High-Quality Surge Protection Factory & Company

The $10/350\ \mu\text{s}$ waveform simulates the severe charge transfer of a direct lightning strike (Class I / Type 1 testing). It reaches peak current in 10 microseconds and decays to 50% after 350 microseconds, packing approximately 10 to 20 times the specific energy ($W/R$) of an $8/20\ \mu\text{s}$ waveform. The $8/20\ \mu\text{s}$ pulse simulates indirect, induced transients or internal switching overvoltages (Class II / Type 2 testing). A Type 1 device must absorb immense heat and mechanical electrodynamic forces without structural casing rupture.

Proper coordination ensures that the robust upstream Type 1 SPD discharges the bulk of high-energy lightning impulse before the more sensitive downstream Type 2 SPD clamps the residual voltage. This is achieved either through physical cable separation (typically minimum 10 meters of distribution conductor to provide inductive decoupling, where $L \approx 1\ \mu\text{H}/\text{m}$) or through engineered coordinated SPDs containing internal decoupling choke inductors or matched varistor/gap trigger thresholds that fire sequentially without relying on line length.

If an SPD experiences a catastrophic end-of-life state—such as continuous Temporary Overvoltage (TOV) far exceeding its Maximum Continuous Operating Voltage ($U_c$)—the MOV can enter thermal puncture, behaving as a short circuit. A coordinated backup overcurrent device (such as a dedicated Surge Circuit Breaker or high-breaking-capacity fuse) quickly isolates the faulted branch without triggering upstream main breakers, guaranteeing continuous electrical supply to the rest of the facility.

Modern Yueqing manufacturing lines utilize automated precision ball milling, spray granulation, isostatic pressing, and computerized continuous tunnel kilns. The sintering profile maintains atmospheric purity and precise temperature curves ($\pm 1.5^\circ\text{C}$ throughout 24-hour cycles), creating uniform microscopic grain boundaries with consistent bismuth and antimony coatings. This guarantees that voltage clamping, capacitive stability, and energy dissipation remain virtually identical across hundreds of thousands of production units.

While both standards certify surge protective devices, they diverge in classification and testing philosophies. IEC 61643-11 designates devices into Classes I, II, and III based on specific waveforms ($10/350\ \mu\text{s}$ for Class I and $8/20\ \mu\text{s}$ for Class II) and evaluates residual voltage ($U_p$). UL 1449 5th Edition categorizes SPDs into Types 1, 2, 3, 4, and 5 based on installation point relative to the service entrance overcurrent disconnect, testing for Voltage Protection Rating (VPR) using a $6\text{kV}/3\text{kA}$ combination wave, and places extreme focus on destructive Abnormal Overvoltage thermal safety.

For a 1500V DC solar array, the SPD's Maximum Continuous Operating Voltage for Photovoltaic applications ($U_{cpv}$) must be rated at least $1.1\times$ to $1.2\times$ the open-circuit voltage ($U_{oc\ stc}$) of the array to account for cold-weather voltage increases. It must strictly comply with IEC 61643-31 (or EN 50539-11), feature a "Y" configuration MOV array to prevent ground-fault fires, and possess a certified Short-Circuit Current Rating ($I_{scpv}$) greater than the combined prospective short-circuit current of the connected PV strings.

Conductor lead inductance plays a critical role in effective protection. Fast transient currents with steep front-edges ($dI/dt$) generate inductive voltage drop according to $\Delta U = L \times (dI/dt)$, where straight wire exhibits roughly $1\ \mu\text{H}$ per meter. For an $8/20\ \mu\text{s}$ strike of $10\text{kA}$, a 1-meter connecting lead can add roughly $1000\text{V}$ of inductive surge on top of the SPD's clamping voltage ($U_p$). Therefore, standard engineering practice dictates that total connecting lead length ($A + B + C$) must not exceed 0.5 meters (50cm) to ensure minimal residual let-through voltage reaches connected equipment.