Surge protective devices (SPDs) are large power system protection devices against lightning and overvoltage damage, and T1 and T2, being the two large categories, often puzzle users with functional differences. This article elaborately explains the differences between the two from technical parameters, application scenes, selection points, etc., to allow users to make correct selections according to their needs.
1、 Core difference: Testing standards and performance parameters
Test waveform and energy carrying capacity
Type 1: Using a 10/350 μ s lightning impulse waveform to simulate high-energy impacts from direct lightning strikes. Its characteristic is that the current rise time is short, the duration is long, and the energy intensity is 17.5 times that of the 8/20 μ s waveform
Type 2: Using an 8/20 μ s induction lightning waveform to simulate the medium energy impact of overvoltage or indirect lightning strikes within the power grid
| Parameter | Type 1 | Type 2 |
|---|---|---|
| Test Waveform | 10/350μs (Direct Lightning Strike) | 8/20μs (Induced Lightning Strike) |
| Discharge Capacity | High energy surge current (≥50kA) | Medium energy clamping (20~100kA) |
| Response Time | Slow (about 100ns) | Fast (<25ns) |
| Installation Position | Main distribution panel/building incoming line terminal | Distribution panel/equipment front end |
| Protection Function | Main discharge of lightning current | Suppression of residual surge voltage |
2. Application Scenarios and Selection Guidelines
Type 1 (T1 category) applicable scenarios
High risk lightning areas: such as areas with frequent thunderstorms, high-rise buildings, communication base stations, etc., need to deal with the impact of direct lightning strikes
Power system entrance protection: installed on the low voltage side of transformers or main distribution cabinets as the first level lightning protection barrier, releasing more than 80% of lightning current
Key facility protection: such as the main power supply inlet end of hospitals, data centers, and industrial control systems
Type 2 (T2 category) applicable situations
Secondary power distribution protection: used in machine room distribution units and floor distribution boxes to limit the residual voltage of Type 1 SPDs
Protection of sensitive devices: e.g., computing equipment, precision devices, and domestic appliances, providing low residual voltage (≤ 1kV) terminal protection
Low risk environment: areas with low lightning activity such as commercial complexes and urban area residential communities
3、 Selection precautions
1. System compatibility
Multi level cooperation: Type 1 and Type 2 need to work together, and a decoupling distance (usually ≥ 10 meters of cable or additional decoupling device) needs to be maintained between the two levels to optimize energy distribution
2. Parameter priority
Type 1 focuses on Iimp value (direct lightning withstand capability), while Type 2 needs to pay attention to In value (nominal discharge current) and Up value (residual voltage level)
3. Brand selection
You can choose ONESTO’s surge protection device, which supports customization and OEM services. And with the most favorable price and 2-year quality warranty, we are your trusted SPD manufacturer
4、 Common Misconceptions
Misconception 1: “Type 2 has a larger nominal current and better performance than Type 1”
Analysis: The 10/350 μ s waveform energy of Type 1 is 17.5 times that of Type 2, and the actual energy of a 12.5kA Type 1 SPD is equivalent to that of a 220kA Type 2 product
Misconception 2: “Installing Type 1 does not require Type 2”
Analysis: Type 1 focuses on leakage, but has high residual pressure; Type 2 further limits voltage to protect terminal equipment. Multi level protection is indispensable
Summarize
The core difference between Type 1 and Type 2 surge protectors lies in their energy processing methods and protection levels. Type 1 is the “first line of defense” against direct lightning strikes, while Type 2 is the “last barrier” for finely protecting sensitive equipment. Reasonable selection should be based on lightning risk, system structure, and equipment tolerance, and follow the principle of “graded discharge and graded voltage limitation” in order to build an efficient lightning protection system.
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