10.1     Relevant Guidelines


Guidelines on limits of exposure to power frequency EMF were issued by the International Commission on Non-ionizing Radiation Protection (ICNIRP) in 1998.  The guidelines were recognised by both the World Health Organisation and the Hong Kong SAR Government.  CLP Power has adopted the guidelines in total.  EMF generated from the proposed overhead line shall comply with the guidelines as in Table 10-1 below.


Table 10-1    Guidelines on Limits of Exposure to 50Hz Power Frequency Electric and Magnetic Fields Issued by ICNIRP


Exposure Characteristics

Electric Field Strength

kV/m (rms)

Magnetic Flux Density Millitesla (rms)








General Public









10.2     Existing Condition
The existing 33kV supply system from Pui O Substation to Cheung Chau Substation transmits via three overhead lines and submarine cable circuits and backup with a limited 11kV circuit. The overhead lines run passing villages – Pui O Kau Tsuen, Pui O San Tsuen, Ham Tin Village, Shap Long Kau Tsuen, Tai Long Tsuen. People living in these areas have been exposing to EMFs, which are actually very weak indeed, associated with the overhead lines. Other areas of the project site are free from transmission lines. Thus the residents or workers in these areas are not exposed to any EMFs emanating from the existing transmission line.


10.3     Prediction of EMF


The calculated values on maximum loading basis are shown in Table 10-2 below.


Table 10-2  Electric and Magnetic Field Calculated for the Proposed 132kV Supply Circuit from Pui O Substation to Cheung Chau Substation



The calculation is based on the assumptions of maximum loading conditions and adoption of overhead transmission lines. The typical pole configuration with the bottom conductor is assumed at the minimum safety clearance from ground level of 6.7m.  Calculation format for EMF values is acceptable to Electrical & Mechanical Services Department.


In fact,For the proposed 132kV and 11kV, 35mVA units new 132kV underground and submarine cable circuits. As a result, the actualcircuits, the predicted EMF at the sensitive receivers will be further reduced.much less than 20% of the limits.


10.4          Mitigation Measures


The assessment results demonstrateIt is expected that the exposure of the public to the EMFs generated from the proposed underground cables, cables in tunnel and submarine cables will not exceed the guideline values laid down by the Government. As a result, no mitigation measure is required.

10.5     Monitoring Requirements


The measurement of similar design circuits and calculations of EMF for the proposed underground cables, cables in tunnel and submarine cables demonstrated that the predicted values would be well under the stipulated guideline limits issued by ICNIRP. In order to verify compliance with the ICNIRP guideline levels, field measurements will be carried out within six months after commissioning of this circuit. CLP will directly make arrangement with EMSD for the necessary measurements at critical locations at both ends close to the respective substations and the tunnel portals.

10.6     Conclusion of the Predicted EMF Effect


The calculations ofpredicted EMFs for the proposed underground cables, cables in tunnel and submarine cablesdemonstrated that the predicted values will be well under the stipulated guideline limits (below 2/51/5 of guideline limits) issued by the ICNIRP.  As such, the existence of EMF associated with the proposed project is not anticipated to pose any adverse impact on public health.