Prof. Brian Norton

Dr. Sarah McCormack

Mr. Kevin OFarrell

Solar Photovoltaic Electric System Protection

Ayda Esfandyari

28/02/2014

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

Outline of the work

Methodology

Timelines

Conclusion

References

Questions

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

Overview of Project

Methodology

Time-Lines

Conclusion

References

Questions

Overview of Project

Global Photovoltaic (PV) capacity has been growing exponentially

( Stand alone as well as grid connected applications )

Important efforts remain in terms of efficiency/performance, cost

and reliability

This project is part of SEAR (Solar Energy Application and

Research)

PV System High-Level Components

Balance of SystemPV Module

PV System

Mounting

Structure

Power

Conditioning

unit

Protection

/Cables

Storage

Protection

Focus

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

Introduction to Fault in PV

Methodology

Time-Lines

Conclusion

References

Questions

Relevant Definitions

Fault is a contingency/transient state, where system deviates from

its nominal state. ( Fault Start Time, Fault Duration, Fault Clearing Time)

Classical Electrical/Thermal Faults

Short Circuit, Open Circuit, Electrical Shocks, Insulation Fault, Reverse Current,

Overloading

Non Classical Faults Non Classical Faults

Arcing, Over Voltage/Surge, Shading

Fault in PV system can be split into A.C or D.C faults

The Protection device provides a form of insurance for electrical

components, by blocking and reducing the duration of disturbance

Standards and limitations

Different Standards, for Protection Requirements of PV Systems [1]

I. IEC 60364-7-712:2002-05 Electrical Installations of Buildings

II. IEC TS 62257-7-1:2006-12 Recommendations for Small Renewable Energy and Hybrid Systems for Rural Electrification

III. IEC 62109-1&2 Safety of Power Converters for Use in Photovoltaic Power Systems

Different Voltage Levels according to IEC [1]

Limitations

Considerations for electrical hazards in PV dominated by higher D.C voltage level i.e., Voltage

levels 120v D.C

Extra Low Voltage (ELV) level is assumed to pose low risk of threat , hence, it is generally

exempt from protection requirements ( Loose assumption which can lead to performance

degradation )

IEC Voltage Range AC DC Defining Risk

High Voltage >1000 Vrms >1500 V Electrical Arcing

Low Voltage 50-1000 Vrms 120-1500 V Electrical Shock

Extra-Low_voltage

Limitations ( continued)

According to standard IEC NFPA 70 article 69(2014):[1]

Hence, level of safety and careful measurements on the Low Voltage (LV) and

Medium Voltage (MV) level for PV protection does not seem to be sophisticated

[2] Current protection practice

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

Specific Objective

Methodology

Time-Lines

Conclusion

Questions

References

Objective

The objective of this research is :

To explore and evaluate the Necessary and Sufficient

protection strategies that currently exist or potentially

may prevail on Extra Low Voltage and Low Voltage

levels.levels.

The two conventional terms Necessary and Sufficient are used to

distinguish between basic and satisfactory level of protections

Note :

Protection scheme in ELV is quite underestimated.

Protection scheme in LV /MV is rather fragile

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

State of the Art

Methodology

Time-Lines

Conclusion

References

Questions

Current State of Research (Protection)

Monitoring and fault detection for hidden faults scenarios

[3]Zhao, Ye, et al. "Challenges to overcurrent protection devices under line-line faults in solar

photovoltaic arrays." Energy Conversion Congress and Exposition (ECCE), 2011 IEEE. IEEE, 2011.

[4]Zhao, Ye, et al. "LineLine Fault Analysis and Protection Challenges in Solar Photovoltaic

Arrays." Industrial Electronics, IEEE Transactions on 60.9 (2013): 3784-3795.

[5] Zhao, Ye, et al. "Outlier detection rules for fault detection in solar photovoltaic arrays." Applied

Power

[6]Xing Wu, 2011, Fault detection and diagnosis of Photovoltaic M.S. Thesis, University of Southern

California

[7]Silvestre, Santiago, Aissa Chouder, and Engin Karatepe. "Automatic fault detection in grid

connected PV systems." Solar Energy 94 (2013): 119-127.

[8]Luebke, Charles, et al. "Field test results of DC arc fault detection on residential and utility scale

PV arrays." Photovoltaic Specialists Conference (PVSC), 2011 37th IEEE. IEEE, 2011.

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

Methodology

Methodology

Time-Lines

Conclusion

References

Questions

Flowchart Plan

Comparing monitored data from experimental phase with simulation predicated results, to identify differences

Experiment

Prediction Isolation

System

Recovery

Simulation

Innovation/ Main

contribution

Analyses of

Problem

Experimental Stage

Experimental stage included number of rig experiments:

I. Standard Steady-State Module Level ( Non Standard Test Condition )

II. Short_Circuit Fault Module Level ( Non_STC)

III. Open_Circuit Fault Module Level ( Non_STC)

IV. Standard Steady-State Cell Level (Standard Test Condition )IV.

V. Short_Circuit Fault Cell Level (STC)

VI. Open_Circuit Fault Cell Level (STC)

Hence, module standard conditions will be presented from cell test results

At this phase of study, no protection element/device/agent is installed

Choosing the fine/the most appropriate sampling time to capture Electrical

Characteristics / measurement variables.

Flowchart Plan

Experiment

Prediction Isolation

System

Recovery

Simulation

Innovation/ Main

contribution

Proof of

Analysis

Flowchart Plan

Experiment

Prediction Isolation

System

Recovery

Simulation

Innovation/ Main

contribution

Proof of

Anlysis

Analyses

YesNo

Fault prediction

Extra Small scale

systemSmall scale system

Examination/ fault

occurrence validation

Fault prediction

Fault prediction

Examination/ fault

occurrence validation

Optimal

System

Recovery

Optimal

System

Recovery

Analyses

Fault prediction

Extra Small scale

systemSmall scale system

Examination/ fault

occurrence validation

Fault prediction

Fault prediction

Examination/ fault

occurrence validation

Optimal

System

Recovery

Optimal

System

Recovery

Analyses

YesNo

Fault prediction

Extra Small scale

systemSmall scale system

Examination/ fault

occurrence validation

Fault prediction

Fault prediction

Examination/ fault

occurrence validation

Optimal

System

Recovery

Optimal

System

Recovery

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

Timelines

Methodology

Timelines

Conclusion

References

Questions

Timelines and Workprograms

WP1: Literature Review/Thesis

WP2: Estimation of Electrical Characteristics using Experimental Rigs

WP3: Assessment of Measurement Variables by Means of Simulation

WP4: Evaluation of System Responses, Protection Mechanism and

Reactions

WP5: PV System Recovery/Restoration WP5: PV System Recovery/Restoration

Workpackages Mar(14)

Aug(14)

Sep(14)-

Feb(15

Mar(15)

Aug(15)

Sep(15)-

Feb(16)

Mar(16)

Aug(16)

Sep(16)-

Feb(17)

Mar(17)

Aug(17)

Sep(17)-

Feb(18)

Wp1 Wp1 Wp1 Wp1 Wp1 Wp1 Wp1 Wp1 Wp1

Wp2 Wp2 Wp2

Wp3 Wp3 Wp3

Wp4 Wp4 Wp4

Wp5 Wp5 Wp5 Wp5

D D/P1 D/P2 D/P3 D/P4/P5

M Transfer Confirmation Thesis

Years 1 1 2 2 3 3 4 4

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

Conclusion

Methodology

Time-Lines

Conclusion

References

Questions

Conclusion

ELV voltage level is treated to be inherently safe, hence, Module power is too

low to cause serious damage ???

There is still potential for fault /power loss and efficiency degradation in ELV (Ohmic losses ,Maximum Power Point Tracking ( MPPT),DC/AC conversion efficiencies, Operating above reference

temperature at module level, Mismatch and non-uniform temperature and irradiance in PV generator, Fault induced lower

irradiance )

Scope for diagnostic analyses, to identify the accountable cause of problem

(ELV)

Level of safety and careful measurements on the Low Voltage (LV) level for PV

protection does not seem to be as sophisticated

These issues all point to room for a novel approach, to provide a

holistic supply security and safety study on the DC side of PV systems

Conclusion

Fault predication and isolation is the current focus of academic

research and industry

PV system restoration has the potential to be explored

PV System Recovery Challenges

System restoration is mostly performed on the standard High and Medium Voltage

level systems(classical power system restoration) !!!!

Formulation of optimal decision based problem ,which is subject

to sets of constraint variables ( time, cost, etc)

Overview of Project

Introduction to Fault/Reliability Problems in PV Systems

Specific Objective

State of the Art

Conclusion

Methodology

Time-Lines

Conclusion

References

Questions

References

[1]www.iec.ch , Accessed Feb 2014

[2] Sizing fuses for Photovoltaic Systems per the National Electrical Code, 2012, Mersen

[3]Zhao, Ye, et al. "Challenges to overcurrent protection devices under line-line faults in solar photovoltaic arrays." Energy

Conversion Congress and Exposition (ECCE), 2011 IEEE. IEEE, 2011.

[4]Zhao, Ye, et al. "LineLine Fault Analysis and Protection Challenges in Solar Photovoltaic Arrays." Industrial Electronics, IEEE

Transactions on 60.9 (2013): 3784-3795.

[5] Zhao, Ye, et al. "Outlier detection rules for fault detection in solar photovoltaic arrays." Applied Power

[6]Xing Wu, 2011, Fault detection and diagnosis of Photovoltaic M.S. Thesis, University of Southern California

[7]Silvestre, Santiago, Aissa Chouder, and Engin Karatepe. "Automatic fault detection in grid connected PV systems." Solar Energy

94 (2013): 119-127.

[8]Luebke, Charles, et al. "Field test results of DC arc fault detection on residential and utility scale PV arrays." Photovoltaic

Specialists Conference (PVSC), 2011 37th IEEE. IEEE, 2011.

Thank you