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about surge

What is surge?

Surge generally called impulse, spike, noise, etc.
means the electrical agitation phenomenon
of high current which appears and disappears for
a very short period of time(Coefficient ns~μs).

Types of surge

Surge can be divided into two types according to the causes.
Lightning surge Surge generated due to lightning can be divided into direct lighting and induced lighting
ㆍDirect lighting - When a building or a railroad into it is struck by lighting,
ㆍInduced lighting - When a place near a building or a railroad into it is struck by lightning,
On/Off
Surge		 Surge generated in a building is usually done by making / breaking of capacitor banks, ON/OFF of large motors, drive of elevators,
ON/OFF of office equipment, arc welding, short circuits, etc.

Lightning surge coupling method

Surge induced from lightning stroke is largely classified into three things. it is induced by each resistance coupling, inductive coupling,
and electrostatic coupling.
Resistance
coupling		 When land is struck by lightning, ground potential raises in a moment. a building (A) and another building (B) around lightning stroke points are mutually connected by power, signal cables, etc. And there are differences of ground potential between (A) and (B) due to differences of distances of lightning stroke points and grounding. There is surge through power or signal cables connected from (A) to (B) due to it.
Electrostatic
coupling		 There is capacitance between two adjacent conductors (The conductor that surge flows (A) and the adjacent conductor (B)). When surge voltage with the high voltage build-up rate (dv/dt) flows in the conductor (A), surge is conducted and generated between the two conductors.
Inductive
coupling		 When a lightning rod is struck by lightning, a lightning current(IL) is discharged to the ground. At this moment, an induced electromotive force (Surge) is generated due to a surge current created in conductors including power or signal cables in a building.
The surge inducement method is shown in each picture.

  • Resistance coupling

  • Electrostatic coupling

  • Inductive coupling

Surge causes fatal damage to digital system facilities according to causes and sizes or brings electrical insulation aging to systems or component parts by effects of accumulated surge.

Damage and risks of surge

Today's buildings necessarily cannot help being mutually connected to various cables for electricity or communication.
There are a lot of signal cables in the buildings. These signal cables include telephone wires, antennas, safety video camera circuits connected to FAX and modem.

When a building is struck by lightning, about 50% of a thunderbolt current coming down from a lightning rod comes in ground and the rest 50% of the current flows into it through gas pipes, water pipes, conduits, wire, and communications lines (In integrated grounding and common grounding).
When a building is struck by lightning, facilities and systems are damaged and there is damage including failure, etc. due to surge directly conducted through a power system.

Even though the building is protected from surge directly conducted to the power system, facilities and systems connected to cables are damaged as there is induced voltage in cables in it.

If there are two buildings near even though the building is not struck by lightning, there are differences in ground potential according to distances between their grounding.
If electrical systems are included in each building and there are no systems connected to the buildings, this ground potential does not cause any problems.
But, if LAN cables are connected to the two buildings, equipment in a building has relatively high ground potential and there is damage in LAN equipment as its insulation is destroyed due to the differences in ground potential. ※ Brain damage and risk expected by type of building
Classification of buildings Type Expected lightning damage and risk
General buildings Houses
(Apartment houses and detached houses)		 Damage of electric equipment by lightning surge, limp (Lightning electron impulse) and direct strokes
Theaters, schools, and department stores Above damage and risk, occurrence of panic by damage including lighting, and failure of fire alarms
Banks and insurance companies Above damage and risk, damage of computers, and occurrence of panic
by data and communication failure
Hospitals and silver homes Above damage and risk, danger of patients in intensive care units, and emergency medical services
Factories Above damage and risk, damage of facilities, and suspension of products
Art museums Damage of cultural heritages
Special buildings Telephone offices, places of mobile carrier business, and power plants Risk of secondary damage in surroundings due to loss and fire of public services
Gunpowder, military supplies factories
and oil petroleum refineries		 Significant effects on plants and surroundings by fire and explosion.
Chemical factories, nuclear power plants, and biochemistry research centers Harmful effects on regions and global environment by fire and inoperable products.

Surge protector's necessity

In the analog era, there were no big problems in installing only lightning arresters of high pressure systems (LA and SA).
However, many parts are replaced by semiconductor as we moved into the digital era.
So it is always exposed to danger of malfunction or damage of electrical equipment as it is extremely and sensitively influenced by 'surge' created by thunderbolts, lightning, electric power system accidents, operation of its switches, and change of adjacent load. Digital devices cannot be protected by lightning arresters any more. The digital era and low pressure surge protectors (SPD/TVSS) are the devices which must vitally, not optionally, be installed.

Damage of surge cannot be prevented by the only existing lightning protection systems. Lightning rods, down conductors, and ground systems with low resistance cannot just protect digital equipment. Damage of induced lighting through ground connection and surge by currents and inducement (EMI) when thunderbolt currents pass through induced conductors bring direct damage to digital devices and programs. Surge generated when an on/off switch works and surge by accidents of electrical grid cause obstacles and damage of automatic control systems.

Statistical data on surge

  • Electricity quality abnormality There is surge (Lightning surge) by lightning. But there is mostly
    surge (Switching surge) when equipment is switched on/off in facilities.
    If parts of equipment or systems are damaged due to surge,
    systems are damaged or less reliable as there are expenses for repair or
    replacement and electricity quality abnormality due to unexpected shutdowns.
  • Places that surge is generated in places of business FLORIDA POWER investigated electricity quality problems shown
    in industrial settings in 1993. The point to take note of is that surge
    of 60% is generated in office machines in an office and 20% is done
    another office next to the use of the same power. In other words,
    surge of more than 80% is generated in internal power.
  • Analysis on damage causes of electrical equipment This was introduced in [The world of electricity] published by KIEE.
    A German insurance company reported it. According to the contents,
    damage of electrical equipment by surge is more than 30%
    of entire failure and has been a four times increase for the recent 10 years.