How to effectively identify and locate power cable faults with Megger

Cable Fault Detection in Singapore: Efficient Solutions for Power Cable Maintenance

Power cable faults can take various forms, with some easier to detect than others. In simpler networks like street lighting systems, where the cable paths are known, fault detection is relatively straightforward. However, finding faults in power cables—especially in underground networks—can be complex and costly. In Singapore, where many cables are buried underground, the cost of excavating to locate a fault can be significant, not to mention the disruption to services and traffic.

So, what’s the solution? A structured approach to diagnosing and locating cable faults using modern testing equipment is both more efficient and cost-effective. Here’s how the process works.

Step 1: Initial Testing

The first stage of fault detection involves continuity and low-voltage resistance checks to confirm the fault. Avoid high-voltage insulation tests at this point, as they may alter the characteristics of the fault, making it harder to locate later.

Step 2: Using a Time Domain Reflectometer (TDR)

Once the fault is confirmed, the next step is to pinpoint its location with a Time Domain Reflectometer (TDR). The TDR sends a low-voltage pulse through the cable and measures the time it takes for the pulse to reflect back from the fault, helping to estimate the distance to the fault. TDRs are particularly effective for identifying open or short-circuit faults.

It’s a good practice to store a reference trace before further testing. This allows comparison of live data with stored data, making it easier to track any changes in the fault’s condition.

Step 3: Dual-Channel TDRs

For more complex situations, dual-channel TDRs can test two cable phases simultaneously. This makes it easier to compare a faulty circuit with a working one. Models like the Megger CFL535G can even test live circuits, eliminating the need for additional blocking filters.

While basic TDRs are compact and affordable, they can still detect a significant number of faults. These are a great option for smaller projects, where investing in more advanced equipment might not be necessary.

Step 4: When the TDR Can’t Find the Fault

In cases where the fault has higher resistance, a standard TDR may not detect the issue. One approach is to "condition" the fault by applying a controlled burn, changing the fault’s characteristics. However, caution is needed, as this could affect future tests.

Step 5: Advanced Fault Location Methods

If standard TDR techniques don’t work, more advanced methods like arc-reflection and impulse current techniques can be used. Arc-reflection sends a high-voltage pulse down the cable, creating a temporary arc at the fault site that behaves like a short-circuit, allowing the TDR to locate it. The impulse current technique triggers a flashover, with transient signals traveling along the cable, allowing the fault’s distance to be estimated.

Step 6: Pinpointing the Fault

Once the fault’s distance is determined, the next challenge is pinpointing its exact location. A surge generator (commonly called a "thumper") sends high-voltage pulses through the cable. These pulses cause a flashover at the fault, creating an audible noise ("thump") and an electromagnetic field. Specialized receivers can detect these signals and identify the fault location.

For buried cables, a shockwave receiver is often used. The operator moves the receiver along the cable path until the strongest sound and electromagnetic field indicate the fault's precise location.

Step 7: Special Cases: Cables in Ducts & Short-Circuit Faults

Locating faults in cables placed in ducts can be more challenging, as sound travels along the duct, complicating pinpointing the fault. In these cases, replacing a section of the cable might be more cost-effective than digging up the duct. Additionally, some faults, like short-circuit faults, don’t produce a "thump" or electromagnetic field, making them harder to locate. In such cases, using a TDR combined with a cable route tracer can help determine the fault’s distance, although pinpointing its exact location remains a challenge.

Why Invest in Cable Fault Location Equipment?

Locating power cable faults can be difficult, but with the right combination of modern testing instruments and a systematic approach, the process becomes much more manageable. Given the potential downtime and costs associated with cable faults, investing in the latest fault-location equipment is a smart, cost-effective choice.

Our range of advanced cable fault detection tools provides everything you need to resolve faults quickly and safely—from compact fault-location tools to comprehensive systems that allow you to locate and identify a range of faults with a simple user interface.

Let us help you keep your power systems running smoothly—contact us today to explore our full range of cable fault detection solutions.