Type 2 AC Surge Protective Devices (Class ll SPDs)
Type 2 / Class ll
1.8/20μs impulse wave is used to prevent induced lightning strikes, line surges and operational overvoltages.
2.It is usually installed in distribution boxes, floor distribution boxes, and at the front end of equipment. It is the most commonly used secondary lightning protection device in the power distribution system.
3.The core feature is the balance between flow capacity and precise protection. After discharging most of the lightning current at the T1 level, the residual voltage is further controlled within the safe range.
Type 2 / Class ll
The T2 surge protector serves as the second line of defense for power surge protection, adept at handling low-energy surges such as induced lightning and line operational overvoltages.
EV Charging Stations SPD->Type 2 / Class ll
Uc(V) :
AC385V
In (8/20 μs):
20kA
Imax(8/20 μs):
40kA
Mode of Protection:
LN,N-PEReference Standards:
IEC 61643-11OEM/ODM Acceptable
Additional Function:
Thermal Tripping Protection, Status Indicator, and Remote Signaling
AC Power SPD->Type 2 / Class ll
Uc:
AC385V/420V/440V
In (8/20 μs):
20kA
Imax(8/20 μs):
40kA
Mode of Protection:
L/N-PE; L-N, N-PEReference Standards:
IEC 61643-11OEM/ODM Acceptable
Additional Function:
Thermal Tripping Protection, Status Indicator, and Remote Signaling
Wind Power SPD->Type 2 / Class ll
Uc(V) :
AC760V/1500V
Un(V) :
AC690V/1140V
In (8/20 μs):
60kA
Imax(8/20 μs):
100kA
Mode of Protection:
L/N-PEReference Standards:
IEC 61643-11OEM/ODM Acceptable
Additional Function:
Thermal Tripping Protection, Status Indicator, and Remote Signaling
PV AC SPD->Type 2 / Class ll
Uc(V):
AC385V/760V/1100V/1500V
Poles:
2P,3P,3P+1(Series connection),4P
In (8/20 μs):
60kA
Imax(8/20 μs):
100kA
Mode of Protection:
L/N-PEReference Standards:
IEC 61643-11OEM/ODM Acceptable
Additional Function:
Thermal Tripping Protection, Status Indicator, and Remote Signaling
PV AC SPD->Type 2 / Class ll
Uc(V):
AC385V/760V/1100V/1500V
Poles:
2P,3P,3P+1(Series connection),4P
In (8/20 μs):
40kA
Imax(8/20 μs):
80kA
Mode of Protection:
L/N-PEReference Standards:
IEC 61643-11OEM/ODM Acceptable
Additional Function:
Thermal Tripping Protection, Status Indicator, and Remote Signaling
PV AC SPD->Type 2 / Class ll
Uc(V) :
AC385V/760V/1100V/1500V
Poles:
2P,3P,3P+1(Series connection),4P
In (8/20 μs):
20kA
Imax(8/20 μs):
40kA
Mode of Protection:
L/N-PEReference Standards:
IEC 61643-11OEM/ODM Acceptable
Additional Function:
Thermal Tripping Protection, Status Indicator, and Remote SignalingWhat is Surge Protective Device?
A surge protective device, also known as a surge protector or SPD, is designed to safeguard electrical components against surges in voltage that might happen in the electrical circuit.
Whenever a sudden increase in current or voltage is produced in the electrical circuit or communication circuit as a consequence of outside interference, the surge protection device may conduct and shunt in a very short period of time, preventing the surge from damaging other devices in the circuit.
Surge protective devices (SPDs) are a cost-effective method for preventing outages and enhancing system reliability.
They are typically installed in the distribution panels and play an important role in ensuring the smooth and uninterrupted operation of electronic devices in a wide range of applications by limiting transient overvoltage.
How Does Surge Protective Device Work?
The basic principle behind SPDs is that they provide a low impedance path to ground for excess voltage. When voltage spikes or surges occur, SPDs work by diverting the excess voltage and current to the ground.
In this way, the magnitude of the incoming voltage is lowered to a safe level that doesn't damage the attached device.
To work, a surge protection device must contain at least one non-linear component (MOV or GDT), which under different conditions transitions between a high and low impedance state.
Their function is to divert the discharge or impulse current and to limit the overvoltage at the downstream equipment.
Surge protection devices function under the three situations listed below.
A. Normal Condition (absence of surge)
In case of no surge conditions, the SPD has no impact on the system and acts as an open circuit, it remains in a high impedance state.
B. During voltage surges
In case of voltage spikes and surges, SPD moves to the conduction state and its impedance decreased. In this way, it will protect the system by diverting the impulse current to the ground.
C.Back to normal operation
After the overvoltage has been discharged, SPD shifted back to its normal high impedance state.
SOLUTIONS
Experimental Facilities
Cresin is equipped with professional-level surge protection device (SPD) comprehensive performance testing equipment, which can fully adapt to the performance testing and trial research of all categories of T1 and T2 level power surge protection devices.
Large constant temperature and humidity equipment
High current generator equipment
RF network analyzer
Type 2 Surge Protection Device – Installation and Wiring Guide
Type 2 SPDs are typically installed within sub-distribution panels or near main distribution boards to provide secondary surge protection for low-voltage AC systems. They operate in coordination with upstream Type 1 SPDs to limit residual surges and protect downstream circuits and equipment, ensuring reliable operation across different electrical environments.
Installation Principles and Wiring Integrity
Type 2 SPDs are installed in parallel with phase (L), neutral (N), and protective earth (PE) conductors.
Used with dedicated circuit breakers or fuses, they respond quickly to transient overvoltages.
Wiring should be short and secure (<0.5 m) to minimize inductive and contact resistance.
Ensure proper connection of modular interfaces if pluggable modules are used.
Remote Signaling Terminals
Type 2 SPDs with remote signaling terminals provide status feedback for monitoring and maintenance.
Dry contact outputs transmit SPD status and fault information to the control panel.
Connect signal wires to monitoring terminals for remote system surveillance.
Fault or abnormal conditions trigger alarm signals, enabling rapid maintenance response.
FAQ
Is Type 2 SPD suitable for most commercial and industrial projects?
Yes. Type 2 SPD is widely used in factories, buildings, electrical panels, machinery, automation systems, power distribution cabinets, and commercial facilities where induced surges are the main risk.
What parameters should I check for a Type 2 SPD?
Important parameters include Uc, In, Imax, Up, pole configuration, system type, backup fuse requirement, and response time. The correct selection depends on the power system and installation environment.
What is the difference between Type 1 and Type 2 SPD?
Type 1 SPD is designed to discharge direct lightning current with a 10/350 μs waveform, while Type 2 SPD is designed to discharge induced surge current with an 8/20 μs waveform. Type 1 is used at the main entrance, while Type 2 is used in distribution panels.
Where should a Type 2 SPD be installed?
Type 2 SPDs are typically installed in sub-distribution boards, control panels, power distribution cabinets, and downstream electrical panels. They are often installed after the main incoming protection device.
What is a Type 2 / Class II SPD?
A Type 2 / Class II SPD is used to protect electrical systems from induced surge voltages and switching overvoltage. It is the most commonly used SPD type in low-voltage power distribution systems.
Related Blogs
SPD Selection Wizard: Match System Voltage, Earthing and Application in 6 Steps
2026-09-23
How to Choose SPD with an SPD Selection Tool and Surge Protector Selector for voltage, earthing, Type, Uc, Up, and protection needs
Surge Protection for Mining, Metallurgy and Heavy Industry: Dust, Vibration and Long Cable Runs
2026-09-22
How mining surge protection is planned for conductive dust, continuous vibration, long feeder runs, surface and underground distribution, weak earthing and maintenance access.
Surge Protection for Hospitals and Medical Facilities: Imaging, ICU and Life-Safety Power
2026-09-22
How hospital surge protection is planned across OR and ICU, imaging suites, laboratories, ELV systems and life-safety power, with distribution zoning and maintenance windows.
2026-09-20
How to plan petrochemical surge protection across hazardous and non-hazardous areas, covering Ex installation rules, corrosive atmospheres, 4-20 mA loops and grounding grids.
Shandong Cresin Electric Co., Ltd. Privacy Policy
Contact Us
Address: No. 978 Tianchen Road, High-tech Zone, Jinan, Shandong,China
CAN’T FIND THE PRODUCT?
The product range includes production technologies for smart capacitors, digital display meters, surge protectors, dedicated backup protection devices for surge protectors, self-resetting over/under-voltage protectors, control and protection switches, and automatic transfer switches for dual power supplies.
Search HistoryClear All Records
- 全部
- 产品管理
- 新闻资讯
- 介绍内容
- 企业网点
- 常见问题
- 企业视频