90% of Projects Get Lightning Protection Wrong – This Critical Step Is Often Overlooked

During the final acceptance inspection of many electrical projects, we often see a puzzling situation: “Everything seems to be done, but the system remains unstable.”

Equipment is installed, surge protective devices (SPDs) are in place, grounding resistance tests pass – yet the system still suffers from frequent issues: communication anomalies, device reboots, or even complete burnouts.

The problem is not whether lightning protection is installed. It is that a critical step is done incorrectly – or not done at all.

The Overlooked Core: Equipotential Bonding

Many designs and installations focus on the “visible” aspects:

How many stages of SPDs are installed

Whether grounding resistance meets standards

Whether lightning rods are present

But the factor that truly determines system safety is more fundamental: equipotential bonding.

Lightning protection is not just about diverting the strike – it is about keeping all equipment at the same potential so that no destructive breakdown occurs.

Why Is Equipotential Bonding So Critical?

When lightning current dissipates into the ground, a typical phenomenon occurs – ground potential rise.

If the system has the following conditions:

• Equipment is connected to different grounding points,

• And those devices are also interconnected via power or signal cables,

• Then when a lightning strike happens, a potential difference is created.

The result is:

• Potential difference + conductive path = equipment breakdown

• Many equipment failures are not caused by a direct lightning strike, but by an internal potential difference within the system itself.

  
  

Typical Mistakes in 90% of Projects

Based on Techwin’s field experience, problems often fall into these categories:

① Separate grounding systems

Power ground, weak-current ground, and lightning protection ground are kept independent. This seems to follow rules, but it actually creates hidden risks of potential difference.

② SPDs installed without an equipotential foundation

The role of a surge protective device is to dissipate surge energy, but it only works if the system is based on a unified potential reference. Otherwise, uneven current shunt paths can actually increase the potential difference.

③ Bonding paths are too long or have detours

Equipotential bonding conductors must be short and straight. Otherwise, two problems arise: Increased induced voltage+Slower response time

④ Metal components are ignored for equipotential bonding

Naturally conductive parts like cable trays, pipes, and cabinet enclosures – if not included in the equipotential system – become hidden lightning entry paths.

From “Point Protection” to “System Protection”

In Techwin’s project practice, we always emphasize one principle: Lightning protection is not about installing devices – it is about building a system.

Three core implementation points:

① Establish a unified grounding and equipotential network

Integrate the power system, signal system, and equipment enclosures into the same equipotential system.

② Graded SPDs + local equipotential bonding

Configure T1 / T2 / T3 SPDs according to the standard. Each SPD must be bonded to the equipotential system at the nearest possible point

③ Shorten bonding paths

Bonding conductors must be short, straight, and thick. Avoid detours and loop structures

Low-Resistance Monitoring Terminal – TDZ-DDJ

In reality, most projects have a "blind spot": Equipotential bonding is implemented, but there is no way to monitor whether it remains effective.

This creates a critical requirement: The bonding resistance of equipotential connections needs to be monitored in real time.

To address this pain point, Techwin introduces the Low-Resistance Monitoring Terminal – TDZ-DDJ.

This device is not one of the traditional lightning protection devices used to divert or suppress lightning currents. Instead, it serves as an equipotential bonding quality monitor, specifically engineered for:

• Equipotential bonding resistance

• Contact resistance

• Connection status of low-value resistors

It achieves online, real-time, visual monitoring.

In real systems, equipotential problems often come from:

• Loose connections

• Corrosion or oxidation

• Poor workmanship

These issues do not cause immediate failures, but they are amplified during a lightning strike.

The role of TDZ-DDJ is to identify these hidden risks before an accident happens.

Product Features

1. Compact size, easy to integrate

DIN-rail mounting allows direct installation inside lightning protection boxes, distribution panels, cabinets – without altering existing structures.

2. Convenient installation and maintenance

Plug-in terminal blocks make on-site wiring and later maintenance highly efficient.

3. Strong communication capabilities

Standard RS485 interface for connection to environment monitoring systems or platforms, with optional expansion for: Ethernet/LoRa/4G.

4. High immunity to interference

Built-in surge protection and anti-EMI design ensure stable operation in complex electromagnetic environments.

Conclusion

In a lightning protection system, the real cause of equipment damage is rarely the lightning strike itself – it is potential difference.

The solution is not about adding more devices. It is about:

Implementing equipotential bonding correctly – and continuously monitoring its effectiveness.