Transient voltage surge suppressors - ABB (OVR series)
Transient voltage surge suppressors - ABB (OVR series)

Transient Voltage Surge Suppressor (TVSS) is a device that every data center or mission critical facility should have.

Why should every data center have one and what does it do you ask?

The purpose of a TVSS is to eliminate or reduce damage to data processing equipment and other critical equipment by limiting transient surge voltages and currents (surges) on electrical circuits.

These transients or surges may come from inside a facility or may be injected into a facility from outside.

What is a transient?

A transient surge is a short blast or pulse of high energy that can either come in its natural form such as lightning or produced by other equipment.

Transients caused by other equipment are usually caused by the discharge of stored energy in inductive components. Some examples are electrical motors, such as those used in elevators heating, air conditioning, refrigeration or other inductive loads. Two other sources are arc welders and furnace igniters. These transients are capable of causing significant damage to equipment and electronics.

The transient causes damage to a device when the transient voltage exceeds the weakest exposed component’s ability to withstand that voltage. Transients normally flow into equipment via electrical conductors, but other paths are common. These paths include: telephone lines, data-com line, measurement and control lines, DC power buses and neutral and ground lines.

To protect against these surges designers recommend the installation of a TVSS devices that connects to all points of potential voltage threat and limit this voltage to a level below the equipment “withstand” voltage. The TVSS device absorbs or diverts all the energy present in the surge and clamping or holding the “let through” over voltage down to a level safe for exposed circuitry.

TVSS protection is typically applied at several points throughout of facility. These locations include the service entrance point, distribution panels, branch panels and the individual circuit.

As you can see a TVSS device is important to mission critical electrical system and its benefits are great. A TVSS is a low cost protection device that will help to reduce downtime or production losses. It helps to extend lighting lamp and ballast life expectancy. The TVSS will help in reducing motor stress and overheating and is a constant protection of data processing and digital equipment.

If you mission critical facility does not already have TVSS devices installed we highly recommend it. If you are not sure if your system has them installed we suggest asking your engineer or electrician to verify. It is a small price for additional peace of min.

Main causes of transient over voltages

1. Lightning Strike

a) A lightning Strike can have a destructive or disturbing effect on electrical installations situated up to several miles away from the actual point of the strike.

b) During a storm, underground cables can transmit the effect of a lightning strike to electrical equipment installed inside buildings.

c) A lightning protection device (such as a lightning rod or a Faraday cage) installed on a building to protect it against the risk of a direct strike (fire) can increase the risk of damage to electrical equipment connected to the main supply near or inside the building.

Direct and indirect lightning strike on overhead line
Left: Direct lightning strike on overhead line; Right: Indirect lightning strike on ground

Lightning strike on lightning rod
Lightning strike on lightning rod

The lightning protection device diverts the high strike current to earth, considerably raising the potential of the ground close to the building on which it is installed.

This causes overvoltages on the electrical equipment directly via the earth terminals and induced via the underground supply cables.

2. Switching operation on the power distribution system

The switching of transformers, motors or inductances in general, sudden variation of load, disconnection of circuit breaker or cut outs lead to over voltages that penetrate the user’s building.
Significantly, the closer the building is to a generating station or substation, the higher the over voltages may be.

Medium voltage disturbance transmitted to low voltage side of transformer
Medium voltage disturbance transmitted to low voltage side of transformer

It is also necessary to take into account mutual induction effects between the high voltage power line and aerial sections of the low voltages lines as well as direct contact between lines of different voltages caused by accidental breaking of cables.

3. Parasitic interferences

These are freak interferences with indifferent amplitudes and frequencies that are re-injected into the electrical supply by the user himself or his environment.

4. Disturbances generated by the user

Disturbance generated by the user
Disturbance generated by the user

These interferences have little energy but their short duration, their steep wave front and their peak value can have harmful effects on the proper functioning of the sensitive equipment causing either disruption or complete destruction.

  1. ABB (Transient Voltage Surge Suppressors OVR Series
  2. The Data Center Journal (where IT, Facilities and Design Meet)

About Author //


Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears.Professional in AutoCAD programming and web-design.Present on


  1. David Dundas
    Jun 20, 2015

    A useful article Edvard, however your examples of transient overvoltages don’t include what I believe is a common, but not recognised occurance in local mains power supplies that arises from a break in the high voltage (HV) supply to the local distribution transformer which then send a HV surge out to consumers. My company had 2 intruder alarms destroyed by such an event and because we could show that this happened at the same time on equipment supplied through 2 separate consumer units, we were able to get compensation from the local power distribution company. I am now facing a similar problem at home in the same town where my fridge defrost timer and the PC board of our gas boiler have both failed at the same time. The PC board is going to cost around £ 500 with the VAT so I was searching for an efficient surge suppressor to protect the new board, when I came to your site. Ask any appliance service men about the small electronic boards built into washing machines, freezers etc about how often they have to replace burnt out boards; you might be very surprised.

  2. mohammed
    Dec 05, 2014

    Please l want to know : is atransient (surge) voltage can damage adistributions transformes ,11/.4 kv

  3. […] temperatures quickly except during very large or long disturbances. This requires correspondingly large surge energies. Also, the materials that constitute the insulation of these components can operate at temperatures […]

  4. […] nature, such as a short-circuit on a transmission line or loss of a large generator.Following a transient disturbance, if the power system is stable, it will reach a new equilibrium state with practically the entire […]

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