POWER FAILURE ON 5TH OCTOBER 1981 (Steps to prevent recurrence)

Mr Ng Kah Ting: To ask the Minister for Trade and Industry (a) if he will ascertain from the Public Utilities Board the cause of the power failure which affected residents and businesses in several areas for some hours on 5th October, 1981 ; (b) what steps are being taken to prevent such recurrences; and (c) whether the PUB has an emergency unit capable of moving into action swiftly to restore any power failure quickly.

Mr Ch'ng Jit Koon: Question No. 22, Sir.

The Minister for Trade and Industry (Dr Tony Tan Keng Yam): Sir, the power failure which occurred at 11.15 am on 5th October, 1981, was caused by a defect in the protection system of three 230kv cables leading to Kallang Basin Substation - two from the Senoko Power Station and one from the Tampines Substation. Power supply to these three cables was switched off by their protection system. The protection system is a subsidiary electrical circuit whose function is to prevent the main power cable from being damaged by excessive flow of current. The circuit is normally dormant but is activated when it detects a fault in the main cable. The cable is then automatically switched off.

Investigation revealed that there was no fault or damage in the three 230kv cables themselves and they were put back into service. The protection system has been isolated. PUB engineers and the manufacturers are investigating the cause of the fault in the protection system.

Power failures can be caused by faulty equipment and damage to cables due to ground subsidence, careless contractors and inclement weather. In planning our electricity supply system, the PUB has taken steps to install equipment and plant that are reliable. There are built-in safety devices to prevent small faults from developing into major ones, that can cause damage to the equipment or, worse. a total system breakdown. Regular preventive maintenance is carried out. Notwithstanding all these precautions, however, equipment failure can still occur in a large complex power system like ours, which has tripled in size within the last decade.

The PUB has installed a computerized System Control Centre costing $8 million at Ayer Rajah, This Centre constantly monitors power transmission and generation and is manned round the clock. When a fault occurs in any part of the system, power is diverted to other parts of the network. Stand-by generators can also be loaded up. In addition, the System Control Centre has facilities for remote control of major substations to expedite restoration of supply.

The PUB has also taken steps to minimize damage to cables that can lead to power failures. Bare overhead lines are being progressively replaced by insulated wires to reduce power failures caused by failing tree branches. Before carrying out excavation work, contractors are required to locate all underground cables within the worksites by checking plans and digging trial holes.

The Electricity Department of PUB also maintains a service and operation centre which is on 24-hour call and can handle minor and localized breakdowns of electricity supply. For the more major ones, the PUB Electricity Department has an emergency plan for the mobilization of all its staff. The System Control Centre in Ayer Rajah is the nerve centre in this plan. Power failures are detected almost instantaneously by the Centre. The severity of the breakdown and the areas affected are immediately assessed by the System Control Engineers who will initiate an alert and contact the Chief Electrical Engineer and other key officers. The reIovent engineers and technical officers follow a course of action in accordance with the procedures spelt out in the plan.

In attending to major failures, all 45 engineers and 74 technical officers in the Trans- mission and Distribution Division are involved. Where necessary, engineers and officers in other divisions can be mobilized. The response is immediate as normal maintenance and repair work is temporarily suspended to accord priority to emergencies.