Technical Data

What surge is

A surge is a very short burst of high energy. Surges often occur on mains supplies and telecommunication cables and may cause electrical equipment to malfunction or be damaged.

Causes of a surge

Surges are caused by lightning and by switching operations on the power supply system.
The most dangerous surges are those caused by direct lightning strikes to a building. Surges due to network switching and adjacent lightning strikes are usually less dangerous, but occur more frequently.
Lightning can cause severe damage to a building, by injecting a very high current into the building’s wiring. Direct strikes to incoming power or telecommunication lines close to the building have the same effect as do strikes to any nearby object such as trees, poles or other buildings...
Surges from nearby strikes are less dangerous than those from direct strikes, but are far more common. Power system switching operations may be switching equipment in sub-stations, industrial machinery (e.g. motor drives or air conditioners) or switch-mode power supplies (e.g. PC power supplies). Static electricity can also be a hazard.

Why surge protective devices (SPDs) is needed

A typical measured surge is shown below. Surges can damage electrical equipment because their amplitude can easily exceed the insulation level. Surges of up to many thousand volts are common. Direct lightning strikes can also inject large currents (of up to 200 kA) into an electrical system. SPDs protect equipment from these surges and hence to save on repair or replacement costs and downtime.

What SPDs are

SPDs protect equipment by limiting the surge voltage to which the equipment is exposed.. At the same time, they divert dangerous surge currents, e.g. those due to direct lightning strikes, to earth and away from sensitive equipment. In simple terms, an SPD may be seen as a switch between mains and earth. Normally, the switch is open and the SPD does not affect the operation of the equipment in any way. Only when a sufficiently high surge appears across its terminals does the switch close and divert the surge away from the equipment.

Lightning protection zones (LPZs)

An electric system is broken up into lightning protection zones (LPZs). These are defined as:
• LPZ 0A – items in zone are subject to direct lighting strikes;
• LPZ 0B – items not subject to direct lightning strikes;
• LPZ 1 – items not subject to direct lightning strikes, and voltage and current surges are attenuated (reduced in magnitude);
• LPZ 2 – items not subject to direct lightning strikes, and voltage and current surges are further attenuated.

Types and application of SPDs

There are two main types of SPDs: current-diverting SPDs (Class I) and voltage clamping SPDs (Class II and III):
• Class I SPDs are able to divert large surge currents and are useful when direct lightning strikes are expected, and
• Class II SPDs are able to survive lower amplitude surges, but are sufficient in cases where direct lightning strikes are not expected.

SPDs are installed at LPZ boundaries as follows:
• Between 0A and 1, a Class I SPD is needed
• Between 0B and 1, a Class II SPD is needed
• Between 1 and 2, a Class III SPD is needed

Data

Name		QFL surge protection device
Number of poles		1-4P
Maximum Continuous Operating Voltage (Uc)		275 V AC (RMS)
Voltage Protection level (Peak) (Up)		1.5 kV
Nominal Discharge Current (Inom) (In)		5 kA (8/20 μs)
Maximum Discharge Current (Imax)		10 kA (8/20 μs)
Short Circuit Withstand*		2.5 kA (50 Hz)
Lightning Protection Zone		OB to 1 or 1 to 2
SPD Class		Class II
Operating Temperature Range		-40 ℃ to +85 ℃
Mounting Options		Dual mounting (DIN & Mini), DIN Rail
Altitude		Certification tests done at altitude ≈ 2000 metres. Will operate at higher altitudes.
Flammability		I3 - Ignition does not persist at 850 °C after glow wire is withdrawn with an oxygen index of ≥ 28
Toxicity		F1 - Smoke index of ≤ 20 which determines the fume class
Pollution Degree		PD2 - Normally only non-conductive pollution occurs. Temporary conductivity caused by condensation is to be expected.

Overall Dimensions