OVRT240660CU datasheet(7/62 Pages) ABB

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Surge

otective

Devices

Low Voltage Products & Systems

16.5

ABB Inc. • 888-385-1221 • www.abb.us/lowvoltage

1SXU000023C0202 Rev. A

General information

UL 1449 Update to 3rd Edition

The Underwriters Laboratories (UL)

standard for surge protective devices

(SPDs) has been the primary safety

standard for surge protection since the

first edition was published in 1985, and

updated to the second edition in 1996.

The objective of UL 1449 has always been to increase safety in

terms of surge protection. Thus, major changes have recently

been made to the surge protection standard.

The latest edition, known as UL 1449 3rd Edition, was published

on September 29, 2006 and took effect September 2009, and is

now also an ANSI standard. A revision was made on February 8,

2011.

To avoid confusion, the objective of this paper is to explain and

summarize the major changes made to the standard.

The key updates are:

• Change in the standard’s name

• The different type designations of surge protective devices

• The measured voltage protection level

• The Nominal discharge current

Change in the standard’s name: From TVSS to SPDs

Prior to UL 1449 3rd Edition taking effect, the devices this

standard covers were known as Transient Voltage Surge

Suppressors (TVSS), operating on power circuits not exceeding

600 V. With the inception of the 3rd Edition, these devices are

now known as Surge Protective Devices (SPDs), and may operate

on power circuits not exceeding 1000 V.

This new designation moves the UL standard closer to the

international designation and to IEC standards. The new edition

is now renamed UL Standard for Safety for Surge Protective

Devices, UL 1449.

The different type designations of surge protective devices

The new UL 1449 3rd Edition places SPDs into five different

Type categories based on installation location within an electrical

system. While Type 1, Type 2 and Type 3 categories refer to

different types of SPDs that can be installed at specific locations,

Type 4 and Type 5 categories refer to components used in an

SPDs configuration.

Type 1 – “Permanently connected SPDs intended for installation

between the secondary of the service transformer and the line

side of the service equipment overcurrent device.”

Type 2 – “Permanently connected SPDs intended for installation

on the load side of the service equipment overcurrent device.”

Type 3 – “Point of utilization SPDs, installed at a minimum

conductor length of 10 meters (30 feet) from the electrical service

panel.”

Type 4 – Component assemblies – “Component assembly

consisting of one or more Type 5 components together with a

disconnect (integral or external) or a means of complying with the

limited current tests.”

Type 1, 2, 3 – Component assemblies – “Consists of a Type 4

component assembly with internal or external short circuit

protection.”

Type 5 – “Discrete component surge suppressors, such as

MOVs that may be mounted on a PWB, connected by its leads

or provided within an enclosure with mounting means and wiring

terminations.”

These new categories are by far the major changes applied to

UL 1449 3rd Edition. SPDs installation location is now taken

into account. The closer an SPD is installed to the equipment,

the better the protection is. This is a push in the direction of

providing stepped protection including external and internal surge

protection.

The measured voltage protection level

One of the last changes found in the new UL 1449 3rd Edition,

is the modification in the measured voltage protection level. The

Measured Limiting Voltage (MLV) is the maximum magnitude of

voltage measured at the application of a specific impulse wave

shape.

When applying a certain surge current on the SPD the measured

voltage at the device terminals is the so called “let-through

voltage.” In UL 1449 2nd Edition, the let-through voltage was

referred to as Suppressed Voltage Rating (SVR) and was

calculated with a 0.5 kA surge wave form at 6 kV. The new

designation is Voltage Protection Rating (VPR) and is calculated

with a 3 kA surge wave form at 6 kV.

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