“The importance of correctly specifying the right cable for AMI metering installations cannot be overstated. Using cables that meet the required standards for signal integrity, environmental durability, and safety is essential for ensuring accurate data transmission, reducing maintenance costs, and ensuring long-term operational reliability. Whether it’s selecting the right shielding, insulation, or mechanical properties, specifying the correct cable is a crucial step in optimizing the performance of metering infrastructure.” – MJ Martin
In the Canadian gas, water, and electrical metering industry, we use a lot of connecting cables to interconnect the meter to the AMI (Advanced Metering Infrastructure) radio. In most cases, customer buy any old cable available to make these connections.
But, it is exactly here where the weakest link in the infrastructure occurs. This is a single point of failure.
The specific percentage of technical infrastructure failures attributed to “craft skills” can vary significantly depending on the industry, the type of infrastructure, and how “craft skills” are defined (e.g., individual expertise, manual techniques, or specialized trades). Generally, studies in fields like IT, construction, and engineering attribute a range of failures to human error, often between 60-80%, which may include issues related to craft skills such as poor workmanship, wrong materials, improper installation, or lack of expertise.
If we were to pinpoint it all further, then cables and connections are the proverbial Achilles heel of the craft skills problem. And, the cable specification is the source of the majority of trouble issues that evolve over time.
Key Factors Influencing Failure:
- Complexity of Tasks: The more complex and specialized the task, the greater the reliance on high-level craft skills.
- Training and Certification: Insufficient training or lack of certification in specialized trades increases the risk of errors.
- Quality Assurance: Failure to adhere to strict QA processes can allow minor craft skill issues to escalate into larger system failures.
Therefore, getting the right cable upfront is a critical issue.
For AMI metering in Canada with our cold winters and hot sunshine in the summers, we must specify the cable to a known and trusted standard. I say this point so often that it is time to document it for clearer instruction going forward.
THE BEST CABLE SPECIFICATION
Fire Rating
In Canada, fire codes related to cabling are governed by the National Fire Code of Canada (NFC) and the Canadian Electrical Code (CEC), with specific rules for cable types and their installation to mitigate fire risks. This is a critical specification that is often neglected.
Key Points:
- Fire-Resistant Cabling: Cabling in buildings must meet certain flame-spread and smoke development ratings, depending on where it is installed. For example, plenum-rated cables are required in air-handling spaces because they emit less toxic smoke and flame.
- Testing and Compliance: All cables must be tested and certified to meet fire safety standards. The Canadian Electrical Code specifies requirements for installation to prevent overheating, sparking, and other hazards that could ignite fires.
- Retroactive Requirements: The NFC ensures that safety levels from the initial building phase are maintained. This includes maintaining or upgrading fire alarm and sprinkler systems in accordance with updated safety standards, which could indirectly affect cabling requirements for these systems.
- Inspection and Maintenance: Regular inspections are mandated to ensure continued compliance with safety standards. Faulty or outdated cabling must be replaced to minimize risks.
In Canada, the fire ratings for cables, including FT1, FT3, and FT5, are defined by the Canadian Electrical Code (CEC) and related standards.
- FT1: This rating is for cables used in areas where fire risk is lower. It tests whether a cable will self-extinguish after being exposed to a flame. The flame is applied five times for 15 seconds each, and the cable should not burn for more than 60 seconds after each application. These cables can be used within a room.
- FT3: This rating is similar to FT1 but focuses more on cables intended for use in residential and commercial buildings. It ensures cables can self-extinguish under stricter testing conditions, limiting the spread of fire in vertical installations. These cables can be used within a room, but if run between rooms they must be enclosed within a suitable conduit.
- FT5: Specifically for portable power cables, particularly in mining or industrial applications. These cables undergo more rigorous testing, including exposure to higher temperatures and electrical current, to ensure they don’t sustain prolonged burning beyond a specified length. These cables can be run within a room, between rooms, or pretty much anywhere in a home or business. However, they are typically Teflon cables so they are very difficult to strip and work with due to the strength of the jacket.
Each rating reflects the cable’s suitability for specific environments, balancing performance and fire safety. For example, FT1 is common in general indoor settings, whereas FT5 is tailored for industrial, high-risk applications
Number of Conductors
For radio connections, we need three conductors for the AWWA UI-1203 communications standard. It is often a false economy thinking that installers buy a four conductor cable instead of three conductors under the assumption that if one conductor fails then a spare conductor strand in instantly available to replace it and quickly restore the service.
However, all of the conductors reside within the same skinny jacket. So, if a staple penetrates the jacket the likelihood is that it will damage several or all conductors and not just one single conductor.
So, just buy a three conductor cable and focus your cable spending on the other attributes, like fire rating and UV tolerance.
Solid Conductors
The choice between solid and stranded 22-gauge conductors depends on the application:
- Solid Conductors: Better for permanent installations where cables won’t move, such as inside walls or fixed outdoor setups. They offer lower resistance and better signal transmission over long distances.
- Stranded Conductors: Composed of multiple small wires, they are more flexible and resistant to fatigue, making them ideal for applications where cables need frequent movement or bending, like portable devices or patch cables.
Both types offer specific benefits depending on mechanical and electrical requirements.
Bending Radius
The bending radius for 22-gauge AMI cables typically ranges from 4 to 6 times the cable’s outer diameter, depending on the type of cable (solid vs. stranded) and its insulation. For example, a solid 22-gauge cable may have a slightly smaller bending radius compared to a stranded one. Exceeding the recommended bending radius can damage the cable, affecting its performance and longevity. Always check manufacturer specifications for exact guidelines to ensure safe installation and proper signal integrity.
Wire Gauge
To connect an Itron ERT (Encoder Receiver Transmitter) to a meter, you typically use a 22 AWG cable. This gauge is common for such installations, as it ensures sufficient durability and conductivity over typical installation lengths, which can be up to 300 feet depending on the ERT model and environmental conditions. It’s crucial to use approved cables by Itron, or whatever manufacturer of radio you are installing to maintain signal integrity and meet compliance standards for accurate meter readings and data transmission.
Sometimes it is smart to select a 20 AWG cable. This thicker gauge will be a better conductor especially on longer cable runs but adds little to no value whatsoever for shorter cable runs less than 25 feet.
Cable Length
For many AMR / AMI radios, such as the most popular Itron ERT radios, a maximum cable length of 300 feet is set as the standard. Other radios from Neptune, Sensus, and Kamstrup may require a different maximum cable length, so check with the manufacturer before planning the installations.
Most AMI radio manufacturers, such as Itron, make in-line connector register cables: 5 feet and 25 feet (ordered separately). You can order a variety of endpoint cables such as bared and tinned stripped conductors (aka pigtails), NICOR connectors, ERT twist-lock, and more,
Inter-cable Connections
Use only 3M or Philips gel caps to make cable to cable connections. Gel cap connectors are designed to quickly connect two (2) or three (3) telecom conductors. Insert the un-stripped wires, and crimp the cap of the connector and this will complete the connection. Connectors are filled with dimethyl silicone fluid insulation that oozes out once crimped to seal the connection and protect the conductors.
Ultraviolet Breakdown
For cables exposed to sunlight or outdoor environments, as these radio cables often are, it is important to choose one labeled as UV-resistant or UV-protected. These cables are specifically designed to withstand prolonged exposure to ultraviolet rays, preventing degradation of the outer jacket material. Look for certifications like UL or CSA listing or compliance with industry standards indicating UV resistance. Popular options include outdoor-rated cables with UV-resistant PVC or polyethylene jackets. You can find these from specialized electrical suppliers or online retailers.
Rodent Protection
Rodent protection in the cable jacket is highly beneficial for AMI (Advanced Metering Infrastructure) cables used in metering. Rodents can chew through standard cable jackets, causing signal interruptions or power outages. Cables with rodent-resistant jackets, often reinforced with materials like metal braid, fiberglass, or specialized polymer compounds, help prevent this damage. This is especially important for outdoor or underground installations where rodent activity is more likely, ensuring reliable data transmission and reduced maintenance costs.
Grounding and Shielding
AMI (Advanced Metering Infrastructure) cables with quad shielding provide superior protection against electromagnetic interference (EMI) and radio frequency interference (RFI). Quad shielding consists of multiple layers of foil and braid, which ensure better signal integrity, especially in environments with high EMI, such as near power lines or substations. This makes them ideal for reliable data transmission in metering applications, helping to reduce errors and ensure accurate, uninterrupted readings. Additionally, quad-shielded cables often include robust insulation, making them suitable for both indoor and outdoor installations.
Conclusion
Specifying the correct cable is crucial for ensuring the reliability, safety, and efficiency of any system, especially in applications like AMI (Advanced Metering Infrastructure). The right cable type provides:
- Signal Integrity: Prevents data loss or corruption due to interference.
- Safety Compliance: Meets fire and environmental safety codes (e.g., UV or rodent protection).
- Durability: Withstands environmental factors like temperature, moisture, and mechanical stress.
- Cost Efficiency: Reduces maintenance and replacement costs by preventing premature failures.
Correct specification aligns system performance with operational and regulatory requirements.
About the Author:
Michael Martin is the Vice President of Technology with Metercor Inc., a Smart Meter, IoT, and Smart City systems integrator based in Canada. He has more than 40 years of experience in systems design for applications that use broadband networks, optical fibre, wireless, and digital communications technologies. He is a business and technology consultant. He was a senior executive consultant for 15 years with IBM, where he worked in the GBS Global Center of Competency for Energy and Utilities and the GTS Global Center of Excellence for Energy and Utilities. He is a founding partner and President of MICAN Communications and before that was President of Comlink Systems Limited and Ensat Broadcast Services, Inc., both divisions of Cygnal Technologies Corporation (CYN: TSX). Martin served on the Board of Directors for TeraGo Inc (TGO: TSX) and on the Board of Directors for Avante Logixx Inc. (XX: TSX.V). He has served as a Member, SCC ISO-IEC JTC 1/SC-41 – Internet of Things and related technologies, ISO – International Organization for Standardization, and as a member of the NIST SP 500-325 Fog Computing Conceptual Model, National Institute of Standards and Technology. He served on the Board of Governors of the University of Ontario Institute of Technology (UOIT) [now OntarioTech University] and on the Board of Advisers of five different Colleges in Ontario. For 16 years he served on the Board of the Society of Motion Picture and Television Engineers (SMPTE), Toronto Section. He holds three master’s degrees, in business (MBA), communication (MA), and education (MEd). As well, he has three undergraduate diplomas and five certifications in business, computer programming, internetworking, project management, media, photography, and communication technology. He has completed over 30 next generation MOOC continuous education in IoT, Cloud, AI and Cognitive systems, Blockchain, Agile, Big Data, Design Thinking, Security, Indigenous Canada awareness, and more.