Isolated phase bus systems

For the theory of neutralization of the magnetic effect on the conductor in a non-magnetic shielding, refer to the continuous enclosures for isolated phase bus systems discussed in Section 31.2.2. As a result of non-magnetic shielding there will be no saturation of the iron core and the V-I characteristic of the reactor will remain almost linear. 

The design criteria and construction details of this system are totally different from those of a non-isolaled phase bus system. This type of enclosure is therefore dealt separately in Chapter 31. 

Figure 31.4(d) Termination of an isolated phase bus system at a transformer (Courtesy Best and Crompton)... 

Watertightness and air leakage test for isolated phase bus systems. 

This test is applicable to all outdoor parts of any bus system and on both indoor and outdoor parts of an isolated phase bus (IPB) system. Each enclosure to be tested (such as the enclosure of one phase in an isolated phase bus system) should be complete in all respects with all its fittings and mounts in place. The length of the testpiece must be the same as that considered for the temperature rise test (Section 32.3.4). 

This test is prescribed by ANSI C-37/20C for isolated phase bus systems after they have been assembled at site. The test is conducted by filling the enclosure with air up to a pressure of 15 cm of water (1500 N/m ). After the air supply is shut off, the pressure must not drop to less than 7,5 cm of water in 15 seconds. All breathers and drain holes must be sealed before the test. 

A detailed discussion of the isolated phase bus system concentrating on types of isolated enclosures and their design aspects... 

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