What is a transient voltage surge suppressor (TVSS) and what does it do

What is a voltage surge

A surge is a transient, a voltage surge is a voltage impulse or wave which is superposed on the rated network voltage. If the increase in voltage lasts for three nanoseconds or more then, it’s called a surge and when it lasts for one or two nanoseconds then it’s called a spike. Transient voltage is an increase in voltage above the rated level in the flow of electricity. If the voltage rises above the specified volts of equipment, then it would be a problem and a surge protector is used to prevent this. So by using the surge protector, we can protect our equipment.

What causes over-voltage

Over-voltage can be caused by

  • Lightning
  • Electrostatic discharge
  • Switching transients
  • Inductive kickback
  • Shorts and other problems in power wiring

What are the harmful effects of transient surges

The most common failures produced by the transients within the electronic device are,

Disruptive effects - these effects are caused when the voltage transients enter an electronic component and the component then interprets the transient as a valid logic command, which would result in system lock up, malfunctions, faulty output or corrupted files.

Dissipative effects – these effects are associated with short duration repetitive energy level surges, which would result in long term degradation of the device.

Destructive effects - these effects are associated with high-level energy surges, which would result in immediate equipment failure.

What is a surge protective device (SPD)

A surge protective device reduces the magnitude of transient voltage surges and this will protect the equipment from damaging effects. SPD’s where known as a transient voltage surge suppressor. Surge protective devices will send the surge away to the ground.

What is a transient voltage surge suppressor (TVSS) and what does it do

A transient voltage surge suppressor can be considered as a very fast switch, which can protect the equipment from AC power line surges. It guards against the power system transients. Transient causes electronic equipment to fail because of the high energy associated with them. TVSS can be used in most of the data centers, the purpose of the TVSS is to eliminate or reduce damage to the data processing equipment and other critical equipment by limiting transient voltages and currents on electrical circuits. These transients may come from inside a facility or may be injected into a facility from the outside. Transients normally flow into equipment through electrical conductors, but it also uses other paths they are telephone lines, data-com lines, measurement and control lines. In order to prevent this TVSS device can be connected to all the points of potential voltage threat and limits this voltage to a level below the equipment withstand voltage.

How does a transient voltage surge suppressor works

A transient voltage surge suppressor is a voltage-sensitive switch, it constantly monitors the AC voltage input and output waveforms. TVSS won’t act under normal conditions, but in a case when the voltage difference between the power source and the protected line gets high enough, the switch closes and diverts the transient away from the electronic equipment. There are three types of transient voltage used today they are clamps, crowbars, and hybrid.

In the clamp type, it will change the surge path to a grounding reference, and the voltage waveform will cut off the surge where the surge exceeds the rating of the TVSS. Mostly used TVSS is clamp type they have a quick response but they can’t handle a large amount of surge current.

Crowbars are slow when compared to clamp types, but they can handle an enormous amount of surge current. It is called as crowbar because they exhibit a negative resistance. But we can’t solely rely on a crowbar because it shorts the AC power conductors to the ground which is hazardous to the electrical system.

Hybrids can be considered as the combination of the crowbar and clamp because they have the fast response of the clamp and the energy capabilities of the crowbar. They are created by a sophisticated process of internally constructing the two with fuses and current limiting impedances. This unit is very expensive and requires careful planning to make sure it won’t harm the equipment powered by AC power lines.

How to select, install, and use a TVSS

There are two basic types of TVSS’s they are plug-in and hard-wired, plug-in TVSS can be installed by plugging them into wall outlets to protect specific appliances or electronic devices. Hard wired TVSS’s can be used as the primary defense of the sensitive circuits or even an entire building. Plugin TVSS must be installed between the equipment which needs protection and its power source. In order to work the plugin TVSS properly proper building wiring and grounding are needed. If there is no ground in a circuit then the TVSS cannot divert the surge to a grounding reference and it won’t work. Locate the TVSS where it is easily accessible so that we can monitor the failure mode indicator. While installing the hard wired units, we must make sure to keep all conductor connections from the power panel to the TVSS as short and straight as possible.