Power Mains Information


There are several ways in which your equipment can be damaged via the power line. One is a lightning strike elsewhere on the power line inducing a surge that travels to your equipment. However, a ightning strike to your tower or a coupled surge to the phone lines can also damage equipment since the power line can provide an alternate path to ground. To ensure survival, all inputs and outputs (I/Os) must not only be surge protected but must be bonded in common via a common low inductance conductor to an earth ground. All grounds should be bonded in the earth to form a single earth ground.

Power mains surge protectors are to be placed at the entrance panels, transfer switches or distribution panels. They should have a low inductance path to the earth system and be installed with the minimal lead inductance (short with gradual bends). For best protection, have an additional in-line power protector at or very near the sensitive equipment. This should not be a surge protector that uses only the wall outlet safety ground. It should be a surge protector that can be mounted/grounded (like the IS-PLDO or IS-MSRP) to your main earth system.

TYPES OF POWER MAINS CONFIGURATIONS Power mains come in several different configurations. The three basic ones are single, bi-phase and three-phase. Three-phase is sometimes called polyphase and has further divisional classes using the letters "Y" (written "Wye", and a triangle denoting the Greek letter Delta).

SINGLE PHASE This is the simplest. It has a live or hot fee, a return called a neutral and a safety ground. This is commonly used for secondary wiring for a normal outlet. It may be any worldwide standard voltage. For the U.S.A., it is 120Vac (see drawing).

BI-PHASE This is a common feed configuration. It may be obtained by either a single transformer, center tapped or by grounding one phase of a three phase delta. The former is often called single phase in the U.S.A. since it often uses a single, center tapped transformer feed from one of three high line phases. These phases are 180 degrees from each other so 120Vac is available as well as 240Vac. This is typical for most houses in the U.S.A. (see drawing).

POLYPHASE OR THREE PHASE This is the feed for large facilities. The phases are 120 degrees apart. The Wye configuration normally always has a neutral return which is grounded. The true delta (called a closed delta) normally does not have a ground. There is an open delta where a high leg (red lead) has a higher voltage to ground than the rest and there is a ground lead. A grounded delta has one leg grounded (see drawings).

VOLTAGES AVAILABLE AND WHERE USED Voltages to 480Vac are used for normal feeds. The voltages will depend on the type of feed and your country. Measure the phase to phase voltages and the phase to ground voltages to determine the type of service, then check the current rating on the (largest) cut-off breaker.

CONNECTIONS FOR SURGE PROTECTORS The connections for the lightning protectors are given for each model and service type. Only the voltages change. The wires are properly color-coded for identification.

SHUNT OR IN-LINE AND WHERE TO USE EACH In-line surge protectors are load bearing; shunt types are not. In-lines are presently available up to 200A. These have redundancy, better surge limiting an provide filtering. Shunt types have no real load current limit, however, the larger the load, the larger the wires, and the more the surge energy will follow the conductors with the largest surface area. This means that more than one surge protector should be used. Two shunt protectors separated by twenty feet of wiring in steel conduit almost equal a single in-line protector. Both types have alarm contacts and field replaceable surge components.

NRTL UL 1449 APPROVAL PolyPhaser employs the services of CSA and MET Laboratories, Inc. to test and certify its products. These Nationally Recognized Testing Laboratories (NRTL) are approved by OSHA in the U.S.A. CSA is also approved by Federal, State, City and Municipal jurisdictions throughout the U.S.A. Both agencies test to all applicable standards including UL, ANSI, IEEE, NFPA, etc. Both agencies are approved by the National Institute of Standards and Technology (NIST) through the National Voluntary Laboratory Accreditation Program (NVAP) and are a National Certified Body in the IECEE Scheme. CSA and MET labels are accepted throughout the U.S.A. and in most countries.


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