EXU3DC-II T2 DC SPD Type 2 800V to 1200V

Fast, Modular, and Built-for-Solar-PV DC Surge Protection Device: HUYU Electric’s EXU3DC-II T2 DC SPD

The EXU3DC-II series from HUYU Electric is mainly designed to be the best device to protect your solar photovoltaic (PV) direct current (DC) electrical systems from Transient Over-Voltage and Transient Current Surges (from lightning strikes or grid switching events). A new Direct Current Surge Protective Device (Type II DC SPD) capable of handling maximum operating voltage of 800V / 1000V / 1200V DC for both Residential & Commercial PV Systems, covering the full range of the PV String voltages currently used in the market today. With a nominal discharge current (In) of 20kA and a maximum surge capacity (Imax) of 40kA, you will have the required surge protective device (SPD) protection factor necessary to protect your rooftop and ground-mounted systems.

With its replaceable module design, built-in visual fault indicator, and remote signaling contacts for easy identification of the spent modules, the maintenance team can determine the condition of each module without opening any enclosures, just by looking at the visual indication or remote alarm. The response time is under 25 nanoseconds, ensuring all fast-rising rates of surge transients are clamped before they impact the sensitive inverter electronics. The EXU3DC-II is certified to IEC 61643-1 and CQC/TUV, ensuring compliance with current international standards for PV system surge protection. HUYU Electric offers factory-direct OEM/ODM solutions with full documentation to solar distributors and panel manufacturers.

Technical Data

The EXU3DC-II is available in 2P and 3P configurations for optimal compatibility with PV systems. The 2P model protects positive and negative DC lines, while the 3P model provides additional protection for bipolar or combined DC/ground systems. Thanks to its replaceable module design, only the expended module needs replacement, significantly minimizing system downtime. The device accommodates wiring up to 25mm² solid or 35mm² flexible, making it suitable for standard PV installations.

Protection for Solar PV DC Systems

PV systems are highly exposed to lightning-induced surges, especially in uncovered areas such as rooftops or open fields. Without effective surge protection, these surges could damage inverter electronics upon reaching the DC input. The EXU3DC-II surge protector intercepts these transient surges, reduces the voltage surge to a safe level within 25 nanoseconds, and diverts the high surge current to ground. Accompanied by a built-in thermal disconnect mechanism, it ensures failed modules are automatically isolated to prevent system failure. Real-time monitoring of each module’s status is simplified through a visual fault indicator (green for operational, red for replacement) and remote signaling.

OEM/ODM Supply – Certified DC Surge Protection for PV Systems

Buyer’s Guide

How to Select a DC SPD for Your Solar PV System

Key selection criteria for the EXU3DC-II in PV array and DC distribution protection.

1. Voltage Matching: 800V, 1000V, or 1200V?

Select the DC SPD maximum continuous operating voltage (Uc) that exceeds the PV string’s maximum open-circuit voltage (Voc) at the lowest expected ambient temperature. For 600V strings, the 800V model provides adequate margin. For 1000V strings, use the 1000V model. For 1500V system designs operating at reduced string voltage, the 1200V model offers the highest protection level in this product family. Always factor in the temperature-corrected Voc when selecting the SPD voltage rating.

2. 2P or 3P Configuration?

Select the 2P model for standard single-string PV circuits where only the positive and negative conductors require protection. Choose the 3P model when an additional pole is needed — typically for bipolar arrays with a center-tapped ground, or for systems where a dedicated ground protection path is required alongside the two current-carrying conductors.

3. Backup Fuse Coordination

The EXU3DC-II requires a maximum backup fuse of 125A gL/gG. This fuse protects the SPD in the event of a sustained overvoltage that exceeds the device’s thermal disconnect capability. Coordinate this fuse with the upstream string protection — typically a DC MCB rated 16A–32A per string will also serve as the SPD backup fuse when installed in the same combiner box.

4. Installation Location for Effective Protection

Install the DC surge protector as close as possible to the equipment it protects — typically in the PV combiner box or at the inverter DC input. Keep the connecting leads as short as possible (<0.5m total for each conductor) to minimize the voltage drop during surge conduction, which reduces the effective clamping voltage at the protected equipment.

Frequently Asked Questions

What is DC SPD?

A DC SPD (DC Surge Protective Device) is a protection component designed specifically for direct current circuits. It protects DC equipment — such as photovoltaic inverters, DC converters, and battery storage systems — from voltage surges caused by lightning strikes or grid switching events. Unlike an AC SPD, a DC SPD must safely extinguish the follow-on DC arc that can form after a surge event, which requires different internal arc chamber design and breaking technology. The EXU3DC-II is a DC surge protection device with a 40kA maximum discharge capacity and ≤25ns response time, purpose-built for solar PV array protection.

What is the difference between AC and DC SPD?

The fundamental difference lies in how the two devices handle the follow-on current after a surge. An AC SPD relies on the alternating current’s natural zero-crossing to extinguish the follow-on arc. A DC SPD has no zero-crossing to assist, so it must incorporate a stronger thermal disconnect mechanism and a larger arc extinguishing chamber to safely interrupt the DC arc. Additionally, DC SPDs are rated for specific DC voltages (e.g., 1000V, 1200V DC) and are tested to DC surge standards such as IEC 61643-1. The EXU3DC-II DC surge protector is specifically designed and certified for DC circuits — using an AC SPD on a DC PV array is unsafe and violates electrical codes.

How to connect DC SPD for solar?

Connect the EXU3DC-II DC SPD for solar in parallel with the DC circuit it protects — typically at the PV combiner box or inverter DC input. For the 2P model: connect the positive terminal of the SPD to the positive DC bus, the negative terminal to the negative DC bus, and the ground terminal to the system’s earth bar. For the remote signaling, connect the switching contact to the monitoring system’s alarm input — this provides a normally-closed contact that opens when the SPD module fails. Keep all connecting cables as short and straight as possible (ideally under 0.5m per conductor) to minimize additional voltage drop during surge conduction. A backup fuse (max. 125A gL/gG) should be installed in series with the SPD connection to the DC bus. Installation must be performed by a licensed electrician in compliance with local electrical codes and the manufacturer’s wiring diagram.

Can I use DC SPD for AC?

No, a DC SPD should not be used on an AC circuit. The internal arc extinguishing mechanism and voltage ratings of a DC surge protector are designed specifically for direct current. Applying AC voltage to a DC SPD can result in the SPD failing to operate correctly during a surge event, potentially causing the SPD to overheat or the protected equipment to remain exposed to surge damage. Conversely, an AC SPD must not be used on a DC PV array — its arc extinguishing is insufficient for DC. Always use a DC surge protection device on DC circuits and an AC surge protection device on AC circuits. The EXU3DC-II is rated and certified exclusively for DC applications up to 1200V.