of-Way. Once the most appropriate software package has been selected, determine which software package and method to use for validation purposes.

Detailed review and use of SESCAD, ROWCAD, SESTLC, Right-of-Way and GRSPLITS-3D and MultiFields.

Carry out a comprehensive analysis of the performance of the substation during steady-state and fault conditions assuming one single type of soil structure along the entire right-of-way model based on the most stringent steady-state and fault conditions encountered during the analysis.

Carry out a comprehensive analysis of the performance of the entire joint-use corridor during steady-state and fault conditions assuming one single type of soil structure along the entire right-of-way model based on the most stringent steady-state and fault conditions encountered during the preceding analysis.

Interpretation of the computation results of all software packages.

4. Validation by Comparison

Using the alternate software package (i.e., the one the one selected above for validation purposes), carry out a comprehensive analysis of the performance of the entire joint-use corridor during steady-state and fault conditions based on the single type of soil structure model selected above and for the most stringent steady-state and fault conditions encountered during the preceding analysis as done above.

Confirm that, in all likelihood, the computer model as built does indeed represent a realistic rendering of the real situation.

Carry out a quick safety analysis of the substation and discuss mitigation measures without implementing them in the computer model.

Understand Stake Holders Issues

Understand reasonably well the concerns of gas and oil pipeline companies, railway companies and communication line companies in order to address all important issues adequately.

Evaluate equipment and material integrity issues and electrical safety concerns along the pipeline route and be able to identify unsafe conditions specific to each utility or industry.

6


5. Mitigation Techniques

Understand the various mitigation techniques that are applicable to a substation under fault conditions and provide economical mitigation techniques to insure the safe performance of the affected substation.

Apply safety mitigation measures to the substation and repeat the computer analysis of the performance of system during steady-state and fault conditions with the selected mitigation measures and prove that all concerns and issues the substation have been resolved using economical solutions.

Understand the various mitigation techniques that are applicable to a specific utility and provide economical mitigation techniques to insure the safe performance of the affected utility.

Apply mitigation measures along the pipeline route and repeat the computer analysis of the performance of the entire joint-use corridor during steady-state and fault conditions with the selected mitigation and prove that all concerns and issues along the pipeline route have been resolved using economical solutions.

6. Validation by Testing

Describe the various field measurement techniques that are required to validate the final design.

Discuss FOP field measurements typical problems and errors and how to avoid them.

Describe touch and step voltage measurement problems and errors and how to overcome them.

Safety issues and precautionary measures required during the field tests.

7


Project Description

A new 500 kV transmission line that feeds a new 500 kV/250 kV substation is being built. The

substation has two star-star grounded three-phase 500 kV/250 kV transformers that feed a

250 kV three-phase GIS building. The characteristics of the transformers are given in Table 1.

Power Rating (P) 750 MVA

Test Frequency (fT) 60 Hz

Primary Winding Voltage (VR1) 500 kV

Secondary Winding Voltage (VR2) 250 kV

Excitation Current (IO) 0.5 %

No-Load Power Loss (𝑂) 56,250 W

Primary to secondary impedance (ZPS) 15 %

Power Loss (𝑆) 253,125 W

Table 1: Three-phase star-star transformers test data

The fault clearing time for both 250 kV and 500 kV faults is 0.2 s.

The substation will be connected to three new 250 kV cables that will feed an existing major

industrial plant. This factory is connected also to an overhead 250 kV transmission line providing

redundant power supply to the plant. A major gas pipeline exists along the 500 kV and 250 kV

rights-of-way.

The model is shown in Figure 1.

Figure 1: Model of the entire network.

The substation and its components are shown in Figure 2.

8


Figure 2: Substation in the middle of the network of Figure 1 with its components

(blue) and the two fault locations on phase C (red).

The 0.5 m depth grid conductors and 3 m long ground rods are made of copper with 1 cm radius.

All elements of the entire network, such as voltage sources, transmission line phase conductors,

shield wires, power cables, transformers, bus bars, GIS structure, GIS building rebar, grounding

system, and shielding system can be included in the HIFREQ model. The Right-of-Way model

will represent only the GIS building grounding system and the focus will be the AC interference

with the nearby pipeline.

The factory is represented by a 100 Ω load on each phase, and has a 0.5 Ω grounding impedance.

The grounding performance of the new substation and the effects of the transmission lines during

steady-state and fault conditions on the pipeline are to be studied.

The transmission line cross-section is shown in Figure 3.

9


Figure 3: Transmission line cross-section. The cross-section is shown looking

eastward down the transmission line, i.e. the right-hand side is south.

The line is outfitted with an optical ground wire (ALCOA 34/52/646) and the phase wires consist of ACSR Flicker conductors. Both the 500 kV and 250 kV source terminals have a grounding resistance of 0.5 Ω. The exposed pipeline has a 0.3 m outer diameter with a 0.01 m wall thickness, and is buried at a depth of 1.7 m (to pipeline center). The steel material has a resistivity relative to copper of 12, a permeability relative to the permeability of free space of 300. The coating resistance has been measured to be 50,000 Ω ⋅ 𝑚2 (1 mm coating thickness), with a relative permittivity of 2.4. If necessary, the installation of gradient control wires has been approved and shall consist of Zinc ribbon (Small Size) and placed at 0.5 m horizontally away from the pipeline center and buried at the bottom of the trench. A valve on the pipeline is located roughly 5.77 km west of the eastern entry of the pipeline into corridor (there is a slight kink on the pipeline center line that indicates its position).

10


The valve site includes a 5 m by 5 m grounding mat, made of 4/0 copper conductors, buried at 0.5 m depth.

In a typical grounding study, it is essential that multiple soil resistivity measurements be carried out in the substation area. For an AC interference study, several resistivity measurements should also be carried out along the exposed utility. For the purposes of this exercise, we will be using three Wenner soil resistivity measurements assumed to be taken along the joint-use corridor. The measurement results are listed in the following table.

11


Table 2: The data is available also in spreadsheet format in a file called SoilResistivityMeasurementData.xlsx.

Traverse 1 Traverse 2 Traverse 3

'a' spacing

(m)

Apparent Resistivity

(Ω.m)

'a' spacing

(m)


(Ω.m)

'a' spacing

(m)


(Ω.m)

0.1 27.9 0.1 100 2 89.6

0.2 17.3 0.2 100 4 103.5

0.3 11.8 0.3 99.99 6 56

0.5 8.5 0.5 99.96 8 56.2

0.7 7.8 0.7 99.88 10 57.6

1 8.4 1 99.65 15 61.8

1.5 7.1 1.5 98.87 20 63

2.5 7.2 2.5 95.38 25 58.7

4.5 5.7 4.5 81.24 30 47.1

6 5.05 6 67.77 35 46.8

7 4.1 7 58.99 40 36.4

9 3.45 9 43.88 50 26.7

11 2.9 11 32.73 60 18.8

15 3.1 15 19.97 70 18

17 3.5 17 16.66 80 15.6

50 4.1 50 10.22 90 16.8

100 4.9 100 10.05 100 13.8

200 5.05 200 10.01

Traverse 1 measurements were taken near the eastern pipeline departure at a right angle from the corridor. Traverse 2 at the 250 kV/500 kV substation, and Traverse 3 at the west pipeline - 500 kV line crossing. The exact location of the traverse centers is indicated on the Google EarthTM map (Level 2 Project Map Data.kml). For the pipeline, the maximum acceptable ac touch voltage at exposed appurtenances under steady state conditions is 15 V, and at inaccessible locations the maximum acceptable GPR under steady state conditions is 50 V. Following NACE SP21424-2018, the maximum acceptable leakage current density from a 1 cm2 holiday is 30 A/m2. The maximum acceptable ac touch and step voltages at the substation and at exposed appurtenances on the pipeline under fault conditions will follow IEEE Standard 80. The maximum acceptable coating stress voltage under fault conditions is the lower limit of the industry standard for coating stress voltages: 3 kV.

12


Data Summary

Power system:

500 kV phase-to-phase with a source Thévenin impedance of 0.5 + j 5 Ω, and 250 kV

phase-to-phase with a source Thévenin impedance of 0.311 + j 3.11 Ω.

Both 500 kV and 250 kV source terminals have a grounding resistance of 0.5 Ω.

The file Level 2 Project Map Data.kml includes:

traces for the pipeline and transmission line center lines

a grid outline

the location of the plant load

soil measurement traverse center locations.

The 250 kV line is identical to the 500 kV line (future upgrade).

Shield Wire (ALCOA 34/52/646, ID: 1438) coordinates are (0,20).

Phase conductors (ACSR – Flicker, ID: 953) are A: (2,17), B: (2,15) and C: (2,13) respectively.

The grounding grid conductors and ground rods are copper with a 1 cm radius.

Traces of the grounding grid and rods are in hi_Grid.f05.

Traces of the cables in the substation are in hi_CablesAndBusses_TraceOnly.f05.

Traces of the GIS in the substation are in hi_GIS_TraceOnly.f05.

Traces of the cable vault rebar are in hi_CableVaultRebarsOnly.f05

Traces of the shielding are available in hi_ShieldingOnly.f05

The equivalent steady state load of the plant is 100 Ω with a 0.5 Ω grounding impedance.

The tower footing is a single 10 cm radius, 3 m deep steel (resistivity relative to copper of 12, a permeability relative to the permeability of free space of 300) pole.

Transformer data (represents one three-phase transformer):

Power Rating (P) 750 MVA

Test Frequency (fT) 60 Hz

Primary Winding Voltage (VR1) 500 kV

Secondary Winding Voltage (VR2) 250 kV

Excitation Current (IO) 0.5 %

No-Load Power Loss (𝑂) 56,250 W

Primary to secondary impedance (ZPS) 15 %

Power Loss (𝑆) 253,125 W

Fault clearing time: 0.2 s.

Exposed pipeline utility:

The steel material has a resistivity relative to copper of 12, a permeability relative to the permeability of free space of 300.

Pipe outer radius of 0.15 m and 1 cm wall thickness

Coating resistance of 50,000 Ω∙m2 (1 mm thick), r. permittivity =2.4

Burial depth of 1.7 m (center).

Approved mitigation will consist of horizontal zinc ribbon, 0.5 m away from the pipeline center, at the bottom of the trench.

13


Soil measurements data provided in spreadsheet: SoilResistivityMeasurementData.xlsx

Steady State Design Criteria:

15 V maximum Touch Voltage at exposed appurtenances.

50 V maximum GPR at unexposed locations.

30 A/m2 leakage current density from a 1 cm2 holiday.

Fault Conditions Design Criteria

IEEE Standard 80 Touch and Step Voltage within the substation area and at exposed appurtenances on the pipeline.

Maximum Coating Stress Voltage of 3 kV.

level 2 certification - sestech level 2... · 3. computer analysis and interpretation of results...

Documents