Docstoc

Transient Voltage Surge Suppression _TVSS_

Document Sample
Transient Voltage Surge Suppression _TVSS_ Powered By Docstoc
					                  Transient Voltage Surge Suppression (TVSS)
                  for Commercial/Residential Applications

                  Introduction
                  Protecting computer equipment can be confusing. There are many options in the market-
                  place, not all of which will provide complete protection. This brochure is designed to help
                  define the best protection for your application. Transient Voltage Surge Suppression (or
                  TVSS) technologies protect microprocessor operations from damage due to switching surges
                  or surges associated with events like power outages.
                  Surge disturbances are very short-duration, high-magnitude voltage fluctuations. Because of
                  their short duration, they may not exhibit any immediately perceptible impact. They can be
                  caused by any switching operation on the electrical system (mechanical or electrical).
                  Surge damage can be: immediate, manifesting as failure, or cumulative, manifesting as
                  failure over time due to a weakened state. Surges can also cause data upset, occuring as
                  temporary malfunctions or system glitches that result in lost production, data or time.
                  TVSS devices are designed to keep harmful surge energy away from sensitive electronic
                  equipment. A TVSS device accomplishes this by diverting this energy to a path away from
                  critical equipment.
                  An investment in sensitive electronic equipment (stereos, televisions, appliances, computers
                  and control systems) can be significant. A properly specified TVSS device is cost-effective
                  insurance for this investment.
                  This brochure will walk you through the information you will need to know to select the
                  TVSS device for your application.

                  TVSS applications
                  TVSS devices can be installed individually for basic protection or they can be installed in a
                  network, designed to provide maximum benefit for a given electrical system. To determine
                  the best approach for your application, it is important to understand the different methods
                  of installation.

                  TVSS installation locations      Clamping Level*              Lowest                  Lower    Low
                  When TVSS devices are            Energy Capability* Highest                           Higher   High
                  installed at multiple locations,
                  make sure that the clamping
                  voltage and energy handling
                  capability are correctly
                  matched for the application.
                  As shown in the diagram, the
                  clamping level should be lower
                  and the energy handling
                  capability greater for the       Commonly shared grounding medium
                  panelboard-mounted device
                                                   * Words and phrases in italics are included in the glossary
                  than would be for an outlet-
                  installed device.

www.bchydro.com
Hardwired devices                                         Separate suppressors can be purchased for your
Hardwired TVSS devices are permanently installed          communication circuits. In this case, the ground
by electricians at circuit breaker panels, transformers   termination for these devices must connect to a
or main service switchgear. The intent of this            power system ground. For these applications it is
application is to provide protection to several           recommended that a wire be connected between
pieces of equipment. A TVSS installed at the              the phone or cable TV TVSS ground terminal and
service panel will provide protection for all             the ground terminal of the receptacle powering
“downstream” electrical components from all               the critical load.
“upstream” surge disturbances.                            There is often a wide difference in performance
                                                          between TVSS devices. The specifications
Point-of-use protectors
                                                          provided by the manufacturer are often the best
Point-of-use protectors are configured in                 indication of these performance differences.
packages that can be installed by the consumer            Specifications important to consider are defined
(e.g., plug strips). However, these devices offer         below.
low energy capability. If these devices are applied
alone, they may not provide complete protection           Specifications for consideration
from all surge disturbances.
                                                          Design
Telecommunications                                        Manufacturers use three basic components in the
It is important that all electrical paths to your         design of surge suppressors. These devices
sensitive electrical equipment be protected               contain sophisticated electronic switches that
against surge disturbances. Cable TV and                  operate when the voltage exceeds a
telephone circuits also require protection from           predetermined level to divert potentially harmful
surge disturbances. Some point-of-use TVSS                energy to an alternative path. They are gas
devices provide options for cable TV and phone            tubes, metal oxide varistors (MOV), and
protection in the same package. Products                  avalanche diodes.
packaged with these options provide a common              The specifications on the TVSS packaging will
ground reference for the power system and                 provide some clue as to the component(s) used.
communications systems surge suppression, and             Higher-quality devices will use multiple
are referred to as surge reference equalizers.            components to benefit from their different
                                                          characteristics.

                                                          Protection modes
                                                          The wiring configuration of these components
                                                          will have a bearing on the overall performance of
                                  Surge                   the TVSS. The table at right summarizes the
       Service                  Reference                 different switching options available.
        Panel                   Equalizer
                                                   CATV



                   Branch Circuit
                  Metal Water Pipe

   Ground Rod

Example of a power & communications ground
reference
Three-phase protection modes
                   L1–N         L2–N            L3–N           N–G           L1–L2           L2–L3          L1–L3        L1–G           L2–G             L3–G
 Basic              X              X             X
 Better             X              X             X              X
 Best               X              X             X              X               X              X             X               X              X              X

Single-phase residential panel                                                       Single-phase wall outlets
            L1–N        L2–N      N–G       L1 –L2       L1–G       L2–G                           L–N       N–G        L–G
 Basic        X           X                                                          Basic          X
 Better       X           X         X                                                Better         X         X
 Best         X           X         X           X          X         X               Best           X         X          X


Design concept
With the components arranged for the desired protection modes, there remain three fundamental
configurations used by manufacturers for surge suppressors, as shown below.

                               Benefits                          Drawbacks                         Price – residential               Price – commercial
Clamping                       Lower cost; utilizes              Will not protect all              Panel                             Panel
Basic                          “Basic” protection                conductors; will not              $35 – $65                         $50 – $200
(See figure 1)                 mode (see previous                divert all surge                  Receptacle                        Receptacle
                               table).                           energy.                           $10 – $25                         $10 – $50
Sine-wave                      Diverts a greater                 Higher purchase                   Panel                             Panel
tracking                       amount of surge                   cost than basic                   $40 – $120                        $200 – $1,500
Preferred                      energy than basic                 clamping; larger                  Receptacle                        Receptacle
(See figure 2)                 clamping; utilizes                number of                         $30 – $75                         $30 – $140
                               “Preferred” or                    components
                               “Best” protection                 increases risk of
                               modes.                            failure.
Hybrid                         Provides filtering                The most expensive                Panel                             Panel
Best                           with surge                        TVSS device                       $130 – $400                       $600 – $8,000
(See figure 3)                 suppression;                      available; filtering              Receptacle                        Receptacle
                               greatest capacity                 function will not                 $50 – $140                        $130 – $300
                               for surge energy                  correct all
                               diversion, utilizes               frequency-
                               “Preferred” or                    dependent
                               “Best” protection                 disturbances.
                               modes.

                     Clamping Level                                                                          Clamping Envelope              Reduced High-
                                                            Clamping Envelope                                                               Frequency Noise

                        Transient: +400v Peak        k
                                                                                                                                                Transient: +400v Peak
                                                                                    Transient: +400v Peak




  Clamping Level                                         Clamping Envelope                                        Clamping Envelope

             Figure 1                                                    Figure 2                                                Figure 3

Once you have determined the design concept and protection mode that suit your needs, you may wish to
make note of it on the evaluation form on the next page.
                         TVSS evaluation form
                         The following tables can be used to compare different TVSS products or to
                         document the different TVSS device specifications for the correct application.
                         Note: the numbers provided are example specifications, typical for TVSS
                         devices intended for a staged application.
Specifications/features desired
                                    Hardwired TVSS                         Receptacle TVSS
                         Sample    Model 1    Model 2   Model 3   Sample   Model 1   Model 2   Model 3
Application voltage      240V                                     120V
MCOV                     300V                                     150V
Peak surge current
Filter freq. range
Energy rating
Response time
Protection modes           5                                        3
CSA approved               X                                        X
Let through voltage      750 V                                    330 V
Operational indicators
Diagnostic indicators
Overcurrent protection
Alarms
Warranty                  5 Yr.                                    1 Yr.
Pricing                  $250                                      $65
Manufacturer name
                                  Communications TVSS
                         Sample     Model 1   Model 2   Model 3
Application voltage      240V
MCOV                     300V
Peak surge current
Filter freq. range
Energy rating
Response time
Protection modes           5
CSA approved               X
Let through voltage      750 V
Operational indicators
Diagnostic indicators
Overcurrent protection
Alarms
Warranty                  1 Yr.
Pricing                  $250
Manufacturer name
Installation guidelines                             • Overcurrent protection devices need to be
                                                      checked regularly to be sure they are fully
The installation of TVSS equipment will normally
                                                      operational.
be straightforward. The following guidelines are
provided to assist you.                             • All TVSS devices should be periodically
                                                      inspected for:
• Comply with Canadian Electrical Code (CEC)          • proper installation
  and provincial requirements.                        • loose terminal connections
• Follow the manufacturer‘s installation              • extension cords being used with TVSS devices
  procedures provided with the device.                • indicator lights registering normal conditions
• Review the manufacturer‘s specifications and        • overheating
  installation guidelines for the chosen device.    • If a TVSS exhibits any evidence of overheating
• All units must be CSA approved.                     (melted enclosures, noise, odour, warm to the
• Verify the voltage of the desired TVSS              touch, blackening of terminal connections), it
  location, and check the condition of all            should be immediately disconnected and replaced.
  components and the integrity of the neutral       For hardwired units
  and ground conductors for the selected
                                                    • Installations must be performed by a licensed
  location. Replace any components that are
                                                      electrician.
  questionable.
                                                    • Each TVSS device must be installed on its own
• Based on the manufacturer‘s recommenda-
                                                      branch circuit.
  tions, install the TVSS in a safe location.
                                                    • Each TVSS device must have its own means of
• All TVSS output leads should be kept as short
                                                      disconnection.
  and straight as possible (about 20 cm). Sharp
  bends should be avoided.                          • Some manufacturers can provide TVSS
                                                      equipment that is rated and suitable for
• All TVSS output leads should be the same
                                                      installation within standard switchgear.
  length.
                                                    • All terminations should be made with
• The ground lead from the suppressor should
                                                      compression-type (preferred) or proper set
  be connected to a common ground. Do not
                                                      screw connections. Do not use wire-nut type
  connect TVSS ground wires to an isolated
                                                      terminations.
  ground.
• Disconnect power to the circuit before             Acknowledgement
  installation.                                      This brochure was adapted from material originally
• Before connecting any critical loads, turn on      published by the Power Quality Service Center,
  the TVSS and verify that all power, protection     Portland, Oregon, and is used under licence.
  system and diagnostic indicator lights are         Legal notice
  functioning. If a condition appears abnormal,      This work has been prepared by Performance Energy
  have your electrician review the wiring before     Partnership, Inc. (PEP) and Ferraro, Oliver &
  activation of unit.                                Associates, Inc. (FOA) under contract with Northwest
• With the TVSS and the selected load switches       Power Quality Service Center (NWPQSC) and
  in the “off“ position, connect your critical       modified by BC Hydro. Neither PEP, FOA, NWPQSC,
  loads directly to the TVSS. Do not use             BC Hydro nor any person on behalf of any of them
                                                     makes any warranty with regard to this material,
  extension cords or plug strips.
                                                     including, but not limited to, the implied warranties
• Switch on the TVSS. Check all status and           of merchantability and fitness for a particular
  diagnostic lights. If any abnormal conditions      purpose. Neither BC Hydro nor Northwest Power
  occur, follow up appropriately (see above). If     Quality Service Center (including its dealers or
  normal conditions are indicated, switch on         distributors) shall be liable to the purchaser or any
  your critical loads, one by one.                   other person or entity with respect to any liability,
                                                     loss or damage caused or alleged to be caused
• Position all cords and wires out of the flow of    directly or indirectly by this manual. Northwest Power
  traffic and away from feet under desks.            Quality Service Center and BC Hydro shall not be
• Indicator lights need to be checked regularly      liable for errors contained herein or for incidental
  to be sure output loads are protected.             consequences damages in connection with the
                                                     furnishing, performance or use of this material.

				
DOCUMENT INFO