Electrical protection of Integrated Wiring System

The Integrated Wiring System is part of smart buildings. Compared with traditional cabling systems, it features compatibility, openness, flexibility, reliability, advancement, and economics, it connects voice, data, Image devices, and exchange devices to other information management systems, as well as external communication networks. It can be said that the Integrated Wiring System is like an expressway of a smart building. With this information expressway, it is very easy to think about any application system. The purpose of Integrated Wiring electrical protection is to reduce the damage to cables and related connection hardware of Integrated Wiring due to electrical faults, and to avoid damage to terminal equipment or devices, ensure the normal operation of the system.

I. Electrical Protection

When an outdoor cable enters a building, it is usually transferred to the room at the entrance. Electrical protection equipment should be installed at the transfer place, in this way, the user's equipment is damaged by the induction potential generated by lightning strikes on the cable or the contact with the power line.

Electrical protection can be divided into overvoltage protection and overcurrent protection. These protection devices are usually installed in a dedicated room or wall at the entrance of a building.

The overvoltage protection of Integrated Wiring can be either gas discharge tube protector or solid-state protector. The gas discharge tube Protector uses the gap of disconnections or discharge to limit the voltage between the conductor and the ground. The discharge gap is formed by two metal poles sealed in the Ceramic Housing and filled with inert gas. When the potential difference between the two electrodes exceeds V of AC or the lightning surge voltage exceeds V, an arc occurs in a gas discharge tube, providing a conductive path between the conductor and the ground electrode.

Solid State protector is suitable for low breakdown voltage of 60 ~ 90 V), and the circuit cannot contain the ring voltage. It uses electronic circuits to drain excessive harmful voltage to the ground without affecting the transmission quality of the cable. The solid-state protector is an electronic switch. It can perform a stable voltage reset before it reaches the breakdown voltage. Once it exceeds the breakdown voltage, it will introduce the overvoltage to the ground, solid State protectors provide optimal protection for integrated wiring.

In addition to Overvoltage Protection, the Integrated Wiring System also adopts overcurrent protection. The over-current protector is connected in series. When the over-current occurs, the line is cut off. For ease of maintenance, overcurrent protection generally uses a Protector with the automatic recovery function.

Ii. Shielding

Electromagnetic interference and radiation are problems of the entire application system. The interference caused by Integrated Wiring cables is only part of the problem, and the radiation energy is related to the voltage and frequency of the sent signal. Shielding is used to ensure the transmission performance of the Integrated Wiring channel in an interference environment. It consists of two parts: reducing the energy of the cable itself radiating outward and improving the cable's ability to resist external electromagnetic interference.

The overall performance of Integrated Wiring depends on the performance of the weakest cable and related connection hardware in the application system and the connection process. In Integrated Wiring, the weakest link is the distribution frame and cable connection components, and the contact parts of the information outlet and plug. When the shielding layer of the shielded cable cracks during installation, it also forms a weak link in the shielding channel. In order to eliminate electromagnetic interference, in addition to non-Intermittent points on the screen layer, the overall transmission channel must be shielded at 360 ° throughout the process. For a point-to-point connection channel, it is very difficult to achieve, because the information plug-in, jumper, and so on are difficult to achieve full shielding, coupled with the corrosion of the shielding layer, oxidation damage and other factors, therefore, no channel can truly block the whole process. At the same time, the shielding layer of the shielded cable has poor shielding effect on the low-frequency magnetic field and cannot resist the low-frequency interference caused by equipment such as motor. Therefore, shielding Cables cannot completely eliminate electromagnetic interference.

Theoretically, in order to reduce the external world, shielding measures can be used to shield static shielding and magnetic shielding. The shielding principle is that the interference current is short-circuited to the ground after the shielding layer is grounded. Therefore, it is very important to properly shield the ground. Otherwise, the interference will not be reduced, but will increase. When the grounding point is incorrectly arranged, the grounding resistance is too large, and the grounding potential is not balanced, it will cause grounding noise, that is, the potential difference is generated at a certain two points in the transmission channel, in this way, the interference current is generated on the metal shielding layer. At this time, the shielding layer itself forms the largest interference source, resulting in far inferior performance to the non-shielded transmission channel. Therefore, to ensure screen effect, the screen must be properly and reliably grounded.

In practical application, in order to minimize interference, in addition to ensuring the integrity of the Screen Layer and reliable grounding of the Screen Layer, you should also pay attention to the working environment of the transmission channel, stay away from various sources of interference, such as power lines, transformers, and electric data centers. When the Integrated Wiring environment is extremely harsh, the electromagnetic interference is strong, and the information transmission rate is high, optical cables can be directly used to meet the electromagnetic compatibility requirements.

Iii. System grounding

Integrated cabling cables and related connection hardware grounding are an important means to improve application system reliability, reduce noise, and ensure security. Therefore, before wiring design and construction, the designers and construction personnel must carefully study the grounding requirements of all equipment, especially the application system equipment, determine the grounding requirements and the relationship between various ground wires. Improper handling of the grounding system will affect the stability of the system equipment, cause faults, and even burn down the system equipment, endangering the safety of the operator. The grounding of the Integrated Wiring System equipment room and equipment can be divided into DC work grounding, AC work grounding, safety protection grounding, lightning protection grounding, anti-static connection and shield grounding.

A set of grounding devices should be used for four types of grounding: AC work grounding, safety protection grounding, DC work grounding, and lightning protection grounding. The grounding system is aimed at the ease of Grounding Current flow, and can also reduce the interference caused by potential changes. Therefore, the smaller the grounding resistance, the better. Therefore, the resistance value of the shared grounding system shall be determined based on the minimum value.

When the lightning protection grounding device is set separately, the AC, DC and security protection grounding should adopt the same set of Grounding Devices. In order to prevent lightning voltage from cracking back on Integrated Wiring and connecting equipment, it is required to maintain a sufficient distance between the lightning protection device and other grounding bodies. However, this requirement is difficult to achieve in engineering design. For example, multi-layer Building Lightning Protection grounding generally uses the main rib of the building and the main rib of the base plate as the grounding wire and grounding body, which cannot meet the safety distance requirements with other grounding bodies and may generate a counterattack. At this time, only various metal bodies in the building and access pipe lines can be strictly grounded, and all grounding devices must be shared and connected in multiple places, so that the potential of the lightning protection device and adjacent metal objects can be as similar as possible, to prevent lightning attacks and ensure the safety of Integrated Wiring and system equipment.

According to the requirements of national regulations, grounding devices should be set up in the entrance area of the building, the floor wiring of the high-rise building, or the second-level switching room. The shielding layer of the Integrated Wiring introduced into the cable must be connected to the grounding device in the entrance area of the building. the shielding layer of the trunk cable should be connected to the grounding device of the wiring room or the switching room with more than 4mm2 copper wires, in addition, the shield layer of the trunk cable must be continuous. The grounding of the wiring room should be welded with multiple copper wires and the grounding bus, and then taken to the grounding device. Unshielded cables shall be laid in metal pipes or metal trough, and metal trough pipes shall be connected reliably to maintain electrical connection and lead to the grounding dry line. At the same time, the distribution frame and other equipment grounding should be connected in parallel with the grounding device, cannot be connected in series.

In short, the electrical protection of the Integrated Wiring System plays an important role in the safe and reliable operation of the system. Only by careful design and construction can the electrical protection system meet the requirements of specifications and equipment, and ensure the normal operation of the Integrated Wiring System.

1. Design and Construction of structured Integrated Wiring System
2. Understand Integrated Wiring and integrated wiring systems