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To ensure the safety of trains, passengers and track workers as well as guarantee uninterrupted traffic flow, the US Rail Safety Improvement Act of 2008 mandates the adoption of a Positive Train Control (PTC) system by December 2015 by any mainline rail corridor sharing freight and passenger operations.

An entrance protector is required for telephone or control lines for the same reason an entrance protector is needed for power lines. The local telephone company usually supplies the building entrance station protector as part of their installation service. This is usually a single gas tube per wire type protector. Ground it to your perimeter ground system. The telco supplied protectors prevent surge currents from entering the building and radiating a magnetic field inside the equipment room.

RF lightning protectors are designed to protect RF equipment by equalizing the potential difference between the center pin of the coax cable and its shield. The majority of RF protectors do not feature indicator lights to show whether or not they are still functioning. Since power is not readily available at some installation points, an indicator light is not practical and would add significant cost to the protector. So how do we know if the protector is still functional? Since the IS-50 and IS-B50 are the most widely used PolyPhaser RF protector series, finding their application in Land Mobile Radio, SCADA systems, amateur radio and many others, this paper focuses on their specific testing condition.

There are volumes of information available on what we believe lightning is and how we think it works, most of it beyond the scope of this modest textbook. We will indulge in a form of pragmatism focusing on a practical approach to equipment protection at a communications site during a lightning “event.” The science of grounding (earthing) for lightning events encompasses both the laws of physics and RF design. Throughout this textbook are proven concepts, which will protect your valuable equipment from direct or induced lightning damage. Whether your equipment is at radio site, pipe line, utility sub-station, telephone central office, maritime, military, or sensitive security installation, the same requirements apply for protection devices, proper device placement, and earth grounding.

Protecting tower mounted electronics requires a protector at both ends of the feed cable. If coaxial cable is used, the protector should dc block the RF path, yet provide a separate, protected path for dc Voltage and control signals. If twisted pair data cables (CAT 5) are used, each pair should be protected in a differential and common mode at both ends.

Most sites in use today separate the coax cables from the tower and route them toward the building entrance panel at a relatively high point on the tower, typically 8 to 15 feet above the tower base. This practice is the single most damaging source of lightning energy directed toward the equipment.

Metal Oxide Varistor (MOV) versus Silicon Avalanche Suppressor Diode (SASD)- Designs Discussion The sole function of a quality surge suppressor is to protect sensitive electronic equipment from transient overvoltages that are present on AC power circuits. It is irrelevant whether these overvoltages are generated by lightning activity or are induced upon the AC power lines by utility grid switching, power factor correction actions, power cycling of inductive loads, or from other sources. A quality surge suppressor must limit transient overvoltages to values that do not surpass the AC sine wave peak by more than 30% as it initially absorbs intense amounts of transient energy. The suppressor must immediately respond to transients before they reach their uppermost voltage values. Suppressor performance should not deviate or degrade with use when called upon to divert extreme levels of transient current.

The use of computers and other electronic systems has skyrocketed, and with it, so has the need to protect these systems from damage and service interruptions. Uninterruptible and Stand-by power systems were created to fill the gap when sudden power disturbances threaten the operation of electronic equipment. However, there is a general misconception that UPS systems offer adequate protection against all major power disturbance problems including outages, noise, line regulation and voltage transients. Unfortunately, UPS systems often do not adequately protect against voltage transients.

Silicon avalanche diode based SPDs (surge protection devices) are increasingly being recommended to protect expensive and sensitive electronic equipment from lightning and surges. This is due to their superior performance characteristics. Silicon diode based SPDs feature.

1. faster response times
2. lower clamping voltages versus other technologies and
3. non-degrading performance in their low-level transient suppression function.

Concrete is a fair conductor and can be used safely and effectively to augment the tower Silicon avalanche suppressor diode (SASD) based surge protection devices (SPDs) provide better performance and longer life than the typical MOV (metal oxide varistor) SPDs. However, significant improvements in performance are available through attention to details of proper design and testing by the manufacturer. This article will explore the difference between standard off- the-shelf SASD and discreet silicon avalanche diode cells.