Philippine Electrical Code 2017 Part 1/Chapter 2. Wiring and Protection/Article 2.85 - Transient Voltage Surge Suppressors: TVSS

Article 2.85 - Transient Voltage Surge Suppressors: TVSS

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2.85.1 General

2.85.1.1 Scope.

This article covers general requirements, installation requirements, and connection requirements for transient voltage surge suppressors (TVSSs) permanently installed on premises wiring systems.

2.85.1.2 Definition.

Transient Voltage Surge Suppressor (TVSS). A protective device for limiting transient voltages by diverting or limiting surge current; it also prevents continued flow of follow current while remaining capable of repeating these functions.

2.85.1.3 Uses Not Permitted.

A TVSS device shall not be installed in the following:

(1) Circuits exceeding 600 volts

(2) On ungrounded systems, impedance grounded systems, or corner grounded delta systems unless listed specifically for use on these systems.

(3) Where the rating of the TVSS is less than the maximum continuous phase-to-ground power frequency voltage available at the point of application

FPN: For further information on TVSSs, see NEMA LS 1-1992, Standard for Low Voltage Surge Suppression Devices. The selection of a properly rated TVSS is based on criteria such as maximum continuous operating voltage, the magnitude and duration of overvoltages at the suppressor location as affected by phase-to- ground faults, system grounding techniques, and switching surges.

2.85.1.4 Number Required.

Where used at a point on a circuit, the TVSS shall be connected to each ungrounded conductor.

2.85.1.5 Listing.

A TVSS shall be a listed device.

2.85.1.6 Short Circuit Current Rating.

The TVSS shall be marked with a short circuit current rating and shall not be installed at a point on the system where the available fault current is in excess of that rating. This marking requirement shall not apply to receptacles.

2.85.2 Installation

2.85.2.1 Location.

TVSSs shall be permitted to be located indoors or outdoors and shall be made inaccessible to unqualified persons, unless listed for installation in accessible locations.

2.85.2.2 Routing of Connections.

The conductors used to connect the TVSS to the line or bus and to ground shall not be any longer than necessary and shall avoid unnecessary bends.

2.85.3 Connecting Transient Voltage Surge Suppressors

2.85.3.1 Connection.

Where a TVSS is installed, it shall comply with 2.85.3.1(a) through (c).

(a) Location.

(1) Service Supplied Building or Structure.

The transient voltage surge suppressor shall be connected on the load side of a service disconnect overcurrent device required in 2.30.7.2, unless installed in accordance with 2.30.6.13(8).

(2) Feeder Supplied Building or Structure.

The transient voltage surge suppressor shall be connected on the load side of the first overcurrent device at the building or structure.

Exception to (1) and (2): Where the TVSS is also listed as a surge arrester, the connection shall be as permitted by Article 2.80.

(3) Separately Derived System.

The TVSS shall be connected on the load side of the first overcurrent device in a separately derived system.

(b) Conductor Size.

Line and ground connecting conductors shall not be smaller than 2.0 mm² (1.6 mm dia.) copper or 3.5 mm² (2.0 mm dia.) aluminum.

(c) Connection Between Conductors.

A TVSS shall be permitted to be connected between any two conductors — ungrounded conductor(s), grounded conductor, grounding conductor. The grounded conductor and the grounding conductor shall be interconnected only by the normal operation of the TVSS during a surge.

2.85.3.5 Grounding.

Grounding conductors shall not be run in metal enclosures unless bonded to both ends of such enclosure.

Other Pages in this Category: Chapter 2. Wiring and Protection

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