Issue link: https://resources.mouser.com/i/1442796
| 20 | Revised Standards Provide Design Options for Primary and Secondary Protection Telecommunications networks are subject to surges from lightning or power line faults, and the effects of these can be extremely detrimental to systems and equipment. The equipment in a telecommunications network needs to be protected from fault voltages and currents induced onto the conductors. Standards provide equipment test requirements guidelines and often are separated into two main classifications: Primary and secondary. Standards such as ITU-T and Telcordia GR-1089-CORE, Issue 6, contain tests in which equipment is tested with the primary protector in place. With vast differences distinguishing one telecommunication network from the next, standards provide a basis for equipment suppliers and customers alike to select the surge protection criteria that best suits their specific network application. The Alliance for Telecommunications Industry Solutions (ATIS) recently updated its coordination document "Electrical Coordination of Primary and Secondary Surge Protection for Use in Telecommunications" (ATIS-0600338.2010) to aid in suitable design. This paper discusses how to ensure system coordination by designing with various series coordination elements as presented in the updated ATIS document. Various system coordination styles and protection technology options will be presented with an emphasis on current-type coordination. Types of Coordination There are three types of coordination covered in the ATIS-0600338.2010 document that can be considered in the design. First, with system coordination no failures occur to a predetermined fault level. In this arrangement, the primary protector external to the equipment can either operate or not operate. Secondly, voltage-type coordination is where the primary protector operates before the secondary protection that is located in the equipment as shown in Figure 1. The equipment will allow the primary protector voltage to be developed across its terminals without the secondary protector operating. Once the primary protector operates, it will shunt all the fault current away from the equipment. Finally, current-type coordination is where the secondary protection at the equipment operates before the primary protector, as shown in Figure 2. This type of coordination is commonly used. A coordination element is included to generate