Transient Voltage Surge Suppression (TVSS)
for Commercial/Residential Applications
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
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 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
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
* Words and phrases in italics are included in the glossary
than would be for an outlet-
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
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.
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
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.
Metal Water Pipe
Example of a power & communications ground
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
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
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.
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.
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
Protection modes 5 3
CSA approved X X
Let through voltage 750 V 330 V
Warranty 5 Yr. 1 Yr.
Pricing $250 $65
Sample Model 1 Model 2 Model 3
Application voltage 240V
Peak surge current
Filter freq. range
Protection modes 5
CSA approved X
Let through voltage 750 V
Warranty 1 Yr.
Installation guidelines • Overcurrent protection devices need to be
checked regularly to be sure they are fully
The installation of TVSS equipment will normally
be straightforward. The following guidelines are
provided to assist you. • All TVSS devices should be periodically
• 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
• Each TVSS device must be installed on its own
• Based on the manufacturer‘s recommenda-
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
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.
• 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
• 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.