Power Supply Technical Information

Planned Outage

To ensure the quality of electricity supply, CEM has to carry out maintenance and improvement works on a regular basis. During the works, we inevitably need to temporarily interrupt the electricity supply.


Prior Notice

CEM will distribute “Electricity Supply Interruption Notice” in advance to affected merchants or building management companies, or post at building entrances. Or you can always check if you are in the affected customer list online. 

View Notice     Enquire Planned Outage


Advance preparation

Turn off large appliances, such as water heater, air conditioner, etc. to prevent sudden increase in load when the power is restored.

Ensure all heat-producing appliances, such as electric stove, oven, iron etc. are turned off to prevent fire hazard.

Keep your refrigerator door closed to protect food from deterioration.

For electrical medical equipment users, arrange backup power in advance to avoid influence during power interruption.

Prepare a portable flashlight with backup batteries.

Make sure electric doors can be manually opened during outage period.

Reserve a light switch in “on” position, so you will know when the power is restored.

For safety reasons, avoid touching or repairing any electrical parts during the power interruption period as power maybe resumed at any moment.

Turn off voltage-sensitive electrical equipment, e.g. computers, medical equipment, to avoid operation affected by voltage fluctuation when the power is restored.

Pay attention to the power outage notice posted in your building.

Unplanned Outage

What to do in case of supply interruption?

  • If the whole building or area is affected, there may be a supply interruption. We will restore your supply as soon as possible.
  • If there is a supply interruption at your home, but not at your neighbors, switch off all major electrical appliances. Then check the status of the main switch in your house. If it remains off, check the service circuit-breaker next to your meter. If it is at the off status, switch it on.
  • However, when the electricity supply at your home is in normal condition, do not arbitrarily switch off the circuit breaker next to the meter or interfere with the meter or electricity supply installation. If for any reasons you need to suspend the power supply at your home, please turn off the main switch.
  • If you have your supply back, the supply interruption might be due to overload. You may need to apply for an upgrade of subscribed demand (enlarge meter size).
  • If the service circuit-breaker is on but there is still no electricity supply, your installation may have a fault. You should consult an experienced electrician.
  • For whatever the reason causing the supply interruption, please call our Emergency Services at 2833 9922. Our Emergency Service Representatives will be happy to help you. Nevertheless, should a brownout/blackout happens, our telephone lines may be busy due to large volume of telephone calls coming in. Don’t worry! Our Emergency Team will take care of the problem and restore the power supply as soon as possible.


Safety tips for supply interruption

Use flashlight instead of candle to avoid fire hazards;

Turn off all major electrical appliances like air-conditioner, water heater, etc.;

Leave any lighting switch on at home so that you will know when the electricity supply has been restored.

Don’t attempt to repair the electrical installation and/or appliance by yourself; you should always consult an experienced electrician.

Voltage Dip

What is a voltage dip?

A voltage dip is not a power interruption because power supply is not interrupted during its occurrence. It is a reduction in supply voltage in the electricity distribution network or in the customer’s installation, lasting from half second to one minute.

Most customers are not affected by a voltage dip but may experience temporary flickering lights. The temporary suspension of in-house supply is caused by the automated activation of the protection device.


Why does it happen?

The reasons of voltage dip on distribution network are various and are mostly due to unforeseen and uncontrollable events. They can originate from high voltage network issues or interconnections issues with mainland China for instance.

The in-house causes of voltage dips are usually due to the switching on of high-current equipment such as starting of refrigerator and air condition compressors etc.


Minimizing Impact of voltage dips

Equipment mostly sensitive to voltage fluctuations will be temporarily impacted, such as elevators, pumping systems, lighting circuits or cooling systems for instance.

Unfortunately, voltage dip cannot be eliminated from the electricity supply network but can be treated at customers’ installation. Customers can protect special devices by installing power conditioners and smart uninterruptable power supplies.

We will be happy to provide your organization more information to assess possible improvement measures to implement in your electricity installation so as to mitigate or minimize the impact of voltage dips.

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