SSTDR Fault Detection in Photovoltaic Systems

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Solution Overview

Problem

Existing methods for detecting faults in photovoltaic (PV) electrical systems, particularly those with numerous interconnections and impedance mismatches, are inefficient and require manual isolation and measurement steps, making it difficult to accurately locate and address faults.

Innovation Solution

The use of Spread Spectrum Time Domain Reflectometry (SSTDR) with a fault detection system that compares SSTDR autocorrelation data against baseline data to identify and locate faults by calculating differences and cumulative differences, allowing for automated fault detection and mitigation in PV electrical systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual isolation and measurement steps are used to detect faults in PV systems, then measurement precision can be maintained, but productivity decreases and loss of time increases

Engineering Contradiction:

Improvefault detection accuracyVSAvoidfault detection efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces manual mechanical isolation and measurement steps with an automated electronic system that uses SSTDR signals to detect faults. The system automatically transmits spread spectrum signals through the PV system, captures reflected signals, processes autocorrelation data, and identifies fault locations without requiring physical isolation or manual measurement procedures, thereby maintaining precision while dramatically improving productivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system enables the PV system to self-diagnose faults by automatically comparing SSTDR autocorrelation data against baseline data and identifying deviations that indicate fault conditions. This self-service capability eliminates the need for external manual intervention while maintaining accurate fault detection

Inventive Principle:

Principle #25Self-service

2Measurement precision

If manual isolation and measurement steps are used to detect faults in PV systems, then measurement precision can be maintained, but loss of time increases

Engineering Contradiction:

Improvefault detection accuracyVSAvoidfault detection time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The automated electronic SSTDR system replaces time-consuming manual isolation and measurement procedures with rapid signal transmission and processing. The system can detect and locate faults in real-time or near-real-time by analyzing reflected SSTDR signals, reducing fault detection time from potentially hours of manual work to minutes or seconds while maintaining measurement precision

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system establishes baseline SSTDR autocorrelation data during normal operation before faults occur. This preliminary action allows the system to quickly compare current readings against the baseline and immediately identify faults without requiring time-consuming manual measurement procedures when a fault actually occurs

Inventive Principle:

Principle #10Preliminary action

3Productivity

If SSTDR is applied to PV systems with numerous interconnections and impedance mismatches, then productivity improves through automation, but measurement precision deteriorates due to signal interference

Engineering Contradiction:

Improvefault detection automationVSAvoidfault detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system extracts and isolates the specific fault-related reflected signals from the complex mixture of signals in the PV system. By using autocorrelation processing and comparing against baseline data, the system can distinguish true fault signals from normal impedance mismatches and interconnection variations, maintaining precision while enabling automated detection across complex PV system architectures

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables efficient and automated detection and location of faults in PV systems, reducing the need for manual steps and improving fault identification accuracy, allowing for timely mitigation and system restoration.

Implementation Method 1

SSTDR typically involves a) transmitting a signal into the electrical network under test (e.g., transmitting a pseudo random binary signal modulated sine wave through a transmission line), b) detecting the reflected signal, and c) identifying impedance mismatches in the electrical network

Methodology Applied

Scientific EffectTime Domain Reflectometry: Echo

Implementation Method 2

identifying impedance mismatches in the electrical network by, inter alia, autocorrelation between the transmitted signal(s) and the reflected signal(s)

Methodology Applied

Scientific EffectAutocorrelation:

Data Source

PatentUS10038401B2Systems and methods for fault detection

Publication Date: 2018.07.31 UNIV OF UTAH RES FOUND

AI summary

A fault detection module acquires Spread Spectrum Time Domain Reflectometry (SSTDR) data pertaining to an electrical system, such as a photovoltaic string. A fault may be detected by use of difference data, calculated by comparing the SSTDR autocorrelation data to baseline SSTDR autocorrelation data previously acquired from the electrical system. The cumulative difference in the SSTDR autocorrelation data may indicate the presence of a fault and/or the location of the fault within the electrical system.