A technician examines a Dissolved Gas Analysis system.

New dissolved gas analysis technology can keep Hong Kong powering ahead

A new technology being piloted in Hong Kong could make the city's world-class power supply even more reliable


Imagine for a moment being the personal physician to a top athlete - a sportsperson who competes internationally at the highest levels and who is expected to be in superb physical condition at all times.

Monitoring that athlete's health and ensuring that he or she is in shape is a big responsibility and one that involves preventative checks and medical examinations to watch for the tiniest symptom of a problem that might impair their performance.

In a 24-hour city with a thriving economy - and where most people live in high-rise buildings - we simply cannot afford to let our power supply sicken or fail, even for a few minutes. If it did, the consequences would be potentially catastrophic.

Today, happily, Hong Kong has supply reliability of 99.999 per cent, equivalent to just 2.6 minutes of unplanned power interruption a year and one of the highest rates anywhere in the world.

But the quest for ever-higher reliability is, by necessity, relentless - and now a new, state-of-the-art technology being piloted in Hong Kong could bring our reliability rating to even higher levels.


The secret lies in the technological equivalent of preventative medicine. Dissolved gas analysis (DGA) is just like the personal physician using the best diagnostic equipment available to carry out medical checks on the top athlete. Rather than blood tests, however, DGA checks transformers in substations and analyses the conditions of insulating oil used for cooling and insulation. When a potential electrical fault develops, gases are generated inside the transformer and can be detected in the insulating oil.

By examining the amount of dissolved gases and their chemical characteristics through DGA, it is possible to detect incipient faults and alert the operator to instances where maintenance is needed.

Some incipient transformer fault cases can be successfully identified so they can undergo necessary maintenance by using DGA. For example, if hydrogen gas (H2), methylene gas (CH2) or ethylene gas (C2H4) are detected in a transformer, it indicates an overheating of the conductor. If acetylene (C2H2) is detected, it indicates a partial discharge of the insulating materials inside the transformer. A conventional approach, by contrast, requires manual extraction of an oil sample and delivery to laboratory for analysis.

Because of the clear benefits of DGA, CLP Power has been phasing in an online DGA system for 132kV and 400kV transformers in stages since 2002. The system conducts real-time monitoring of the condition of the transformers and alerts engineers to potential problems through an information technology network so that maintenance can be arranged before the problem develops.


Online DGA uses sensors to detect gases dissolved in the insulating oil of a transformer and sends the data to a centralised system for analysis. Engineers are notified once a potential fault is detected, allowing them to conduct further checks to determine what action is needed.

Online DGA allows for a condition-based maintenance approach, which has advantages over the traditional maintenance approach. Without it, engineers have to schedule maintenance for each transformer and piece of equipment, whether it is needed or not. With online DGA, engineers are alerted to potential faults before they develop into problems and are able to target resources where they are needed. Installation of on-line DGA for 500 132kV and 400kV transformers in CLP's power grid was completed in 2010.


If we are going to maintain competitive edge of Hong Kong as a cosmopolitan city, we simply cannot afford to stand still for a moment. We must continue to improve and enhance our network, such as the implementation of smart grid technologies, to give Hong Kong a power supply to match its capacity for growth and development.

This article appeared in the South China Morning Post print edition as: Keeping our city powering ahead