Battery String Ground Fault Location Using Bypass Diagnosis

Solution Overview

Problem

Locating ground faults in large energy storage systems is challenging, leading to prolonged maintenance times and safety risks due to the difficulty in pinpointing the exact fault location, which disrupts system operation and increases personnel exposure.

Innovation Solution

A method using pole unbalance voltage, energy storage system voltage, and string unbalance to identify potential ground fault locations, followed by successive bypassing of energy storage units to confirm the fault string, reducing the need for on-site personnel and accelerating fault resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual search method is used to locate ground fault, then personnel can physically inspect the system, but maintenance time increases and system downtime increases

Engineering Contradiction:

Improveground fault location precisionVSAvoidmaintenance time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces manual mechanical inspection with an automated electrical measurement system. The control unit automatically measures pole unbalance voltage and performs calculations to determine ground fault location, eliminating the need for personnel to physically search through the system while achieving precise fault location.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system performs self-diagnosis by automatically detecting ground faults and locating them without external intervention. The control unit continuously monitors pole unbalance voltage and autonomously determines fault positions, allowing the system to service itself rather than requiring manual inspection.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If manual search method is used to locate ground fault, then personnel can physically inspect the system, but system availability decreases due to prolonged downtime

Engineering Contradiction:

Improveground fault location precisionVSAvoidsystem availability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces manual mechanical inspection with an automated electrical measurement system. The control unit automatically measures pole unbalance voltage and performs calculations to determine ground fault location, eliminating the need for personnel to physically search through the system while achieving precise fault location.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system performs preliminary identification of ground faults and their locations continuously during operation. By monitoring pole unbalance voltage and calculating potential fault positions in advance, the system prepares fault location information before actual maintenance is needed, enabling faster response when faults occur.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If manual search method is used to locate ground fault, then personnel can physically inspect the system, but personnel safety is compromised due to increased exposure

Engineering Contradiction:

Improveground fault location precisionVSAvoidpersonnel safety risk

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces manual mechanical inspection with an automated electrical measurement system. The control unit automatically measures pole unbalance voltage and performs calculations to determine ground fault location, eliminating the need for personnel to physically search through the system while achieving precise fault location.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control unit acts as an intermediary between personnel and the potentially hazardous electrical system. It performs all dangerous measurements and calculations automatically, allowing personnel to receive fault location information without direct exposure to live electrical components, thus mediating between human operators and harmful electrical fields.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The method efficiently locates ground faults off-site, minimizing maintenance time, enhancing system availability, and ensuring personnel safety by automating the fault detection process.

Implementation Method 1

identifying a potential ground fault location associated with at least one energy storage unit candidate based on a number of energy storage units in the string, a pole unbalance voltage and an energy storage system voltage

Methodology Applied

Scientific EffectPole unbalance voltage measurement: Electric Field

Data Source

PatentUS20260023132A1Method for locating a ground fault, a control unit and an energy storage system

Publication Date: 2026.01.22 HITACHI ENERGY LTD

AI summary

There is disclosed herein a method for locating a ground fault in an energy storage system comprising a plurality of parallel strings. A string comprises a plurality of energy storage units connected in series and an energy storage unit includes one or more energy storage modules and a bypass circuit. The method comprises for each string of said energy storage system, identifying an energy storage unit candidate as a potential ground fault location based on a number of energy storage units in the string, a pole unbalance voltage and an energy storage system voltage, and determining in which string the ground fault is located by successively bypassing, one string at a time, at least some of the identified energy storage unit candidates and identifying the string for which a deviation from an expected behaviour is measured.