Tenaga Nasional Berhad

Table 2-4: Short-circuit levels for various voltage levels
Supply Voltage Level S.C Rating
275kV 40 kA for 3s
132kV 31.5 kA for 3s
33kV 25 kA for 3s
22kV & 11kV 20 kA for 3s
6.6 kV 20 kA for 3s
415V & 240V 31.5 kA for 3s
2.5 PROTECTION REQUIREMENTS
2.5.1 Basic Requirements
In all cases, the basic requirement is that the consumer’s arrangements for protection at the connection point, including
types of equipment and protection settings, must be compatible with standard practices on the TNB’s system, and be as
TNB specifies during the application for supply process. This is especially critical for MV and HV consumers.
2.5.2 Specific Requirements
Consumers shall take into consideration the following specific protection practices of TNB in designing their
installation:
(a)
(b)
(c)
Maximum clearance times (from fault current inception to fault clearing) must be within the limits established
TNB in their short circuit rating policy for the distribution system.
Auto-reclosing or sequential switching features may be used on TNB’s distribution system. TNB will provide
details on the operating sequence utilised for the supplies on the proposed installation so the consumer can plan
for this in the design and protection of his facility.
On some of TNB’s distribution systems, certain types of faults may cause disconnection of one phase only of a
three-phase supply.
40 TENAGA
NASIONAL B E R H A D