SPD

Archive for the ‘SPD’

Downconductors, Bonding and Shielding

Lightning is a capricious, random and unpredictable event. Its’ physical characteristics include current levels sometimes in excess of 400 kA, temperatures to 50,000 degrees F., and speeds approaching one third the speed of light. Globally, some 2000 on-going thunderstorms cause about 100 lightning strikes to earth each second. USA insurance company information shows one homeowner’s damage claim for every 57 lightning strikes. Data about commercial, government, and industrial lightning-caused losses is not available. Annually in the USA lightning causes more than 26,000 fires with damage to property (NLSI estimates) in excess of $5-6 billion.

The phenomenology of lightning strikes to earth, as presently understood, follows an approximate behavior:

1. The downward Leaders from a thundercloud pulse towards earth seeking out active electrical ground targets.

2. Ground-based objects (fences, trees, blades of grass, corners of buildings, people, lightning rods, etc., etc.) emit varying degrees of electric activity during this event. Upward Streamers are launched from some of these objects. A few tens of meters off the ground, a “collection zone” is established according to the intensified local electrical field.

3. Some Leader(s) likely will connect with some Streamer(s). Then, the “switch” is closed and the current flows. We see lightning.

Lightning effects can be direct and/or indirect. Direct effects are from resistive (ohmic) heating, arcing and burning. Indirect effects are more probable. They include capacitive, inductive and magnetic behavior. Lightning “prevention” or “protection” (in an absolute sense) is impossible. A diminution of its consequences, together with incremental safety improvements, can be obtained by the use of a holistic or systematic hazard mitigation approach, described below in generic terms.
Lightning Rods

In Franklin’s day, lightning rods conducted current away from buildings to earth. Lightning rods, now known as air terminals, are believed to send Streamers upward at varying distances and times according to shape, height and other factors. Different designs of air terminals may be employed according to different protection requirements. For example, the utility industry prefers overhead shielding wires for electrical substations. In some cases, no use whatsoever of air terminals is appropriate (example: munitions bunkers). Air terminals do not provide for safety to modern electronics within structures.

Air terminal design may alter Streamer behavior. In equivalent e-fields, a blunt pointed rod is seen to behave differently than a sharp pointed rod. Faraday Cage and overhead shield designs produce yet other effects. Air terminal design and performance is a controversial and unresolved issue. Commercial claims of the “elimination” of lightning deserve a skeptical reception. Further research and testing is on-going in order to understand more fully the behavior of various air terminals.
Downconductors, Bonding and Shielding

Downconductors should be installed in a safe manner through a known route, outside of the structure. They should not be painted, since this will increase impedance. Gradual bends (min. eight inch radius) should be adopted to avoid flashover problems. Building steel may be used in place of downconductors where practical as a beneficial part of the earth electrode subsystem.

Bonding assures that all metal masses are at the same electrical potential. All metallic conductors entering structures (AC power, gas and water pipes, signal lines, HVAC ducting, conduits, railroad tracks, overhead bridge cranes, etc.) should be integrated electrically to the earth electrode subsystem. Connector bonding should be thermal, not mechanical. Mechanical bonds are subject to corrosion and physical damage. Frequent inspection and ohmic resistance measuring of compression and mechanical connectors is recommended.

Shielding is an additional line of defense against induced effects. It prevents the higher frequency electromagnetic noise from interfering with the desired signal. It is accomplished by isolation of the signal wires from the source of noise.
Grounding

The grounding system must address low earth impedance as well as low resistance. A spectral study of lightning’s typical impulse reveals both a high and a low frequency content. The high frequency is associated with an extremely fast rising “front” on the order of 10 microseconds to peak current. The lower frequency component resides in the long, high energy “tail” or follow-on current in the impulse. The grounding system appears to the lightning impulse as a transmission line where wave propagation theory applies.

A single point grounding system is achieved when all equipment within the structure(s) are connected to a master bus bar which in turn is bonded to the external grounding system at one point only. Earth loops and differential rise times must be avoided. The grounding system should be designed to reduce ac impedance and dc resistance. The shape and dimension of the earth termination system is more important a specific value of the earth electrode. The use of counterpoise or “crow’s foot” radial techniques can lower impedance as they allow lightning energy to diverge as each buried conductor shares voltage gradients. Ground rings around structures are useful. They should be connected to the facility ground. Exothermic (welded) connectors are recommended in all circumstances.

Cathodic reactance should be considered during the site analysis phase. Man-made earth additives and backfills are useful in difficult soils circumstances: they should be considered on a case-by-case basis where lowering grounding impedances are difficult an/or expensive by traditional means. Regular physical inspections and testing should be a part of an established preventive maintenance program.

Posted by aliaswn in SPD Comments Off

Need Lightning Protection

Why You Need Lightning Protection:

Lightning protection systems have changed drastically since Benjamin Franklin first invented lighting rods in 1752. Today’s systems must protect modern appliances, electrical systems and building constructions - they have to keep up with tile changing requirements of modern technology.

Underwriters Laboratories Inc. (UL) keeps up with these changes. Our experience in the safety testing field has earned UL worldwide recognition and respect. jurisdictional authorities, government agencies, insurance representatives and consumers alike have looked for the UL Mark on products and systems for almost100 years. When you see the Mark, it means that the product or system on which it appears compares with UL’s internationally recognized Standards for Safety.

In the lighting protection field, UL has been serving home and building owners since 1908. Today, UL has a large number of trained lighting protection field representatives located throughout tile United States. UL inspects sites ranging from cow barns to missile silos, front golf Course shelters to high-rise building systems. In fact, some of the most famous buildings in the world are protected by UL Master Labeled lightning protection systems, including the White House, the Sears Tower and the Washington Monument.

The Need for Lightning Protection:

Lightning can strike anywhere on earth - event the North and South Poles! In any U.S. geographical location, lightning storms occur as few as five times or as many as 100 times per year (see Fig. 1). -The Northeast United States has the most violent thunderstorms in the country because of the area’s extremely high earth resistivity (see Fig. 2). High earth resistivity (the earth’s resistance to conduct current) increases the potential of a lightning strike. If struck, structures in these areas will generally sustain more damage when there is no lightning protection system present.

Each year, thousands of homes and other properties are damaged or destroyed by lightning. It accounts for more than a quarter billion dollars in property damage annually in the United States. Lightning is responsible for more deaths and property loss than tornadoes, hurricanes and floods combined, but of these violent forces of nature, lightning is the only one we call economically afford to protect ourselves against.

Some properties have a higher risk of lightning damage. When considering installation of a lightning protection system, you may want to assess this risk. A risk assessment guide for determining lightning loss for all types of structures can be found in Appendix I of the National Fire Protection Association’s Lightning Protection Code, NFPA 780. This guide takes into consideration the type of structure, type of construction, structure location, topography, occupancy, contents and lightning frequency. Information may be obtained from tile NFPA, I Batterymarch Park, Quincy, MA, 02269, (800) 344-3555.

How a Lightning Protection System Works:

Lightning is the visible discharge of static electricity within a cloud, between clouds, or between tile earth and a cloud. Scientists still do not fully understand what causes lightning, but most experts believe that different kinds of ice interact in a cloud. Updrafts in the clouds separate charges so that positive charges moves end up at the top of the cloud while negative flow to the bottom. When the negative charge moves down, a “pilot leader” forms. ‘This leader rushes toward the earth in 150-foot discrete steps, ionizing a path in the air. ‘The final breakdown generally occurs to a high object the major part of the lightning discharge current is then carried in the return stroke which flows along the ionized path.

A lighting protection system provides a means by which this discharge may enter or leave earth without passing through and damaging non-conducting parts of a structure, such as those made of wood, brick, tile of- concrete. A lightning protection system does not prevent lightning from striking; it provides a means for controlling it and preventing damage by providing a low resistance path for the discharge of lightning energy.

FIG. 3 Lightning protection system for a dwelling: 1) air terminals spaced 20 feet apart along ridges and within two feet of ridge ends; 2) down conductors; 3) minimum of two groundings at least 10-feet deep; 4) roof projections such as weather vanes connected to system; 5) air terminal located within two feet of outside corners of chimney; 6) dormers protected; 7) antenna mast connected to roof conductor:- connect gutters or other grounded metals as required; 9) surge arrester installed at service panel to protect appliances; 10) transient voltage surge suppressors installed in receptacles to which computers and other electronic equipment are connected.

FIG. 4 Lightning protection system commercial/industrial installation 1) air terminals spaced 20 feet apart around the perimeter of the building; 2) down conductors; 3) ground rods at least 10-feet deep; 4) art handling units bonded to system (may be in need of air terminals mounted on unit); 5) air terminals mounted within two feet of outside corner; 6) mid-roof conductor and air terminals at maximum 50-foot spacing; 7) grounded metal bodies bonded into system; surge arresters installed at main electrical panels; 9) transient voltage surge suppressors installed in receptacles to protect computers and other office equipment.

UL’s Role in Lightning Protection:

UL’s Master Label Program for lightning protection involves periodic factory testing and inspection of system Components, along with field inspection components of completed installations. The program requires that all installers comply with UL’s internationally recognized Standards for lightning protection components and systems. UL,’s field representatives countercheck compliance with these Standards.

As a home or building owner, you should make sure that your installed system complies with the UL requirements. Here’s how:

Make certain that your installer is listed by UL and that a Master Label application is submitted to UL for your installation.When You request a Master Label for your system, your installer will ask you to sign the owner’s statement on the Master Label application form. The fourth (yellow) copy of the application is for your records. This should be done before the installer submits the Master Label application to UL for issuance of the Label. Make sure you receive the Master Label from the installer and place it on the protected structure as requested.

Buildings that are changed structurally or provided with additions can be re-examined under UL’s Reconditioned Lightning Protection Program. Under this program, the entire system must comply with the current UL Standards.

Posted by aliaswn in SPD Comments Off

High voltage surge protective devices.

Institute of Electrical and Electronics Engineers, Inc. (IEEE) and American National Standards Institute (ANSI) standards, guides, and recommended practices regarding high voltage surge protective devices.

IEEE Std 32TM-1972 (R1997) IEEE Standard Requirements, Terminology, and Test Procedures for Neutral Grounding Devices

This standard applies to devices used for the purpose of controlling the ground current or the potentials to ground of an alternating current system. These devices are: grounding transformers, ground-fault neutralizers, resistors, reactors, capacitors, or combinations of these.
Keywords: IEEE 32, IEEE Std 32-1972
Transferred to PES Transformer Committee (2002)

IEEE Std 1312TM-1993 IEEE Standard Preferred Voltage Ratings for Alternating-Current Electrical Systems and Equipment Operating at Voltages Above 230 kV Nominal

Preferred voltage ratings above 230 kV nominal for alternating-current (ac) systems and equipment are provided, along with definitions of various types of system voltages. You will receive an email from Customer Service with the URL needed to access this publication online.
WG 3.4.18

IEEE Std 1313.1TM-1996 IEEE Standard for Insulation Coordination— Definitions, Principles, and Rules

Reaffirmed 2002
The procedure for selection of the withstand voltages for equipment phase-to-ground and phase-to-phase insulation systems is specified. A list of standard insulation levels, based on the voltage stress to which the equipment is being exposed, is also identified. This standard applies to three-phase ac systems above 1 kV.
Keywords: 1313.1, 1313
WG 3.4.18

IEEE Std C62.1TM-1989 (R1994) IEEE Standard for Gapped Silicon-Carbide Surge Arresters for AC Power Circuits

Describes the service conditions, classifications and voltage ratings, design tests with corresponding performance characteristics, conformance tests, and certification test procedures for station, intermediate, distribution and secondary class arresters. Terminal connections, housing leakage distance, mounting and identification requirements are defined. Definitions are provided to clarify the required test procedures and other portions of the text.
WG 3.3.12 (dissolved)

IEEE Std. C62.11TM-2005 IEEE Standard for Metal-Oxide Surge Arresters for AC Power Circuits (>1 kV)

Revision of IEEE Std C62.11-1999
This standard applies to metal-oxide surge arresters designed to repeatedly limit the voltage surges on 48 Hz to 62 Hz power circuits (>1000 V) by passing surge discharge current and automatically limiting the flow of system power current. This standard applies to devices for separate mounting and to those supplied integrally with other equipment. The tests demonstrate that an arrester can survive the rigors of reasonable environmental conditions and system phenomena, while, at the same time, protect equipment and/or the system from damaging overvoltages caused by lightning, switching, and other undesirable surges.
Keywords: Metal-oxide surge arrester, MOSA, surge arrester, valve arrester, lightning protection, discharge current, discharge voltage, duty-cycle voltage rating, maximum continuous operating voltage, MCOV.
WG 3.3.11

IEEE Std 1313.2TM-1999 IEEE Guide for the Application of Insulation Coordination

Reaffirmed in 2005
The calculation method for selection of phase-to-ground and phase-to-phase insulation withstand voltages for equipment is presented. This guide gives methods for insulation coordination of different air-insulated systems like transmission lines and substations. The methods of analysis are illustrated by practical examples.
WG 3.4.18

IEEE Std 1299TM/C62.22.1TM-1996 (2003) IEEE Guide for the Connection of Surge Arresters to Protect Insulated Shielded Electric Power Cable Systems

Reaffirmed 2003.
IEEE Std C95.3-1991 specifies techniques and instrumentation for the measurement of potentially hazardous electromagnetic fields. The recommendations apply to hazards to personnel. However, the measurement techniques and instruments described are also applicable to the measurement of fields in the neighborhood of flammable materials and explosive devices, even though exposure standards for these situations have not been established.
Keywords: IEEE Std C62.22.1-1996, C62.22.1, Electromagnetic fields , RF fields , microwave fields , potentially hazardous fields , RF microwave survey instruments , SAR measurement , RF hazard determination , RF microwave instrumentation , RF microwave instrumentation calibration.
IC B6

IEEE Std C62.2TM-1987 (R1994) IEEE Guide for the Application of Gapped Silicon-Carbide Surge Arresters for Alternating Current Systems

Withdrawn Standard. No longer endorsed by the IEEE.
The application of gapped silicon-carbide surge arresters to safeguard electric power equipment against the hazards of abnormally high voltage surges of various origins is addressed. General considerations with respect to overvoltages, valve arresters, protective levels, insulation-withstand, separation effects, and insulation coordination are discussed. Procedures for the protection of stations and distribution systems are provided.
WG 3.4.14

IEEE Std C62.21TM-2003 IEEE Guide for the Application of Surge Voltage Protective Equipment on AC Rotating Machinery 1000 Volts and Greater

This guide covers the application of surge voltage protective equipment to AC rotating machines rated 1000 volts and greater. The guide does not cover motors applied in solid-state switched adjustable speed drives. Part 1 covers the insulation surge withstand strength of motors and generators with windings having form-wound multi-turn coils and the application of surge protection to form-wound multi-turn coil motors. Part 2 will cover application of surge protection to generators with form-wound multi-turn coils, plus insulation surge withstand strength and surge protection of single-turn coil generators and motors. Project purpose: This guide is intended to aid engineers at all levels of surge protection knowledge in deciding whether particular machines should have surge protection. The guide may be used in estimating the surge withstand capability and switching surge exposure of ac rotating machinery in usual, not extreme exposure, installations. The manufacturer should be contacted for specific insulation surge voltage withstand values for machinery of particular interest or importance. For those machines, which should be protected, the purpose is to provide guidance in selecting and applying the protective devices. A simple look-up method using tables and a graph is provided for quick estimation of surge rise times and surge voltage levels, and for general use where accuracies in the order of 10% to 15% are acceptable. This method is based on single-phase analysis, neglecting the influence of ground mode surge propagation. A more complex method is provided by formulas to model the three-phase and ground mode propagation. The formulas can be used with calculators or personal computers.
Keywords: IEEE Std C62.21-2003, C62.21.
WG 3.4.9

IEEE Std C62.22TM-1997 IEEE Guide for the Application of Metal-Oxide Surge Arresters for Alternating-Current Systems

The application of metal-oxide surge arresters to safeguard electric power equipment against the hazards of abnormally high voltage surges of various origins is covered. Step-by- step directions toward proper solutions of various applications are provided. In many cases, the prescribed steps are adequate. More complex and special solutions requiring study by experienced engineers are described, but specific solutions are not always given. The procedures are based on theoretical studies, test results, and experience.
WG 3.4.14

IEEE Std C62.23 TM -1995 (R2001) IEEE Application Guide for Surge Protection of Electric Generating Plants

This standard consolidates most electric utility power industry practices, accepted theories, existing standards/guides, definitions, and technical references as they specifically pertain to surge protection of electric power generating plants. Where technical information is not readily available, guidance is provided to aid toward proper surge protection and to reduce interference to communication, control, and protection circuits due to surges and other overvoltages. It has to be recognized that this application guide approaches the subject of surge protection from a common or generalized application viewpoint. Complex applications of surge protection practices may require specialized study by experienced engineers.
Keywords: Power lines, switchyard, power plant, and remote ancillary facilities.
WG 3.4.13

IEEE Std C62.92.1 TM -2000 IEEE Guide for the Application of Neutral Grounding in Elec. Utility Systems, Part I: Introduction

Reaffirmed in 2005
This guide is the introduction to the C62.92 series of five IEEE guides on neutral grounding in three-phase electrical utility systems. It provides system grounding definitions and considerations that are general to all types of electrical utility systems.
WG 3.5.7

IEEE Std C62.92.2 TM -1989 (R1993, 2001) IEEE Guide for the Application of Neutral Grounding in Electrical Utility Systems, Part II: Grounding of Synchronous Generator Systems

Reaffirmed in 2005
General considerations for grounding synchronous generator systems are summarized, focusing on the objectives of generator grounding. The factors to be considered in the selection of a grounding class and the application of grounding methods are discussed. Four generator grounding types are considered: unit-connected generation systems, common-bus generators without feeders, generators with feeders directly connected at generated voltage, and three-phase, 4-wire connected generators.
WG 3.5.7

IEEE Std C62.92.3 TM -1993 (R2000) IEEE Guide for the Application of Neutral Grounding in Electrical Utility Systems, Part III: Generator Auxiliary Systems

Reaffirmed in 2005
Basic factors and general considerations in selecting the class and means of neutral grounding for electrical generating plant auxiliary power systems are given in this guide. Apparatus to be used to achieve the desired grounding are suggested, and methods to specify the grounding devices are given. Sensitivity and selectivity of equipment ground-fault protection as affected by selection of the neutral grounding device are discussed, with examples.
WG 3.5.7

IEEE Std C62.92.4 TM -1991 (R2002) IEEE Guide for the Application of Neutral Grounding in Electric Utility Systems, Part IV: Distribution

Reaffirmed 2002
The neutral grounding of single- and three-phase ac electric utility primary distribution systems with nominal voltages in the range of 2.4–34.5 kV is addressed. Classes of distribution systems grounding are defined. Basic considerations in distribution system grounding–concerning economics, control of temporary overvoltages, control of ground-fault currents, and ground relaying–are addressed. Also considered are use of grounding transformers, grounding of high-voltage neutral of wye/delta distribution transformers, and interconnection of primary and secondary neutrals of distribution transformers.
WG 3.5.7

IEEE Std C62.92.5 TM -1992 (R1997, 2001) IEEE Guide for the Application of Neutral Grounding in Electric Utility Systems, Part V: Transmission Systems and Subtransmission Systems

Reaffirmed 2001
Basic factors and general considerations in selecting the class and means of neutral grounding for a particular ac transmission or subtransmission system are covered. An apparatus to be used to achieve the desired grounding is suggested, and methods for specifying the grounding devices are given. Transformer tertiary systems, equipment-neutral grounding, and the effects of series compensation on grounding are discussed.
WG 3.5.7

Posted by aliaswn in SPD Comments Off

What is a Surge Protective Device

What is a Surge Protective Device (SPD)?
Electrical events, such as lightning, can couple into metallic conductors and cause damage from the excessive system voltages and currents (surges) generated. SPDs are used to mitigate these coupled surges in both High Voltage (HV) and Low Voltage (LV) power systems and communication systems. An SPD has a non-linear voltage-current characteristic that reduces voltages exceeding the normal safe system levels by a rapid increase in conducted current. SPDs are also called voltage limiters or overvoltage protectors or (surge) arresters.

What is the Surge Protective Devices Committee (SPDC)?
The SPDC is a technical committee of the Institute of Electrical and Electronic Engineers (IEEE) Power & Energy Society (PES). It is the Working Groups (WGs) of the SPDC Subcommittees (SCs) that create and maintain SPD related IEEE Standards, Guides and Practice documents. These documents are classified here by their voltage and application:

HV (>1000 V rms) Power SPDs
LV (<1000 V rms) Power SPDs
LV (<1000 V rms) Communications SPDs
LV (<1000 V rms) SPD Components

Posted by aliaswn in SPD Comments Off

Surge Protection Devices (SPDs)

PART 1 GENERAL

1.01 SUMMARY

This section covers required specifications for Transient Voltage Surge Suppression (TVSS), also referred to as Surge Protection Devices (SPDs), for protection of electrical equipment and installations from the damaging effects of lightning and switching transient induced surges. This section covers SPDs for use on AC Service Entrance, Power Distribution Circuits, and Point of Use / Electronic Equipment applications. Specifications for SPDs to protect communication and data lines are covered under Section 16289-2.

1.02 SECTION INCLUDES

A.Performance Specifications
B.Approved Manufacturers and Model Numbers
C.Functional and Operational Guidelines

1.03 RELATED SECTIONS

A.
Section 16289-2 – Communication and Data Signal Transient Voltage Suppression

Section 13100 – Lightning Protection

Section 16493 – Surge Arrestors

1.04 REFERENCE

IEC 1024-1: 1990/ENV 61 024-1:1995/DIN V ENV 61 024-1/VDE V 0185 part 100: 1996-08. Protection of structures against lightning - Part 1: general principles

NEC 2002, The National Electrical Code Article 285

EN50022: 1977/DIN EN 50 022: 1978-05. Low voltage switchgear and control gear for industrial use; mounting rails for fixing terminal blocks

IEEE C62.41.1-2002. IEEE Guide on the Surge Environment in Low Voltage (1000V and less) AC Power Circuits.

IEEE C62.41.2-2002. IEEE Recommended Practice on Characterization of Surges in Low-Voltage (1000V and Less) AC Power Circuits.

IEC 529: 1989/EN 60 529: 1991/DIN VDE 0470-1: 1992-11. Type of protection through housing (IP Code).

DIN VDE 0675-6: 1989-11, draft. Surge arresters for use in ac supply systems with rated voltages ranging from 100 to 1000V.

IEC 61643-1. Surge Protective Devices Connected to Low Voltage Power Distribution Systems – Performance Requirements and Testing Methods

IEC 61643-12. Surge Protective Devices Connected to Low Voltage Power Distribution Systems – Selection and Application Principles

NEMA LS-1-1992. Low Voltage Surge Protection Devices

UL 1449, 2nd Edition. Transient Voltage Surge Suppressors

ISO 9001:2000. International Quality Management System

1.05 SUBMITTALS

Product data shall include 8/20µs and 10/350µs rated surge capacities, relevant IEEE and IEC specifications, installation instructions, and operating characteristics.

The product submittals shall include:

1. UL 1449, 2nd edition documentation

2. UL 1283, electromagnetic interference filter documentation (where appropriate)

3. Dimensional drawing of each SPD type

4. Circuit diagram of SPDs internal components

5. UL 1449 Surge Voltage Rating (SVR - 6kV / 3kA combination waveform)

6. Maximum 10/350µs lightning test current impulse capability (only for service entrance and outdoor field mount applications)

7. Copy of manufacturer’s ISO 9001:2000 Quality Registration Certificate

Manufacturer’s statement of warranty.

1.06 WARRANTY

SPDs shall be warranted against failure due to results of lightning or switching transients for a period of 10 years for service entrance protection, 5 years for all other areas.

PART 2 PRODUCTS

2.01 GENERAL

Transient Voltage Suppression (surge protection device) equipment shall be supplied by an ISO 9001:2000 certified company in the business of manufacturing SPDs for a period of greater than 20 years.

All wiring, hardware, and connection means shall be in compliance with the National Electrical Code and/or applicable local codes.

Transient Voltage Suppression (surge protection device) equipment shall be supplied by Phoenix Contact Inc, Harrisburg, PA or proven equal.

2.02 MOUNTING

All SPD components shall have integral mounting brackets to attach to 35mm DIN rail conforming to DIN EN50022. The SPDs may be pre-mounted on a rail or electrical enclosure. The DIN rail and enclosure will be electrically grounded.

The SPDs shall be mounted as close as possible to the equipment or service being protected.

Mounting guidelines will be followed as indicated in installation instruction provided by manufacturer.

2.03 WIRE CONNECTIONS

Wires shall be attached to the SPD by means of a cable-clamping terminal block activated by a screw. Connections shall be gas-tight, and the terminal block shall be fabricated of non-ferrous, non-corrosive materials.

All wiring points and plug connections shall be “touch safe” with no live voltages that can make contact with a misplaced finger in accordance with IEC 529.

Both Service Entrance and Sub-Distribution protection devices shall be wired on the load side of the service or panel distribution box.

2.04 EQUIPMENT – SERVICE ENTRANCE SPDs:

Protection Against Lightning and Switching Transients

The service entrance SPDs shall have protection in the L-N (GND) mode only as neutral to ground bonding is required at the service entrance by NEC 2002. Therefore, no separate N-GND protection is necessary.

The SPD technology shall consist of coordinated two-stage protection to provide protection against IEEE C62.41.1-2002 defined Scenario II direct strike lightning events and Category C switching transients. The two-stage protection concept includes current limiting arc gap lightning arrestor components and MOV TVSS components defined below.

The lightning arrestor components shall provide the following:

1. The lightning arrester components shall have a protection level of 900 volts for systems with nominal voltage < 230VAC L-GND and 1.5kV for systems with nominal voltage > 230VAC L-GND.

2. The lightning arrester components shall have a maximum rated operating voltage of at least 330 VAC from line to ground

3. The lightning arrester components shall be tested to withstand at least 50 kA of lightning test current of a 10/350ms waveform described by IEC 1024/Application Guide A and by IEEE C62.41.2 Appendix A.

4. The lightning arrester components shall be able to quench 50 kA of follow (short circuit) current without properly sized over-current devices opening.

5. The lightning arrester components shall have a response time of 1 µs or faster.

6. The lightning arrester components shall have an operating temperature range of -40 oC to +85 oC.

7. The lightning arrester components shall be wired in series with a fuse capable of withstanding at least 100kA 8/20ms surge current and which has a 200 kAIC rating. This fuse shall be specifically designed for use with surge protection devices.

The TVSS components shall provide the following:

1. The TVSS component shall be designed to withstand a one time surge of up to a 40 kA test current of a (8/20)ms waveform according to IEC 1024 Application Guide A and ANSI/IEEE C62.41.1 Category C Area.

2. The TVSS components shall have a SPDT contact rated for 250 VAC, 1 amp used for remote indication/visual indicator of circuit integrity.

3. The TVSS components shall have a rating of IP20 according to IEC 529.

4. The TVSS components shall be modular with field replacement capability without the removal of any wires nor shall it interrupt the power to the protected. Bases shall have the ability to be coded to accept only the correct voltage plug.

5. The TVSS components shall have integral label holder to mark each terminal block

6. The TVSS components shall have an operating temperature range of at least -25°C to +75°C.

The SPD shall be UL listed or recognized to UL 1449, 2nd edition.

The SPD shall have the following UL 1449 measured SVRs in the Line to Neutral (Ground) mode:

1 1.2kV for 480Y/277 systems

2 800V for 208Y/120 systems

3 1.8kV for 480 DELTA systems

The SPD shall have the following Measured Limiting Voltage while discharging 50kA of surge current

1. < 1.5kV for 480Y/277 systems

2. < 900V for 208Y/120 systems

3. < 2.0kV for 480 DELTA systems

OPTIONAL: The SPD shall have visual indication of TVSS component and fuse failure.

Acceptable Part Numbers for External Enclosure Mount Systems Include:

1 For 480/277 VAC systems incorporating front-panel TVSS and fuse status indication: Phoenix Contact model “SYS N4/I FT+CT-VAL 480/277”, part number 5602201

2 For 208/120 VAC systems incorporating front-panel TVSS and fuse status indication: Phoenix Contact model “SYS N4/I FT+CT-VAL 208/120”, part number 5602202

3 For 240/120 VAC Split Single Phase systems incorporating front-panel TVSS and fuse status indication: Phoenix Contact model “SYS N4/I FT+CT-VAL 240/120”, part number 5603416

4 For 480/277 VAC systems: Phoenix Contact model “SYS N4 FT+CT-VAL 480/277”, part number 5602744

5 For 208/120 VAC systems: Phoenix Contact model “SYS N4 FT+CT-VAL 208/120-240”, part number 5602745

6 For 240/120 VAC Split Single Phase systems: Phoenix Contact model “SYS N4 FT+CT-VAL 240/120”, part number 5602856

7 For 480/277 VAC systems incorporating front-panel TVSS and fuse status indication in a corrosive resistant enclosure (NEMA 4X, 316 Stainless Steel): Phoenix Contact model “SYS N4X/I FT+CT-VAL 480/277”, part number 5602746.

8 For 208/120 VAC systems incorporating front-panel TVSS and fuse status indication in a corrosive resistant enclosure (NEMA 4X, 316 Stainless Steel): Phoenix Contact model “SYS N4X/I FT+CT-VAL 208/120”, part number 5602747.

9 For 240/120 VAC Split Single Phase systems incorporating front-panel TVSS and fuse status indication in a corrosive resistant enclosure (NEMA 4X, 316 Stainless Steel): Phoenix Contact model “SYS N4X/I FT+CT-VAL 240/120”, part number 5603317.

10 For 480/277 VAC systems in a corrosive resistant enclosure (NEMA 4X, 316 Stainless Steel): Phoenix Contact model “SYS N4X FT+CT-VAL 480/277”, part number 5602732

11 For 208/120 VAC systems in a corrosive resistant enclosure (NEMA 4X, 316 Stainless Steel): Phoenix Contact model “SYS N4X FT+CT-VAL 208/120-240”, part number 5602733

12 For 240/120 VAC systems in a corrosive resistant enclosure (NEMA 4X, 316 Stainless Steel): Phoenix Contact model “SYS N4X FT+CT-VAL 240/120”, part number 5603167

Acceptable part numbers for internal DIN rail mount assemblies include:

1. For 480/277 VAC systems as a rail assembly kit (mounts in user supplied enclosure): Phoenix Contact model “SYS FT+CT-VAL 480/277”, part number 5602794

2. For 208/120 VAC systems as a rail assembly kit (mounts in user supplied enclosure): Phoenix Contact model “SYS FT+CT-VAL 208/120”, part number 5603415

2.05 EQUIPMENT – DISTRIBUTION CIRCUIT AND PANEL SPDs

The distribution circuit and panel SPDs shall have protection in the L-N and N-GND modes

The SPDs shall provide the following:

1. The SPD component shall be designed to withstand a one time surge of up to a 40 kA test current of a (8/20) ms waveform according to IEC 1024 Application Guide A and ANSI/IEEE C62.41.1 Category C Area.

2. The SPD components shall have a SPDT contact rated for 250 VAC, 1 amp used for remote indication/visual indicator of circuit integrity.

3. The SPD components shall have a rating of IP20 according to IEC 529.

4. The SPD components shall be modular with field replacement capability without the removal of any wires nor shall it interrupt the power to the protected. Bases shall have the ability to be coded to accept only the correct voltage plug.

5. The SPD components shall have integral label holder to mark each terminal block

6. The SPD components shall have an operating temperature range of at least -25°C to +75°C.

The SPD shall be UL listed or recognized to UL 1449, 2nd edition.

The SPD shall have the following UL 1449 measured SVRs in the Line to Neutral mode:

1. 1.2kV for 480Y/277 systems

2. 700V for 208Y/120 systems

3. 700V for 240/120 Split Single Phase systems

The SPD shall have a response time < 25µs.

The SPD shall have a leakage current to ground of <1µA.

Acceptable Part Numbers for External Enclosure Mount Systems Include:

Phoenix Contact “SYSTEMTRAB Enclosure series”.

Acceptable Part Numbers for internal DIN rail mount assembly include:

1. For 480/277 VAC systems: Phoenix Contact “VAL-MS 320/3+1/FM-UD”, part number 2856689

2. For 208/120 VAC systems: Phoenix Contact “VAL-MS 120/3+1/FM-UD”, part number 2856692

2.06 EQUIPMENT – POINT OF USE / ELECTRONIC EQUIPMENT SPDs

For Protection of Single Phase Equipment

SPDs for single phase equipment shall be designed to withstand up to a 10kA test current of a 8/20µS waveform according to IEC 1024 Application Guide A and IEEE C62.41.1-2002 Category C area.

The SPD technology for single phase equipment protection shall be hybrid – MOV / Gas Discharge Tube.

SPDs for single phase equipment shall have visual status indication and a dry contact rated for at least 250 VAC, 1 amp for remote status indication.

SPDs for single phase equipment shall provide a method of landing both input and output wires using a feed-through terminal block. Maximum operating current through the block shall be no more than 20 amps.

Operating temperature range shall be at least -25°C to +75°C

SPDs for single phase equipment shall be modular with field replacement capability without the removal of any wires nor shall in interrupt the power to be protected. Bases shall have the ability to be coded to accept only the correct voltage plug.

The SPD shall be UL Listed or Recognized to UL 1449, 2nd edition

The SPD shall have the following UL 1449 measured SVR:

1. For 120VAC single phase: L-N = 500V, N-GND = 900V

2. For 24VAC (DC) single phase: L-N = 150, N-GND = 600V

The SPDs shall have a leakage current to ground of < 1µA

The SPDs shall have integral mounting brackets to attach to 35mm DIN rail conforming to DIN EN50022. The mounting bracket of the SPD shall make ground connection to the DIN rail; therefore, minimizing ground impedance connections.

Acceptable Part Numbers include Phoenix Contact models:

1. 24 VAC (DC): PT 2-PE/S-24AC… (ST and BE)

2. 60 VAC: PT 2-PE/S-60AC… (ST and BE)

3. 120 VAC: PT 2-PE/S-120AC… (ST and BE)

4. 230 VAC: PT 2-PE/S-230AC… (ST and BE)

For Protection of Single Phase Equipment with additional EMI/RFI noise filtering (sine wave tracking)

SPDs for single phase equipment shall be designed to withstand up to a 10kA test current of a 8/20µS waveform according to IEC 1024 Application Guide A and IEEE C62.41.1-2002 Category C area.

The SPD technology for single phase equipment protection with EMI / RFI noise filtering shall be sine wave tracking type with low pass filter circuit and MOV surge protection circuit.

SPDs for single phase equipment shall have visual status indication of MOV status on the input and output circuits and a dry contact rated for at least 250 VAC, 1 amp for remote status indication.

SPDs for single phase equipment shall provide a method of landing both input and output wires with a maximum operating current through the SPD of no more than 20 amps.

Operating temperature range shall be at least -40°C to +85°C

The SPD shall be UL Listed or Recognized to UL 1449, 2nd edition and UL 1283.

The SPD shall have the following UL 1449 measured SVR:

L-N = 400V, N-GND = 400V

The SPDs shall have integral mounting brackets to attach to 35mm DIN rail conforming to DIN EN50022.

The SPD shall be packaged in a metallic housing to shield the components from RFI therefore increasing the filter circuit performance.

The SPD shall have an attenuation of greater than -40dB @ 100 kHz as determined by a standard 50-ohm insertion test.

The SPD shall exhibit sine wave tracking characteristics as described by the following IEEE C62.41 defined ringwave tests:

1. Category A Ringwave: L-N = 100V, N-GND = 390VAC

2. Category B Ringwave: L-N = 195 V, N-GND = 400VAC

Acceptable Part Numbers include Phoenix Contact Model:

1. SFP 1-20/120AC, Part Number 2856702

For Protection of Three Phase Equipment

The Three Phase Equipment SPDs shall have protection in the L-N and N-GND modes

The SPD components shall provide the following:

1. The SPD component shall be designed to withstand a one time surge of up to a 40 kA test current of a 8/20 ms waveform according to IEC 1024 Application Guide A and ANSI/IEEE C62.41.1 Category C Area.

2. The SPD components shall have a SPDT contact rated for 250 VAC, 1 amp used for remote indication/visual indicator of circuit integrity.

3. The SPD components shall have a rating of IP20 according to IEC 529.

5. The SPD components shall have integral label holder to mark each terminal block

6. The SPD components shall have an operating temperature range of at least -25°C to +75°C.

The SPD shall be UL listed or recognized to UL 1449, 2nd edition.

The SPD shall have the following UL 1449 measured SVRs in the Line to Neutral mode:

1. 1.2kV for 480Y/277 systems

2. 700V for 208Y/120 systems

3. 700V for 240/120 Split Single Phase systems

The SPD shall have a response time < 25µs.

The SPD shall have a leakage current to ground of <1µA.

Acceptable Part Numbers for internal DIN rail mount assembly include:

1. For 480/277 VAC systems: Phoenix Contact “VAL-MS 320/3+1/FM-UD”, part number 2856689

2. For 208/120 VAC systems: Phoenix Contact “VAL-MS 120/3+1/FM-UD”, part number 2856692

2.07 EQUIPMENT – ACCESSORIES

Additional automated test equipment shall be provided for each job to perform verification testing on the modular SPDs. This testing equipment shall have the following capabilities:

1. Bar code scanner and touch pad key entry for modular plug identification

2. LCD display for diagnostics and test results display

3. Reporting output capability with RS232 interface

Acceptable part numbers for automated test equipment include:

1. Phoenix Contact Model “CHECKMASTER”.

PART 3 EXECUTION

3.01 INSTALLATION OF SURGE PROTECTION DEVICES

Install service entrance SPDs on the load side of the main service disconnect, with ground lead bonded to service entrance N-GND bond.

Install all SPD devices with conductors or buses between SPD and points of attachment as short and straight as possible.

Comply with manufacturer’s written recommendation for conductor and circuit-breaker size for connecting SPDs to distribution system. Match circuit breaker size to conductor size. Coordinate with drawings.

Installers shall follow manufacturer’s installation instructions.

Installers of SPDs shall be knowledgeable, and if required, certified, in all applicable electrical practices, standards, codes and wiring techniques as they pertain to installing SPDs

3.02 FIELD QUALITY CONTROL

Engage a factory-authorized service representative to inspect equipment installation, including connections.

1. Verify that electrical wiring installation complies with manufacturer’s written installation requirements.

Perform periodic verification testing on modular SPDs with automated test equipment. Replace any failed modules at this time.

Posted by aliaswn in SPD Comments Off

LIGHTNING? SPD

Lightning has long fascinated the technical community. Ben Franklin studied lightning’s electrical nature over two centuries ago and Charles R Steinmetz generated artificial lightning in his General Electric laboratory in the 1920’s. As someone concerned with premises data communications you need to worry about lightning. Here I will elaborate on why, where and when you should worry about lightning. I’ll then discuss how to get protection from it.

6.1 WHY WORRY ABOUT LIGHTNING?

It is unfortunate, but a fact of life, that computers, computerrelated products and process control equipment found in premises data communications environments can be damaged by high-voltage surges and spikes. Such power surges and spikes are most often caused by lightning strikes. However, there are occasions when the surges and spikes result from any one of a variety of other causes. These causes may include direct contact with power/lightning circuits, static buildup on cables and components, high energy transients coupled into equipment from cables in close proximity, potential differences between grounds to which different equipment’s are connected, miswired systems and even human equipment users who have accumulated large static electricity charge build-ups on their clothing. In fact, electrostatic discharges from a person can produce peak Voltages up to 15 kV with currents of tens of Amperes in less than 10 microseconds.

A manufacturing environment is particularly susceptible to such surges because of the presence of motors and other high voltage equipment. The essential point to remember is, the effects of surges due to these other sources are no different than those due to lightning. Hence, protection from one will also protect from the other.

When a lightning-induced power surge is coupled into your computer equipment any one of a number of harmful events may occur.

Semiconductors are prevalent in such equipment. A lightning induced surge will almost always surpass the voltage rating of these devices causing them to fail. Specifically, lightning induced surges usually alter the electrical characteristics of semiconductor devices so that they no longer function effectively. In a few cases, a surge may destroy the semiconductor device. These are called “hard failures.” Computer equipment having a hard failure will no longer function at all. It must be repaired with the resulting expense of “downtime” or the expense of a standby unit to take its place.

In several instances, a lightning-derived surge may destroy the printed traces in the printed circuit boards of the computer equipment also resulting in hard failures.

Along with the voltage source, lightning can cause a current surge and a resultant induced magnetic field. If the computer contains a magnetic disk then this interfering magnetic field might overwrite and destroy data stored in the disk. Furthermore, the aberrant magnetic field may energize the disk head when it should be quiescent. To you, the user, such behavior will be viewed as the “disk crashing.”

Some computer equipment may have magnetic relays. The same aberrant magnetic fields which cause disk crashes may activate relays when they shouldn’t be activated, causing unpredictable, unacceptable performance.

Finally, there is the effect of lightning on program logic controllers (PLCS) which are found in the manufacturing environment. Many of these PLCs use programs stored in ROMS. A lightning-induced surge can alter the contents of the ROM causing aberrant operation by the PLC.

So these are some of the unhappy things which happen when a computer experiences lightning. But you may say, “Come on, equipment hit by lightning, that’s like winning the lottery. It has never happened and I doubt that it ever will.” This is a typical reaction and unfortunately it is based on ignorance. True, people may never, or rarely, experience, direct lightning strikes on exposed, in-building cable feeding into their equipment. However, it is not uncommon to find computer equipment being fed by buried cable. In this environment, a lightning strike, even several miles away, can induce voltage/current surges which travel through the ground and induce surges along the cable, ultimately causing equipment failure. The equipment user is undoubtedly aware of these failures but usually does not relate them to the occurrence of lightning during thunderstorm activity since the user does not experience a direct strike.

In a way, such induced surges are analogous to chronic high blood pressure in a person; they are “silent killers.” In the manufacturing environment, long cable runs are often found connecting sensors, PLCs and computers. These cables are particularly vulnerable to induced surges.

6.2 SHOULD YOU WORRY ABOUT LIGHTNING? This question primarily relates to the geographical location of computer equipment end-users. When other interfering phenomena which can cause a deterioration of performance is considered, it matters little where the equipment is geographically located.

When do you have to worry during a thunderstorm? Typically, thunderstorms are characterized as intense individual rain cells or showers embedded in a broad area of light rain. These intense cells are only over a fixed location for a few minutes. They are on average, several miles in each direction. In the continental United States thunderstorm cells move from west to east along a squall line as shown in Figure 17. This squall line is about 12-30 miles in width and up to 1,250 miles long. The speed at which the thunderstorm cell moves is generally 30 knots (approximately 34.4 statute miles per hour).

6.4 EQUIPMENT PROTECTION

Coming right down to it, a lot can be done as far as protection is concerned. However, it is best to begin by describing the magnitude of the threat from which you need protection.

The first stroke of lightning during a thunderstorm can produce peak currents ranging from 1,000 to 100,000 Amperes with rise times of 1 microsecond. It is hard to conceive of, let alone protect against, such enormous magnitudes. Fortunately, such threats only apply to direct hits on overhead lines. Hopefully, this is a rare phenomenon.

More common is the induced surge on a buried cable. In one test, lightning-induced voltages caused by strokes in ground flashes at distances of about 5 km were measured at both ends of a 448 meter long, unenergized power distribution line.

Typical test results are illustrated in Figure 19. Notice that the maximum-induced surge exceeds 80 Volts peak-to-peak. This is more than enough to destroy semiconductor devices and computer related equipment. Yet, 80 Volts is well within the range of affordable protection.

Conceptually, lightning protection devices are switches to ground. Once a threatening surge is detected, a lightning protection device grounds the incoming signal connection point of the equipment being protected. Thus, redirecting the threatening surge on a path-of-least resistance (impedance) to ground where it is absorbed.

Any lightning protection device must be composed of two “subsystems,” a switch which is essentially some type of switching circuitry and a good ground connection-to allow dissipation of the surge energy. The switch, of course, dominates the design and the cost. Yet, the need for a good ground connection can not be emphasized enough. Computer equipment has been damaged by lightning, not because of the absence of a protection device, but because inadequate attention was paid to grounding the device properly.

The basic elements used as protective switches are: gas tubes, metal oxide varistors and silicon avalanche diodes (transorbs). Each has certain advantages and disadvantages.

Because they can withstand many kilovolts and hundreds of Amperes, gas tubes have traditionally been used to suppress lightning surges on telecommunications lines. This is just what is needed to protect against a direct strike. Because gas tubes have a relatively slow response time, this slowness lets enough energy to pass to destroy typical solid state circuits.

Metal oxide varistors (MOVS) provide an improvement over the response time problem of gas tubes. But, operational life is a drawback. MOVs protection characteristic decays and fails completely when subjected to prolonged over voltages.

Silicon avalanche diodes have proven to be the most effective means of protecting computer equipment against over voltage transients. Silicon avalanche diodes are able to withstand thousands of high voltage, high current and transient surges without failure. While they can not deal with the surge peaks that gas tubes can, silicon avalanche diodes do provide the fastest response time. Thus, depending upon the principal threat being protected against, devices can be found employing gas tubes, MOVS, or silicon avalanche diodes. This may be awkward, since the threat is never really known in advance. Ideally, the protection device selected should be robust, using all three basic circuit breaker elements. The architecture of such as device is illustrated in Figure 20. This indicates triple stage protection and incorporates gas tubes, MOVs and silicon avalanche diodes as well as various coupling components and a good ground.

With the architecture shown in Figure 20 a lightning strike surge will travel, along the line until it reaches a gas tube. The gas tube dumps extremely high amounts of surge energy directly to earth ground. However, the surge rises very rapidly and the gas tube needs several microseconds to fire.

As a consequence, a delay element is used to slow the propagation of the leading edge wavefront, thereby maximizing the effect of the gas tube. For a 90 Volt gas tube, the rapid rise of the surge will result in its firing at about 650 Volts. The delayed surge pulse, now of reduced amplitude, is impressed on the avalanche diode which responds in about one nanosecond or less and can dissipate 1,500 Watts while limiting the voltage to 18 Volts for EIA-232 circuits. This 18 Volt level is then resistively coupled to the MOV which clamps to 27 Volts. The MOV is additional protection if the avalanche diode capability is exceeded.

As previously mentioned, the connection to earth ground can not be over emphasized. The best earth ground is undoubtedly a cold water pipe. However, other pipes and building power grounds can also be used. While cold water pipes are good candidates you should even be careful here. A plumber may replace sections of corroded metal pipe with plastic. This would render the pipe useless as a ground.

Posted by aliaswn in SPD Comments Off

Surge Protective Devices

* Bandwidth
* Combined Impulse
* Degree of Protection
* Disconnection Capacity / Follow Current Extinguishing Capability
* Frequency Range
* Insertion Loss
* Lightning Impulse Current
* Mains-side Overcurrent Protection / Backup Fuse
* Max. Continuos Voltage
* Max. Discharge Current
* Max. Transmission Capacity
* N-PE Surge Arresters
* Nominal Discharge Current
* Nominal Load Current (Nominal Current)
* Nominal Voltage
* Operating Temperature Range
* Operating Time
* Protective Circuit
* Protective Conductor Current
* Response Time
* Return Loss
* Series Impedance
* Sheild Attenuation
* Short-circuit Withstand Capability
* Surge Protective Devices
* Thermal Disconnection Device
* Voltage Protection Level

Surge Protective Devices
Surge protective devices are items of equipment whose basic components are voltage-controlled resistors (varistors, suppressors diodes) and/or spark gaps (discharge paths). The function of surge protective devices is to protect other electrical equipment and installations against impermissibly high surges and/or to establish the equipotential bonding.

Surge protective devices are classified
a) upon their application in

* Surge protective devices for power supply systems and equipment
* Surge protective devices for IT systems and equipment
* Isolating spark gaps for earth-termination systems or for equipotential bonding

b) upon their impulse current discharge capacity and their protective effect in

* Lightning Current Arresters
* Surge Arresters
* Combined Lightning Current and Surge Arresters

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Nominal Voltage Un
corresponds to the nominal voltage of the system to be protected. The nominal voltage is indicated in case of surge protective devides for IT installations for type designation purposes. For ac voltages it is indicated as rms value.
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Max. Continuos Voltage Uc
(max. continous operating voltage) is the root mean square (rms) value of max. voltage which may be applied to the correspondingly marked terminals of the surge protective device during operation. It is the maximum voltage on the SPD in the defined non-conductive state which ensures that this state is regained after response and discharge.
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Nominal Load Current (Nominal Current) IL
is the highest permissible operating current which may be permanently conducted via the correspondingly marked terminals.
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Max. Transmission Capacity
defines the max. HF capacity that can be transmitted via a coax surge protective device without interfering with the protective component.
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Nominal Discharge Current In
is the peak value of an impulse current, waveform 8/20 μs, which the surge protective device is rated for, according to a certain test programme.
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Max. Discharge Current Imax
is the max. peak value of the impulse current 8/20 μs, which can be safely discharged by the device.
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Lightning Impulse Currentimp
is a standardised impulse current curve, with a waveform 10/350 μs. Its parameters (peak value, charge, specific power) simulate the loads of natural lightning currents.

Lightning current and combined lightning current and surge arresters must be capable of discharging such lightning impulse currents several times without consequential damage to the equipment.
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Voltage Protection Level Up
The voltage protection level of a surge protective device is the max. instantaneous value of the voltage on the terminals of a surge protective device, defined out of the standardised individual tests:

* Lightning impulse sparkover voltage 1.2/50 μs (100%)
* Response voltage at a steepness of 1kV/μs
* Residual voltage at a nominal discharge current Ures

The voltage protection level characterises the capability of a surge protective device to limit surges to a residual level. If used in power networks, the voltage protection level defines the location of use via the overvoltage category according to DIN VDE 0110-1:1997-04 (EN 60664-1, IEC 60664-1). For surge protective devices designed for protection of IT networks, the voltage protection level has to be adjusted to the immunity of the equipment to be protected (DIN EN 61000-4-5: 2001-12).
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Disconnection Capacity / Follow Current Extinguishing Capability Ifi
The disconnection capacity is the uninterfered (prospective) rms-value of the mains follow current, which can automatically be extinguished by the storage protective device at the presence of Uc. It is proved at the operating duty test according to E DIN VDE 0675-6/A1: 1996-03
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Short-circuit Withstand Capability
is the value of the prospective power-frequency short-circuit current controlled by the surge protective device in case it is furnished with an upstream backup fuse.
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Mains-side Overcurrent Protection / Backup Fuse
is an overcurrent protective device (e.g. fuse or circuit breaker), which is installed outside of the surge arrester on the supply side to interrupt the power-frequency follow currents, if the breaking capacity of the surge protective device is exceeded.
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Operating Time ta
is the time passing until the automatic disconnection from the power supply at a failure of the electrical circuit or equipment to be protected. The response time is an application-specific value resulting from the intensity of the fault current flowing and the characteristics of the protective device.
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Combined Impulse UOC
is generated by a hybrid generator (1.2/50 μs, 8/20 μs) with a virtual impedance of 2 Ω. The open-circuit voltage of this generator is defined as UOC. UOC is preferably indicated for SPDs Type 3.
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N-PE Surge Arresters
are surge protective devices exclusively designed for installation between the N- and PE conductor.
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Operating Temperature Range
indicates the range where the devices can be used. In case of devices without self-heating, it is equal to the ambient temperature range. The temperature rise at devices with self-heating must not exceed the max. value indicated.
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Response Time tA
Response times generally characterise the response performance of the individual protection elements used in surge protective devices.

Depending on the steepness du/dt of the impulse voltage or di/dt of the impulse current, the response times can change within certain limits.
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Thermal Disconnection Device
Surge protective devices for power supply systems, which are furnished with voltage-controlled resistors (varistors), mostly have an integrated disconnection device isolating the surge protective device from mains at overloads and indicating this state of operation.

The disconnection device reacts on the “joule heat” generated by an overloaded varistor and disconnects the surge protective device from mains, if a certain temperature is exceeded.

The disconnection device is designed to disconnect the overloaded surge protective device in time to avoid a fire hazard. It is not designed to ensure the protective measure of “protection at indirect contact”.

The function of these terminal disconnection devices is tested via simulated overloads/ageing of the SPD.
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Degree of Protection
The degree of protection IP corresponds to the subdivision into the degrees of protection in accordance with DIN EN 60529 (VDE 0470 Part 1).
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Protective Circuit
Protective circuits ae multi-stage, cascaded protective devices. The individual protection stages can consist of discharge paths, varistors, semi-conductor elements. The energy coordination of the individual protection stages is realised with decoupling elements.
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Series Impedance
is the impedance inthe direction of the signal flow between input and output of the SPD.
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Bandwidth fG
defines the frequency-dependent preformance of an SPD. Bandwidths are frequencies causing an insertion loss (aE) of 3 dB under certain test conditions (see EN 61643-21:2000).

If nothing else is indicated, the value of the frequency refers to a 50 Ω system.
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Frequency Range
characterises the transmission band or the let-through frequency of an SPD according to the described attenuation characteristics.
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Return Loss aR
indicates at high-frequency applications, how many rates of the “forward” wave are reflected at the protective device (”transition point”).

It is direct measure for rating the adjustment of the protective device to the surge impedance of the system.
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Insertion Loss
At an indicated frequency, the insertion loss of a surge protective device is defined via the relation of the voltage value at the installation site before and after the insertion of the SPD. If no other value is indicated, the value refers to a 50 Ω system.
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Sheild Attenuation
Relation of the power feeded into a coaxial cable to the power radiated through the cable from the outer conductor.
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Protective Conductor Current IPE
is the current flowing through the PE connection when the surge protective device is connected with the max. permanent voltage UC, corresponding to the installation instructions and without load-side consumers.

Posted by aliaswn in SPD Comments Off

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Need Lightning Protection

High voltage surge protective devices.

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