Hangzhou Huadian Jiangdong Thermal Power Co., Ltd. 380V Cable Fault Location Test Report

I. Pre-Test Preparation

II. Test Process

Step 1: Determining the Fault Nature
The insulation between each phase was measured using an on-site insulation megohmmeter, and the fault nature was initially determined as follows:

Initial determination: Phase A is intact, while phases B and C exhibit high-resistance faults.

Step 2: Fault Pre-Location
The low-voltage pulse method was used to test the good phase A of the cable, as shown in Figure 1. The total cable length was measured to be 198 meters. Measurements were taken for phases B and C, and the fault distance was determined to be approximately 39 meters , as shown in Figure 2. A joint was known to be located at approximately 30 meters, therefore, high-voltage surge was directly applied to pinpoint the fault location.

Figure 1. Cable Length

Figure 2. Low-Resistance Fault Waveform

Step 3: Cable Path Locator

The approximate cable routing is shown in Figure 3.

Figure 3. Cable Path Diagram

Step 4: Precise Fault Location

Based on the on-site situation, information from the customer, and feedback from the low-voltage pulse waveform, there is a joint in the cable at 49 meters. Therefore, the faulty cable was directly surge testing was directly applied for fault pinpointing . After confirming the cable path, an 8 kV high-voltage surge was applied directly to the cable. On-site personnel, ensuring safety, moved to the cable joint location for acoustic detection . A clear discharge sound was detected at the fault point , as shown in Figure 4.

Figure 4. Fault Location

III. Test Summary

1. Before conducting cable fault testing, it is advisable to analyze the surrounding environment as much as possible and obtain cable information from the customer. Inquire about any recent construction work along the cable path and the characteristics of cable faults.

2. If the location of the cable fault is unusual, such as the fault at the joint in this case where the path is clear, direct surge testing can be used for pinpointing .

3. When we pre-locate the fault, we use the discharge signal of the fault point to locate the fault. Therefore, if conditions permit on site, we can use a variety of pre-locating methods to pre-locate the fault or test at the other end to verify the fault distance.