Fiber-Optic RTD Monitoring for UL 2200 Generator Isolation

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Solution Overview

Problem

Resistance temperature detectors (RTDs) are not suitable for medium and high voltage generators due to non-compliance with circuit separation and signal accessibility requirements, as per UL 2200 Third Edition standards.

Innovation Solution

A system comprising a resistance temperature detector (RTD) module, a controller area network (CAN) module, and an optical interface, where the RTD module is positioned in a high voltage compartment and connected to the CAN module through a fiber-optic cable, allowing for optical signal conversion and isolation, ensuring compliance with UL 2200 standards.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If RTD monitors are used for temperature monitoring in generators, then temperature measurement capability is provided, but compliance with UL 2200 circuit separation requirements cannot be achieved

Engineering Contradiction:

Improvetemperature measurementVSAvoidcompliance with UL 2200 standards

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system is divided into two separate modules: an RTD module positioned in the high voltage compartment for temperature sensing, and a CAN module positioned in the low voltage compartment for signal processing and communication. This segmentation allows each module to operate in its appropriate electrical environment while maintaining functional integration through optical coupling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An optical interface using fiber-optic cable serves as an intermediary between the RTD module in the high voltage compartment and the CAN module in the low voltage compartment. This optical intermediary transmits signals without electrical connection, providing galvanic isolation that satisfies UL 2200 circuit separation requirements while maintaining reliable temperature monitoring capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If RTD module is positioned in high voltage compartment for direct temperature sensing, then temperature monitoring accuracy is improved, but risk of short circuits and electrical hazards increases

Engineering Contradiction:

Improvetemperature sensing accuracyVSAvoidshort circuit risk and electrical hazards

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The fiber-optic cable acts as an electrical intermediary that transmits temperature data from the high voltage compartment without conducting electrical current. This allows the RTD module to remain in the high voltage compartment for accurate temperature sensing while the optical interface prevents electrical hazards from affecting the low voltage control systems.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electrical signal transmission system is replaced with an optical transmission system. Instead of using electrical wires to connect the RTD module to the control system, the patent uses optical signals through fiber-optic cable, eliminating the risk of electrical short circuits while maintaining signal integrity for temperature monitoring.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If optical interface is used to isolate high voltage components, then compliance with circuit separation requirements is achieved, but system complexity increases

Engineering Contradiction:

Improvecircuit separation complianceVSAvoidsystem architecture

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system architecture is segmented into standardized functional modules (RTD module, optical interface, CAN module) that can be independently designed, tested, and maintained. This modular segmentation manages complexity by creating clear boundaries and interfaces while ensuring UL 2200 compliance through the optical separation between high and low voltage compartments.

Inventive Principle:

Principle #1Segmentation

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 system provides effective temperature monitoring for generators while meeting UL 2200 requirements by isolating high voltage components, preventing short circuits, and enabling programming without panel tagging.

Implementation Method 1

The resistance temperature detector (RTD) module can be configured to convert first optical signals from the optical interface to first RTD signals and to convert second RTD signals to second optical signals for transmission through the optical interface to the controller area network (CAN) module

Methodology Applied

Scientific EffectOptical signal conversion: Photoelectric Effect

Data Source

PatentUS12418223B2System, apparatus, and method for monitoring a generator

Publication Date: 2025.09.16 CATERPILLAR INC

AI summary

Generators, systems, and methods can comprise a resistance temperature detector (RTD) module; a controller area network (CAN) module; and an optical interface between the RTD module and the CAN module. The optical interface can be directly connected to each of the RTD module and the CAN module. The RTD module can be configured to convert first optical signals from the optical interface to first RTD signals and to convert second RTD signals to second optical signals for transmission through the optical interface to the CAN module. The CAN module can be configured to convert the second optical signals from the optical interface to first CAN signals and to convert second CAN signals to the first optical signals for transmission through the optical interface to the resistance temperature detector (RTD) module.