Shielded Twisted Pair Antenna Cable for Partial Discharge Monitoring

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Solution Overview

Problem

Coaxial cables suffer from poor common mode RFI immunity, leading to radio frequency interference issues, especially in environments with high interference, which complicates the detection of partial discharge events in electric power assets and limits the effectiveness of wireless sensor systems.

Innovation Solution

The use of shielded twisted pair cabling to carry multiple antenna signals, including partial discharge monitoring signals, which reduces common mode RFI by using a cable sheath that is not part of the signal transmission path, allowing for diversity antenna operation and improved electromagnetic compatibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If coaxial cable is used for antenna connection, then signal transmission is achieved, but common mode RFI immunity deteriorates due to the outer conductor acting as an antenna

Engineering Contradiction:

Improvecommon mode RFI immunityVSAvoidradio frequency interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the problematic outer conductor antenna function from the coaxial cable system by transitioning to shielded twisted pair cable where the shield does not serve as a signal carrier. This separation removes the source of common mode RFI injection while preserving signal transmission capability through the twisted pair conductors.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the fundamental cable construction parameters from coaxial geometry to twisted pair geometry with separate shielding. This parameter change transforms the cable's electromagnetic characteristics, eliminating the common mode antenna effect while maintaining signal integrity through balanced differential signaling.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If coaxial cable outer conductor is used for signal transmission, then signal carrying capability is achieved, but electromagnetic radiated emissions compliance deteriorates due to reflected signals

Engineering Contradiction:

Improveelectromagnetic emissions complianceVSAvoidreflected signals

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces balanced differential signaling as an intermediary mechanism between the signal source and transmission medium. This intermediary approach converts single-ended signals to differential signals, which inherently reject common mode reflections and reduce radiated emissions through balanced electromagnetic field cancellation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If coaxial cable is used in high interference environments with motors and generators, then connection is established, but noise floor increases limiting sensor system performance

Engineering Contradiction:

Improvenoise floorVSAvoidenvironmental interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent converts the potentially harmful electromagnetic interference from motors and generators into a manageable common mode signal that can be rejected by the balanced differential receiver. The twisted pair construction and differential signaling transform environmental noise into a form that cancels out at the receiver, improving measurement precision in harsh environments.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Adaptability or versatility

If coaxial cable is used for antenna connection, then signal transmission is achieved, but multiple sensor types and feed points cannot be supported within a single cable

Engineering Contradiction:

Improvemultiple sensor types supportVSAvoidcable configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent makes the shielded twisted pair cable universal by designing it to accommodate multiple sensor types and antenna feed points within a single cable assembly. The multi-pair construction allows different pairs to be assigned to different functions (antenna elements, partial discharge sensors, temperature sensors, humidity sensors), enabling a single cable to replace multiple specialized cables.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11313895B2Antenna connectivity with shielded twisted pair cable

Publication Date: 2022.04.26 ROSEMOUNT INC

AI summary

A sensor system for an electric power asset includes a sensor instrument coupleable to sensors associated with the electric power asset to receive sensor signals therefrom, and an antenna connection cable coupled to the sensor instrument. The antenna connection cable includes a cable sheath and a plurality of twisted pair signal carriers contained within the cable sheath to carry sensor signals received from the electric power asset. A first subset of the plurality of twisted pair signal carriers carry antenna signals and a second separate subset of the plurality of twisted pair signal carriers carry signals for partial discharge monitoring.