Raycap - Transient Voltage Surge Suppressor_4006895_02

7/25/2019 Raycap - Transient Voltage Surge Suppressor_4006895_02

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Issue Date: 11/22/2004 Rev. Date: 00/00/0000 Revision: # / 01

Author: Chris Salmas Page 1 of 20 Content ID:

TVSS Transient Voltage Surge SuppressorsWhen Should A TVSS be used in a system? 2

Over Voltages - What Causes Them and What are They? 2

How does a TVSS reduce the over voltage levels on a system? 2Figure 1.01 Wave form before TVSS 3

Figure 1.02 - Ideal Wave form after TVSS 3

Configurations and Ratings of MOVs for use in TVSS equipment 31.1

Design methods 3

Figure 1.03 Conventional MOV Construction 4

Figure 1.04 Cross Section of Raycap Strikesorb TVSS Construction 4

1.2 Design ratings 4

Figure 1.05 Parallel MOV Circuit Board 5

Figure 1.06 Basic side view and Typical Ratings for Raycap TVSS 5

1.3

Lead Length to MOV Connection Point 6

Figure 1.07 Raycap Strikesorb TVSS connected in-line with equipment 7

Figure 1.08 Raycap Strikesorb TVSS connected in-line with 815 kVA SpeedStar SineWave Drive 8

Figure 1.09 3-Phase 3-Wire Connection Block Diagram Using a Conventional TVSS 9

Figure 1.10 3-Phase 3-Wire Connection Block Diagram Using a Raycap (in line) Strikesorb TVSS 10

Appendix a 40/80-380 UL Approval For Use Behind An 800 Amp Breaker 11

Appendix B Ferraz Shawmut I

2

T Destructive Test on Raycap Strikesorb TVSS Engine

12Appendix C - 40-380 Module Test Acceptance Summary 15

Appendix D 80-380 Module Test Acceptance Summary 17

Appendix E Raycap Warranty Document 19

Appendix F Raycap Legal Name Changes for Strikesorb and Rayvoss 20

Copyright Statement This document remains the property of Schlumberger and is Confidential and Trade Secret.

Do not disclose, use, or reproduce without written approval from Schlumberger


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When Should A TVSS be used in a system?

A TVSS is used to protect against lightning strikes, power line surges, and other transients that may be

present on the system. The TVSS achieves this by providing voltage suppression when over voltage conditions

appear on an electrical system. There are two main causes of over voltages, voltage spikes and systems transients.

These over voltages could cause the immediate loss of equipment and/or reduce the reliability (MTBF-mean time

before failures) of equipment; therefore, a TVSS should be installed into a system whenever there is the chance that

over voltages may occur. In some cases a power system study may be required to determine whether the use of a

TVSS is warranted. Proper selection should be the result of a thorough diagnostic evaluation of the customer

systems and environment. Schlumberger EPC Power Systems Group offers diagnostic expertise.

Over Voltages - What Causes Them and What are They?

The causes of over voltages can be grouped into four categories:

1. Lightning a natural phenomenon that produces severe and/or destructive levels of over voltage.2. Local Electrical Utilities can introduce transients and over voltages depending on the quality of the

utility service.

3. In-house systems Electrical equipment that introduces over voltages due to the operation of

equipment (e.g. Variable Speed Drives, rectifiers, etc.)

4. Adjacent facilities Introduction of the over voltages may be caused by equipment in an adjacent

facility down stream.

Over voltages are voltage levels that exceed the insulation rating of electrical equipment which will causes

degradation of insulation. This degradation of insulation will result in a reduction of reliability and possibly the

destruction of the equipment. If the voltage rises into the reliability impairment zone, the MTBF will be reduced

proportionally. The result will be that equipment will have to be replaced more often, increasing net operating costs.

If the voltage rises above the impairment zone then immediate destruction will occur, again increasing net operatingcosts. Most of these over voltages can be reduced or even eliminated with the installation of a TVSS.

How does a TVSS reduce the over voltage levels on a system?

Almost all TVSS manufactures use MOVs (Metal Oxide Varistors) in their design. MOVs are composed of a

thin disk wafer of material (metal oxide) that has a known voltage breakdown characteristic. At low voltages, the

MOV conducts very little current (micro-amperes). As the voltage approaches breakdown, the MOV then begins to

conduct current. At voltages slightly above the break down, large currents flow, effectively clamping the output

voltage. This clamping feature allows the higher voltage levels to be shunted to ground preventing over voltages onequipment. Refer to Figures 1.01 and 1.02 for examples on waveform clamping.

Copyright Statement: This document remains the property of Schlumberger. It is Confidential and Trade Secret

and not to be disclosed, used, or reproduced without written approval from Schlumberger.


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Figure 1.01 Wave form before TVSSFigure 1.01 Wave form before TVSS

Voltage Spikes

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Figure 1.02 - Ideal Wave form after TVSSFigure 1.02 - Ideal Wave form after TVSS

Configurations and Ratings of MOVs for use in TVSS equipmentConfigurations and Ratings of MOVs for use in TVSS equipment

Design methodsDesign methods

The conventional connection method used by most manufacturers for MOV construction is a soldered

connection of the conductor onto a thin coating of conductive material on the face of the MOV, as illustrated in

Figure 1.03.

The conventional connection method used by most manufacturers for MOV construction is a soldered

connection of the conductor onto a thin coating of conductive material on the face of the MOV, as illustrated in

Figure 1.03.




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Figure 1.03 Conventional MOV Construction

A problem with this type of construction becomes apparent when a high-energy surge is applied to the

MOV-connection-conductor. When a fast rising surge exceeds the capacity of the assembly (not the wafer disk), itpunches through the wafer between the connecting wires. Because the energy is not spread evenly across the

MOV face, the connection becomes its weakest link and when several MOVs are placed in parallel this can create

a domino effect where the TVSS fails catastrophically.

The Raycap Strikesorb TVSS design solves the problem of using multiple conventional MOVs by creating

one single MOV capable of handling the high-energy surges. The design also allows the energy of the surge to be

equally dispersed throughout the varistor surface. The varistor is also held in place with 1500+ pounds of pressure.

This design encourages the rapid dispersion of energy across the whole surface of the MOV, which removes the

problem of weak links and increases the energy handling capabilities of the device. Refer to Figure 1.04.

Figure 1.04 Cross Section of Raycap Strikesorb TVSS Construction

Design ratings

Most TVSS designs use multiple MOVs in parallel on a circuit board. The module rating or energy handling

is calculatedby multiplying the rating of one MOV by the number of MOVs in the circuit; the assumption being that

the surge will be shared equally by all MOVs and that each MOV has exactly the same operating characteristics as

depicted in figure 1.05.




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Figure 1.05 Parallel MOV Circuit BoardFigure 1.05 Parallel MOV Circuit Board

Testing of parallel MOV modules does not support this assumption: they fail at a much lower value. It is

impossible for all the parallel MOVs to clamp at the exact same voltage: thus, when subjected to a surge the lowest

clamping MOVs will clamp first and take on most of the surge energy; hence, this causes further degradation within

the MOVs and eventually leads to failure at its weakest link as described in Section 4.1 - Design Methods. Whenthe MOVs fail it could explode and/or cause a chain reaction of events leading to a destructive breakdown and

debris contamination, even when encased in epoxy.

Testing of parallel MOV modules does not support this assumption: they fail at a much lower value. It is

impossible for all the parallel MOVs to clamp at the exact same voltage: thus, when subjected to a surge the lowest

clamping MOVs will clamp first and take on most of the surge energy; hence, this causes further degradation within

the MOVs and eventually leads to failure at its weakest link as described in Section 4.1 - Design Methods. Whenthe MOVs fail it could explode and/or cause a chain reaction of events leading to a destructive breakdown and

debris contamination, even when encased in epoxy.

The Raycap TVSS rating is not based on calculation but rather on actual lab testing on a single MOV module

as illustrated in Figures 1.04 & 1.06. Refer to Appendices C & D for actual lab test certifications.

The Raycap TVSS rating is not based on calculation but rather on actual lab testing on a single MOV module

as illustrated in Figures 1.04 & 1.06. Refer to Appendices C & D for actual lab test certifications.

Figure 1.06 Basic side view and Typical Ratings for Raycap TVSS




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Lead Length to MOV Connection Point

The lead length to the MOV plays a very important role in the value of clamping that will be offered by the

device. The conventional TVSS requires the use of leads and fusing to connect in parallel to the load side breaker

and cannot be mounted inside equipment due to the catastrophic failure condition of the device if it fails during ahigh-energy event. The length of the leads adds inductance to the circuit and increases the clamping voltage of the

TVSS. This results in clamping voltages that are higher than desired and may not protect equipment effectively.

The Raycap TVSS is installed in-line with the load (TVSS is installed in-line in the Toshiba plant for

all SS2K and SWD models), minimizing unnecessary connection leads and maximizing the level of protection by

keeping the lead length no more than 8-10 away from the TVSS as illustrated in Figure 1.07, 1.08 and 1.10. The

reduced lead length is made possible due to the fact that the Raycap Strikesorb TVSS does not fail catastrophically

and contains the energy within itself; this allows the TVSS to be installed on the load side of the breaker as depicted

in Figure 1.08. Refer to Appendix B for destructive test results and descriptions/pictures of the Raycap Strikesorb

TVSS that has operated to a short. Typical connection block diagrams for ESP applications of both types of TVSS

can be found in Figures 1.09 & 1.10.

The connection point also plays a large role in the way in which the protection to the device is offered. As

part of the requirement when connecting a conventional TVSS to the line side of the breaker, a fuse must be placed

in series with the TVSS to protect TVSS against a high inrush of current, which could lead to the catastrophic failure

of the TVSS. When the fuse is blown all protection is lost and any transients that are entering the system, after the

fuse has blown, is now entering the unprotected equipment. The Raycap 40/80-380 Strikesorb TVSS can be

connected on the load side of the breaker without any additional fusing up to its UL rating of 800 Amps (refer to UL

rating in Appendix A) or behind a fuse rating of 1200A at 100kA of available short circuit. The I2T rating of the Raycap

Strikesorb TVSS can handle much higher levels (approximately 500 times more) of inrush when compared to the I2T of

a breaker as depicted in by the Ferraz Shaumat test results in Appendix B. In the rare case that the TVSS rating is

exceeding during a high-energy event the TVSS will short to ground thereby tripping the breaker and isolating the

load from damaging energy. The event is contained within the TVSS enclosure and no external damage occurs.

This, in turn, ensures that the breaker will trip during an extremely high I2T and will isolate the system from any other

transients that may follow. Refer to Appendix B for a cut-away picture of a TVSS unit that has operated to a short.




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Figure 1.07 Raycap Strikesorb TVSS connected in-line with equipment




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Figure 1.08 Raycap Strikesorb TVSS connected in-line with 815 kVA SpeedStar SineWave Drive




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Note: TVSS connection could be from load or line side of breaker. Load side connection depicted in this

diagram.

Figure 1.09 3-Phase 3-Wire Connection Block Diagram Using a Conventional TVSS




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Figure 1.10 3-Phase 3-Wire Connection Block Diagram Using a Raycap (in line) Strikesorb TVSS




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Appendix A 40/80-380 UL Approval For Use Behind An 800 Amp Breaker




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Appendix B Ferraz Shawmut I2T Destructive Test on Raycap Strikesorb TVSS Engine




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Appendix C - 40-380 Module Test Acceptance & Summary




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Appendix D 80-380 Module Test Acceptance & Summary




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Appendix E Raycap Warranty Document




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Appendix F Raycap Legal Name Changes for Strikesorb and Rayvoss


Raycap - Transient Voltage Surge Suppressor_4006895_02

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