Surge Protection for Local Operating Networks

Surge Protection for Local Operating Networks

Created by: Glen Zhu | Updated Date: January 20th, 2024

Local Operating Networks Surge Protection

There is a common question regarding the ability of engineers to select the best sensing and control devices from different manufacturers and seamlessly integrate them for optimal performance.

While centralized control products with point-to-point wiring and hierarchical logic systems have advantages, there is a growing user preference for a flat system architecture where each point contributes to control processing.

Local operating networks (LONs) offer the solution to have all sensing and control devices from a range of manufacturers work together seamlessly and transform Building Automation Systems (BAS) with its peer-to-peer networking capabilities and adaptability to various communication channels.

As these networks become indispensable conduits for seamless communication within diverse systems, the threat of power surges looms large, necessitating a comprehensive surge protection strategy.

What is a local operating network?

LonWorks technology is a widely used communication protocol designed for building automation and control systems. Developed by Echelon Corporation, LonWorks enables devices and systems to communicate seamlessly over a common network, fostering interoperability and efficient control.

When used in an industrial environment, LonWorks stands out as a fully peer-to-peer network, distinguishing itself from other popular device busses. Additionally, it exhibits flexibility by not being confined to a single physical communication layer, allowing the use of twisted pair, Ethernet, or even a power line as its communication channel.

Figure 1 – Structure of a LonWorks node with neuron clip, transceiver and I/O circuit

In LonWorks networks, intelligent nodes, each equipped with a neuron chip, communicate with one another using the LonTalkProtocol®. These nodes perform specific functions, ranging from simple tasks like controlling switches to more complex operations such as regulating temperatures in buildings or managing industrial processes.

The communication between nodes is facilitated by transceivers, which allow the exchange of data over various transmission media, including two-wire connections, 230 V, optical fiber cable, coaxial cable, LAN, and radio. This flexibility in transmission mediums enables LonWorks to adapt to diverse automation requirements.

Each node features an Input/Output (I/O) circuit, enabling connections to devices like switches, relays, and measurement systems. The decentralized intelligence of LonWorks nodes allows them to make autonomous decisions, contributing to the scalability and flexibility of the overall automation system.

Free Topology Transceivers (FFT) and Link Power Transceivers (LPT) are often used in LonWorks networks, providing the flexibility to place the two-wire bus cable in free space. These transceivers, along with surge protection measures, ensure the reliability and robustness of the network.

LonWorks technology emphasizes interoperability, enabling nodes to seamlessly communicate and work together. The nodes collectively form a distributed network where information is shared, and tasks are coordinated to achieve automation and control objectives.

Two-wire bus cable

The two-wire bus cable serves as a fundamental transmission medium in various communication systems, facilitating the exchange of data between nodes and devices within a network. Commonly employed in technologies like LonWorks, this cable, often exemplified by types such as J-Y(ST)Y 2x2x0.8, is designed to support the specific communication protocols required for seamless connectivity.

Its versatility and adaptability make it a vital component in enabling reliable and efficient data transmission, contributing to the robustness of networks in diverse applications, from industrial settings to building automation systems.

Transceivers associated with the two-wire bus cable, such as J-Y(ST)Y 2x2x0.8, exhibit distinct transmission rates (kbit/s), influencing maximum network expansion based on cable length (measured in meters). Capitalizing on the flexibility to position the two-wire bus cable in free space, devices within LON building installations are predominantly equipped with Free Topology Transceivers (FFTs) and Link Power Transceivers (LPT).

These LPTs are seamlessly compatible with FTTs operating on the same bus. In FTT/LPT networks, transceivers specify core/core and core/earth capacitances, detailed for reference. When surge protective devices are integrated, their capacitances (core/core and core/earth) become pivotal considerations, leading to a proportional reduction in the maximum allowable number of transceivers.

LPT vs. FTT Transceivers

LPTs focus on combining communication and power delivery over a two-wire bus cable. FTTs support Free Topology Networks, allowing for flexible device placement and communication over various mediums.

LPTs are beneficial in applications where efficient power distribution and streamlined wiring are priorities. FTTs are suitable for applications where the physical layout of the network needs to be adaptable or where traditional bus structures are impractical.

LPTs simplify the wiring infrastructure by providing both communication and power over a single cable. FTTs enhance scalability and ease of installation by enabling communication over diverse mediums, eliminating the need for a strict physical bus layout.

In summary, LPTs primarily address the integration of power and communication in a wired environment, while FTTs cater to applications requiring flexible device placement and communication over various mediums in a network with adaptable physical layouts.

Capacitances of surge protective devices

The capacitances of transceivers in FTT/LPT networks are crucial for ensuring proper electrical performance, signal integrity, and network stability. It is important for engineers and designers carefully manage capacitance values to optimize the overall functionality and efficiency of the network.

Each transceiver has two relevant capacitances: core/core and core/earth. Core/core capacitance refers to the electrical storage capacity between the data transmission lines within the transceiver. Core/earth capacitance measures the storage capacity between a data line and the ground connection.

Why it matters:

Signal Distortion: High core/core capacitance can create signal reflections and crosstalk, where data traveling in one direction interferes with data going the other way. This can corrupt the information being transmitted and lead to communication errors.

Reduced Network Reach: Higher core/earth capacitance affects the voltage levels on the bus cable, limiting the maximum network length achievable. Shorter networks mean fewer devices can be connected, potentially compromising functionality.

Table 1 – Capacitances of transceivers in FTT/LPT networks

Surge Protection Device (SPD) Compatibility: SPDs also have their own capacitance, and choosing SPDs with capacitance values incompatible with the network transceivers can further exacerbate signal distortion issues.

Table 2 – Capacitances of surge protective devices

How power surges affect local operating systems?

Lightning strikes are a common cause of power surge. A massive surge of electrical energy could be introduced into local electrical system, affecting connected devices and local operating systems.

Electronic devices running operating systems are susceptible to power surge, a sudden increase in voltage will exceed their safe limits and damage or destroy the components. Local operating systems should be carefully protected from the influence of electromagnetic inductions.

An induction loop occurs when conductors form a closed loop, and a changing magnetic field induces an electrical current in that loop. Therefore, good care should be taken not to form the induction loops when routing the cables.

Figure 2 – Induction loop caused by two nodes

The two nodes are connected by a wire in a circuit, once current flows through this wire, it generates a magnetic field around it. If this wire is placed proximity to another wire, the magnetic field from the first wire can induce a current in the second wire, even though they’re not physically connected. Thus, an unintended electrical pathway, a loop, between the two nodes created.

Figure 3 – Induction loop caused by a magnetic valve attached to a metallic pipe

This phenomenon, called electromagnetic induction, explains how the pipe becomes “charged” with electricity even though it’s not directly connected to any power source. Metal pipes are good conductors, a changing field can create an electrical current flowing to nearby metal pipes. The stronger the change, the stronger the current.

The way to avoid the formation of loops, carefully route wires to avoid creating loops or placing them too close together. Use shielded cables to block magnetic fields and reduce induction effects. Properly ground equipment to provide a safe path for induced currents to dissipate. Maintain appropriate distance between sensitive wires and potential sources of magnetic fields.

Surge protection

Surge protection is crucial for both LPT and FTT network in LonWorks technology to safeguard against power surge and ensure the robustness of the systems.

Installed a type 3 surge protective device at the entry of power line, designing to divert excess electrical energy away from the network.

DIN-rail mounted Class D SPD to protect sensitive equipment

For signal lines, FRD2-48 is recommended to protect the function of local operating systems. As the feature of LPT, it combines data transmission and power supply into a single chip, this eliminates the need for separate power line, simplifying installation and reducing cable clutter. Additional FRD-48 is placed beside the node to prevent the induction loops from power surge.

Figure 4 – Surge protective devices for an LPT in a combination topology

Figure 5 – Surge protective devices for an FTT in a combination topology

The FTT network use a flexible topology, unlike LPTs, FTTs don’t provide power to node. This means they require separate power lines. Devices within an FTT network are independent and can communicate without a centralized controller. Each device has its own intelligence and can perform control processing independently, contributing to a more resilient and scalable network.

Another FRD2-24 should be mounted to protect the data transmission and control signal independently.

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