What is the SPD(Surge Protection Device)logo？

The markings for SPDs (Surge Protective Devices) can be divided into two main categories: Physical Markings on the Product and Graphical Symbols on Circuit Diagrams.

I. Physical Markings on the Product Itself

When you have an SPD unit in hand, you can identify it by the following markings:

1. Direct Inscription "SPD"

This is the most direct marking.Many manufacturers will print "SPD" or "Surge Protective Device" directly on the device housing.

2. Certification Marks and Model Number

Certified SPD products will comply with the safety standards of their country or region and have a specific model number.This information is typically found on a label attached to the product.

• Common Certification Marks:
• UL 1449: This is the core safety standard for SPDs in the North American market. The product will be clearly marked with "UL 1449" and its Type (Type 1, Type 2, Type 3, Type 4).
•  IEC 61643-11: This is the International Electrotechnical Commission standard, widely used globally (except primarily in North America).
•  CE Marking: Indicates conformity with European standards.
• China's CQC Certification: SPDs sold in the Chinese market usually have this mark from the China Quality Certification Centre.

3. Key Electrical Parameters

This is the most important identifying information for an SPD,usually provided on a label attached to the device.

• Maximum Continuous Operating Voltage (Uc): The maximum AC or DC voltage at which the SPD can operate safely indefinitely.
• Voltage Protection Level (Up): The SPD's ability to clamp the voltage. A lower value indicates better protection performance. This is a key parameter for evaluating an SPD.
• Nominal Discharge Current (In): The peak value of an 8/20 μs current wave that the SPD can withstand multiple times (for Type 2 SPDs).
• Maximum Discharge Current (Imax): The maximum peak value of an 8/20 μs current wave that the SPD can withstand once.
•  Impulse Current (Iimp): The peak value of a 10/350 μs current wave, simulating a direct lightning strike, that the SPD can withstand (primarily for Type 1 SPDs).

Example Image of a Physical Unit:

(This is a typical SPD parameter label, usually containing the key information mentioned above)

II. Graphical Symbols on Circuit Diagrams

In electrical design drawings, distribution board schematics, or product manuals, SPDs have specific graphical symbols.

1. Basic Graphical Symbol (Most Common)

The most common SPD symbol is arectangle with an internal arrow and a branch line representing the connection to earth.

This symbol clearly indicates its function: to divert overvoltages (the arrow symbolizes the surge) to the ground (earth symbol).

2. Symbol with Additional Information

• Sometimes,the symbol includes more details, such as:
• SPD Status Indicator: A small square added to the basic symbol, representing a window or light that shows whether the SPD is functioning correctly.

Remote Alarm Contacts: Represented by a pair of switch contacts. If the SPD fails and needs replacement, these contacts change state (Normally Open become Closed or vice versa), sending an alarm to a remote monitoring system.

3. Representation in Power Distribution System Diagrams

In a building's main electrical diagram or single-line diagram,the SPD is typically drawn at the main power intake or within various distribution boards, with lines connecting it to the Phase (L), Neutral (N), and Protective Earth (PE) conductors. Its type and key parameters are often noted nearby, e.g., SPD, Type 2, Up: 1.5kV.

In simple terms:

· Finding the physical unit: Look for the letters "SPD" and a detailed parameters label on the device.

· Reading a diagram: Look for a rectangle with an arrow inside pointing to an earth line.