Downstream Feeders

When all the overcurrent curves are plotted for the main generators, transformer feeders, large motors and downstream feeders, they tend to be located close together , and without much room for adjustment. This is made more difficult when there are -... 

The star-point connection to earth is provided with a current transformer and a sensitive relay. The relay (51 G) is of a definite time delay or inverse time delay type so that it can be graded as back-up protection to earth fault relays at downstream feeders and consumers. 

Some drawbacks to the weigh belt are that it is a zero-reference device and thus needs frequent caHbration (re-zeroing). Buildup on the belt and roUers affects accuracy and operation, as does belt tension and dusty or floodable materials. Flexible connections are required to isolate the feeder from upstream and downstream equipment, unless the belt feeder/weigh idler concept is used. 

At the downstream end of the pipeline it is necessary to disengage the solids front the gas and this is most usually carried out in cyclone separators (See Volume 2, Chapter 8). However, there may be a carry-over of tine particles which must be eliminated before the gas is vented, and gas filters or electrostatic precipitators may be used for this purpose (See again Volume 2, Chapter 8). At the upstream end, the particles must be introduced using some form of positive feeder, such as a rotary valve or a blow tank. 

In the split feed process, the additives are fed into the polymer melt via a side feeder downstream of the plastification zone. Here, gravimetric feeding is always used (see Fig. 4.32). 

The intake behavior is also substantially influenced by the resistance of the downstream plastification section. If discharged at atmospheric pressure, e.g., via screw feeders, the throughput rate is considerably higher than if the same feed section is succeeded by a plastification section (Fig. 11.4). For instance, if metering a product with a bulk density of 0.35 g/cm3 and a melt phase density of 0.7 g/cm3, it is clear that considerable quantities of gas will have to be extracted upstream through the intake hopper. 

Fresquez PR, Armstrong DR. 1994. Radionuclide concentration in game (surface feeders) and non-game (bottom feeders) fish upstream and downstream of Los Alamos National Laboratory. New Mexico Conference on the Environment Albuqerque, NM. 

As one moves away from the batch feeder, a sharp increase in the average measured crown incident radiant heat flux is observed between locations 1 and 2. Crown incident radiant heat flux levels of approximately 555 kW/m were measured at location 2. This location is approximately 3.4 m farther downstream of location 1 and thus experiences less direct influence on incident radiant heat flux due to the previously discussed lower... 

Measurements in the combustion space indicate that the average glass surface temperature profile rises sharply from a low near 1700 K closest to the batch feeder to about 1850 K at the next downstream location, then continues to rise steadily down the axial length of the furnace along the centerline to a peak of approximately 1910 K in the region of ports 4 and 5. The molten glass surface temperature then drops to near 1800 K at the measured location closest to the furnace working end. 

Moulded case circuit breakers are also available for incoming and busbar section purposes, with ratings up to 6000 A and service voltages between 220 V and 660 V. (At 415 V a 4000 A circuit breaker would satisfy the duty of a 2500 kVA feeder transformer with about 15% spare capacity.) These are also available as 4-pole units. Circuit breakers having ratings of 800 A and above are often provided with several adjustments that widely modify the shape of the complete protection curve, as described in Chapter 12. This enables the curve to coordinate with almost any other protective device or equipment that is immediately upstream or downstream of the circuit breaker. Some circuit breakers with the higher rated currents are also provided with integral earth fault protection facilities. 

The type of feeder cables described in this section are those between switchboards within an oil industry site, rather than those between a utility power plant and an oil industry site. These feeders may be described as primary feeders as opposed to secondary feeders downstream in the system. Feeders from a utility power plant or a transmission network have protective relaying systems that are more sophisticated than those described herein, e.g. multi-zone distance protection, admittance relays, carrier protection schemes. 

A time delayed 51 N relay may be preferred so that some coordination and back np can be provided to downstream devices. The primary feeder shonld not trip in response to a fanlt in a consumer circuit. The consumer circuit should have its own fast-acting earth fault 50 N relay or element. 

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