Keep up to date with our latest company news and relevant industry knowledge.
Time: 2025-03-16 12:23:17 Source: Henan Province Jianyun Cable Co., Ltd.
High-voltage power cables are the backbone of modern urban power grids, and ensuring their reliability is no small task. A recent study published in Wire & Cable (December 2024) by Cheng Feng and colleagues dives into the challenges of testing 220 kV long-distance, large-cross-section cross-linked polyethylene (XLPE) cables—specifically, how to perform on-site acceptance voltage tests effectively. With cities growing fast, these cables are increasingly vital, but their length and size make testing tricky. This article breaks down the study’s findings in simple terms, explores its practical implications, and offers insights into why this matters for the cable industry and beyond—all while boosting your understanding and our website’s visibility!
Imagine a 14.45 km-long cable—longer than 140 football fields laid end-to-end—designed to carry 220 kV of electricity. Before it can power a city, it must pass an acceptance test to prove it’s safe and reliable. The study focuses on a real-world example: the Mawangdui-Shaping double-circuit 220 kV line in Changsha, China. Cables like these can get damaged during transport, installation, or accessory attachment, leading to hidden defects. To catch these issues, standards like Q/GDW 11316-2018 require an AC voltage withstand test—a kind of stress test for cables.
But testing a cable this long and thick (2500 mm² cross-section) isn’t straightforward. Its large capacitance—think of it as the cable’s ability to store electrical charge—creates challenges for traditional testing methods. The researchers compared two approaches: series resonance and series-parallel resonance, then simulated and tested them on-site to find the best solution.
The cable in question, model ZC-YJLW03-Z 127/220 1×2500 mm², is a beast. Here’s a quick look at its specs:
Table 1: Cable Specifications
| Parameter | Value |
|---|---|
| Rated Voltage (U₀/U) | 127/220 kV |
| Maximum Operating Voltage | 252 kV |
| Cross-Sectional Area | 2500 mm² |
| Outer Diameter | 152.7 mm |
| Length | 14.45 km |
| Single-Phase Capacitance | 3.3524 × 10⁻⁶ F |
| DC Resistance (20°C) | 0.0115 Ω/km |
This cable’s huge capacitance (3.3524 µF) means it needs a lot of power to test, which is where resonance techniques come in.
The study pits two testing methods against each other:
Both methods aim to hit the test voltage of 216 kV at a frequency between 10–300 Hz, applied for 60 minutes per phase across two circuits (six phases total).
In the series setup, eight reactors (each 4 H) were connected in parallel, giving a total inductance of 4 H. The current in the circuit is calculated as:
I=UCxLI = U \sqrt{\frac{C_x}{L}}I=ULCx
Plugging in the numbers (U = 216 kV, Cₓ = 3.3524 × 10⁻⁶ F, L = 4 H), the total current is 197.7 A, with each reactor handling 24.7 A—well below their 25 A limit. This setup works, but it’s pushing the reactors hard.
The series-parallel setup pairs reactors (L₂ with L₃, L₄ with L₅) in series, then connects these pairs in parallel with a main reactor (L₁). The equivalent inductance is calculated as:
L∗=2L3L4L3+L4L^* = \frac{2 L_3 L_4}{L_3 + L_4}L∗=L3+L42L3L4
The test frequency is:
f=12πL1L∗L1+L∗×Cxf = \frac{1}{2\pi \sqrt{\frac{L_1 L^*}{L_1 + L^*} \times C_x}}f=2πL1+L∗L1L∗×Cx1
This yields a frequency of 10 Hz (meeting the 10–300 Hz requirement) and a total current of 120 A. The currents through the reactors—81.15 A for L₁ (rated 83 A), 18.2 A for L₃, and 20.5 A for L₄ (both rated 25 A)—stay safely below their limits.
Table 2: Reactor Parameters
| Reactor | Rated Voltage (kV) | Rated Current (A) |
|---|---|---|
| L₁ | 400 | 83 |
| L₂, L₃ | 250 | 25 |
| L₄, L₅ | 250 | 25 |
Using PSCAD software, the researchers modeled the cable’s capacitance rise—a phenomenon where the cable’s charge storage increases under high voltage. The series-parallel setup kept this under control. On-site tests confirmed that equipment temperatures stayed within safe limits, with no overheating even after 60 minutes at 216 kV.
The study concludes that series-parallel resonance is the better choice for 220 kV long-distance cables. It handles the high capacitance more efficiently, keeps currents lower, and ensures equipment stays cool and safe.
The series-parallel method shines because it balances power delivery with equipment safety. For a 14.45 km cable, the capacitance is massive, and the series-only setup pushes reactors to their limits (24.7 A is close to 25 A). The series-parallel approach cuts the total current to 120 A, giving each reactor more breathing room. This reduces wear and tear, making it a practical choice for real-world testing.
This isn’t just lab talk—it’s based on a real project in Changsha. Long cables like these are common in urban grids, where sprawling layouts demand reliable power over vast distances. The study’s findings could save time, money, and headaches for engineers testing similar setups worldwide.
Overheating is a silent killer for test equipment. The fact that the series-parallel method kept temperatures in check is a big deal—it means fewer failures and safer operations. For manufacturers and utilities, this translates to lower maintenance costs and higher reliability.
The study nails the comparison, but it’s light on specifics about capacitance rise. How much does it increase, and how does it affect long-term cable health? Future research could dig deeper here. Also, testing at higher frequencies (closer to 300 Hz) might reveal more about the setup’s limits.
This approach could become a gold standard for testing long XLPE cables. It meets Q/GDW 11316-2018 requirements and offers a blueprint for other high-voltage projects. Companies could cut testing downtime and boost confidence in their cables’ performance—key for keeping cities powered up.
If you’re in the cable industry, this study is a game-changer. It shows how to test monster cables without breaking the bank or the equipment. For the rest of us, it’s a peek into the tech keeping our lights on. Better testing means fewer outages and safer grids—something we all benefit from.
Cheng Feng’s team has cracked a tough nut: how to test 220 kV long-distance XLPE cables effectively. By favoring series-parallel resonance over series-only, they’ve found a way to handle massive capacitance, keep equipment safe, and meet strict standards. It’s a practical, proven solution that could shape how high-voltage cables are tested globally. Next time you flip a switch, you might just owe it to a smart resonance test keeping the power flowing.
