SHORTAGE OF POWER

Press, Volume LXXIV, Issue 22590, 21 December 1938, Page 20

SHORTAGE OF POWER

CITY'S DRAINAGE ENDANGERED

PROPOSALS MADE TO BOARD

DECISION DELAYED UNTIL CONFERENCE

How close the city was during the recent power shortage to a serious disruption of the drainage system, was disclosed in a report to the Christchurch Drainage Board last evening. The board discussed briefly a report on the situation from its engineer (Mr J. Cullens). but decided to do nothing until receiving further advice of the proposed conference on the South Island power supply, among representative authorities.

The report emphasised the possibility of a serious partial shortage of power, with a consequent hold-up of the drainage facilities for the whole city. Measures to meet this eventuality were outlined. The report stated: —

The Electricity Department of the Christchurch Cit- Council supplies the electric power to 25 of the board's automatic pumping stations and main station (Tuam street). Nineteen of these stations are supplied from the ordinary distribution network in a similar manner to that of the ordinary consumer* Nos. 6, 7, 8, 10, 11, and 20 stations, however, have independent lines from the council's sub-stations. In four of these stations, new pumping units are being installed, and in the other two. new units will shortly be required. The independent lines to these six stations will consequently have to be replaced very shortly with larger conductors to give the necessary extra power, and it is suggested that, in view of the possible power shortage and the necessity for the board's additional requirements, the whole position regarding supply be now reviewed.

Independent lines were originally installed (this board paying half cost) to enable electricity to be readily cut off in the council's sub-stations from all domestic consumers while still assuring power to the Drainage Board's pumping stations in time of shortage. During the Coleridge failure of June 22, 1938, no effort was made by the Municipal Electricity Department to give the board adequate power by cutting off other power users. Unless the council is prepared to guarantee the board all the Dower available and at full voltage, the board will gain little benefit from paying half-cost of these lines. If the council ■ will guarantee that any power that is available will be given for essential services such as drainage, at full voltage, then the board would be warranted in arranging for independent lines to all pumping stations.

Power Failures It is improbable but not impossible that there will be a complete power failure of long duration in Christchurch. The most likely trouble will be a shortage of power due to faults in portions of the power supply system, or to inadequate generating facilities. Power shortage implies rationing of the available power. In the Coleridge failure this year, the rationing was achieved by giving Christchurch users some power at very low voltage and frequency. This was entirely unsatisfactory, as mentioned in a previous report, and another hour under euch conditions would have caused serious trouble. Further, with the modern protective relays required with the new plant, the motors will stop with a 10 per cent, drop in voltage, and had the new plant been installed and operating last June, the sewers would. have been overflowing everywhere two hours, before the voltage crept up to about normal value. Another method of rationing during a power shortage of several hours' duration would be to cut oft sufficient consumers until the load equalled the power available, in which case voltage and frequency would be normal. If provided with independent lines, the pumping stations could then remain supplied with power even if all domestic consumers were deprived of the use of electricity. Purchase and Distribution

The following proposals for supply of power to the pumping stations have been investigated and a brief summary is submitted herewith:—

(a) To install a generating plant with sufficient reserve and flexibility to enable the board to generate all its own power quite independent of Government supply, and to distribute the same to all stations would entail a capital expenditure ol approximately £57,000. Interest and working costs of generation would be approximately the same as the present cost of power from the City Council. The interest on and maintenance costs of distribution would create new annual charges, excessive for any advantages likely to be obtained.

(b) The cost of underground cable, transformers, switch-gear, and necessary buildings, to enable the board to distribute power to all stations from its Tuam street station, would cost approximately £37,000. It is therefore obvious that only an exceptionally favourable agreement for bulk purchase of electricijty would warrant the board taking over the distribution of power. (c) The City Council has a favourable agreement with the Government for the purchase of power, and has the distribution network for other consumers, which enables it to retail power at a rate sufficiently low to be competitive with other forms of power. Suction gas, town gas, oil or diesel engines could be installed at the various stations, which would be reliable and cheap to run, but would require a considerable" capital outlay and extra staffing, so that even as a standby proVision, the step* is hardly warranted.

(d) The staff and facilities behind the council's electricity department are of definite importance in the event of trouble with local reticulation, and provided the board can arrange a satisfactory agreement with the council, it is recommended that the whole of the electrical distribution remain entrusted to them.

"Danger Remote"

The danger of complete power failure for more than an hour or two is remote except for act of God or act of war. With Coleridge, Waitaki, and Waipori linked up, modern technique and equipment, and the interconnexion of transmission lines should enable faults to be cut out and power, in some measure, restored within an hour or two. If after restoration the measure of power is limited, then sewerage and other essential services should have first call on any power available, but such power should be within 5 per cent, of full voltage. If then the board and the City Council can come to agreement on this point, the board would be justified in meeting half the cost of power lines from the council's substations to the board's pumping stations. There are other advantages in independent, lines, . such, as freedom from interference -with or. by other users. One final point might be considered by the board. The whole of the city's electricity supply is dependent on the Addington sub-station. If an act of God, such as an earthquake or other emergency, or of war such as a bomb-1