Bus section

FIG. 17-69 Design curves for electrostatic precipitators for fly ash. Collection efficiency for various levels of percent sulfur in coal versus a) specific collecting surface, and (h) bus sections per 100,000 ftVmin (4.7 mVs). °C = (°F — 32) X (Ramsdell, Design Criteria for Precipitators for Modern Central Station Power Plants, Amen c m Power Conference, Chicago, III., 1968. )... 

Diversity factor this applies to column 7 of Table 13.13. Whenever a bus section has to feed a number of outlets, one can apply the diversity factor as discussed in Section 13.4.1 (4) to optimize on the size of busbars and also the size of the main incoming feeder (Example 13.1). 

Figure 28.12 Skin effect in different bus sections of the same phase...

To calculate the sectional modulus (or moment of resistance) of the four bus sections in parallel we have multiplied the sectional modulus of one bus by 4. This is a simple method when the busbars of each phase are in the same plane and equally spaced as in Figure 28.33(a) with no additional spacers between them to hold them together. 

We have considered each phase composed of lour bus sections to calculate F, to be on the sale side. In fact the current of each phase is split into two circuits in this arrangement similar to the arrangement of interleaving and hence the actual F will also be only half that considered above. 

Figure 28.39 Illustrating Example 28.12(c), with tubular bus sections...

Make the joint by using the correct size of bolts, nuts and washers. Refer to Table 29.1 for the recommended number and size of fasteners for different widths of bus sections and Table 29.2 for the recommended size of washers for different sizes of bolts. See also... 

For jointing large bus sections it may be advisable to use pressure plates to avoid excessive local pressure. 

Refer to Figure 29.7 when making a tee Joint with a larger section of bus to tap for the outgoing feeders in a PCC or MCC from the main bus. A smaller overlap up to the width of the feeder bus section will be sulTicienl to provide an adequate contact area and boiling surface. 

Depending on the rating and length of the bus system, a flexible-end joint may be necessary at the panel end also to absorb expansion of the busbars and also to assist in making the end connections when the configurations of the bus sections in the equipment are different or have a mismatch, although there are no vibrations at the panel end. 

Effect of solar radiation on the outdoor part of the bus section °C)... 

For LT bus systems The length of the test piece will be a minimum 6 m as in lEC 60439-2 with at least one Joint. The Joints must be both in the conductor and in the enclosure in each phase. If the total length of the bus section is less than specified, the entire length of the bus system in the fully assembled form will then be tested. 

For the tap-offs in a power-generating station, connecting a VAT through the main bus section between the generator and the generator transformer... 

For the tap-offs, connecting a UAT through the main bus section between the generator and the generator transformer, however, as discussed above, the momentary peak current will depend upon the short-time rating of such tap-offs. The likely ratings are noted in Table 13.8. 

L = length of the bus section on which the voltage drop has been measured in metres... 

Suppose that X denotes the time to failure of a bus section in an electrostatic precipitator. Then X is a continuous random variable whose range consists of the real numbers greater tlian zero. 

Theodore et al. employed Monte Carlo metliods in conjunction with the binomial and Weibull distributions to estimate out-of-compliance probabilities for electrostatic precipitators on tlie basis of observed bus section failures. The following definitions apply (see Fig. 21.6.1). 

Bus section. A region of the precipitator tliat is independently energized a given bus section can be identified by a specific chamber and field... 

A leading utility in tlie nortlieast had requested out-of-compliance information to better schedule outages (plant shutdowns). The time to failure, T, of a bus section was assumed to have a Weibuill distribution, tlie parameters of which were estimated by the metliod of maximum likelihood on tlie basis of observed bus section failures shown in Table 21.6.1 for tlie utility s 5x8... 

For each of the 36 bus sections tliat had not already failed, the Weibull distribution was used to detennine tlie probability of failure before tlie next outage. Under assumption (a), tliis probability is P(T < 3301T > 209) i.e., tlie conditional probability of failure before 330 days, given tliat tlie bus section lias survived 209 days. Under assumption (b), tlie corresponding probability is P(T < 330 T > 230). For part (b), tlie estimates of the Weibull distribution parameters used in part (a) were modified to take into consideration tlie absence of failures for 3 additional weeks. 

Assume tlie time to failure T of a bus section lias a Weibull distribution with a = 1.3 X 10 and p = 0.77. 

L. Theodore, J. Reynolds, F. Taylor, and S. Errico, "Electrostatic Precipitator Bus Section Failure Operation and Maintenance," paper No. 84-96.10, presented at die 77di Aimual Meeting of Air Pollution Control Association, San Francisco, 1984. 

A third alternative is to rate the transformer in-feeds for single supplies but to arrange for automatic switching of the bus section and two incomers in the event of loss of supply to one section. A rapid transfer switching to the remaining supply in the event of loss of single supply can prevent the total loss of motor loads. In such a situation, the effect of the current taken by motors to which the supply has been restored must be taken into account. 

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