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Low voltage surge protection devices

Technical terminology in IEC61643 standards-2

2.1.20 Reference Voltage Uref

In the area where the volt-ampere characteristics of the metal oxide resistor will transition from the weak electric field area to the strong electric field area, a suitable current is selected as the reference current, and the voltage corresponding to this current is called the reference voltage.

Note: The reference current value is determined by the manufacturer, usually 1mA. But this value should be related to the size of the metal oxide resistor, usually in the range of 1-20mA.

The maximum continuous operating voltage Uc should be lower than Uref.

2.1.21 voltage protection level Up

A parameter that characterizes the performance of the limited voltage between the SPD terminals. The value should be greater than the highest value of the measured limit voltage. The value can be selected from a list of priority values.

Note 1: When applying voltage protection level parameters, pay attention to the corresponding discharge current peak value, lightning voltage, lightning current waveform and wavefront steepness.

Note 2: Regarding the voltage protection level, IEC 61643-1 refers to the maximum discharge voltage under the specified impulse voltage wave (1.2/50µs) for the voltage switch type SPD; for the voltage limited type SPD refers to the maximum residual voltage under the specified current waveform (Type I test) In Iimp, II type test in In) or specified compound wave test

The maximum residual voltage under the open circuit voltage of the smart plug high low voltage protector (Type III test is in Uoc); for the combined SPD, it refers to the larger of the maximum discharge voltage and the maximum residual voltage.

2.1.22 measured limiting voltage Ulim

The maximum voltage peak value actually measured between the SPD terminals when an impulse of the specified waveform and amplitude is applied.

Note: When measuring the limited voltage, impulse voltage is applied to the voltage switch type SPD, and the discharge voltage is measured; impulse current is applied to the voltage limit type SPD, and the residual voltage is measured (Type I, Type II test) or compound wave is applied, and the residual voltage is measured () Class test); for compound SPD, impulse voltage

Both the impulse current and the impulse current are applied, and the discharge voltage and residual voltage are measured.

2.1.23 residual voltage Ures

When the discharge current flows through the SPD, the voltage peak appearing between its terminals.

2.1.24 coordination between SPD stages

It means that the configuration of the SPD at all levels should not only meet the impact resistance level of the protected equipment, but also prevent the SPD characteristics from being improperly matched with the installation position and exceeding its current capacity under lightning current.

2.1.25 Short-circuit withstand current short-circuit withstand Isccr

The maximum expected power frequency short-circuit current value (effective value) that the SPD can withstand.

2.1.26 Follow current Ifi

After the SPD acts under a lightning strike, the current (effective value) flowing into the SPD from the power system.

Note: It is a parameter of voltage switch type SPD.

2.1.27 Rated disconnecting freewheeling rating Ifi follow current interrupting rating Ifi

SPD itself can be disconnected freewheeling (effective value).

2.1.28 rated load current IL

The maximum continuous current (effective value) that is allowed to pass from the SPD input terminal to the output terminal to provide to the load.

Note: This parameter is only applicable to two-port SPD.

2.1.29 voltage drop (in per cent)

 U%=[(Uin-Uout)/Uin]×100% where:

 Uin——SPD input terminal voltage

Uout——The SPD output terminal voltage measured at the same time when the rated resistive load is connected. Note: This parameter is only applicable to two-port SPD.

2.1.30 Two-port SPD two-port SPD

The SPD with two sets of input and output terminals has a special series impedance between the input and output terminals.

2.1.31 1.2/50 impulse voltage 1.2/50 voltage impulse

The apparent wavefront time (the time from 10% to 90% of the peak value) is 1.2µs, and the half-peak time is an impulse voltage of 50µs.

2.1.32 8/20 current impulse

The apparent wavefront time is 8µs, and the half-peak time is 20µs.

2.1.33 combination wave

The composite wave is generated by the impulse generator, which can apply 1.2/50μs waveform impulse voltage to the open circuit and 8/20μs waveform impulse current to the short circuit. The voltage, current amplitude and waveform provided to the SPD are determined by the above-mentioned impulse generator and the impedance of the SPD under the action of the impulse generator. The ratio of the peak open-circuit voltage Uoc to the peak short-circuit current Isc is taken as 2

Ω: This ratio is defined as the virtual impedance Zf.

2.1.34 Nominal discharge current In Nominal discharge current In

The peak value of the current flowing through the SPD with 8/20 waveform. This current is used for the SPD classification of the II test and the pretreatment test of the SPD of the I and II tests.

2.1.35 Impulse current Iimp

The impulse current Iimp is defined by the current peak value Ipeak and the charge quantity Q. The test is carried out according to the procedure of the action load test, and is used for the SPD classification test of the I level test.

Note: The charge quantity Q=0.5Ipeak required by the impulse current test, in which the unit of charge quantity is Coulomb (C), and the unit of current is kiloampere (kA). Q should pass within 10ms. If the current waveform is a single pulse, the peak time is T1, the half-peak time is T2, and T1<<T2, then Q=(1/0.7)IpeakT2, and the 10/350µs waveform is a waveform that can meet this requirement.

2.1.36 maximum discharge current for class II test Imax

 The peak value of the current flowing through the SPD with an 8/20 waveform is determined by the operating load test procedure of the Class II test. Imax is greater than In.

2.1.37 class I tests

Test with nominal discharge current In, 1.2/50µs impulse voltage and maximum impulse current Iimp.

2.1.38 class II tests

Test conducted with nominal discharge current In, 1.2/50µs impulse voltage and maximum discharge current Imax.

2.1.39 class III tests

 Experiment with complex wave (1.2/50µs, 8/20µs).

2.1.40 sparkover voltage of a voltage switching SPD Uf

The maximum voltage value before the breakdown discharge occurs between the gap electrodes of the voltage switch type SPD.

Note: The protection components of voltage switch type SPD are not all gaps, please refer to term 2.1.11.

2.1.41 SPD disconnector of SPD

A device that can disconnect the SPD from the system when the SPD is damaged. It prevents continuous system failures and gives a visual indication of SPD damage.

2.1.42 backup overcurrent protection

The over-current protection device (such as: fuse, circuit breaker) at the front end of the SPD, when the SPD fails and its internal disconnector cannot cut off the power frequency short-circuit current, it can separate the SPD from the main power circuit and prevent the main circuit from overcurrent The protection action interrupts the main power supply.

2.1.43 maximum continuous operating voltage UCS

 The maximum voltage of the grid that may appear at the SPD installation point. It takes into account voltage regulation and fluctuations, but does not take into account harmonics, faults, transient overvoltages, and transient overvoltages.

2.1.44 temporary overvoltage of the network UTOV

 A power frequency overvoltage with a relatively long duration (typically several seconds), usually caused by operation or faults in the high-voltage or low-voltage system (such as sudden load shedding, single-phase faults) or non-linear phenomena (ferromagnetic resonance, harmonics) ).

2.1.45 Transient withstand voltage UT

 SPD can withstand power frequency or DC voltage that exceeds UC and lasts for a certain period of time.

2.1.46 TOV failure Test TOV failure Test

 Transient overvoltage on metal oxide SPD specified by <GB 18802.1-2002 Surge Protector (SPD) for Low-Voltage Distribution System Part 1: Performance Requirements and Test Methods (IEC 61643-1:1998, IDT)> Failure test,

It is a special test for strict test of metal oxide resistors. The test voltage is in accordance with the requirements in Table B.1 of Appendix B of this standard.

2.1.47 TOV Characteristic Test TOV Characteristic Test

By <GB 18802.1-2002 Surge Protector (SPD) for Low-Voltage Distribution System Part 1: Performance Requirements and Test Methods

Method (IEC 61643-1:1998, IDT)> specified transient overvoltage characteristic test on metal oxide SPD, used to

Special tests are carried out to strictly test metal oxide resistors. The test voltage is in accordance with the requirements of Table B.1 in Appendix B of this standard.

2.1.48 surge protection level of structure

The level of the overall surge protection scheme composed of single or multiple SPDs and other auxiliary devices, which is determined by the importance of the protected equipment and the lightning protection conditions of the building, is arranged within a building.

Note: The building surge protection level does not refer to the level of a certain SPD.

2.1.49 Surge immunity Uimu

The ability of a device, equipment or system to work without deterioration under the interference of a surge.

Note: The surge immunity in this standard is characterized by the voltage peak value under a certain waveform.

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